Referbishing a Commodore 64 326298 Rev A 1982(FAB 326295 Rev D)

I picked up another Commodore 64 quite cheaply. This poor system had been stored in some bad conditions. I am not sure the conditions, but it had been wet at one point at least and damp quite a lot. When it was put there, it was probably pretty rough looking as far a browning of the plastic. This was an early Commodore 64 from 82 originally. Oddly the serial number label had no serial number printed on it. I have seen some labels that ink can be removed from by some cleaners, so I don’t know if it had been wiped off or never had a number.

Internally it as all there. The old paper foil shield was dirty and had mold on it. There was dirt and dead bugs all inside it. The first thing I did was pull the paper shield and toss it out, I then pulled the keyboard and mainboard out. Next I hosed the worst of the dirt and bugs out of the case with a hose.

Next I removed the bottom shield from the mainboard. It showed quite a bit of corrosion on it.

Before I tried to fire the board up, I did a bit of cleanup on the board itself. Then I looked it over to see if anything needed addressed before trying to power it on. I first checked that the power switch was making good contact. I then checked the Fuse was good. I also pushed all of the socketed chips in to make sure they were tight.

Looking over the board it was dated as 1982. There are some odd things about this board, it has had all the main chips socketed (all “wide” chips). The main chips are also all dated 1984. Three of the ram chips have been replaced and are also dated 1984. The remaining chips are all from 1982.

Here you see all t he main socketed chips. CIAs, the 3 Roms, the CPU, SID, PLA and VIC II from 1984

The next odd thing about this board is that it has a 8 Pin Video Socket instead of the 5 Pin Video Socket that was originally on it. julrod over at Lemon 64 said he had heard that Commodore service centers had upgraded the 326298 boards with 8 Pin Video Sockets. I have yet to test if the 8 Pin socket includes the added Chroma signal for S Video like video output (It does work and it works very well). Looking around the 8 Pin Video socket I saw 4 cut traces (some on the bottom some on the top) around it and there are two wires on the bottom side leading off to points on the board.

Here are the two wires off of the Video Socket, you can see some of the cut traces too.

I connected the cleaned up board to a display and my power supply. It actually came up to the normal startup screen showing all of the memory. The video was noticeably poor compared to my other later Commodore (a 1984 model). It has bad Jail Bars on the screen for one. I then connected up my full test harness an test cartridge. The board passed all of the tests. I fired it up with my Pi1541 and started up a game.

The next day I spent doing a lot more cleaning of the computer. The case was cleaned with some CLR Mold and Mildew cleaner, a brush and a toothbrush. It still looks bad due to the lack of the badge, the bad browning of the plastic. The plastic is streaked oddly in the browning as it isn’t very uniform. The top has a crack on the right front corner. Three of the mainboard mounts are sheared off. The narrow right tab is missing that holds the back on. Two keys are missing and the posts are broken on the keyboard. The keyboard worked, but it wasn’t very responsive. It is quite dirty as well of course.

Most of the screws are rusty. Some of them are very badly rusted, anything in the “front edge, including the case screws. I put them into some vinegar. After soaking in it for awhile, the rust was removed from them. It left them looking a bit different, but they were in much better shape. I also did the same with the keyboard springs.

I removed the cage around the VIC II area. It was quite rusted, and I don’t like them anyways, as it makes it hard to get to the parts inside. It may be a decent heatsink for the VIC II though, I replaced it with a real heatsink though. The computer has a factory mistake where R10 by the VIC is 300 Ohms where it should be 120 Ohms. Ray Carlsen recommended putting in a 220 Ohm resistor in parallel across the existing R10 to bring the resistance to what it was supposed to be. This corrects the resistor in at R10 brings the strength of the Composite Video output to what it should be.

Here you can see the new Blue 220 Ohm resistor stacked on the original R10 just to the right of the VIC II

Here is the keyboard disassembly.

I lightly cleaned the keyboard pcb with some IPA. Once it was put together again, it did seem like it was more responsive. I haven’t tested it fully though. Keep in mind that too much cleaning of the contacts will rub the carbon off and they won’t work properly.

For the keyboard I turned to a little inspiration from Perifractic at Youtube. I had to tear down the whole keyboard to clean it properly. It also wasn’t making good contact on some keys, so I decided I would clean the pcb on it. I don’t have spare keys, or posts. I decided I would try repairing the broken keyboard posts with some pieces of Lego Cross posts. It does look like it may work, I don’t know for how long though. The one key the “pound” key is one that I doubt I will end up using, so having a repaired post there shouldn’t be a big deal. The other key was the 8 key so I decided to move that post to another position where it will get less use. To do this was a combination of a drill bit, using a Dremmel, and Xacto knife. While the Lego Cross axel looks like the key post top, the problem here though is that it is just a bit too large. A Lego piece that accepts the Cross Axle will go on a Commodore Post, but a Commodore Key won’t got on the Lego Axle. I don’t know if some of the Lego Axles are a little different or what though the ones I had wouldn’t work with the keys properly. I ended up using a small file to file them down to a more fitting size. I found that superglue won’t get a great bond on Legos, Bondic doesn’t either. I did try some model glue, which was said to be able to fuse Lego pieces. I don’t know how well it is holding. I may eventually replace the damaged posts, but for now they are hopefully ok. I still need to get 2 springs and two keys.

I reassembled the keyboard with the repaired posts.

I also took the top off of the Modulator and cleaned and polished it up. The plate on the Cartridge Port had some bad rust on it as well. I desoldered it from the board so that i could get it properly cleaned up. They both turned out to be a good improvement. I was going to paint these pieces but decided not to. Instead I put some teflon liquid to try to protect them from rusting quickly. I also used it on the screws. It puts a bit of a coating on stuff and is used to protect tools from rusting as well. The other part/parts I pulled to clean up were the two parts of the Fuse Holder. They were badly corroded. I desoldered them and polished them.

The board now looks quite a bit better. I also installed heatsinks on the VIC II, SID, PLA, and CPU.

The conditions left the metal plate around the power LED corroding and the paint lifting off. I ended up cleaning it as best I could. I have to figure out what to do with it for painting etc. The main case badge was missing, and from the condition of the browning of the plastic , it must have been missing for a good while.

In an effort to get the old case looking a little better, I scrubbed the case with a paste of Baking Soda to get some of the marks off of the plastic. It did get rid of some of them. The plastic is still streaked brown.

For the crack in the right front corner on the top, I melted the plastic from the inside with my solder iron set to a lower temperature. This held the part in place, but for the crack on the outside, I used some model glue, that seems to have fused the plastic there pretty well. I also put a little on the inside to even out the melted plastic. Be careful about getting too much of that stuff on the plastic, it will dissolve it making it soft. It may not harden properly again if that happens.

Some of the pins in the components were rusted, and rusted badly on the bottom side. So I thought I would just clip them closer to the board. When I clipped at least two of these they just came right off. They were rust clear to the solder. I don’t think they were rusted below the solder. I tried to remove as much rust as I could. The presence of rust encourages the formation of more rust unless I am mistaken in what I have heard.

So far restoring this old beat up 64 has mostly been a lot of cleaning and some physical repairs. I did do the R10 fix. I still have more to do with it, and I am not sure when I will find the proper replacement keys. I was thinking of just ordering any key to put on the keyboard so I have a full keyboard, but I am not sure yet. I will probably recap the board. I have to fix those 3 board mounting standoffs that are broken off. I may fix the broken case tab on the right as well. The heatsink on the 5 Volt regulator is a bit loose, so it won’t be making the greatest thermal transfer to it. I will see about fixing that up before using the computer too much as well.

I am looking at the options for replacing the case badge. I also plan to paint this case and not to try and retrobright it or anything like that. The letters on the keyboard keys are also yellowed. On the left side it isn’t too bad, but as you go across the keyboard it gets quite bad. This computer will never be the best show piece. I think I like it though for the 8 Pin Video on the early board, and the main chips being socketed. I could easily use this board to test most of the typical breadbin primary chips. Being is such poor physical shape gives me a bit of freedom as this case will never be “like new” again, I can do what I want and not have to feel like I am harming it. It is a bit unique and it will remain so. I didn’t check the Chroma output on that 8 Pin video port yet, but I will get around to that probably later this week.

Once I was done cleaning it up, and I finally put the keyboard back together I fired it up again to try out a game again. I “think” it looks a little better onscreen. It still has noticeably worse jail bars than my other Commodore 64. I am only using it on my little 7″ composite display so I don’t know how bad for sure until I put it on a bigger display.

As I make progress on the restoration of this Commodore 64 I will probably do a followup post on it.

Commodore 1541ii Replacement Power Supply

My 1541ii didn’t come with a power supply. I initially tested the drive with some pins on power leads from my variable power supplies. That worked to test that it was functioning. It certainly wasn’t the best way to use the drive long term. I had a MeanWell dual output 5Volt and 12Volt supply I picked up for another project and had ordered in a 4pin Din connector. The next time I used the 1541ii drive, I had wired it up with that drive. Well right as I started using it the drive failed on me (see prior post). It turned out the SRAM failed for some reason. I don’t know if it had anything to do with the MeanWell supply or not. That supply requires a minimum load on both outputs for it to work properly. I don’t know if it wasn’t getting that load and was sending the wrong voltages to the unit.

After that I went back to using my regulated variable supply for the 12Volts and a 5Volt fixed bench supply I have to test the drive from there on. The MeanWell is intended for another project, but it my not be used for that project either as I don’t think I will be providing the “minimum load” on it.

I decided to order in a used dual voltage power adapter from Ebay to become the new supply for this drive. The one I picked up is 5Volt 1.5Amp and 12Volt 1.5Amp. So it is more than sufficient for the job, provided the quality and condition of the unit is good.

The supply I picked up to convert for the 1541ii

All I really needed to do was cut off the existing 4Pin Mini Din connector and replace it with a properly wired 4Pin Din connector. While I could have purchased a cheap new supply and done the same thing with it, I felt this “old” supply was probably going to be better quality than the cheap replacements. It did come in looking a bit dirty like the picture above, but it cleaned up well and tested fine.

Here is an image of an original supply. Notice the Pinout there. Only 3 of the pins are used on the 1541ii Supply. It is said that the ratings on these original supplies were rather low, potentially causing them to overheat and be unreliable. That sounds a bit like the original Commodore 64 supplies now that I think of it..

Here is the supply with the connector changed out.

While I don’t normally wire the “ring” of the Din Connector up to anything, I did wire the second ground to it as it was a convenient way to keep it out of the way, and I don’t know if that 4th pin goes to anything inside the 1541ii. I probably should have taken pictures of the connector before closing it up.

After soldering on the wires to the pins in the Din connector I insulated all the pins and wires with Liquid Electrical tape. It has a bit of hold to the wires, but mostly is to help prevent shorting in the connector in case a wire pulls loose. There isn’t much room in there to get normal heat shrink on the pins, as it is best to keep the casing to wrap the clamp part of the connector to. I did the same thing with the Commodore 64 power connector, and my new video/monitor cable.

I did put a piece of heat shrink on the cable under the strain relief cover of the Din plug. That piece of heat shrink builds up the end of the cable just a little and makes the strain relief bit grip well. Without it, that relief tends to pull back easily and will likely tear prematurely. I have done the same thing on my Commodore 64 Power Supply’s Din plug. I wish I had done it with my new video cable I made. My old original video cable could have really used it as well, but I don’t want to take apart the connectors and redo all of the soldering on them. There is a bit of risk in damaging the Din plugs as they melt easily when the heat is applied to solder and desolder the wires.

The supply seems to work fine with my 1541ii. The Din Plug quality is rather lacking though, I think it will hold up ok, but the fit isn’t the nicest.

Commodore 1541ii Repair. already..

Watching some videos, I noticed the 1541II had a grounding wire going from the one screw on the mainboard up to the right side of the drive assembly. I happened the have a braided ground cable of approximately the proper length that I salvaged recently and was on the bench still. I cut it down a bit and soldered a second lug to it and put some heat shrink on that end. The original one that I saw was not insulated, but as this one was already covered in heat shrink I figured I would leave that. I also picked up some new 10uF 25Volt Panasonic Electrolytic caps with my last order from Console5.com. I figured I would swap out the 3 original capacitors on the board. I went ahead and replaced the capacitors and reassembled the drive with the additional of the grounding strap. I had rigged a Meanwell dual voltage power supply with a power cable for the drive and figured I would test it out. I fired up the Final Cartridge III+ and brought up the Disk utility and checked the status of the drive, it came up normally. I attempted to read the disk and it failed then it started blinking an error. I turned it off and reset it and then it only blinked the light with a somewhat slow blink and kept turning the drive.

I rechecked everything, made sure again the capacitors were installed correctly, that nothing had shorted. That the power supply was supplying the proper voltages. I swapped the VIA chips. The board is fully socketed, so I removed and reinstalled all of the chips. I used my IC identifier on all of the 74 logic chips and they all read fine. I don’t know if that IC checker is just an identifier, or if it really checks for proper operation. I also tried both in normal mode and in JiffyDOS mode.

After all of that I also tried powering the drive with my fixed 5 Volt linear power supply and my variable regulated supply set to 12 Volts. The same results pretty much every time. I did a search and couldn’t find anything on that issue. So I had done all I could, I went to the Lemon64 forum to see if I could get any feedback on the issue. Someone pointed me to Ray Carlson’s 1541II troubleshooting text file, and after reviewing it there was a reference that the issue may be the SRAM and if not that the next would possibly be the DOS Rom.

The SRAM socket was an ugly thing so I figured I would start replacing it. I pulled that cut up socket and installed a new old stock one I had around. That didn’t fix the issue though.

Here is the old “socket” (for U5) after removing the solder. The socket for the 7406 (U7) is also desoldered. That socket was not seated flush to the board and was leaning toward the U5 socket making it just a bit too tight a fit. I put it down flush to the board like it belonged.

New Old Stock socket on the left and the original “socket” on the right.

Here is the new socket installed for U5 before putting the chips back. Yes it seems to be a gold plated socket.

Next I desoldered the SRAM chip from my spare 1541 board as it is the same type of chip on it. I installed the salvaged chip and the drive worked. Well it quit blinking constantly.

I then assembled the drive and connected it back to my Commodore 64. I went to check the status and it came up normally. I went to read a disk and it just error blinked. So I took the top back off of the drive, it seems the head wouldn’t move under it’s own power. I checked if it was free, and it would move with the power off, but there is some resistance. I don’t know how free it should normally be though. I then used the Alps drive test built into the Final Cartridge III+ to move he head around, it moved out but it didn’t move back the first time. The next time it did move back. I tried a few times and then I put in a disk. I was then able to read the disk normally. I read a few of the programs on it and it seemed to be working again.

I am going to get some silicone grease put on the rails to keep them freed up. I hope this drive will keep on working properly now. I am on to getting a proper power supply wrapped up for it as well.

Commodore 5 1/4″ Drive Transit/Transport Card

I currently have a 1541 and a 1541ii drive. Neither (as well as the third parts drive) came with their Transit Card. I found info on the cards at Ray Carlson’s site. The cards are to protect the heads from banging around and getting damaged while being transported. They do a combination of pushing the head to the back by the head stop position and hold it there during transport to prevent damage to the drives.

So I took the images from Ray’s site into Gimp 2 and recreated the text and boxes etc. I did grab a color copy of the commodore logo from a Google search, and put on it to replace the original. It worked out great, except my printer can’t handle cardstock that is stiff enough to make the cards. I did a test print on some cardstock, but it was too lightweight. I then used that as a template to mark and cut one onto a heavier piece of stock that worked out very well. The overall dimensions minus the back tab are 5.25″ by 5.25″ with the 7/8th inch tab offset on the back. The card needs to be stiff enough that the tab on the back does not bend when inserted. If the card it too wide, of course it won’t fit into the drive. If it it too deep it will not let you latch the drive shut on it. The second card I cut from the thicker material did fit my 1541ii drive fine, but my Alps drive didn’t latch because it was hitting the front of the card just a little bit. I knew it was slightly deeper than the original I had printed, but that showed there isn’t much wiggle room in there. I trimmed that little bit of excess off of the front of the card and it fit perfectly in to the ALPS drive.

The shape of the card is based on the 251171-003 that fits the 1541, 1541ii and 1571 drives. It is a bit of a pity that I spent so much time recreating the card graphics, but I can’t print one on heavy enough stock with my printer. Overall I think it turned out well though.

Yes, I know I did not put in the proper foreign characters..

The base information for the card was from Ray Carlsen’s site:

http://personalpages.tds.net/~rcarlsen/cbm/1541/

Commodore 128 Power Supply Recap

I also have a Commodore 128 and original power supply. The supply was in working order. As console5.com had a capacitor kit for it, I figured I would take care of replacing the Capacitors in it. The main trick is that my supply’s model number doesn’t match the contents.

The model on this drive seems to indicate the internal supply should be
310416-05 but the internal is actually a Mitsumi 252449-01. I checked the supply before so I knew which kit I needed.

The supply came with 4 plugs in the screw holes in the bottom. They aren’t always the easiest to get out. One was already missing and the next two came out easily. The final one I ended up drilling a small hole in it to pull it out. I wasn’t worried about putting them back in.

The supply with the original Capacitors.

This a rather simple job. There are only two capacitors in this model of supply. The replacement ones are a good bit shorter, and have a very slightly smaller diameter. They are good quality and 105 Degree rated, as well as low ESR types for proper operation in this switching power supply.

Here you can see all of the flux still over the bottom of the board from the factory.

Here is the board after I switched the Capacitors and cleaned the flux from it.

Here is the board after installing the capacitors. I also touched up a few other connections. I cleaned the old flux from the board as well, it looks much better cleaned up.

Here is the completed supply reinstalled in the case with the old capacitors beside it. I tested them and they do appear to likely be fine, but I don’t have way to test them for power leakage that happens with capacitors as they age. I trust the supply better with the new capacitors in it and expect the supply will be more reliable long term.

Assembly of a Final Cartridge III+ for the Commodore 64

I ordered in a Final Cartridge III + Kit from bruktmoped on Ebay. Considering the distance coming from Norway to the US it arrived more quickly than I expected. The parts in the kit were of good quality. The board was very nice, the resistors and diodes had “real” leads like they used to 20 years ago, not the ultra thin ones that are typical of today’s cheap resistors that I get in from the east. Yes, I buy the cheap stuff for my hobby work. I don’t know if they were new old stock like some I have purchased, or if you buy them from an electronics supplier that they are still like that. Either way, I couldn’t have been more pleased with the quality of the parts.

The Final Cartridge III+ is a reproduction of the old Final Cartridge III. The chip came already programmed. You can apparently make your own up with additional programs, but mine here is just setup as bruktmoped shipped out the Eprom. I laid over the electrolytic capacitors and raised the LED off the board, as I was installing this into a 3d printed cartridge case that I again picked up from ibuy24 on Ebay. I have picked up a number of 3d printed cartridge cases from ibuy24 now.

The only thing that was lacking was a jumper (and instructions) on what to do with JP1 there. I didn’t know what that was for, and no instructions came with the kit. I did initially try it without the jumper at all and it did not operate at all like that I did some searches on the FCIII+ and found some pictures and a bit of info on that. That jumper seems to set the board up for the type of Eprom that is on the board. For the size of Eprom the board came with, it needs to be in the left position. I did install a jumper header though rather than soldering in a permanent jumper. To get the case to fit I had to use an extra short jump, which I did happen to have in my surplus jumper bin.

Here is the top cover which I drilled for the Freeze and Reset buttons.

Here on the front I drilled for the LED.

Here on the back I hollowed out on the back side so the LED could get closer to the surface. I also had to take a little out of that support platform around the screw standoff .

So I drilled out for the Reset and Freeze buttons on the top as well as the LED with my drill press. The drill press gives more control than a hand drill, but you could do it with one. I would probably have used my Dremel instead of a hand drill though if I didn’t have the drill press. My drill press isn’t anything fancy, it is just the cheap model from Harbor Freight which I picked up for around $50 with one of their coupons. I did have to take a little out of that support area for some clearance issues for the short jumper as well. The case came with a nice brass thread for the screw as well, which I think was a nice touch. Another nice touch as you can see the case has an insert plate for the label area. I am going to make a custom label for on it before securing it permanently to the case.

Here is the cartridge installed into the Commodore 64 and powered up.

Here is a quick view of the menu system on it. You can navigate with the function keys and select the option with the Commodre “C=” Key. You can alternately navigate the menus with a Joystick, or I guess a mouse if you have a compatible one.

I really enjoyed putting this kit together. The board and components were of good quality, and it and was a lot of fun for someone like me that is. I would far rather put stuff together to use than buy it prebuilt. It isn’t like I did a lot, although the case took a bit of time to get the buttons just right and such. While the bare board looks very nice, I am happier with a cartridge in a case. The case makes inserting the cartridge so much easier because it aligns it to the slot, and aids removal by providing a good grip as well as protecting the circuitry from static shock and such. The case has a good solid feel to it as well.

I worked up a little label for it. It looks a bit better with it.

Commodore 64 Repair and Restore 250407

I picked up an old Commodore 64 last December. When it arrived it looked well maybe not great, but mostly clean.

You can see it still has part of a keyboard cover unit attached. That was quite difficult to remove actually without causing damage..

Internally it looked fairly clean as well. I took the computer out of the case and cleaned the case mostly with soap and water as well as an old toothbrush. I did use some Baking Soda and a bit of water to make a paste like cleaner to scrub some stubborn spots. The case ended up looking pretty good, it is browned a bit but overall not too horrible.

Here I have cleaned the case and keyboard.

Unfortunately the above images are what I was getting out of the computer when I first connected it up. It was flipping through a lot of garbage, I couldn’t even make it out. The camera picked up these images though showing me that something was working. Based on these images I expected a likely issue with the PLA to start. I ordered in a new modern PLAnkton chip to replace it.

Here is the board with the new PLAnkton PLA replacement, and a few caps replaced.

Here she is working after putting in the new PLAnkton.

The computer was working again after replacing the failed original PLA with a new PLAnkton chip. I had to desolder the original chip and solder in a new IC Socket. Then the computer powered up normally except an issue with the Keyboard. It acted like there was a stuck key, after disconnecting the keyboard it still acted like a stuck key. I pulled the left CIA chip there in the upper left corner. It is the CIA that controls the keyboard input. With it out the key wasn’t showing pressed. It was replaced at some point in the life of the computer so it was in a socket. So that seemed to mean the CIA chip was bad. I ordered a replacement chip. As the CIA was super tight in that socket I decided to replace it before putting in the new chip. I actually happened to have a new old stock socket in my stash of the proper size. I installed it and figured, I would test the CIA and see if I could do anything with it. The CIA fit better into this new socket, and it worked perfectly as well. So now I had a fully working Commodore 64.

I did do additional changes, such as replacing all of the electrolytic capacitors. Removing the metal shield around the VIC chip, and installing heatsinks on many of the chips. I also put heatsinks on the Cassette transistor and 12 Volt regulator. I replaced the heatsink compound on the 5Volt regulator. I purchased a full capacitor replacement kit from console5.com.

I also purchased the heatinks, new Din plugs for the Power Supply port, Serial Port, and Monitor ports from Console5.com. I used a new plug for the power port make myself a new safe power supply for the C64 (See my other post on that). I used one of the 6Pin plugs to make a Serial test plug for the Diagnostic Harness (see my other post on the Diagnostic Harness) as well as another for a Pi1541. I picked up the Horseshoe Din for the Monitor/Display Port and made a new Composite Video cable with the audio going to two connectors so I would have copied “mono” audio on my TV. I will be making a S-video cable out of another connector at some point provided I come across a display with S-video on it.

It seems a bit across the board as to “replace the Electrolytic Capacitors” or others will say “Don’t”. I will say if you aren’t using good quality capacitors, don’t waste your time, the old ones may be better or last longer if the new ones are junk. If they are leaking everyone says replace the leaking ones. I say if some are leaking, then others likely could at any time. So far as my experience went on the Commodore 64, I did find that at least some of the old capacitors were giving unexpected values. The old 10uF capacitors varied from 10.8uF to as high as 15uF with 6-8.4% v loss and 3.1 to 25 Ohms ESR. The new 10uF varied from 10.5uF to 10.71uF all at basically 1.2% v loss and 2.9 to 3.2Ohms ESR. I feel at the least that 25 Ohm ESR one was likely to become a problem, I am not so sure about several others. I have to say as the Capacitor kits at Console5.com are $5 to $8 (depending on the board revision) for good brand name capacitors it was certainly worth it for me. They carry them for all of the Commodore 64 Revisions, as well as the Commodore 128, the Commodore 128 Power Supplies (well at least two variants) and the 1541 drives. They also have the Commodore 64 Saver kit.

The keyboard was quite clean overall. I believe the cover was on it most of the time it was out of the box considering it was nearly pristine and only a couple of the springs had any rust on them. I took all of the key caps off with a key cap puller. I then hand washed all of the keys with soap and water. I brushed off the keyboard base and cleaned it with some
91% Isopropyl Alcohol as well, but I didn’t have to take the keyboard apart beyond that.

Black Screen failure..

Shortly after replacing the last of the capacitors it decided to act up and black screen on me. I ran the dead test cartridge and it told me the one ram chip was bad. First I retested my new power supply that it hadn’t went into an over voltage state. It was perfectly fine. I ordered in a replacement ram chip. When I went to desolder the chip, I found the one leg had been clipped off (the VCC pin) at the top and the soldered back on, as well as one of the other ram chips. The only chips that ever seemed to have been changed out was the left CIA and the VIC. I guess it was having an issue and someone was trying to troubleshoot it, I am not sure if that was back when the PLA originally failed or some other point. Anyways I finished removing that ram chip, being careful not to have that leg fall off. I then installed a new socket and put in the replacement Ram chip. I still had the black screen. I pulled the left CIA just in case, as it was socketed and not required to get a display. I then tried pulling the VIC and used contact cleaner on it and on the socket for it. Finally I decided it was time to desolder the SID, I really didn’t want to do that because there was a risk in ruining the chip in the process. I didn’t have anything else to try at that time, short of desoldering more ram chips, which I didn’t have replacements for. I did have sockets for the SID chip as well. When I went to desolder the SID I found the leads weren’t clipped at the factory, and some were folded over. The one lead was touching an adjacent trace. I believe that was causing the fault. I had gotten that far and decided to desolder the SID anyways. I removed it and tested the system, and it came up normally (well normal for no SID or left CIA. I soldered in a new socket and retested, the system still operated fine. After that I went back to the SID and finished straitening the legs out and installed it into the new socket. I was so glad to find it still worked after that as well. I then reinstalled the CIA and swapped back in the original Ram chip, it also worked. After that I ran the diagnostic cartridge with the full test harness through quite a few cycles for good measure. I finished installing the Heatsink on the VIC as I had removed the metal case around it. The VIC is quite hard to get an IC Puller in at with that case nearly touching the bottom edge of it. I actually removed that case before pulling the VIC. Later C64s didn’t have that case over the VIC so I figure I don’t really need it there.

Completed repair, capacitors and heatsinks.

Beyond that I cleaned the mainboard with an ESD Safe black brush to get the loose dirt off and some 91% Isopropyl Alcohol to get residues off of it as well as a bit of flux from the various new sockets as well as around the cartridge and power switch and the various ports.

It was fun getting this old machine going. I didn’t have one back in the day, although I had a used TI 99/4a at some point in the early 90s. So I guess that was my first computer, I didn’t really get to do much with it back then as I had nearly no software for it. I always liked the Apple IIs and such we used in school, and remember writing basic programs for them as well as later on doing that with our 486DX2 66mhz with Dos 6.2 and Windows 3.11 for Workgroups. I worked on the old 80s era IBMs including a few 5050s I had in the late 90s. I guess now I wish I had kept them. I even had a working luggable IBM 5155.. Well I never thought they would be worth anything more than scrap. Still I don’t know that I would have done anything with them. I worked on the IBM PS/2s in school, but never had one, even then I thought they were “weird”. The Commodore 64 is a fun system, and reasonably easy to work on.

It is a nice change working on these old computers compared to working on “modern” computers like I do during the day. It is nice getting into component level troubleshooting and repair.

After getting a second C64, I have found this unit has a only partially working SID. The third voice is not working on it. I only noticed it due to the other C64’s SID playing back more sound on the Diagnostics cartridge tests. If I used it more, I may have noticed some odd audio, but not being familiar with these computers back in the day, I don’t know how long that would have taken. I am figuring on getting a replacement, but I think I want to go with an ArmSID. Maybe next month I will be up to ordering one and see how it goes. My 128 has the same SID model in it, I could check it out to swap it, but I do currently have a fully working C64. I don’t have a good feeling for the chances of picking up a fully working original SID certainly a price that is much better than an ArmSID or other modern replacement. I like to keep them original as much as I can, but these chips are old, and not being made anymore, I don’t expect them to keep running another 3 decades.

Commodore 64 Test Harness

When trying to get my Commodore 64 up and running, I ended up buying a combination Dead Test and Diagnostic Cartridge for it. The Diagnostic side of the cartridge uses a special test harness to test out the operation of the various ports on the C64. I figured I might as well make a full test harness for it. It was a fun project to me, but I am sure there are others out there that would rather buy a completed harness. There are several people selling them. I found a nice modern made one on Ebay for a fairly reasonable price. There are others doing it as well as there is someone on Lemon64 selling them.

I am not including schematics and such, but I have posted the link to the website for the schematics I based my harness off of at the bottom of this post. I will say the Joystick Test portion of the circuit is hard to follow on the schematics with how they are setup. It really looks far more complex than it is. I color coded and traced all of the lines back across the two sheets (one of the big draw backs is the two sheets issue itself), and then I was able to sort out what was going where. The image of the User Port harness does have the layout I sorted from the originals, simply because I had made it and had it available when I took the picture. I did make some changes additions such as, 4 indicator LEDs that indicate power at 4 of the ports. I didn’t put an indicator on the User port although you could. The Serial port has no power pin so it can’t have an indicator. I also moved the joystick test circuitry to the Cassette Port which you will see later on in the post.

The easiest was the Serial Loopback, so I started there. It is just a couple wires on a 6 pin Din plug. I did put a loop of heavy wire on the casing so it could be used to aid in pulling the connector if needed, or to hang it up or such.

The next was a loopback for the Keyboard. The instructions I found for it included that you could make it out of an old IDE Ribbon Cable the earlier 40 wire model. Unfortunately I didn’t have any of those and only had an 80 wire type cable that they said can not be used. They were right the 80 wire type won’t work without some changes to it. The reason it won’t work is there is a center set of contacts that creates links between various pins. I took the connector apart and removed the center strip that was doing that. I then took a bit of the wire (from an 80pin IDE cable) and did the loopbacks directly on the connector.

It worked for the testing like that, but I decided to go back and add a LED and resistor to the loopback, as was mentioned on the Tynemouth Software site. This is good in my opinion, because if you have the keyboard loopback attached, you almost certainly have disconnected the power LED and have no indication there is power in that board. I put the connector back together and attached a pull loop on it to make it easier to remove. I also put a pin into the key pin so it couldn’t be installed incorrectly.

Power LED. There are only 1 wires attached to the LED. The extra wires are only there for extra support but do not go to the LED.

Then I did the User Port Loopback. It is just a series of wires on the pins once the components of the Joystick Test are removed from it. On the original Test Harness from Commodore it was put in what looks to be a modified “cartridge” case and it did have wires going from the Cassette Port and some 4066 ICs to test the Joystick Ports. In my situation I decided to put the 4066s and the Joystick Cables into the Cassette Port test unit instead. It was closer to the joystick ports, and they needed a data signal from there anyways. I also had a nice metal case available to build the board and install it all into. Initially I had installed a wire as a pull assist to remove the User Port Loopback. The connectors I picked up for the User port (and Cassette Port) are very very tight, so that wire did not work very well. I purchased a DSub Case for a 37pin DSub port (sizing chosen by a reference I found saying they fit into them, The Cassette port unit can alternately be mounted in a DB15 enclosure.) and installed the User Port Loopback into that. The DB37 enclosure gives better leverage to let me pull it strait back, it also does prevent it going in as deep, but it still makes good contact.

Original configuration with the pull wire.

Here I have removed the wire and put it in the DSUB enclosure. The line indicates Pin1.

The bottom of the User Port Loopback is Labeled with Red to help point out it is upside down.

The last part of the harness was the Cassette Port and Joystick Ports. The Cassette Port is fairly simple itself, but it actually sends a signal over the 4066s for the Joysticks. Looking at the schematics, I found it rather intimidating trying to figure them out. Being that it was two pages and the “joining” connections were flipped from one page to the other that didn’t help one bit. I am very very glad they are available, but that seems like a an odd choice to make. The 4066s have 4 sets of “switches” in them basically. When a signal is sent to that switch via the Cassette port the switches close and create a connection between the two wires going into it. There are 5 of those switches used by the test harness. The Up, Down, Left, Right and Fire buttons of the two joysticks are wired to each other when those are active. So Joystick 1 fire is wired to Joystick 2 fire and so on. The Paddle pins are each wired through a 120k resistor to 5Volts to give a known voltage on them apparently. I also added a Power LED to the Cassette Module, that shows the power is there on the Cassette port, as I am using the power from it for the 4066s. I decided to add Power LEDs for Each Joystick port as well with Yellow LEDs. They show that each Joystick ports are getting good contact on their 5Volts and Ground pins. The original harness doesn’t test the Ground pin on the joysticks, and if it wasn’t there they wouldn’t work.

Here is an internal view. The “blue” things are 1.5k old stock precision resistors.

Here is the completed unit. Don’t mind the Mislabeling. Note the Power L1 and L2 LEDs. L1 and L2 show that the 5Volts is working on Joystick Port 1 and Joystick Port 2. I thought of putting a another LED at the Input hole again and making it so that it lights when the Joystick ports get their signal from the Cassette port during testing. I doubt I will get around to that though, I am a bit curious what it may look like though.

I also put the Test Cartridge into a 3D Printed case I purchased from ibuy24 on Ebay. It has a 3d printed label plate and the hole in it that lets you toggle the mini switch to change the cartridge mode.

Here is a full test of the harness shortly after completing it. I didn’t have the case for the User Port unit yet.

Overall this required proper card edge connectors, 2 4066 ICs, some decoupling capacitors, a number of resistors and 4 LEDs. It also used a 6 Pin Din for the Serial and a strait through 9 pin Serial Cable that I cut in half to make the joystick cables. Beyond that I used a protoboard for the 4066 joystick circuitry and a salvaged metal enclosure, then the 37Pin DSUB cover as added later.

I based my test harness on the the schematics at Peter Schepers’ webpage http://ist.uwaterloo.ca/~schepers/diagnostic.html

I also took some ideas from the post over at Tynemouth Software. Such as the Keyboard Power LED. http://blog.tynemouthsoftware.co.uk/2014/10/commodore-64-diagnostics-test-harness.html

For supplies I purchased the 6 pin DIN plug at http://www.console5.com where I picked up all my DIN plugs heatsinks and Electrolytic Capacitors for my Commodores. I purchased the card edge ports from China via Ebay, although they are quite tight, I think there may be an alternate one that is made for “thicker” boards? I picked up the 4066s via Ebay as well although they can be sourced for many electronics suppliers. I purchased the DB37 DSUB Cover at http://www.unicornelectronics.com they should have 4066s and such as well I expect. I don’t know if they have card edge connector plugs or not in the proper sizes. I picked up the DB37 cover there when I ordered new ram for my Commodore 64 as well as some other 74 logic chips and various other bits.

Commodore 64 New Powersupply

I purchased an old Commodore 64 Breadbin style computer in December, and it didn’t come with a power supply. That is not exactly a bad thing as the old power supplies are responsible for killing a lot of C64s over the years. When those supplies fail, they often start sending to much voltage into the 5Volt line burning out many of the chips on the board. To see if it made sense to try to bring this old C64 back to life, I hooked it up with a 9Volt Ac Transformer that I had in my spare parts, and my regulated variable power supply. It sort of worked, it did need repaired, but that will be a post for another time.

I did manage to repair the Commodore 64, so it was time to make a proper and safe power supply for it. I took my 9Volt 1Amp Transformer (well 9.5Volt ) and picked up a new Mean Well RS-15-5 5Volt DC 3Amp power supply. I also picked up an enclosure, 4 conductor wire, and finally a proper DIN power connector from console5.com. The other items I had around, the IEC power jack, power cord, fuse holders etc.

I cut an opening in the back of the enclosure for the IEC power port. I also drilled the front for the outgoing power cord and installed a rubber grommet to protect the cable. I used my small drill press to start the holes then for the IEC being obviously not a circle, I trimmed out the rest with my Dremel and a hobby knife. The material the case is made of is reasonably soft and not too bad to work with. Just don’t try to drill or cut to fast, let the tool do the job.

The bottom of the case had some standoffs for mounting. I cut a piece of raw circuit board material to fit into the bottom. I then drilled holes to put screws into it to hold it to the standoffs. This let me have a solid base to attach the heavy transformer and power supply to without putting holes through outside of the case itself. I then mounted the Mean Well supply and the Transformer to the board and installed it into the case.

I really should have the mesh/screen grounded, that is not shown here though.

In the top I mounted a fuse holder, and later a power switch beside it. All of the exposed connections were sealed with Liquid Electrical Tape on the IEC port and the little bit at the base of the Fuse holder that wasn’t covered by the heat shrink for added protection if someone ever opens it up. I also cut out a fairly large opening for ventilation. I figured if I was going to open it up, I might as well make it worthwhile. I had a piece of screen from an old computer case and cut it down to fit and shaped it to bulge into the opening. I don’t know that much heat will be generated, but it certainly should have enough passive cooling going on with that much ventilation. The grill is pretty small, so the odds of anything falling in should be minimal. Also with all of contacts well insulated it shouldn’t be a problem. Something could get in the screw terminals on the Mean Well maybe. To put in the grill, I started by drilling in the corners for the opening with a Forstner Bit with my drill press to make the rounded corners of the hole. I then cut the rest out with the Dremel to get it close and then a utility knife and such to try to keep it clean and strait. It is slightly out of square, but still looks pretty good overall. Of course I did test the supply before attaching it to the Commodore 64.

Here is the completed supply after I added the power switch.

Here is the supply after I finished assembly on the Commodore 64.

It was a relatively simple project. It also was not very expensive overall. The Mean Well was pretty cheap I believe $10.00 with shipping. The next was the case which was around the same price. The 4 conductor wire I used is not very flexible, but even with what I purchased it ended up being more that $20, although I do have a good bit of wire left over. The wire is a stranded alarm system wire, it is only a couple strands and not very flexible. I would also probably crimp badly if it is wrapped up tightly. I figured if the wire becomes an issue, I will end up replacing it with a more appropriate wire. Overall I may have not saved all that much money making it myself compared to the cost of some of the units available theses days, but it certainly means more to me knowing I made it myself. There is not a Commodore 64 Saver circuit in it, but the Mean Well supply does have protection built into it. I did purchase a Commodore 64 Saver kit that I thought of possibly adding to the unit, but I did not have enough space in the case to get it in there. I did later build up the Saver kit, but the trigger voltage drifts with temperature changes. I don’t feel confident the Saver circuit would be all that reliable.

I’ve built a second Commodore 64 Power Supply and done some minor changes/additions. It is a near direct copy of the first model, with a few corrections to make some items easier or better, fuse placement etc.

Commodore 64 New Powersupply 2

1541 two to one

I recently picked up an old 1541 Commodore Disk drive for my Commodore 64. It was a bit ugly so I cleaned it up on the outside and inside before testing it.

I started by taking the case off of course as seen in the pictures. First I used some WD40 to break down the adhesive on the sticker on the top. Then I tried some Isopropyl Alcohol on the permanent marker, but it did not do much. I guess the marker was protected by the dirt.. I went on and used water and regular dish soap with paper towels and a toothbrush for the grills. From there I went to baking soda with a little water to make a paste to scrub the various black marks and the permanent marker with an old toothbrush. It didn’t get all of the marker but it make a big improvement. I then washed it all down with some dish soap again to get any remaining Baking Soda off the pieces. Once I dried it off, I took 91% Isopropyl Alcohol to the remaining marker, and it was able to take care of it just fine. The case is quite browned from the sun, but I don’t know if I will do anything about that.

Internally it was quite dirty too, but I did not think to take any pictures of it. Here is what it looked like cleaned up.

It looked far better and seemed like it may have been in working order. Unfortunately after I put a disk in it was unable to read it, although it attempted to. It turned out that the read write head of the drive was burned out. This is a very common failure on these Newtronic Mitsumi based drives back in the day due to corrosion in the heads or something. Based on the IC dates on the board it is a late 85 or maybe 86.

Above is a picture of the bad head pulled from the drive mechanism. The unit seems to operate normally in every other way, but new heads just aren’t available. With the head being a common failure I considered the odds of getting another Newtronics Mitsumi drive that had a good head as being a big risk. So I looked around for another 1541 listed as needing repaired that had the ALPS drive mechanism instead.

Well we need parts so..

The parts drive came in, it was reported as not working. It made a noise when plugged in but no lights on the front. I looked at the label here, and being in the US the “220V” just won’t work here. The drive wasn’t getting enough voltage to power the 5Volt electronics. It was getting enough to run the 12Volts for the drive motors though atleast to some degree. There may have been nothing wrong with this drive other than that. Still I picked this up for parts. The drive unit itself actually, as this is the ALPS style unit. The drive units are fully compatible, and it is just a matter of pulling the unit and putting it over into my other drive that had the bad head for the Newtronics drive.

220V on the left 117V unit on the right.

While I was in there I did look at the transformer sections. For the 220V there is a “red” tap connected to the fuse, and for the 117V unit the black wire is connected to the fuse. Both transformers are almost the same model number, and both have red and black taps, with the extra tap insulated. Even though they look about the same, minus the last few bits after the dash on the model number, they are different transformers. I did check if switching the Red wire for the Black one on the 220 Volt would change it over to work like the 117 Volt one, but it doesn’t. The only Voltage conversions I have seen on these drives involved swapping out the transformer, basically like I did. The transformer could be changed, also it would be possible to put in and bypass the existing regulators, or supply a proper voltage that can be regulated down by them.

This ALPS 220V unit has the same board model as the Newtronics.

Here is the board in the Newtronics drive, after I had installed the ALPS drive into it.

The boards are the same revision in both drives and appear to have been built just a couple years apart.

Here is the working drive after installing new Electrolytic Capacitors.

The main 6800uF capacitor was dented, so I picked up a set of new Electrolytic Capacitors for the drive from Console5.com. After testing it the capacitors I found one with a ESR of 40 Ohms, so it probably was a good idea to get them replaced. I also redid the solder at the serial ports and a few touch ups of connections that could have been a bit better out of the factory but were ok.

Here is the combined drive assembled. I did basic testing and the drive did read a disk and format a disk fine. I will look to do an alignment check shortly, but it looks like it should be finally working. I have since cleaned up the case from the 220V unit and swapped the converted 117V drive setup back into it. It is less “brown” overall, and doesn’t have a light patch on the top where the sticker was on this one. It did however have a large sticker on the right side, but still looks a fair bit better overall. The change of case doesn’t look significantly different in a picture so I won’t be positing a specific picture of it.

I have also looked over the board from the 220V unit. Someone tampered with it, I don’t think “repaired” is the proper term. I think they realized the 5Volt wasn’t working and removed it and reinstalled it (poorly), they pushed the traces off of the board. I repaired that and a capacitor they had pulled and very poorly reattached as well as one of the jumpers. I also touched up a few of the original solder joints that could use a bit of attention. I then cleaned the board and tested it. The board seems to operate fine, I didn’t do any extensive testing, but is did respond. I figure it is either working fine, or should be reasonable to repair. At this time I am only keeping it for a spare so I packed it up in an anti-static bag for safe keeping.

I am tossing the idea around of turning the extra 1541 chassis into a Pi1541 & Tapuino. I am not sure I feel right putting extra holes into an otherwise good case though. All of the controls would be on the 5.25″ Plate, but it would involve quite a few holes in the back of the case than are there now.