Digitech - PDS 1002 Delay  [schematic]

All about modern commercial stompbox circuits from Electro Harmonix over MXR, Boss and Ibanez into the nineties.
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Fender3D
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Post by Fender3D »

edit:
just realized you might be in Europe...
look for Banzai or Musikding

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hgamal
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Post by hgamal »

I took much time to make mine work again.
I have tested all ICs and all of them were ok.
After a long and big fight, I realized the problem were on the electrolytic capacitors. Because the pedal was turned off for much time, some electrolytic capacitors went out of specification.
In order to "revive" the old capacitors, I turned on the pedal, and maintained it on for some hours. This action made the device works again. I will change all electrolytic capacitors later.

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ramonovski
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Post by ramonovski »

edit:
just realized you might be in Europe...
look for Banzai or Musikding
No, I'm in America.
I did tried in Smallbear, Mammoth and Jameco aswell, I couldn't find any 4007 IC...
I took much time to make mine work again.
I have tested all ICs and all of them were ok.
After a long and big fight, I realized the problem were on the electrolytic capacitors. Because the pedal was turned off for much time, some electrolytic capacitors went out of specification.
In order to "revive" the old capacitors, I turned on the pedal, and maintained it on for some hours. This action made the device works again. I will change all electrolytic capacitors later.
I will definitely try this!
Obrigado!

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hgamal
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Post by hgamal »

I know its sounds like an aggravated assault, but, try this:

https://www.ebay.com/itm/MC14007UBCPG-4 ... 2c73913a5b

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Dirk_Hendrik
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Post by Dirk_Hendrik »

Sorry. Plain out of planes.

http://www.dirk-hendrik.com

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ramonovski
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Post by ramonovski »

Heh, this is embarrasing. I was looking for the original Motorola IC though... :oops:

Thanks for that Dirk_Hendrik.

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Post by Dirk_Hendrik »

You'd have a tough time. The division of Motorola that made these devices (discretes, standard analog, standard digital) spun off as On Semiconductor in 1999. The upper segment (CPU's, DSP's) became Freescale. Therefore there is no Motorola anymore as a semiconductor manuafacturer.

You'd be looking for MC4007 in that case ;)
Sorry. Plain out of planes.

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ramonovski
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Post by ramonovski »

OK, an update, just for future reference .

The pedal is now working and I don't know why...

1st day:
I got nothing but (barely heard) ground noise.

2nd day:
Deoxit on all pots, got clean sound but no wet signal.
However, I got no sound at all when the "mix" pot was after 6-7, it was like a "voltage divider" ( ? ) or an inverted "volume" pot.

3rd day:
I have left the pedal plugged in and turned on for ~8 hours (as someone has recommended in this thread), nothing has changed.

4th day:
Got new ICs, have played with the 4 trim pots, nothing has changed.
Went back to stock ICs.

5th day:
Got new pot replacement (W100K, WTF?) for "mix" and suddenly, delay is working fine!!!
Weird noise around 1-2 in "Delay Time" pot, have tried new pot and same results (although I didn't have the pots soldered to the PCB yet).

6th day:
Tried the stock pot in "mix" and I have dry signal! (uh?)
Resolder the stock pots again and now everything is working...

Wet signal, all pots working, zero noise/scratches, clean and digital delay, all trim pots working fine.

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noiseman
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Post by noiseman »

Hi,

I'm treying to repair my PDS1002, I'm having the same behavior as others in this thread (clean sound OK, infinite repeats and delay +LED non working).

I'm having trouble with the schematic, I have located the chips mentioned here (U7 and the NE570) but I can't relate Q11 with a specific trannie on the board,

Could someone PLEASE point me to Q11 from the picture below? also, in the schematic, Q11 is a 2N5088 and there is none on the board, I have a bunch of PN100a wich seem to be a substitute.

Thank you very much in advance!
Attachments
1002.jpg

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DrGonz78
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Post by DrGonz78 »

I too am having the same issue with this pedal. Dry signal but no effect signal. I am tracing it out but this board is really tough to trace out. Pulling Q11 or Q113 makes no difference and replacing U7 still same problem. I have not replaced or fully traced (need to do more work on it) the NE570 chip and I am begining to think it could be bad. Will post more later.

Really wanted to post this for noiseman and let him know where Q11 is located... Refer to pic that I posted.
http://dropcanvas.com/i514r/1

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DrGonz78
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Post by DrGonz78 »

To fix this pedal I think in my case it was bias pots were out of whack. I did some adjusting until I had signal on the NE570 chip. I had dry signal but it was not feeding my signal through to the delay effect. Eventually I found a setting where I starting getting signal flowing through NE570 on different pins and I noticed signal was going through delay pots. I was signal tracing and decided to plug in a guitar to see what was coming out of the unit. Sounds great! I do notice that when I first turn on the unit that it takes a second for the delay to kick in, but will have to test to see if the electros are a problem or not. Either way it is as if the effect unit just woke up. I did hit a couple solder joints that might have been culprits, but not really sure right now what it was exactly. Either way the pedal is working finally! YAY! This thread was actually very helpful and I thank all the members here for the info provided.

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DrGonz78
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Post by DrGonz78 »

Since I am not sure I better ask someone who might know here... When I first turn on my unit it takes about 5 seconds for the delay effect to start up. Then if you switch between delay times it takes another 5 seconds for each one to start up, just like it did when it is first powered on. Is this behavior normal or is there something still wrong with this unit? I mean it is working fine now, but I find it strange that it takes 5 seconds for the delays to kick in. Anyone know?

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Post by Fender3D »

Q13 and its neighbors provide a power on delay, muting wet signal when powering on,
the same should happen when switching delay times... (thanks Q7)

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gitaar0
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Post by gitaar0 »

i have a pds 8000 that behaves that way. i used to have pds 2000 that also did that. I always assumed it was part of the deal....

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DrGonz78
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Post by DrGonz78 »

Well thanks for the confirmation!! I guess it's all repaired and ready to be put back together again. This is a great site, thanks again.

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drummer4gc
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Post by drummer4gc »

Could someone help explain to me what is going on with Q11? I've got the same issue as everyone else - no wet signal, hold function doesn't work/LED flashes, etc. I've replaced the 4007s with no luck. However, when I pull Q11 out, I do get repeats. What does pulling Q11 do to let the repeats through? What is the fix? I've replaced it with a 2n5088, but I only get repeats if it is out of the circuit.

Thanks!

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Post by drummer4gc »

Update: Got it working by hooking it up to power for about 20 minutes. Thanks for the suggestion! Will replace electrolytics shortly.

Still curious about what's going on with Q11 if anyone wants to explain!

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Post by Fender3D »

With a positive voltage at its base, Q11 (and Q13, at start up) shorts 570's rectifier cap pin (pin1), thus blocking 570's expander mode gain cell; result: no output from expander...

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Post by Valco »

I know this is an old thread sorry for the bump.i just got a 1002 running properly that had the dry only no infinite repeats LED issue. My fix was to replace all the switching circuit and delay selector circuit 10uf electrolytic capacitors. In fact , I replaced all of the 10uf electros and a few others since most of them measured out of their 20% tolerance range had high voltage leakage and high ESR readings. Thanks to everyone who has posted on this thread, it would have been a longer repair process without you all.

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Al Green
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Post by Al Green »

Old thread, new member.

I'm working on a Digitech PDS 1002. Among other problems is a broken Input pot shaft. The back reads "E.C.I. Alpha C500K." I'm having a heck of a time finding one online that matches. Has anyone else replaced this?

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