Vintage Synth Repair

BTW, the 3 images contained nothing - zip - nada.   Thought I'd mention it.

Tracy


--------------------------------------------
On Thu, 5/3/18, 'Hamblin, Scott' scott.hamblin@... [vintagesynthrepair] <vintagesynthrepair@yahoogroups.com> wrote:

 Subject: RE: [vintagesynthrepair] Help With a Chroma Polaris - Please?
 To: vintagesynthrepair@yahoogroups.com
 Date: Thursday, May 3, 2018, 3:30 AM


  








      




 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
   
   






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