Loss of Echoplex repeats

rgorke · Post by **rgorke** » Mon Jul 01, 2013 3:50 pm

So, one of my Echoplex EP3s seems to loose repeats even with the sustain knob turned up pretty high 7-8. Adjusting the trim pot on the board on the left (Q1,Q2 board from this thread http://forum.metroamp.com/viewtopic.php ... 58#p412407" onclick="window.open(this.href);return false;) is what has been successful in the past. I had this problem about 2 weeks ago, adjusted the trim pot and then just yesterday I notices that I only get one or two repeats where a week ago, I was getting 5 - 10-15 seconds on repeats based on where the knob was.

wondering if 1) the trim pot could be going bad, or 2) whatever "stores" the repeats in the unit and "manages" the amount of repeats is going bad. Not sure what that might be. Could the JFETs be going bad? TIS58 or TIS98s?

I don't know, just guessing....

rgorke · Post by **rgorke** » Mon Jul 01, 2013 8:37 pm

Ok, I know all you guys were gravely concerned...and I appreciate your concern....

I had switched out the electrolytic caps on the "Q1/Q2" board. With this unit (and all of them) being 30-35 years old, the traces on board with the components on it has begun to delaminate from the board itself. So, what happened is that C20 did not have a good contact and was slightly cockeyed (probably got knocked putting the unit in the box). So, a slight push and all the echos come back, as strong as they ever have been. So, I can get the unit to runaway echos where it just goes on and on...

So, here is another win for the "just wiggle a couple of components (safely with wood stick so you don't get shocked)" type of fix. The simplest solution is usually the correct one.

Thanks for listening....

stef · Post by **stef** » Mon Jul 01, 2013 8:47 pm

Xplorer · Post by **Xplorer** » Sun Jul 07, 2013 9:04 am

glad you could easyly find this one.
i haven't yet figured and master the echoplex beast, to orient it where i want in any case or bug. but time will perhaps let me access to this "level"

rgorke · Post by **rgorke** » Mon Jul 08, 2013 11:28 am

Xplorer wrote:glad you could easyly find this one.
i haven't yet figured and master the echoplex beast, to orient it where i want in any case or bug. but time will perhaps let me access to this "level"

Hah, you're implying that I know something...I was just wiggling things and fixed it. The cap was kind of bent over and I straightened it. So, the Q1/Q2 board is not just for the SOS. The trimmer pot on that board, as well as the one on the T1 board need to be in balance to get the best repeats.

I am finding that the Echoplex with the silver chassis has a lusher sound than the one with the black chassis. Not sure what to contribute that to but I like the lusher sound better. Although, the lusher sounding one is a bit noisier. Ugh, if its not one thing, it is the other...

Xplorer · Post by **Xplorer** » Mon Jul 08, 2013 11:36 am

you got me interested into this cap on the Q1/Q2 board ... which one would you say it is, based on my layouts ?

yes, i understood once how the signal goes through this board, with a part of it splitting and coming back from the echo or something. The value of the résistors going to the ground, on these two stages Q1 and Q2, as well as this cap as you say, seems important for the rest of the circuit, being responsible of the feedback intensity, echo repeats, record pes etc.

i have to take a look. me too i prefer the later version, but i don't see what différences there really are

still didn't take the time to look at how i'll improve my ep3's, but i feel that there's something manageable.

rgorke · Post by **rgorke** » Mon Jul 08, 2013 1:15 pm

This cap right here....(yellow arrow). Seems to impact the amount/quality of repeats it looks like it feeds into the trimmer pot.

Xplorer · Post by **Xplorer** » Mon Jul 08, 2013 1:23 pm

C20, ok. Thanks ! I wonder if what we want is a bigger or smaller value. Definitely need to play with this.

Haze13 · Post by **Haze13** » Mon Jul 08, 2013 3:03 pm

If I'd have an Echoplex, I'd definitely would made a new PCB with new audio grade components.
That's exactly what I panning to do for my Maxon AD80.

Xplorer · Post by **Xplorer** » Mon Jul 08, 2013 3:12 pm

That's what i exactly did

, on an original pcb.
I've got some more q1/q2 spare boards, populated.
Now i need to play with a few values.

rgorke · Post by **rgorke** » Mon Jul 08, 2013 7:39 pm

I'll confirm what I have for C20 when I get home. Where did you get the extra boards? NOS or did you have them made?

Xplorer · Post by **Xplorer** » Mon Jul 08, 2013 7:52 pm

well, this ep3 came with .... four ( !!! ) Q1/Q2 boards. i can sell you one if you want, 40 $ + shipping.

rgorke · Post by **rgorke** » Tue Jul 09, 2013 9:54 am

I checked and my C20 is 100uf electrolytic. These are new ones that I installed to try and reduce the noise/hum.

I may take you up on the board. Does it have components on it or is it bare?

Xplorer · Post by **Xplorer** » Mon Jul 15, 2013 9:21 am

Hi ! i read your reply the other day but got busy at this moment. Sorry. Yes , it has all stock components on it.

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Loss of Echoplex repeats

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