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Old 1st June 2008, 09:22 AM   #1
varde is offline varde  Finland
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Default yamaha dg stomp

I'll try to make this as short as possible:

I borrowed this cadget to a friend who put it in his amps effects loop with preamp circuit turned off (or so did he say). The goal was to use it only as an fx-device.

Friend told that almost immediately after switching equipment on he heard extremely loud sound (and he means a huge earblowing kind of). So he turned quickly all off.

Later when he tried to switch dg stomp on there was no responce. All the ledligts etc. were dark. Seemed like it didn't receive power at all. So he let it be for a few days.

After few days I tried to switch the power on and I saw somthing happening. Some leds were flashing and on the number screen there was three lines: _ _ _. When I tried to push buttons --> no responce. I switched the stomp on and off few times and eventually happened that it didn't start at all. So I left it to be few months without doing anything.

After few months I decided to try again and I was amazed when there was "E5" message on the screen. So I replaced the backupbattery. After that I switched power on and what the heck it started and responded to all tweaking of the knobs.

This situation lasted less than a minute before it jammed again in the way I have told above. Finally there was no power, no lights, no nothing.

So if somebody could have suggestions what kind of damage has happened I would be very happy. In a nutshell the main symptom is that first the dg stomp might turn on but when power is switched on and off it refuses to start at all.
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Old 13th June 2008, 03:15 AM   #2
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i've seen such devices suffer from DECS, Dry Electrolytic Capacitor Syndrome. with the bypass caps in the power supply dried out, digital circuitry tends to false trigger and lock up from it's own noise spikes. the unit might need a "recap" which dor small digital devices shouldn't be very expensive since most of the caps are probably 10uf/16V at about $0.05 each
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Old 19th June 2008, 01:31 PM   #3
varde is offline varde  Finland
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Yeah! This is something I thought it could be. The 'computer' part of the device seems to be working fine so the problem is before that (ie. in the power supply). And first working - then not -situation might indicate failure in capacitor(s)

I downloaded stomp's service manual to have a look on circuit diagrams (from yamaha.com). Based on my little knowledge I noticed at least 9 caps. six around regulators and three more right after power input jack, around transformer. Am I even on the right track with this speculation?

Is there some way I can test which caps are not working or should I just replace them all?
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