Metropoulos Forum

How do we make this thread a sticky? It has a ton of information thanks to Xplorer's work.

Also, I think to darken the tone there are some caps that can be switched.

I came across this thread today discussing the changes in the circuits.

http://www.thegearpage.net/board/showth ... ?t=1020906" onclick="window.open(this.href);return false;

kind of you well, it's an unfinished work anyway. but probably a good base to open some secret doors, to deserve the echoplex, preserving these old machines for the futur, and have fun with it !

Ok, to keep this ultimate Echoplex thread going...one of my units has had a lot of noise on when the echo is engaged and the echo volume is above, say 1.5. It is background noise that once it is there at 1.5 on the knob it stays the same all the way to 10 on the knob.

So, while doing some maintenance work, I inadvertently created a connection between two of the points of connection on the board below...the "+" and "O" connections on the left of the picture. The "+" is where the purple wire from the "echo/sos" switch and the "O" is from the Echo volume pot. So, I created a link between the two and the unit is very quiet no.

So, the question is "why"? Is it another section that isn't grounded properly? I have done more chopstick poking and haven't found anything loose.

Xplorer wrote:The "Q1Q2" board

mmmh, interesting ! i think i'll test it miself.
i have no idea why.

well, on mine, if i connect 0 and +, i have no more sound, no more signal. so your Q1 Q2 board or something else may have something that differs ?

That's what I am thinking. Something is wrong somewhere else and this fixes it.

Hey "Xplorer", does your first EP-3 (the one you did not restore) use any MPS8098 transistors instead of the usual TIS58's?

hi, well, i restored both. but one still needs work. the other might still need it but it sounds great the way it is, so i may not touch it, or move the heads. ( moving the heads, even a tad can change drasticaly your tone ! once it sounds ok to your ears, hope that it won't ever change. tough to tweak, very empiric.
i think both feature tis58. not sure. i think that what's important is the amplification from stage to stage, starting from Q1, Q2 .... like on a fuzz or on an amp.
and the range of the variable capacitors ( not the same on the early and the later one ). the later ep3 have a better variable cap range, and it's much better. you can have a little cap in parrallel, to increase the range of this white variable cap on the middle board for example.
about the fet transistor, i remember that swapping the S and G helped recuding the noise. stock , there was apparently a mistake

I was performing routine cleaning on both of my EP3's (original and it's clone) so I decided to take some voltage and resistive measurements on both units....Figured it might help someone in the future. There were some resistive and voltage measurements I wasn't able to get due to accessibility, but I did get most of them. Likewise, some of the resistive measurements might seem wierd. This is from adjoining components in parallel effecting the measurement. For the most part both units are fairly close in measured values. As for performance, the original goes into run-away mode a bit earlier than the clone. This is probably due to the fact that the clone has an old (somewhat abused) tape. The original goes into run-away mode with the Sustain at 5.5 and the Volume at 3. The clone needs the Sustain at almost 7 and the volume at almost 4. The clone is a bit quieter probably because it's full of carbon film resistor whereas the original is stuffed with carbon composition resistors. Plus, the original has all the original components still so I'm sure some of the capacitors aren't up to specs anymore which maybe contributing to the noisier operation.
Here's a link to the schematic of the original:
http://i1293.photobucket.com/albums/b59 ... iginal.jpg" onclick="window.open(this.href);return false;

And here's the schematic for the clone:
http://i1293.photobucket.com/albums/b59 ... 2Clone.jpg" onclick="window.open(this.href);return false;

wow ! Very useful work ! thanks !!

"Xplorer", do you still have the original potentiometers that you changed on your restored EP3? If so, do you think you could measure the potentiometers taper?....This would be the Log (audio) pots used for the Record Level & Echo Volume.

hi, sorry for the long delay, i had forgot.

i used the schematic values , to replace the pots. the original record level pot is 695k .on one ep3, and 550k on the other one.
the volume pot , i'm not sure of where it is. probably in the ep3.
just use the schem values it should be fine.

Hi friends,

I need help.

I believe that aluminum capacitors are not the original factory.
Only the Sprague Atom TVA1315 Orange must be the original factory.

My Echoplex is working, but I noticed that his departure is a bit weak for some time now.
I wonder if I change the electrolytic capacitors (Sprague Atom TVA-1315 - total 4 units) solve the problem?

http://s1277.photobucket.com/user/ponte ... f.jpg.html
http://s1277.photobucket.com/user/ponte ... d.jpg.html
http://s1277.photobucket.com/user/ponte ... 6.jpg.html
http://s1277.photobucket.com/user/ponte ... 3.jpg.html
http://s1277.photobucket.com/user/ponte ... 9.jpg.html

Hi friends,

I need help.

I believe that aluminum capacitors are not the original factory.
Only the Sprague Atom TVA1315 Orange must be the original factory.

My Echoplex is working, but I noticed that his departure is a bit weak for some time now.
I wonder if I change the electrolytic capacitors (Sprague Atom TVA-1315 - total 4 units) solve the problem?

http://i1277.photobucket.com/albums/y48 ... dd498f.jpg
http://i1277.photobucket.com/albums/y48 ... 44f73d.jpg
http://i1277.photobucket.com/albums/y48 ... b782a6.jpg
http://i1277.photobucket.com/albums/y48 ... 6880f3.jpg
http://i1277.photobucket.com/albums/y48 ... 7d1469.jpg

Welcome to the forum!! I am not sure what you mean. The Echoplex works but what is weak?

pontes1970 wrote:My Echoplex is working, but I noticed that his departure is a bit weak for some time now.