Faulty 501 Complex Random v2?

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banksean
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Faulty 501 Complex Random v2?

Post by banksean » Fri Sep 03, 2021 1:45 pm

I recently purchased a 501 Complex Random v2 module, but it doesn't seem to be working.

I get nothing (or verrry little, but constant voltage) out of outputs 1,2 and 4, and only a constant roughly 5v out of 3. Knobs and switches have no effect as far as I can tell. 3rd led stays dimly lit no matter what I do with switches or knobs, but none of the others comes on at all.

I definitely triple checked that I had connected power to the correct power rails port on the back and that the power was connected properly to the bus before turning it on.

Output jumpers don't seem to make any difference either. I have them all set to 10v right now.

Does anyone here have any advice for troubleshooting this issue?

I hack on some microcontroller projects so I have a USB-serial connector, in case there are some diagnostics I could run that way (I see some apparently outdated docs on updating the firmware using a USB-serial adapter, but the links to the firmware .zip are broken). Similarly I have a multimeter, soldering gear etc for DIY kits I've built in the past in case those might help too.

Appreciate any help or advice you can provide.

Cheers.
-Sean

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waveglider
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Re: Faulty 501 Complex Random v2?

Post by waveglider » Fri Sep 03, 2021 2:05 pm

I was going to say check to make sure you didn't plug power into the expander, since they are the EXACT same amount of pins. I did this by accident and cooked the module. The other thing to check is make sure all the PCBs are connected to each other correctly. It's been a while and I might be confusing the 501 v1, but the stacked boards could be taken apart and the loose connections between them could be an issue. Make sure all socketed components are seated firmly.

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banksean
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Re: Faulty 501 Complex Random v2?

Post by banksean » Fri Sep 03, 2021 5:29 pm

[edit: Thank you for the response, waveglider!]

It's all SMD so there aren't any socketed components AFAICT.

I did continuity checks on all of the pins connecting the two boards while they were connected, but I didn't find any breaks. Getting my multimeter probes in there while the two boards are connected was kinda tricky.

Visual inspection (see attachments): I can't see any obviously fried components. None of the pins looks burnt. No visible cracks or epoxy etc leaking out of any of the IC packages. Maybe I've missed something?
PXL_20210903_215809019.jpg
PXL_20210903_215840187.jpg
I've fried modules before so I've become kinda paranoid about checking power connections. This particular module design does practically *beg* the unwary user to plug power into the expansion socket and fry it though.

I don't *think* that's what's wrong with this one however. The previous owner says it worked for him before mailing it to me, and I'm inclined to trust him. He shipped it in an antistatic bag, even. Which was nice. I get a lot of modules shipped in plain old bubble wrap. That said, I'm not sure about the ATMEGA328P's internal condition (maybe cosmic rays scrambled it en route?), hence my question about diagnostics over USB-serial connection.

Maybe just re-writing the firmware it would fix it? I'd try that next, but the instructions doc for updating the firmware: https://www.addacsystem.com/contents/pr ... date_0.pdf links to a firmware file that gives me a 404 NOT FOUND error: http://addacsystem.com/firmwares/ADDAC501_HEX.zip

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