Delay Problem

nicovlogg

Hey all, recently bought a Digitech pedal second-hand. Tried it out at the guys house, worked perfectly. But upon taking it home, it's only worked once or twice. I took it apart, nothing appears to be loose (which normally I would think is the cause of an intermittent fault). Could the switch be broken? What can I look at?

Gearhead

If you took it apart, you may or may not have seen a crack in the PCB; if it has a cracked PCB it's almost impossible to repair. Otherwise, you can fix it 99.99% sure.

You could try checking the jack sockets; if they're loose they will give problems like this. Does the LED come on when you switch the effect on? If not, look at the power circuit. Does the pedal pass through your guitar signal when switched off/on?

nicovlogg

PCB appears to be fine, I fastened the sockets and cleand it out with spray, no help there. When it's off a signal comes through fine, it's not true bypass either. I'm pretty stumped..

dee

Are you running it from a power supply, or a battery? Does the light come on when there is power?

matta

Gearhead wroteIf you took it apart, you may or may not have seen a crack in the PCB; if it has a cracked PCB it's almost impossible to repair. Otherwise, you can fix it 99.99% sure.

I disagree... do you know how many PCB's I've had to repair where traces have broken off completely? You just jumper the trace either with a piece of component offcut or wire jumper, it obviously depends on the damage but it in most cases it is fixable unless it is a multiple layer board where traces run INSIDE the board as with a computer mother board. 90% of pedals are either single sided or double sided at best, so can be repaired.

Nicovlogg, digital units are always harder to trace out than analog ones. RE not being true bypass, it can still pass the signal if it is off is the FET used to switch the audio is arranged by default to route the in to the out, a momentary switch when powered will then direct the signal into the effected path, so you can't use that as a basis for building diagnosis.

Cheers

Matt

nicovlogg

I'm running it with a battery, when I tested it and it worked perfectly I was using a DC adaptor. However, it has worked with a battery before. No light comes on.

Matta: How could I test the switch? That wouldn't be too tough to replace, if I could find a similar one. I've also thought that it might be the plugged in cable (input) which carries the ground power and isn't connecting, so no input detected -> no switch on.

matta

Little confused, so it works with a DC Adaptor but NOT a Battery? Seems then to indicate that the battery snap might have come loose, generally the battery snap and DC jack are daisy chained to each other.

RE the switch, depends how it works, many of these switches at momentary, make to break, or normally open switches, if you hold it down you should be able to make continuity between the poles... assuming it is NO vs NC, which would operate inversely to the NO switch.

You can check the jack as well, as you pointed out the LED will not come on if your input jack doesn't mate with the circuit.

Cheers

Matt

nicovlogg wrote I'm running it with a battery, when I tested it and it worked perfectly I was using a DC adaptor. However, it has worked with a battery before. No light comes on.

Matta: How could I test the switch? That wouldn't be too tough to replace, if I could find a similar one. I've also thought that it might be the plugged in cable (input) which carries the ground power and isn't connecting, so no input detected -> no switch on.

nicovlogg

No, it only works occasionally with a battery - I thought it might be a loose battery snap but the circuit tests out fine.

Perhaps I should just check it with a DC adaptor

nicovlogg

Ok, it seems to be the battery holder then - works fine with a DC adaptor. Thanks for the help!

matta

nicovlogg wrote Ok, it seems to be the battery holder then - works fine with a DC adaptor. Thanks for the help!

My pleasure, where do I send your bill? Hah Hah!!! Get that battery snap sorted because one day you might sell it and if you forget about it the next buyer might also think it is broken.

Cheers

Matt

nicovlogg

Good point, it's just a real pain to open these things up - the knobs are really flimsy and it's just made to never be repaired. Sigh.. thanks for the advice!