Digitech pds 1002 repairs/trimpot question



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Digitech pds 1002 repairs/trimpot question

Postby shovelhands » Wed Jul 01, 2020 8:13 pm

Hello yall, please let me know if this isn't the right spot to ask for some guidance re: getting a Digitech pds 1002 back in working order. I bought this pedal in a fairly beat up state, and since the price was decent I decided to pull the trigger on it, planning to try my hand at getting it fully working and optimized (first time doing so with any audio equipment, at least to this extent).

When I received it, the infinite hold footswitch was a little spotty, but after powering the unit on and hitting the switch 5-10 times, it'd start to latch/unlatch consistently without any trouble. Bypass footswitch never gave any issues. Repeat oscillations were very low, with the regen knob kranked I could get about five repeats. No worries, I knew before buying that there's an internal trimpot to adjust this to my liking. I fully disassembled the unit so I could clean all the grime off the footswitch/knob areas. Three of the five knobs were ultra grimy and had seized up on me, but after applying a fair amount of contact cleaner they seem to have loosened somewhat (there's still some unwanted resistance to them, so they may get another spray soon).

Put the unit back together, and had the opportunity to test it out once again earlier today (with the intent of finally adjusting the regen trimpot so it'd self-oscillate). But now I'm not getting anything? No delay repeats to speak of. The mix, input, and output knobs seem to still function, and the dry signal still passes through with the effect engaged or bypassed, but can't get the delay time or regen knobs to have any effect. The infinite hold footswitch seems to have given out fully since the last time I used the pedal, but that's not the primary concern right now (I'll be buying a set of dod footswitch button replacements soon).

I guess my main reason for posting is to see whether anyone in this community has familiarity with working on the digitech pds series? If you have a pds 1002 to reference, could you possibly take a peek inside your unit to note the trimpot positions? I'm afraid that I either mistakenly knocked/readjusted the delay clock trimpot while I had the pedal taken apart for cleaning (could this be the primary suspect for no delay signal?), or that I mistakenly plugged in the internal sockets backwards when reassembling, and caused harm to the components by powering it back up improperly (I was a fool for not noting the proper orientation for these internal sockets. In <1sec bursts, I very quickly tried two or three inversion combos until I could see the effect bypass LED turning on/off properly with the footswitch).

I was able to get some helpful info from http://www.sonicurbs.com/digitech1000/ , but the images provided there are still a little vague. There's a local music store that I could take it to, and may just end up doing so. The owner seems more than capable of dealing with this sort of repair. But honestly I'd like the satisfaction of making this thing work "on my own" if you know what I mean. It being my first bona fide gear repair undertaking.

Thank you in advance for any and all guidance on how to move forward fixing these issues!
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Re: Digitech pds 1002 repairs/trimpot question

Postby Scruffie » Thu Jul 02, 2020 6:35 am

Fortunately the schematic shows there is a polarity protection diode so hopefully no harm done from potential backwards power. Unless you mean you were putting in the chips backwards because then they're dead.

There's 4 trimmers I see on the schematic, one is compander bias, one is regen amount and two are clock adjustments. Thing about trimmers though, is if photo positions were useful, they wouldn't be trim pots in the first place... measuring the compander output voltage is one step to see if you mistakenly adjusted that as that would prevent delay signal passing.

But... this is really the wrong pedal to take on as a first project even as just a refurb, I would really recommend finding a good tech.
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Re: Digitech pds 1002 repairs/trimpot question

Postby chromandre » Thu Jul 02, 2020 9:14 am

shovelhands wrote:or that I mistakenly plugged in the internal sockets backwards when reassembling,

double check this first!!!

This is gonna sound crazy but sometimes those digitech pds delays you just leave em on for about an hour (use the shortest delay time) and it comes back to life. the infinite footswitch will not trigger the LED until the sound from the delay returns. all the trim pots can be set by ear
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Re: Digitech pds 1002 repairs/trimpot question

Postby Scruffie » Thu Jul 02, 2020 10:02 am

That's not crazy, that's time to replace the electrolytic capacitors.
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Re: Digitech pds 1002 repairs/trimpot question

Postby shovelhands » Thu Jul 02, 2020 12:33 pm

Thank you both for the insight, Scruffie and chromandre!

I had a feeling the issues at play might be beyond my current skills. I appreciate your patience in helping me out, and for taking the time to reference the schematic. I was wasting all my time trying to hunt down the original manual, which wouldn't have really helped in any way. I'll bring in a copy of the schematic for the tech to reference. Just for clarification: never handled any of the chips, those all stayed intact.

I'm giving the hour-long test a shot this afternoon, and I'll call the tech tomorrow
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