65 Echoplex Repair

Scott_F

Scott_F

Flushologist
Staff member
Chasing down some extraneous noise in the EP2. Got with my friend Echoplex repair guru Pete out in LA and had some fun chasing it down. What a rats nest cluster inside. Found a cold solder joint on one cap and then replaced an old black beauty cap on the oscillator circuit that was failing.

Best part is learning hands on with a foreign circuit and overall "amp" theory that is totally new to me.

Don't be scared of grabbing an old tape echo. Easy to work on.

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Re: 65 Echoplex Repair

I love this stuff. The transmitters and receivers we currently use out here are 60's technology/design. Unfortunately they'll be replaced shortly and the opportunity to get in a properly fix stuff will go with them.
 
Re: 65 Echoplex Repair

what praytell is the pink thing next to the 6c4?

my deluxe reverb crapped out last night at a gig but since its not a modern amp, ill throw it on the bench today and my guess is within the hour figure out and hopefully fix it. if it was a modern amp or god forbid digital id be looking for another amp.
 
Re: 65 Echoplex Repair

jeremy said:
what praytell is the pink thing next to the 6c4?

my deluxe reverb crapped out last night at a gig but since its not a modern amp, ill throw it on the bench today and my guess is within the hour figure out and hopefully fix it. if it was a modern amp or god forbid digital id be looking for another amp.
Click to expand...

Looks like an inductor or an air core transformer of some sort. I suppose it would depend on how it is wired.

Here's a manual with schematics: http://www.vintagewindings.com/gen pop/8299543VW8335/ProAudio1/Echoplex Manual.pdf

Looks like it's part of an oscillator circuit.
 
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Re: 65 Echoplex Repair

trevorus said:
Looks like an inductor or an air core transformer of some sort. I suppose it would depend on how it is wired.

Here's a manual with schematics: http://www.vintagewindings.com/gen pop/8299543VW8335/ProAudio1/Echoplex Manual.pdf

Looks like it's part of an oscillator circuit.
Click to expand...

It's the bias oscillator. You need a bias signal to get the sound onto the tape. It also feeds the erase head signal. I can't quite figure the bias removal in the circuit but some times the play back head contributes to that. There will also be Pre-empasis and de-emphasis EQ circuitry in there. Getting sound onto tape is a mildly convoluted process.

_ https://en.wikipedia.org/wiki/Tape_bias -
 
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