Pico 2 DRAM Tester

Lee of More Fun Making it on Youtube made a video building and testing the Pico-dram-tester. I like building up these types of projects, especially when the device is useful. I believe Lee mentioned he would like a power jack, as the intended power method was using test points. It can be powered by the Pico2’s USB port, but that wasn’t recommended, also such ports are easily damaged, and it would make it so you couldn’t update the device etc.

Original Github Project: https://github.com/schlae/pico-dram-tester

Lee’s Video: https://www.youtube.com/watch?v=7orsBI78VHI&t=799s

Lately when I have been ordering PCB designs by other people, I have found there were little changes I would have preferred to have made before ordering them. So I decided this time I would take the time to make some of those changes. I just didn’t want to use Test Points for powering it. I modified the design to include a DC Barrel Jack, center Positive 5Volts. The other primary change was I wanted to make it easier to “bodge” in the more common generic Rotary Encoders that I have. I didn’t know for sure if the generic Rotary Encoder would work, so I didn’t do anything too fancy in the first pass. I also made other minor routing changes throughout.

Because I picked White for the PCB, the tracks are very hard to see on photos. Somehow I put the wrong month reference on the board silk screen. I guess I should have labeled it as Revision 2.1. It was based on the Revision 2 with those minor changes. I did remove 1 Ground Test Point footprint, both were wired identically. There was no point in keeping it, and I didn’t have room for it.

The build went fairly strait forward. The primary recommendation is to put the Pico 2 on first. Don’t be confused by the project name “pico-dram-tester”, it doesn’t use a “Pico” it uses a “Pico2”. I put on the Resistors on next, then the 100nF Capacitors and then the taller components. I did use the Adafruit LCD so U9 was not required.

I did have to cut a trace at the Rotary Encoder, and put in a single bodge wire connection to ground. The common Generic Rotary Encoder lower center pin needs to be grounded, where the specified Panasonic Rotary Encoder that pin is a second “B” directional pin. (Note: “my” Rev 2.2 variant doesn’t need this done)

Once it was finished, I used it to test some 4116 chips and 4164s. It failed all of the bad 4116 chips I had, and passed the good ones, as well as the 4164s all passed. I found the 4164s pass to their speed specification and did fail if I set the tester to test for higher speeds.

The 4116 chips verified the -5 and +12 is working as well. I don’t have any of the other types of DRAM ICs to test.

With it working with the Generic Rotary Encoder, I just had a few finishing touches on this built. I needed a knob that fit the D shaped encoder. I found a knob that fit nicely.

https://www.printables.com/model/347536-encoder-knob

I also wanted a case, a full case isn’t very practical. I did find a Tray/holder case for it.

https://www.printables.com/model/1248424-pico-dram-tester-case

The case didn’t require any changes to accept the DC Power Jack because there were already all of the Test Points there. The DC Power Jack does hang off the edge, which was intended, due to lack of space and I wanted it to be flush with any case it may be put in, rather than deep inside the case.

I did also print some spacers and install some M2.5 screws in the LCD PCB to keep it supported and solid. I put a bit of Red paint on the 4116 IC Socket. I also swapped out the button cap I had on the Back button.

Finally I put some stick on feet on the bottom.

While this little build is done, there were some things I wanted to change on the PCB after putting it together. I went back and reworked the PCB for Revision 2.2.

The new changes primary include a set of solder pad jumpers to configure the Encoder to either use the Panasonic Encoder, or the common Generic Encoder. The other changes are mostly Silkscreen changes. I prefer when the Component Values are on the Silkscreen as well as the part designations. There were some other minor routing changes, changes to via placement and such. I have uploaded Revision 2.2 to Github: https://github.com/Markeno76/pico-dram-tester

Below you can see renders of Revision 2.2 The solder pads can be seen to the left of the encoder footprint, instructions for JP1 are on the back of the board. Component Values have been added, also the Back button now has the “Back” text displayed.

I did find there is another fork of the project, that includes changes to the firmware. I want to look into that, as there are changes to work better with the Generic Encoder such as I have used. It works fine, but I believe you will get less “bouncing” with the alternate firmware. I do plan to look into trying that firmware, and see if I can bring it into my fork.

Update: 9/1/25: The original project has had the firmware updated several times since I built this and posted my revised pcb design. Now supports 4108 and 4132s the half good/bad chips used in some 8bit computers back in the day. I just found out about the firmware update watching another of Lee’s videos last night. I have merged in the updates into my fork, but those are current as of 9/1/25 so check the original github project for future updates.