Delay pedal help, please.

ralpheo

ralpheo

Stuck in Neutral
Ok modders,
I need some help with a Digitech PDS1002 I bought 2 weeks ago on ebay. I had one of these from about '86 until I sold it in 1999. Stupid move! :(
I tested it out and found that when I have both the effect out and the dry out connected to the inputs on amps or any other such device, I get absolutely no sound. If I use a use a means to split the signal (in this case a Zoom 504 acoustic fx pedal) before the input of the PDS1002, I get a normal output.
At this point I would actually be ok with that solution, except that I have now found that I have about 5 minutes of use before the signal starts to decay and disappear. I thought at first that my battery might be dying, but that's not the case. (The led never goes dim, I used the battery for quite awhile in my tube screamer, and tried a second and third battery in the delay pedal.)
If I disconnect and leave the unit off for a few hours or days, it's ok, but again only for a few minutes and then it's useless.
I'm wondering if:
1) a capacitor could be worn out, heating up and discharging at too high a rate and if so which one do I replace?
2) one of the delays is worn out and again, which one?
3) something else entirely? :confused:

I would appreciate anyone's help on this. I'm not afraid of digging into this thing, but at the same time I don't want to wind up with a box of $80 worth of useless circuits.

I'm going to include a stock photo of the guts, but I haven't located a schematic yet.
Thanks guys.
 

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Considering the age of the unit, my first move would be to replace every electrolytic capacitor.

As an aside, I have a very good method for testing electrolytic capacitors.
It's called the Sink Test. Remove all the capacitors, get a boat, go to the centre of Sydney Harbour (or any other appropriate excessively deep body of water that is handy), and toss them all over the side.

If they sink to the bottom, they WERE OK.
If they float, they're no good anyway.

:D
 
This sounds like a problem with a component failing when it gets warmed up.

Get yourself a can of freon or equivalent. Shoot the freon on random parts until the thing comes suddenly back to life. Test several times to make sure you know which component it is. Once you've narrowed it down to a part or two, resolder all the solder joints in that area. If that doesn't help, replace those components.

Thermal failures could occur anywhere, but the most likely components are those that get really hot---linear voltage regulators, discrete transistors (in some circuits), current-limiting resistors (and/or voltage divider resistors), etc. So try things that are attached directly to the power bus traces off the battery first, then try hitting the chips.

I wouldn't expect it to be capacitors, honestly. If this had an AC power supply with filter caps, then those could fail and make things misbehave massively (hum for an analog device, crashing for a digital device), but powered off a battery, any caps are likely to be more for signal filtering, in which case they don't do that much work.... My bet would be a cracked solder joint somewhere---probably at the corner of a chip.
 
Thanks dgatwood. I'll give it a shot. Will compressed air in a can do the trick, or something more specific? I have dust remover spray from RS.
I'll be getting to it later this week, so I'll update you guys on what I come up with over the weekend.
Thanks guys.
 
Simple Fix

Good afternoon all,

Just to update you all:

The infinite repeat switch on my Digitech PDS1002 was weak and only engaging after several pushes on it. I went to radio shack today and got a replacement. It's a good bit smaller than the original and had a longer shaft, so I added a couple jumpers and cut about half of the shaft off and filed it a little.:cool:
Works perfectly!:D
I'm not quite sure why this particular switch was making the effect degrade and disappear after a few minutes, but I realized today that it was not doing so until after I engaged the infinite repeat. I figured that it couldn't hurt to try a new switch. Sure enough.
I'm so glad that buying this pedal was not a waste of my money, which is what I feared when I encountered the problem. But this is what I think of as probably the best digital delay pedal (not looper) ever made.:D
I am a little pissed at the ebay seller who bullshitted me about not having ever opened it up, when he obviously had. The handwriting on the outside, which he said he had put there for his own purposes, was the same as the handwriting on the board inside. I hate a fucking liar.:mad: Just tell me the truth so I know what to expect. Right?
Anyway, I'm happy I got it figured out. Now I've got the sound I have been missing for ten years! Yay!
Later, thanks for your suggestions gentlemen.
 
ralpheo said:
Thanks dgatwood. I'll give it a shot. Will compressed air in a can do the trick, or something more specific? I have dust remover spray from RS.
Click to expand...

No, if it had been a thermal issue, you would need something that cools down a lot more than compressed air does. You should be able to find freeze spray at any electronics house.
 
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