Synth-DIY Yahoo! Groups Archives

Troubleshooting help - VCO section & Arpeggio/Programmer

2013-09-29 by <etmachina@hotmail.com>

I've got a Polysix that nearly works for years now, with little or no battery damage that I don't think is an issue.

When bought it had minor problems, all of which I fixed, but in the process I messed up the VCO section...I've tinkered with it a lot over the years, unfortunately not knowing what I was doing early on. Since then I've built a couple xoxboxes and a 9090 kit, but I'm self-taught with still much to learn...

After a lot of checking traces and resoldering connections, verifying continuity and good solder joints over and over, I just can't get the VCO section pots working -- I'm still stuck with a saw-ish wave at what I guess is 8', all VCO section knobs unresponsive. All the other sections work, so it's playable and sounds nice, but it's crippled.

Years ago, the VCO section worked (briefly); I have heard the PW/PWM and sub-OSC etc before... I assume I've destroyed an IC (or several) or have a bad transistor? I assume this would be on KLM-367?

Could anyone point me at suspect IC's (28,29,30,31,33?...or the 4558's as well?), and how I might test them, if possible, with a multimeter?

If I can't test them, and would do just as well just blindly replacing chips (with sockets!) and transistors..Which ones should I replace?

Also, up until very recently the VCO was the only problem, but now the arpeggiator has stopped working (as well as midi sequencing with the CHD midi kit, which had been working). I assume this is a problem in the Key Assigner on KLM-366...Any tips for troubleshooting/testing? Could it be the TL072? IC1 or IC2? I blew the fuses once while probing around in the key assigner area...I'm fairly certain something is shorted there...?

Any help really, really appreciated! I'm dying to get this thing fully-working, it's been so close for so long!

Re: [PolySix] Troubleshooting help - VCO section & Arpeggio/Programmer

2013-09-29 by Bob Stewart

Sounds to me like you should find someone with some experience and get them to have a look.

It looks like you've already found out the hard way that it's really easy to damage stuff if you're not careful.

I'm back in the workshop on Monday, so will have a look at the service manual, and see if I can point you in the right direction.

On Sunday, September 29, 2013, wrote:

I've got a Polysix that nearly works for years now, with little or no battery damage that I don't think is an issue.

When bought it had minor problems, all of which I fixed, but in the process I messed up the VCO section...I've tinkered with it a lot over the years, unfortunately not knowing what I was doing early on. Since then I've built a couple xoxboxes and a 9090 kit, but I'm self-taught with still much to learn...

After a lot of checking traces and resoldering connections, verifying continuity and good solder joints over and over, I just can't get the VCO section pots working -- I'm still stuck with a saw-ish wave at what I guess is 8', all VCO section knobs unresponsive. All the other sections work, so it's playable and sounds nice, but it's crippled.

Years ago, the VCO s ection worked (briefly); I have heard the PW/PWM and sub-OSC etc before... I assume I've destroyed an IC (or several) or have a bad transistor? I assume this would be on KLM-367?

Could anyone point me at suspect IC's (28,29,30,31,33?...or the 4558's as well?), and how I might test them, if possible, with a multimeter?

If I can't test them, and would do just as well just blindly replacing chips (with sockets!) and transistors..Which ones should I replace?

Also, up until very recently the VCO was the only problem, but now the arpeggiator has stopped working (as well as midi sequencing with the CHD midi kit, which had been working). I assume this is a problem in the Key Assigner on KLM-366...Any tips for troubleshooting/testing? Could it be the TL072? IC1 or IC2? I blew the fuses once while probing around in the key assigner area...I'm fairly certain something is shorted there...?

Any help really, really appreciated! I'm dying to get this thing fully-working, it's been so close for so long!