Maestro Echoplex EP-3 help

[Enzo]

Darn, thought we were onto something. Check the two transistors. They may not have collector shorts, but if one of them turns on hard, it can ground the thing.

Try this. Go to RG's Geofex site and look for the tech tip on transfomer testing. Your ohm meter doesn;t reveal a short, but there could be shorted turns.

Got some clip wires? Set the transformer nearby, clip a wire from pin 2 of it back to the 13/17 point in the circuit. Now clip another wire to pin 1 or 3 of the transformer. Fire up the circuit. Now watch the voltage at 13 as you momentarily touch that loose clip wire to the collector of one of the transistors. Does it drop the 13 voltage? Does it matter which transistor you touched?

And for that matter, if everything seeems OK, try putting the transformer back in and see if it works now.

Check the four orange caps. A shorted one or for that matter an open one I suppose - could leave this oscillator not oscillating, and if both transistors just turn on, that could drag you down.

Hell there ain;t much left.

[eurekaiv]

I did the clip test... when I touch pin two and three the voltage drops to about 19V on one of the transistors and 15V on the other and voltage then slowly continues to drop from there while the 100Ω resistor slowly started heating up. On a whim, I soldered the transformer back in and repeated the test with pins 1 and 3 un-soldered. Connecting either to pin two that way also produced the same result. This is certainly different behavior then what I had before... a total short.

I haven't tried anything else yet as I'd need to buy a neon bulb to do the geofex transformer test.

So what exactly did the test above accomplish?

[Enzo]

You beat me to the next step, you did it already. if you wired pin 2 back up but left 1 and 3 open, and the thing didn;t drag your voltage down, that leads me to think MAYBE your problem is in those transistors. At this point I might wager that if you stick something in the footswitch jack there to open the grounding contact, your voltage would rebound.

On the other hand, those transistors may be fine and they are trying to drive a shorted tranny.

Is the resistance the same 1-2 and 2-3 on the tranny?

[eurekaiv]

I think I tried a jack in the footswitch before and it was still shorting out but I'll do it again to double check. The meter reads .3Ω between 1 and 2, 2 and 3, and reads .4Ω between 1 and 3. This isn't enough resistance for a coil of wire in a transformer core is it? If a pickup read that little it'd be dead.

[DaveST]

Hi,

I'm getting ready to sell my ep3 maestro echoplex. It echoes perfectly. However, when I flip the switch down to sound on sound, all I hear is loud static. Any ideas on how to repair this? You advice is greatly appreciated. Thank you.

Dave S

[52 Bill]

The sound on sound switch changes which head is selected and which feedback signal goes to the record circuit. My first guess would be a dirty or bad switch. If you have some DeoxIt, try spraying a little into the switch and toggle it back and forth a few times.

[DaveST]

The problem is not the switch, It's when I switch over to sound on sound, the whole playback is just static. It doesn't play back what it was recording.

The sound on sound switch changes which head is selected and which feedback signal goes to the record circuit. My first guess would be a dirty or bad switch. If you have some DeoxIt, try spraying a little into the switch and toggle it back and forth a few times.

[Enzo]

So the SOS head is not working. maybe it is open. maybe the switch is not cleanly shunting the playback head. And the switch has the other section which could be imnvolved. Verify with ohm meter.