Echoplex ep3 hiss and heads ? problem

[Xplorer]

hi everyone !

if somebody has some knowledge and experience abour such problem on an echoplex, i'd be glad to know it ; )

i'm writting while i'm reading the maintenance manual of the echoplex 3, so i can tell properly the issues :



- first they talk about hiss , that can be adjusted with the volume on 1 and 9, that would be the same thanks to the record level control.

my echoplex isn't loaded with a tape right now, but i'm testing, and on the echo position, well, anyway, quite a lot of hiss on position 8 ( because on 9, the pot doesn't work ), and in the sos position, a bassy hiss all the time. no effect from the record level pot.

at this point, i don't know if i may change some caps, and what caps, if it's the problem. but i don't know what caps i should change. i assume i'm on a 110 volts, 60 hz power. no tape right now. the echoplex has been cleaned. the belt is new. the pressure pad could be replaced but still ok. the black roller could be replaced but still really ok. i've restored the rail, much more straight now.


- now the heads : i've realigned them, but the little square of the middle of the playback head seems to have expanded itself a bit. it works, but since i've realigned the heads, i may have force a bit too much, and the trebly shimering pitch bending of the echo is a bit lost into the frequencys repeated. i'm sad about that.
it's strange, if i move a little bit the playback head, it goes into another shimering tone, more bassy and bassyer, opposite of trebly i mean. don't know what to do.

i think i did a terrible mistake, i couldn't wait to get a demagnetizer, and i was thinking of using a big magnet close to it, to see what would happend .......
it works, but maybe not at its best, i don't know, and i'm not sure that the magnet damaged it. when i realigned heads, it was ok, but one more movement on the head, and perhaps on the CONNECTION of the head, and the shimmering disapeared quite a lot.




i've ordered some quantegy 478 tape, i think it's not as good as a fidelipac lubricated tape, but i could perhaps use it for a little while.
tha tape i've got now get stuck into the combo head sometimes, i don't know why. and it brings the moving head to the playback head when it's blocked.

i'd really like to restore this machine, cause i think it's possible, there's no reason why it would be impossible. except perhaps that i couldn't spend too much money.

thanks for any help !
Best,
Adrien

[52 Bill]

Welcome to the place.

NEVER bring a permanent magnet anywhere near the heads of any tape machine! You will cause the head to become magnetized, which will cause a loss of frequency response to the unit.

Get a demagnetizer and carefully follow the directions to demagnetize the heads and all of the metal in the tape path.

Reload the cartridge with new tape stock and then do the head alignment and bias adjustments.

A certain amount of hiss and noise is normal, what you need to judge is how much hiss and noise is present compared to the recorded tape signal. If you try and do these repairs with an old dead tape, it will just be a waste of your time.

I prefer the lubricated tape stock, as it was designed for cartridge use, but there are many people who prefer the mastering stock. Either tape stock will work fine once your machine is correctly set up for it.

Good luck with your rebuild.

[Xplorer]

thank you bill,

i'm ordering a demagnetizer right now.
yeah, unfortunately i did a stupid big mistake with this magnet, hope it's not damaged too much. i guess it pulled some kind of chrome inside, out of the little square in the middle of the playback head. i'm so stupid.
i will order some new pots too, and caps, as orbit electronics says it has to be done : i guess they know what they're talking about. but i don't know what caps to change.
new heads are expensive.
it works but ... it could be much better i think. but i like to make old things as new.
i'll wait for this non lubricated tape until i can get some lubricated new one. i wonder if there's a way to lubricate some mastering tape at home ... could be great.
i was almost ready to sell it back but this machine can be repaired, just a matter of money and care.

really too much hiss on the sound on sound position, not normal. on the echo position it can be ok but if i can fix it it could be great. this machine is supposed to have the same noise level with the volume on 1 or 9, not the case of mine. i keep mine on 3 , with the record level almost at max and it's fine for now.

i wish i could post some pictures of the heads, they are nice, but i don't know how to do.

thanks a lot Bill

Adrien

[Xplorer]

Hi again !

guys, do you know the use of the three trimmers found on three different boards into the echoplex ?
i didn't touch yet the one on the side of the motor, the others don't have that much effect.

i've totaly cleaned my echoplex, eplaced sustain and volume pots, i replaced the electrolytic caps, as well as the blue 1 uf tantalum caps by some electrolytic caps. i replaced the 47 uf caps by some 33 uf, as tony from orbit electronic send me a cap kit.

still a lot of hum, maybe more now ! bassy hum. and still a much bigger bassy hum on the sos position. damn ... how can i do ...

the sound is really good, if only i could mod this to have an acceptable transparency. that's not normal.

i didn't demagnetized the heads as i didn't received my demagnetizer yet. i guess it'll enhence the sound, but it won't deal with the noise problem.

also, i don't know what connection i should do, to remove the electrical charge, once unplugged, and work safely.
i didn't find numbers on my multimeter ( i also don't know how to set it ; ) what kind of voltage ... 200 volts , or Ampers, ... )
i've been shoked three times allready, but it's ok, it's only 110 volts, not 220 volts like here in France ; ) but damn i hate it ! ; )

i think that my problems, if solved, would be interesting as a data base to solve echoplex problems for the others. cause they might not be the easyest one.

cheers,
Adrien

[Xplorer]

one thing i've found at least, but not really solving the problem :
the inside trimmer, on the side of the motor, would control the sustain intensity pot.
the volume pot might be controled by the trimmer on board wich is on the side of the pots.
at least, the motor doesn't produce big noises sometimes. i've lubed the axe a little bit.
and the tape doesn't stop itself suddenly like before, thanks to some adjustments, and cleaning.
but the tone could be better maybe, more adjusted, less hum.

[Xplorer]

now, the sustain is set perfectly, i don't touch it anymore.
but something wierd : the volume pot : it's like the blending doesn't occur from 1 to 9, but between 2 and 2,05 ...... !!!

before 2, the echo is very weak, and just after 2 it's coming very strong. after 2,1, the hum becomes very present. the change occurs into a hair of movement on the volume pot.
but on the sweet spot, with an echo just a tiny bit weaker than the signal, the hum is acceptable.
i don't know how to tune the volume. i'm worried about this change of caps from 47 uf to 33 uf, and the tantalum replaced by some aluminium electrolytic caps. maybe it is the reason ? or a trimmer, the the second trimmer doesn't really seem to affect this problem.

[52 Bill]

The first photo shows that you have changed the blend pot. Did you use the same taper as the original?

If the hum is only on the delayed signal, then check for bad grounds and shields in the head wiring and the SOS switch.

[Xplorer]

Well , i had these pots from Tony AT orbit. The echo double pot works fine. The volume pot is a 500 k , this one has problems, but isn't it from the circuit ? What do you know about the trimmers ?
Yeah, i'll Check the SOS head wiring.
I don't know were to install a ground , for a new grounded plug i should put. Anywhere on the châssis ?
Do you know how to remove the electrical charge once unplugged ?
The volume pot seems to work between no écho, and quickly : more écho than a signal sound. Not much weaker écho possibilitys than the original signal. I have to move the volume pot like a hair further or before the sweet spot. Before that change it was better. But i touched many things since that ...

Thanks

[52 Bill]

The volume pot is a 500 k , this one has problems, but isn't it from the circuit ?
Yes, 500K is the correct resistance value, but it should be a linear taper pot. Check your new pot to see that when the shaft is at the center of its rotation there is 250K from the wiper to either end terminal.

What do you know about the trimmers ?
One controls the SOS record level, the other one sets the recording bias level.

I don't know were to install a ground , for a new grounded plug i should put. Anywhere on the châssis ?
Yes anywhere you can get a clean grounding terminal.

Do you know how to remove the electrical charge once unplugged ?
Take a small resistor, like a 1K ohm and temporarily attach it across the first filter cap to bleed off the residual charge. In other words ground out the voltage on the first filter cap.

[Xplorer]

ah thanks Bill, you're a great help.
did you repair a lot of echoplex ?

well, mine is a log pot ? A500K ? should be B500K then ...
but it's strange that tony send me the wrong pot ... i had a special double pot or something, the right one for the sustain knob, and two A500k pots, one for the record level, that i didn't change, to preserve the complex connections, and it was working allready, and another A500k for the volume.
i'll check out this. i'd love this to be the reason, because if not, it'll be complicate ...

i couldn't find a bad ground issue for the sos, or the other one. i should perhaps unsolder it, and veiry again, without the switch, for each. if the noise continue, then the ground problem would be after that, on some board, or in the head itself, if it was touched too much and damaged perhaps.

well, i'm looking at the schematic, and at the echoplex, but i really don't know where is this first filter cap.

so, the sos record level would be the one on the board installed on the side of the pots, and the recording bias level ( that worked for me as a sustain intensity adjuster , so it makes sens ) is on the board installed near the motor and the transformer. ok.
that's why i couldn't hear anything while changing the value of the trimmer on the front, that's because it was affected to the sos, ok. i'll try this, maybe it'll solve something.

it's great when you discover a machine, that you appropriate yourself the knowledge that has to be known about it, so you can fix anything on it later. i like the idea of having some vintage things, that work perfectly ; )

ok, i'll install a ground as soon as i can find an american 110 volts plug. i wonder if this transformer could be used differently, for 220 volts , but i think i won't change anything on it. this machine burned two 220/110 volts tranformers allready .... i wonder if it's because of the ground or something.

cheers,
Adrien

[Xplorer]

Bill,

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.

[52 Bill]

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 .

That is the shield of the cable. It should only be connected at one side to ground. When you ground both sides of a shielded cable inside of an amp or pedal, you create a second ground path that can cause a ground loop. So re-connect the shield to the ground terminal at the PC board.

[Xplorer]

thanks.

yeah, i'll resolder it ( maybe directly on the chassis ? a shorter wire maybe ? ) , but i wonder if this kind of shielding could be even better, you know ... more shielding everywhere it could produce hum ... to eliminate the maxium of noise.
would that be a nice idea ? do you know if it would just be replacing all the wires by some shielded wires, with all their shields soldered to the chassis directly ?

do you think that if i unsolder the sos head, i'll hear nothing, no hum ? just to verify if it's the head itself that should be replaced ? i don't know how to test a head separatly.

i've discovered that when i record some stuffs on the echo position, and that i hear it by switching the sos switch, there's less hum than if i record those stuffs directly on the sos position, hearing it after a turn.
that could mean several things i guess.

i've just bought a technic book, related to the echoplex : several problems that a tech reported on a note book. but's it's more about the ep2. i didn't receive it yet, i'll tell you. it's supposed to solve the hum problems, but ... ep2 , not ep3 ....

can resistors cause hum sometimes ? transistors ? other caps than electrolytic caps ?

on my metroamp, some wires had to be perpendicular, not parrallele ... and some others had to be torsaded together to prevent from noise.
my amp is as silent i want, that's cool ! ; )
but i just followed carefully the manuals. for the echoplex, that's another story.

[52 Bill]

Before you get into changing everything, have you demagnetized the tape path and heads yet? If the heads are carrying a magnetic charge, you will not be able to get a good signal to noise ratio on the tape, which will add to your hum and noise problems.

Please get the unit working correctly before you start changing things and getting yourself confused.

[Xplorer]

Yes you're right, and i just received the demagnetizer today.
i've used it two times today, moving veery slowly, demagnetizing every parts, heads... and going away very slowly.

i didn't receive the manual yet. i've resoldered the shield, and i studied the schematic, to understand how the switch was working.

but i'm sending you a link by pm, with a recording i did so i can show you how it sounds.
just right click on the link, and do save as, or enregistrer sous, and you'll save a 9 mo mp3 file. it's better than words ; ) isn't it ?
an early jeff beck strat with some suhr v60 lp pickups, a little bit of vibrato from a megavibe, a 69 superlead plexi with el34 tubes, a transducer ( analog speaker simulator, veeeeery good ) , then cubase, altiverb for the room ambiance, a little virtual tape echo, oriented on the right.

first : no music, echo position, turning progressively the volume on 9-10.
then, switching on the sos position : you can hear a buzz, bassy hum ...

and after that , going back to the volume on 3, some music, some stuffs to show the kind of tone that this echoplex produces. and what the sos can produce, after one cycle of the tape. i'm satisfyed with this, for the echo, and the volume on 3 but it could be better for the rest i guess ...
and then, turning the music on a volume at 9.

what do you think ? did you hear many echoplex in your experience ?
i'd love to use it with an early 62 fender showman ... this would be my next amp if i had the money.