EH - Polychorus

Discussion regarding early stompbox technology: 1960-1975 Please keep discussion focused and contribute what info you have...
ChrisFFTA
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Post by ChrisFFTA »

-i

My old Polychorus which was working just fine a few weeks ago is playing up.

Basically the on-off switch makes a lot of clicking thump type noise when switched and no signal passes unless the blend switch is on. Otherwise there is total silence.

Now I cant look at it myself but I was wondering if anyone would have some 'clues' so that when I take it to Mr Fixit Man I dont sound like a gormless twit. :)

Thx

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Post by Dirk_Hendrik »

I have trouble determining, from schematic, as well as from online photo's of the thing, as well as from the real thing, which switch you refer to as the blend switch?
Sorry. Plain out of planes.

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ChrisFFTA
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Post by ChrisFFTA »

Dirk_Hendrik wrote:I have trouble determining, from schematic, as well as from online photo's of the thing, as well as from the real thing, which switch you refer to as the blend switch?
ok i am a schem noob so will describe as per looking att the box from above

the on-off switch is on the left hand side of the unit, the blend the right side. it is not a footswitch but similar to the on-off i would assume

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Post by Dirk_Hendrik »

So that would be the Sweep filter on switch?
Image
Sorry. Plain out of planes.

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Post by ChrisFFTA »

on that image it is sweep, on my pedal it is blend

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Post by paperhouse »

ChrisFFTA wrote:on that image it is sweep, on my pedal it is blend
that means you have an original pedal, not a RI. often the switches just go bad. i'd try replacing the switch first. i replaced the switch on my dlx electric mistress RI (the switches are the same, i beleive) with a radioshack switch. it's the exact same size except it isn't threaded so i had to buy some new nuts and bolts to attach it.

but i'd try just jumpering the switch so that it's stuck on one side before replacing anything. that way you know that it's not the switch stuck "in between" the two modes.

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Post by ChrisFFTA »

an old one? cool, i thought it was a reissue...

i will now speak with some authority when i take it to the tech

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Post by paperhouse »

ChrisFFTA wrote:an old one? cool, i thought it was a reissue...

i will now speak with some authority when i take it to the tech
yeah, see how the pic above says "stereo" above "poly"? that means it's a RI.

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Post by ChrisFFTA »

well apparently a few of the caps were buggered... tech is doing a few more tests to make sure its aok... he also said the older eh stuff had very poorly made boards and they suffer over time... is this others' experience(s)?

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Post by analogguru »

ChrisFFTA wrote:... he also said the older eh stuff had very poorly made boards and they suffer over time... is this others' experience(s)?
That´s true I got my Polychorus very cheap cause a lot of tracks were broken - especially near the potis switches. It is necessary to solder very carefully cause the glue which should keep the tracks on the board is very weak.

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Post by nelson »

Just for reference

http://electroconducive.googlepages.com/ehxpolychorus

The Schematic for the pedal is in the schem section.

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Post by Fernando JFET »

has anyone any guts from that pedal????? (my engish is very poor!)

sfx
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Post by sfx »

I have both the stereo reissue and an original Polychorus, I'd be happy to post some guts when I get the chance. Might be a fun project to convert to MN3007's or the Coolaudio chips...

The blend switch toggles between the wet/dry mix and wet only btw.

FWIW, the original seems like the better of the two to me.

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Post by sfx »

Here's a long overdue bump with a quick gutshot of my Polychorus. I can't seem to find my tripod at the moment, so you'll have to forgive the flash in the picture.

You can't see it but the jacks all use the chasis for ground and there are ICs hidden under a few of the pots as well.

Check out that one trimmer on the bottom left, it looks like it has oxidized itself completely. Weird.
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Post by borislavgajic »

it would be nice to see trace side also :)

thanks for the picture


boris

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Post by sfx »

Here you go. Again, sorry the pics aren't the greatest. I'll replace them with better shots at some point.
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Post by SonOfChaos »

Oddly, a polychorus is my dream build, of course I need a lot more experience and skill and knowledge first with simpler circuits but ONE DAY I will have one.

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Post by borislavgajic »

sfx wrote:Here you go. Again, sorry the pics aren't the greatest. I'll replace them with better shots at some point.
sfx_polychorus_guts2.jpg
2polys.jpg

pictures are great....!!! thanks a lot

boris

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Post by SonOfChaos »

I keep thinking to myself, WHY does the Polychorus have to be so expensive.

Then I look at the guts and go 'OH'.

Anyone have a good comparison of the differences between the RI and the original. I heard the RI is true bypass somewhere.

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Post by soulsonic »

Hey! I've been repairing alot of these lately for a customer who collects them. I've worked on two Echoflangers, and now I'm working on a couple PolyFlangers. They really are incredible sounding effects.
I can provide some more photos if any are needed, though Nelson's pdf pretty much gives all you need, and I've found it a very useful reference while doing my repairs because his layout matches the original's very closely.

I've found that when fixing them up, replacing all the electrolytic caps will go a long way towards helping it to sound new again. Most of the chips seem to hold up ok, but sometimes you'll get a bad SAD1024... and that can be a problem to replace. One of the ones I'm working on right now appears to have a bad switching chip, but those are cheap and easy to replace.

I'd love to design a modern version that uses commonly available BBD chips.
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