Echoplex Restoration Story

[Xplorer]

i'm impressed, building an echoplex from scratch , that really makes you a serious builder.
would you pm me a picture of your project perhaps ? i'm curious of what it looks like. but i'd understand if you prefer not.
many thanks for the advices.

do you remember which hfe you selected for the transistors ?

i'm thinking about an "improvement" for my ep3's .. since i'm in France, i would maybe change the transformer some day, to have 230v directly in , instead of a step transformer for 230v then 110 ...
it would produce less groundloops and parasites ..
or, something with a chargeable battery, inside the ep3 .... i could use it a few hours without having it plugged on a wall's voltage ^^.

i'll also implement a tape splicer on each of my ep3's. i have them. bib tape splicer. it'll be cool.


i should do a clip of this ep3 now, while it sounds crappy, to compare it to when it'll sound right !

[Tazin]

I actually don't have any pictures of the EP-3 clone I built. The Transitors were all NOS stuff and I don't remember were I have the datasheet info for them. I don't even remember if I independently checked the hfe prior to installing them. The important thing was that the clone sounds indentical to the original. I did deviate from the original on some of the metal parts though. I used stainless steel on some parts verse chrome plating as found on the original.

[Tazin]

i'm thinking about an "improvement" for my ep3's .. since i'm in France, i would maybe change the transformer some day, to have 230v directly in , instead of a step transformer for 230v then 110 ...
it would produce less groundloops and parasites ..
or, something with a chargeable battery, inside the ep3 .... i could use it a few hours without having it plugged on a wall's voltage ^^.

You'd have to change the motor too then since it is designed for 120VAC.

[Xplorer]

oh, ok. i didn't imagine this. i thought that the little transformer inside the ep3 transformred 120 vac to a much lower voltage.
i'll edit the excell file soon. it could be useful.

[Tazin]

The mains transformer does step down the incoming wall voltage from 120VAC to 24VAC, but the motor is not feed from the transformer output. It's connected in parallel with the mains transformer input(s) so it always sees the wall voltage.

[Xplorer]

mmmh, thanks for this precision. too bad but nevermind, i'll keep it stock.

The transformer of my ep3 I had a screw coming in , i can't know if it affected the wire inside. once ep3 II will be restored, i'll can compare, swap parts ...

[Tazin]

I noticed that you changed the tape guide located near the pinch roller. Make sure the new tape guide is chrome plated or perhaps polished stainless steel otherwise it will destroy your tape. You might be able to get away with steel with a nice nickel plating, but I've never tried it myself.

[Xplorer]

yes, sure, this is important. i used a very polished part, but i suppose it's aluminium. if some day i find a little roller i'l use it here, or move the pinch roller axe to another place, just like the later ep3 if i can.


Edit for the part list :

[Xplorer]

Hi guys, i'm preparing my selection of components. i think i've scored a mistake in my ep3 I. i replaced the electrolytic caps, but for C7 i've follow the schematic. it seems to say 0,1 uf, because there's a little point just before the "1".
on my ep3 II, stock, C7 seems to be 1uf !
Please, could anyone check on his ep3, just to be sure ?

Anyway, i still have the blue tantalum caps from my ep3 I, and they're all 1uf. i don't remember if these things are polarised or not. ( ? )

one other mistake i've scored is the switch pot, i replaced it with a 1M instead of 500k. i'll use one like this but with a 1M resistor in parrallel.

i'd like to ask you too if C14 and C19 are both polarised ( ? )

i've tested different msp8098 and they varie a lot, from 130 to 270hfe ...

i think i'll use some tis98 i have instead, they seem very constant from one to the other... mostly 240 hfe.
All NPN transistors.

if anything looks wrong to anybody, please let me know ...

now i have to select the right tis58 or 2n5457

[rgorke]

My C7 is an polarized 1.0 MFD electrolytic cap. It is a white Mallory cap.

[Xplorer]

Thanks a lot ! yes, me too on my ep3 II.
it seems that the original schematic had some bug , maybe because of the print, maybe a dust transforming it into 0,1 mfd ..

i figured out that C8 and C22 are 1 mfd polarized too ( at least on my ep3 II , same mallorys )
but on the schematic C8 and C22 don't appear to be polarized.

that makes several bugs corrected now.

now the most essential after the heads i have to test again for the highest impedance, the transistors. my tis98, well i'll give them a try. they're all 240 hfe, hope it'll be right.
there is bug probably due to a mod, on my ep3 II : the Q5, supposed to be a tis58 fet, appears to be a tis98 but i don't see very well. and one of the transistors has been replaced by a metal can transistor.

i'll have to figure out where is S, where is D and G, on the tis58 or 2n5457 i'll drop in.

[Tazin]

Here's the info from my EP-3 for the capacitors you mentioned.
C7 1uF/50v polorized electrolytic capacitor
C14 35uF/25v polorized electrolytic capacitor
C19 35uF/25v polorized electrolytic capacitor
C8 1uF/50v polorized electrolytic capacitor
C22 1uF/50v polorized electrolytic capacitor


Oops, I was looking at the wrong capacitor for C22.

[Xplorer]

Thanks a lot ! So it seems that the schematic has some differences with all of our echoplex.
I've started to work on it, taking all the boards and most connections out of it.
I'm replacing the electrolytitc caps, resistors, trim pots, pots ...
i'll show you the progression.

[rgorke]

Thanks a lot ! So it seems that the schematic has some differences with all of our echoplex.
I've started to work on it, taking all the boards and most connections out of it.
I'm replacing the electrolytitc caps, resistors, trim pots, pots ...
i'll show you the progression.

It would be great to have PCB boards that you could just populate and drop in if you need a fix. In one of mine, I substituted a 2.2 instead of a 1. Doesn't seem to add or subtract anything.

[Xplorer]

It would be great to have PCB boards that you could just populate and drop in if you need a fix

ths is actualy what i do

here are the parts i 've selected and the boards, chassis ...