Not sure if it’s helpful or not, but many times the sliders used in filters and audio circuits are logarithmic. Fitting the wrong ones (linear) could cause these symptoms.
It would be worth checking the service documents to confirm what type your Polaris should have.
We’ve all been caught before, replacing like for like components only to find that somebody in the past had installed the wrong spec part.
From: vintagesynthrepair@yahoogroups.com [mailto:vintagesynthrepair@yahoogroups.com]
Sent: Monday, 30 April 2018 3:03 PM
To: vintagesynthrepair@yahoogroups.com
Subject: [vintagesynthrepair] Help With a Chroma Polaris - Please?
Hi Everyone -
I have just undertaken refurbishing my Polaris. I fixed the output jacks, did a mod on my headphones (absolutely NO NOISE!), replaced the entire faceplate (Paul DeRocco) (because of faulty original strips), soldered in an LED and swapped out two sliders after
repairing and cleaning them.
To me, that's about 4 hours work. But I love my Polaris sound. I wouldn't do all that for another keyboard, except for... anyway, here's my woes...
1) Filter Cutoff. when you first start to slide, it's sort of dead but then comes to life. Slide back to bottom and the sound completely goes away. Dead space. It's not the slider because I just changed it and received the same results as before. Exactly
the same, but better movement.
2) Resonance - next to the Cutoff - related problem? I just replaced the slider and received the same results, although the slider was cleaned and so forth. When I hit the top, it gives resonance, but also some when I pull it all the way down. Ridiculous.
Also much better movement.
3) I replaced the top left motherboard a while back with a used one (hence the broken LED) but that works now over Noise. Minor issue, can't complain. I had similar problems before with the old top left motherboard, but the sliders were a little bent and
gave a slightly different result. This tells me it goes deeper than surface.
4) Now - when these problems occur, hitting the patch number I was playing brings back the original patch with no deformities / abnormalities. That's nice, but when I want a little Cutoff, I get totally "cut off" (pun intended).
5) The sliders on Cutoff and Resonance and smooth with no bumps / bruises since they'd been cleaned / replaced. At least I'm learning some good techniques here. There's a guy on YouTube who demonstrated how to do it properly and I think I have that part down
now.
Observation: Methinks the Cutoff and Resonance have a chip / board problem but I wouldn't know where to look. I'm getting handy with a soldering gun, but not with schematics. I have 25 years repairing PCs but little multi-meter experience, especially when
the specs aren't available. I have the Polaris schematics and service manual but I need to research it to get a clue as to what I'm up against.
If anyone can help me here, I have the remainder of the old top left motherboard, minus a few sliders and an LED that I'd gladly send to you in exchange for the info. The sliders sell on eBay for a few $ and it would be a small gold mine of parts.
Thanks for reading. I hope to hear from someone on this - even a clue!
Tracy Barber
Polaris Fiend