Debugging a non-functioning JamMan Stereo looper unit

[drummer4gc]

Hey all,

I bought a Digitech JamMan Stereo off eBay. It was advertised that it would not turn on, which I was hoping would be a simple cold solder joint or burnt out polarity protection diode. It wasn't.

I understand there is a checklist to fill out for pedal debugging, and I am happy to answer those questions/post pictures when I have the unit in front of me later today, but I am more looking for just an idea of where to start debugging this thing. Most of the circuitry is surface mounted/tiny things. A ribbon cable connecting two boards appears to have a lead that is broken/in the process of breaking...i'll post pics later and hopefully someone can help me figure out where to buy a replacement. I'm planning on replacing the two electrolytics involved in the power supply (which is 9 VAC, kinda strange....) because the solder job was poor and it couldn't hurt.


Any other ideas of things to check?

Thanks,
Matt

[Mark Hammer]

AC wallwarts are frequently used when the circuit needs more than one supply voltage; for example 5V for the digital stuff and 9 or even 12vdc for the analog.

Running AC to the chassis lets you keep the dang transformer out of there so it can do the least harm, and lets you stick all the regulators and things on the board.

One of the disheartening things about the wholesale conversion to surface mount is that it will become harder and harder for mere mortals like us to buy semi-working stuff on e-bay and resurrect it.  Not harder to FIND, mind you; just harder to debug and fix.

[drummer4gc]

here is a picture of the ribbon cable i'd like to replace. any idea where to find a replacement? you can see some of the corrosion on the conductors at the top, and one is completely seperated from the cable....i'm beginning to think someone spilled a drink in this thing and that it might be beyond repair at this point...