Possibly fried pedal, where to start

[Adamo]

I plugged an old analog delay pedal that takes AC power into my PP2 (DC power). It made an odd humming noise and now I get no delay out of it. The pedal engages and the LED comes on but all i get is a clean signal. Where should I start to try and bring this thing back to life? I opened it up and there are no signs of 'burning' or anything like that. Thx

[armdnrdy]

"where to start"?

You might start by telling us which "old analog delay pedal that takes AC power" you are referring to....
and if a schematic is available on the internet...a link to that page.

We can't help if we don't know what we're working on! 

[Adamo]

Sorry, Ampeg A8 Analog Delay. Can't find a schematic.

[armdnrdy]

Nope....I can't even find a picture...but I found this: https://www.youtube.com/watch?v=W34qYFfBt8w

Is this the beast?

If so...considering the date of manufacture of these things (early 80s)...and the size...(small) I highly doubt that they were powered by AC.

Does it say on the unit?

[GGBB]

9VDC

From http://www.effectsdatabase.com/model/ampeg/a/8



Did you try running it with a 9V battery?

[Adamo]

I couldnt open video but here it is:

http://www.effectsdatabase.com/model/ampeg/a/8

[Adamo]

Wow, that's the pedal but the sticker is peeled off of mine. Thanks for clearing that up.

Now, assuming, its not fried and it turns on and off but only gives a clean signal is there something(s) I should do first? I've opened it up and checked the wiring and connectors and there was nothing obvious that was causing issues.

[armdnrdy]

Okay....now the plot thickens...

I found an image of the A8 and an accompanying partial gut shot which depicts a MN3005.

A MN3005 powered with 9 volts? Maybe a DM2 clone?

[armdnrdy]

Do you have a meter?

[GGBB]

A MN3005 powered with 9 volts? I believe that would be a first for me. The lowest I've seen the MN30XX series powered with is 12 volts. The A8 sound sample does sound pretty distorted....

If its got a 9V battery slot then its 9VDC - doubt that era would have a voltage doubler.

Now, assuming, its not fried and it turns on and off but only gives a clean signal is there something(s) I should do first? I've opened it up and checked the wiring and connectors and there was nothing obvious that was causing issues.

Without a schematic it will be tough to help, but there a probably a few here who might be able (definitely not me).

Provide as much of this as you can.

[Adamo]

Do you have a meter?

Yes, I do have a meter.

There is so little info about this pedal available. Every 'Ampeg' search produces amp info and stuff about the Scrambler. Would a gut shot help?

As of yesterday, the pedal was working (?) but very, very scratchy. Coincidentally, I plugged it into my PP2 and it was making a quiet humming noise and then I stopped getting any delay out of it. Since then, the scratchiness is totally gone but all I get, whether the pedal is engaged or not, is a clean signal. I found the pedal listed on effectsdatabase and it said that it takes AC power so I panicked and thought I fried it. To clarify, I opened it up and poked and prodded all the caps and resistors and moved the wires around but got no signs of the delay temporarily kicking back on.

By the way, thanks for being patient with knucklehead newbs like me.

[armdnrdy]

Would a gut shot help?

Yes....

Both sides if you can.

I'm sure that it's a clone of something else. I doubt that Ampeg went into the pedal production business. This pedal series is most likely manufactured by another well known company. Once we identify what it is...hopefully we can use a schematic and the gut shots to take voltages.

[Adamo]

Sorry for huge pics

[armdnrdy]

[armdnrdy]

The two electro caps bent over the IC/ICs....

Is that one 16 pin IC or two 8 pin ICs?

[Adamo]

The two electro caps bent over the IC/ICs....

Is that one 16 pin IC or two 8 pin ICs?

It's one 16 pin IC and it's labelled 'NE571N 8213'

[armdnrdy]

Does anyone know of a delay circuit that uses a MN3005, a compander, and no op amps?

I looked at the Boss, Ibanez from that era...the circuits have at least one dual op amp for the input and output.

[Quackzed]

wiggle the socketed chip?

[WhiskeyMadeMeDoIt]

Have you worked the potentiometers back and forth through the full sweep? Sometimes the will be oxidized and need to be worked around to get contact.  If you have it spray some deoxit on them and work them with the power off. I have had a few pieces of old equipment not work because of that.

[armdnrdy]

The effects database listed about 4 other "brands" that this circuit was being sold under.

I had a hit on one of them...and it looks like the same animal: