Maestro Universal Synth

Jaicen_solo · May 10, 2006, 12:08:38 PM

Hey guys, I was just wondering if any of you have heard/own this strange beast. I've got one in surgery at the minute but I'm not sure where to start with it really. I don't have any voltages from a working unit, but I do have the schems from Aron's gallery. Using an audio probe, the input signal disappears immediately after the input capacitor, which i'm sure is not right!
Anybody got any thoughts or suggestions?

analogmike · May 10, 2006, 01:13:08 PM

Have one among the 650 pedals in my shop.

It's like several seperate Maestro effects in one box, so just treat it that way and fix them one at a time. See the WHAT TO DO IF IT'S NOT WORKING at the top of the page and start from there.

Good luck!

Jaicen_solo · May 10, 2006, 01:42:34 PM

That's pretty much what I was expecting, thanks Mike.
I don't suppose you have any idea how it's wired do you? Looks like the on/off switches are just SPST.

Dan N · May 11, 2006, 12:44:05 AM

How lovely if it just needed a new input cap.

Paul Perry (Frostwave) · May 12, 2006, 07:26:00 AM

Sometimes, the very first transistor in an effect dies when the input is struck by lightning (or mains voltage, or by something that the owner will never confess to having plugged it into). This can convert the first transistor to a conductive blob, so it's shorting out the input cap. Worth checking, anyway (havn't seen the schematic, but same philosophy if it goes to an op amp).

MartyMart · May 12, 2006, 09:36:48 AM

True Paul, recently had a "dead" TS808 which was the opamp, must have taken a "spike"

MM.

Dan N · May 12, 2006, 03:27:18 PM

The schematic for anyone wanting a quick glance:

http://users.rio.com/senorris/junk/uss1sch.gif

Jaicen, I'd love to see a photo of the guts of that beast!

Mark Hammer · May 12, 2006, 04:20:09 PM

Hey thanks for that link. There had been a schematic posted around for a while, but it was chopped in two and I think the two parts were not contiguous with each other, so this one-piece version really helps.

Jaicen_solo · May 14, 2006, 07:06:51 PM

That certainly is helpful. Still think it will have to be printed over two pages though.
I haven't had time to look at it since my last post, hopefully i'll get some time tomorrow. But yeah, fingers crossed it's just a bad input cap. Something tells me i'm not gonna be that lucky

I haven't even got started on the SIEL synth I also have to look at...

Paul Perry (Frostwave) · May 14, 2006, 07:58:07 PM

Quote from: Jaicen_solo on May 14, 2006, 07:06:51 PM
I haven't even got started on the SIEL synth I also have to look at...

OH NO! you really are doing it hard... Siel synths aren't an easy fix, usually!

Jaicen_solo · May 15, 2006, 06:01:30 AM

Oh thanks for that paul....

Nah,i'm just gonna have a look at it and see if I can do anything with it really. There is a tiny bit of sound coming out of the outputs, so the DCO is still working. I think it's been stood on as a lot of the slider/switches are bent. Hopefully it shouldn't bee too hard....

Jaicen_solo · May 17, 2006, 10:12:57 AM

Quick a bit of an update on these two casualties!
I think I've traced the problem with the siel synth to the 14013/4049 logic chips which control the 'FREE' programming state. I'm going to replace the chips as soon as I can source a 14013 and hopefully it will all be good.
As far as the USS goes, i'm still scratching my head. The signal is in fact getting to the input of the first op-amp (PIN 3), after which it disappears. Measuring the voltages, pin 4 is -12v, and pin 8 is +12v. That should be ok for a bipolar supply, however there's voltage on pin 3 as well (I think it was +12, but could have been -), which is obviously not right. Do you guys think I should try replacing the op-amp, or could it be something else? I'm loath to do too much unless i'm sure i'm on the right track.
I'll have some pictures of the guts up soon, just gotta charge my batteries so I can download them.

News:

Maestro Universal Synth