So brief history. I have been recently into the synth repair world for under
a year diy - modding- etc but collecting for ever. Friend calls me up with the
normal battery damaged p6 among other things.. It has a long history with
various issues that i think all summed up into its current state. So the battery
damage we got lucky and it only affected a small amount of trace. The traces
cleaned up did not need jumpering and all tested. ICs were healthy as well as a
few components around the area (on a side note i had a poly 61 recently and it
was about as bad as it gets so i have gotten to see the two extremes). However
the other main issues were..
1. At some point something very heavy fell
on the case hard enough to make a large dent across the metal panel and bend a
few pots. Now this apparently didnt affect it at first but i think it did over
time and i will come to that later.
2, The owner accidentally turned on
phantom power to the synth. This was when it primarily stopped working properly
with a large hum and incredibly reduced audio output. Once again i will return
to this point...
Below is a short list of what i was able to find and
repair through this endeavor.
Battery area was cleaned tested and
replaced. The synth functions and generates sound with all switches and buttons
and pots,voices working. Tape back up and patch restoration worked.
PSU
was tested and trimmed to spec.
Keys were cleaned restored 5 keys were
not working, now all keys work.
All tac switches were replaced with NOS.
Now the audio issues all resided on the KLM 368 board. We had the brief
opportunity to purchase one and did not move fast enough so i began to inspect
and repair it. As i first pulled it out i noticed some small areas of oxidation
perhaps from the battery and cleaned and tested traces and they were fine. Im
assuming due to the heavy thing falling on it, there was a small section of the
PCB corner next to one of the screw mounts that had broken off however it
doesn't seem to affect the board and was small and not near the traces, however
it was an omen i think of what was to come. I'm assuming due to the 48v,
the quad opamps were dead along with many of the duals and OTAs on the board.
There were a few bad caps, all were bad components were replaced and low and
behold the synth was making healthy albeit loud sound This was when i could test
the ARP, EG, and other functions. Then after 5 or so minutes a loud POP and it
would dive off again into a noisy crackling thing with the sound present but
incredibly reduced, or sometimes just not there. Also you could literally tap on
lightly move the synth and it would come or go with a loud pop each time. So
after calling around and getting some tips (some i read in here) i pulled the
board for a closer inspection i noticed that the CN at the top of the board were
sort of loose not in the connection sense but as in loose on the board. i put
the board back in and with the synth on i probed around with a non metallic
probe just pressing on portions of the board and also ice spray with some
components. This was after the sound dropped out and as i probed in areas around
the connection it would crackle loudly and come back to life.. sit there and POP
die again. BTW there was +15/-15 tested coming into the board and signal
as well was coming in fine to the board. So something more mechanically
wrong it seemed. So after a kind soul sat down with me in conversation about
what i could have missed in problem solving. He said pull it again and really
look at it and inspect it see if it has cracks etc.. So i pulled it and tried to
see why the CNs were loose i was about to desolder the Power CN and that was
when i saw that the solder pads had come up form the board. At this point I am
thinking that ( and this is where that heavy thing comes into play) when the
heavy thing fell on it it could have literally pushed the components into the
board so hard causing this issue. the pads on the other CNs look okay but until
there is power to this board i wont know again.
So Replacing the pads is
a total PITA however with all the attention to the 367s it seems the 368s to
find are rarer than hens teeth, many places i have written do not have
replacements and haven't seen them in a while. Is there anyone out there with a
replacement 368 . Or can someone point me in the direction of a solid pad repair
kit? For all the soldering and desoldering i have done i havent come across the
lifted pads. It was bound to happen i know its common but i dont think i was
ready for it.. trying everything to test and check components and ICs and then
it ends up something like this..
All responses are
welcome
--HIll
PS im in Europe.
Message
Re: [PolySix] Long time lurker but finally have a problem i have to post about.
2015-09-05 by <backshall1@bellsouth.net>
I would guess that you are fated to fix what you have. I’ve never heard of
a pad repair kit and finding a replacement KLM-368 at a reasonable price is
unlikely. Just hope it is only the +-15 power CN and you don’t find more
problems later.
Don B.
Sent: Saturday, September 5, 2015 8:58 AM
Subject: [PolySix] Long time lurker but finally have a problem i
have to post about.
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