Rocktek BBD Delay. No Power. Please, I need Troubleshooting Help. Hi Def Photos.

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fubusmaximus
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Post by fubusmaximus »

My trusty 80s Rocktek BBD Delay died. I have soldering skills luckily, and a little experience troubleshooting electronics, but only the easy stuff like blown caps/diodes/burns/shorts. I have a great multimeter that does everything, oscilloscope, soldering iron, and adjustable power supply that will display watts being used.

I tried multiple 9V center negative power supplies that work with others, then I tried a battery, no luck. When I plug it all up and I kick it on/off (I can't tell when it is on or off because no LEDs turning on) via the footswitch, there's no sound either way.

I know what a burned cap smells like and I don't smell that. None of the diodes looked blown/burnt up to me either. I also don't see any burn marks on the blank side. This pedal was working just a little tiny while ago, and it was just sitting in my unused pedal box temporarily since xmas.

Here are a bunch of photos of the board. I'm still trying to find a schematic. You can see gigantic versions by clicking on a pic below and then on the page that comes up click "Zoom."

https://postimg.cc/gallery/kgSRnqf

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lolbou
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Post by lolbou »

Hi, check for voltages at ICs power pins with a fresh battery (input jack plugged in!) or power supply.

Considering you have no LED and don't even have bypass sound, my guess is that you don't have any power at all, it may be shorted or disconnected somehow (provided the dry signal is always on).

Double check power wiring, continuity at input jack (battery saver "switch"), and check for voltages at ICs power pins and power supply circuitry. If all voltages are correct, check the voltages on the 4072 flip flop for bad logic states too.

Let us know!
- Are you a mod or a rocker?
- Uh, no, I'm a mocker.
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CheapPedalCollector
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Post by CheapPedalCollector »

Check the power jack is passing voltage through it as they get corroded, check the zener at D3, check solder joints, check the input jack.
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fubusmaximus
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Post by fubusmaximus »

Yeah, I had checked the voltage at the solder points and it was good.

I'll double check the D3 Zener with a meter, but I'd already visually inspected all of them. Can a diode go bad without any visual indication?

Someone else told me to check the 4072 as well, so I'm sitting down to do that now, after the diode.
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CheapPedalCollector
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Post by CheapPedalCollector »

yes, diodes can go bad without visual indication, any part can really
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fubusmaximus
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Post by fubusmaximus »

The switch is momentary, which was a surprise. I replaced it anyway, but it accomplished nothing. I'm not sure how to test the flip flop? I have an oscilloscope and hooked up to where the clock should be and I just saw straight 9v, no very fast square wave.

D3=.725V
D2=.610V
Oh, it's D1!

I'm going to replace and let you all know
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