PreenFM > preenfm2 and preenfm3

[SOLVED] Fresh PreenFM2, but with display problem

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Holyver:
Hi,

A couple of days ago I built the PreenFM2, which I'm pretty exited about. I want to thank Xavier for the great work!

However, there's a problem with the display. Between the third and the fourth line, there are pixels lighting up which shouldn't be lit. I hope you can see it in the pictures. The pixels only light up when there's text on the third and/or fourth line, and which pixels light up depends on what is showing in these lines. Luckily, the synth works perfectly besides that.
I've already reflown al solder joints for the display connection, both on the display board and the main board, but that didn't help. Does anyone have any idea about what I could check to cure this problem?

Thanks in advance!

Xavier:

You have a non-working OLED.
I don't think you can do anything to fix that.

I'll ship you a other one this week.

Xavier

Holyver:
Wow, that's very nice! Thank you for this great service.
Keep up the good work on this great synth!

(I'll PM you my details)

Olivier

6581punk:
Yup, seems like a faulty part. The Preen just writes text to the display, it isn't a graphical display. So any malformations will be down to a fault in the display.

Holyver:
Indeed, a malfunctioning OLED was the culprit, and the replacement display (kindly provided by Xavier) completely cured the problem. Thanks!

For future readers, some more findings:


* I can report that a TDK TF250 4GB USB Flash Drive also works. It was the cheapest I could find in the store (€ 5.99). For my first tests I used a really old TrekStor 1GB stick, and (to my surprise) that also worked, but was notably slower than the new one.
* I wanted to include a powerswitch, and I found out that you can fit a small SPDT-toggle in the left side panel without drilling any extra holes. Just use the hole from the preen logo, and make sure to cut the legs from the tactile switches underneath it to avoid causing any short circuits by the body of the switch.
* For me personally, for the display installation, I found it slightly easier to plug the low profile header into the female headers on the mainboard first. Then place the displayboard onto the headers and the spacers, and secure the bolts. Then solder the header onto the displayboard. This way, the angle between the header and the displayboard is already in the correct position, and there is never any strain on the displayboard. It could be that this method is not recommended for reasons of heat transfer to the main board, but I doubt it could hurt, since you have to solder the female headers onto that board anyway.

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