Echoplex ep3. Anyone knows it well ?

[Xplorer]

Hi !

i've bought an Echoplex ep3, it's absolutely great. But i had to restore it a bit. i've cleaned inside nd outside, used some help from the site of Regis :

http://www.regiscoyne.com/echoplex/" onclick="window.open(this.href);return false;

i've changed the electrolytic caps, the 500 uf by some 470 uf, the 47 uf by some 33 uf ( i had a kit from tony at orbit electronic ) , the 100 uf, and the tantalum 1uf by some aluminium electrolytic 1 uf caps ( tantalum is better but well, he said i wouldn't hear a difference).
i've changed the sustain pot and the volume pot.
i've adjusted the heads positions, lubed some stuffs, and the tape, and i'll use a demagnetizer as soon as i can.

BUT, there's still a big hum noise on the sound on sound position, maybe a ground problem somewhere, but i can't see it.

the echo position is ok, but still some hum i'd like to elminate, don't know how.

by the way, i'm notsure about how to add a ground on it, for a grounded plug : the ground could be anywhere on the chassis ?


the biggest problem now, is the volume pot : below 2, no echo, and over 2, the echo is stronger than the original signal sound. so ... i have only a sweet spot, difficult to determine, moving the pot like from a hair or two ... i don't like it. it wasn't that bad before i changed the pot, with a new A500k pot.
over 2, the hum is becoming very present, not useable ... too bad.

the trimmers : i realised that the trimmer on the side of the motor is adjusting the sustain intensity.

for the volume, i don't know....

i'd love to know how to remove the electrical charge from this machine, once unplugged, it's been three times that i was shocked ! i know how to do it on my superlead but not here.


Did anyone had any experience on an echoplex work ?
i think that we could perhaps start a topic to store some database about how to make such machine to survive over the time, and how to restore the electronic, or the other problems. that could help many, and i'm sure that you all appreciate such tape echo . into a plexi it's total heaven.

Any Help appreciated ! ; )

Thanks,
Adrien

[Xplorer]

pics attached

[Xplorer]

Some more

[demonufo]

One thing many people neglect to check on, is whether or not the heads need demagnetising. Which can be a cause of hum. But I suggest you have other issues causing it, by the sound of it.

Head demagnetisers aren't the easiest of things to find these days. (Well, not good ones anyway)
Studiospares do a good one, but for around £50. And of course, that's based over here in the UK, which isn't much use for many.

[Xplorer]

thanks ; )

well, i'm still waiting for the demagnetizer i bought on ebay, easy to find. i hope it'll be good enough. i live in France, so England is next door ; ) but 50 £ is a lot for me these days.

i don't remeber if an A500k pot is lin or log pot ... i would need a linear pot for the volume, as one told me, and that would maybe be the problem i have with the volume right now ...

but the bassy hum i have with the sos head is quite important ... it could certainly be something else, but what, i don't know ... i can't see bad ground issues ....

and even for the echo position, when the echo is stronger than the signal, with the volume over the sweet spot , the noise is very present ...
when they say to work on the record level, to have a noise equal from one to 9 on the volume pot, i can laugh , because it really doesn't apply to me ... the noise is about ok until 2, and after that, the noise is 10 times more !

[demonufo]

thanks ; ) i don't remeber if an A500k pot is lin or log pot ... i would need a linear pot for the volume, as one told me, and that would maybe be the problem i have with the volume right now ...

An A pot could be logarithmic, or linear depending on who manufactured it. Alpha and CTS for example, are different.
Volume pots are normally log, but I'm not familiar with the circuit on these at all.

[Xplorer]

ah, ok, this is an alpha one.

wierd that i the world, they decide to say A or B and not being agree on some rules like : lo means log, and li means linear ...
what the F ... !!!!!

[demonufo]

ah, ok, this is an alpha one.

Then it is a logarithmic pot, as I suspected.

wierd that i the world, they decide to say A or B and not being agree on some rules like : lo means log, and li means linear ...
what the F ... !!!!!

Yes, quite! If only the industry could agree on a standard.

[Xplorer]

i've put back the original pot, and it's a bit better.

i've discovered something veeery wierd !
on a picture i'll post , you can see a metalic wire disconnected ( i've disconnected it ) , and when you touch it, it produces a buzz , just like when you touch a guitar jack plugged into an amp.
i've disconnected it because on the other side ... it's not connected !!!! and i didn't see why it would exist then.
now i'm suspecting that the sos buzz would come from there .

the picture would tell more. i don't know what test i should do to track the buzz origin. what would be the smartest thing ?

And the new thing now that i'vedisconnected it, is that i think that the buzz decreased a little bit, but now when i increase the sos trimmer value, found on the same board that you see, well , it produces some whale sounds ! beautiful actualy, like an old radio , feedback, or whale, singing, changing, becoming a robot ...
i guess i should resolder this wire but i'm intrigued, and i'm hunting this buzz origin.

[demonufo]

If that is a shielded cable, and that cable is signal carrying, then that shield should be grounded, at one end only.
Reconnect it and let us know what happens. (I'm assuming it went to ground, right?) If the buzz increases, and that lead does not go directly to earth, it could simply mean you have a bad earth elsewhere.

[Xplorer]

ah ... the shield arround the signal cable has an effect o the signal, even if it's not connected to anything ? the ground must "protect" the signal cable arround it, ( to prevent from buzz ? ) ? is there some kind of magnetic field or frequency that would affect this signal cable, with a ground shield wire even not connected to it ?

i don't know if this shield was connected to the ground : the connection where it was connected probably is a ground, but i don't know about it.

if i reconnect it, it doesn't change much, only the whales song would disapear, for when the trimmer is set way up, over 1/2 , 2/3 .

yes, i maybe have a bad earth elsewhere, i'll have to see, i don't know.
at least, the echo position offers quite a clean sound, on the spot i prefer, with an echo a little bit weaker than the original signal. that's a good thing.

i'd like to discover these earth problems, and also, to discover the secret recipes to prevent the machines from hum, so i could make it better than it was brand new. dead silent, except for the guitar.

[demonufo]

yes, i maybe have a bad earth elsewhere, i'll have to see, i don't know.

Sounds like a definite to me.
The shielded cable is to reduce radio frequencies and other parasitics from getting into that input cable. Any signal carrying cable that has a lot of gain applied is prone to picking up all sorts of nasty noises, and shielding helps prevent that. Especially in magnetic tape circuits where there are massive amounts of gain.

BTW, remember that hum could also be induced by poor electrolytic capacitors. I really don't know what's in that circuit, but since nobody else seems to be offering any help, it's something you ought to look into.

[Xplorer]

yes, thanks again, you have some nice help. indeed, i did change all the elctrolytic caps, no much change into the sound. yes, bad earth somewhere, and now, to investigate, i don't know where to start, and i'm affraid to break anything.
do you have an idea, a methodic way to test such circuit , with some point where to start ? maybe if i disconnect and unsolder the head, i'll see what's going on, to determine if it's the head or not, first ?
and maybe searching elsewhere later ?
i'll reply to tell if there's more or less hum with the shield cable connected or disconnected.
i should perhaps do a better shielding, with much more metal arround the signal cable, coming from the head ? a shorter one ? or add some connections between the boards grounds, and the chassis ?
with a strat, i'd know how to shield it, but here .....
you don't find wires that are turned on themselves, just like for the wires connecting the preamp tubes of an amp, on a plexi...

my plexi is really silent, i made it well ; ) with the manual.

[demonufo]

Another important thing is to check that the heads themselves are well shielded. And that you have no noisy flourescent lights on (including energy saving lightbulbs) anywhere near them. And keep the heads aways from transformers too. If there are any metal parts surrounding the heads, they should also ideally be shielded (although chances are they will be grounded to the chassis).
I think really we need to find you an expert before any devaluation is done to that sweet old piece of kit though.

[Xplorer]

yes you're right.
what i have in mind when you say shielding the heads is to replace every wire going to the head, by some shielded wires, with the shield going as close as possible to the head ( i don't think i couldconnect both sides of the shield, the shield would stop near the head, and the wire would still go into the head. and the other side of the shield would be soldered to the chassis, each shield , so many of them.

but i think i'm totaly wrong ! lol

i've just bought on ebay a maintenance book about the echoplex, talking about many problems ( including buzz and hum noise issues ) solved during 40 years, noted by a tech.

i'll try to read that, and i'll tell you the advices of this guy if it can provide some help if you have any trouble.

after reading that, i'll demagnetize it, as i think i should get my demagnetizer soon.