Yes they say bad luck strikes in threes and this month my EHX pedals from the past have been bitten by the bug.

First, my vintage Bass Micro Synthesizer has been in the shop for 3 weeks trying to identify a mysterious lack of sub-octave. It’s been returned to me twice. The first time, the sub-octave and the square wave no longer worked, but everything else did. The second time, the sub-octave and clean signal didn’t work, but everything else did. It’s much more frustrating for the guy fixing it, i’m sure! Does anyone have a Bass Micro Synthesizer hard-wire schematic? It’s actually one with white lettering instead of green, if that matters.

Second, my Stereo Polychorus (Revision C, mid 90’s pointer knob) stopped working very abruptly. When a friend and I opened it up, one transistor and one diode had completely, completely burned away into char and dust! That pedal has never left my board and only runs through its power supply through an insulated power brick. I’ve attached a picture of a Polychorus C board with the two parts that got destroyed highlighted, can anyone please help me confirm the values of them so I can get replacements? The PCB board beneath them is blackened so I can’t see.

Third, I just bought a Deluxe Octave Multiplexer off eBay and it’s in far worse shape than the seller described. The attached power cable is frayed in two places, the screws that hold the internal power adapter in place are missing, one knob was literally a piece of wood with a screw SCREWED into the pot itself, and the fuzz circuit does not work. If anyone knows where I can find a schematic (of the silver 4 knob version), what type of power cable is appropriate to replace the factory one with, and what size of screws hold the power adapter in place, it would help me get this pedal back up to snuff.

Thanks for your help!!

Polychorus:  I’d say the resistor is a 150 ohm 1/2W.  The diode is the 1N4747A zener diode (20v, 1W).

Deluxe octave Multiplexer:  The screws are 4-40 for both the transformer mount and the back plate.  For the power cord, just cut a new one off some trashed piece of electronics.
Schematic can be purchased here: http://www.ronsound.com/index.php?main_page=index&cPath=11_18&zenid=4c562024612329bf057add81a9db7e24

Thanks, EH Man.

Another question, there seems to be a lack of replacement pots around that are d-shaft. Do you know of any that I could buy somewhere? I have seen these on eBay (don’t know if the values are correct, just wonder if the type will work)
http://cgi.ebay.com/8-x-B50K-Potentiometer-pots-Tone-Control-D-Shaft-15mm_W0QQitemZ320360059505QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item4a96f29271&_trksid=p3286.m20.l1116

nneekolas - 14 September 2009 12:54 PM

Thanks, EH Man.

Another question, there seems to be a lack of replacement pots around that are d-shaft. Do you know of any that I could buy somewhere?

No, but email me your address and I’ll send you a replacement shaft.  It’s easy to replace.

Email sent. One more stupid question though: are you advising to buy a new pot of the same value and then replace the shaft, or to use the same pot and replace the shaft? Sorry for all the questions, El Guru.

Keep your original pot, open it up and replace the shaft.  It’s simple and you probably won’t even have to unsolder the pot.

These projects are coming along. The Deluxe Octave Multiplexer is back up to full power again, the Micro Synthesizer… will never have a working sub-octave voice (I have given up :( ), and now the Polychorus. Does anyone have a Stereo Polychorus schematic, especially Revision C ? I see that EH Man doesn’t sell it, but does anyone else?

nneekolas - 09 October 2009 01:59 PM

These projects are coming along. The Deluxe Octave Multiplexer is back up to full power again, the Micro Synthesizer… will never have a working sub-octave voice (I have given up :( ), and now the Polychorus. Does anyone have a Stereo Polychorus schematic, especially Revision C ? I see that EH Man doesn’t sell it, but does anyone else?

The sub-octave is a product of a 4013 IC, I believe.  Have you replaced it?

Bass Micro Synthesizer is fully functioning again with a new 4013 IC. EH Man you are a genius. Thanks for your help with all 3 pedals.

Hello,

I think I might be having the same problem as nneekolas,
When I use the Micro synth (reissue version) the subocatve is not noticeable.
When cranked up the preamp a bit he became clearer (but also the rest of te pedal as well, so it was way too loud!) but even then, sometimes signal of the subocatve falls out.
Might this problem as well be solved by replacing the IC4013?

nneekolas - 09 November 2009 09:57 AM

Bass Micro Synthesizer is fully functioning again with a new 4013 IC. EH Man you are a genius. Thanks for your help with all 3 pedals.

Nice info I have the same problem, can I change the 4013 IC myself? is it just a plug? Thank you.

No, it’s not a plug.  It’s an integrated circuit.  It should be in a socket so it’s easy to replace.

The EH Man - 18 October 2011 07:34 AM

No, it’s not a plug.  It’s an integrated circuit.  It should be in a socket so it’s easy to replace.

Thanks lightningfast reply EH Man Will now order one from Ebay, maybe you know were I can find an adapeter(norwegian 220V) for this unit? They don`t have them in stock in Norway anymore and never will have since they have run out of production( I was told so) Regards Thor

Just get a UK one with a plug adapter.

The EH Man - 18 October 2011 07:47 AM

Just get a UK one with a plug adapter.

I got one, but the adaptersockets do not fit most norwegian el outlet, since all new outlet have ground. the adapter only fits norwegian unground outlets from the 70`s and 80`s.. any other suggestion? Thanks

Thorbass - 18 October 2011 07:54 AM

The EH Man - 18 October 2011 07:47 AM

Just get a UK one with a plug adapter.

I got one, but the adaptersockets do not fit most norwegian el outlet, since all new outlet have ground. the adapter only fits norwegian unground outlets from the 70`s and 80`s.. any other suggestion? Thanks

pics of the old and new sockets?