PreenFM > preenfm2 and preenfm3

No buttons or encoders - solved

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Road_Kill:
Hello Xavier,

I just built a PreenFM2 kit and had an issue I haven't seen on this forum before that I thought I would share.  When I first turned my preen on, I got the boot loader screen and none of the buttons or encoders would work.  After poking and prodding, I could get the synth to boot normally, but still with no encoders or buttons. A reboot would simply put me back to the boot loader screen.  After much more poking and prodding, I came to find that if I so much as lightly touched the leads around the resistor networks, I could boot into the normal screen.  Every subsequent reboot would take me to the boot loader screen until I lightly touched the leads anywhere around the control scanning circuits a which point I could reboot to the normal screen again.  I suspected a poor solder joint but could never locate one.  Eventually I got the schematic and systematically checked connections until I realized that pin 1 from both 74165s were not reaching pin 6 of the 405.  This turned out to be a defective trace on the pcb as opposed to anything I did or didn't do while assembling the circuit. A small wire soldered between pin 6 on the 405 and pin 1 on one of the 74165s was all it took to have my preen up and running! Now it's hooked up to an Undead Instruments Timefrog purring in the background while I write this email. Time to go play with it some more!

Xavier:

Thanks for the feedback and congrats for fixing the problem.
From what i remember, this is the first PCB trace problem i hear about.
They are rare but very very annoying.

Glad to read your preenfm is now working  :)

Xavier:

Just a question : did you order the PCB from me or did you make it yourself ?
Note that i don't have any problem at all with the latter when not for resale  ;)

I ask that because i tried to find what batch was your PCB from and i don't see any PCB associated with your email.

Thanks,

Xavier

Road_Kill:
I picked up the kit from Van Daal.  I'm not 100% certain where the trace is broken, but I suspect it's where it passes between the pins (9&10 I think) of the 74165.

Xavier:

--- Quote from: Road_Kill on February 09, 2016, 09:42:29 AM ---I picked up the kit from Van Daal.  I'm not 100% certain where the trace is broken, but I suspect it's where it passes between the pins (9&10 I think) of the 74165.

--- End quote ---

Ah OK thanks.
That's my latest PCB batch.
Sorry to ask that but are you sure it was not a bad soldering point ?

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