Circuitbenders Forum

Please login or register.

Login with username, password and session length
Advanced search  

News:

Author Topic: Korg kpr-77 High pitched whine on output - HELP!  (Read 7434 times)

davethedoobie

  • Newbie
  • *
  • Karma: 3
  • Offline Offline
  • Posts: 36
Korg kpr-77 High pitched whine on output - HELP!
« on: September 18, 2010, 06:40:05 PM »

Hi, I have been restoring a dilapidated Korg KPR-77 back to life after the previous owner left the batteries in and they leaked twenty years ago.  I have managed to get all but the toms working again (their is a faint sound - so that's another problem to solve).  It took much sourcing of the parts I can tell you.  However, I have an issue that the is annoying and I seek your help.  The problem is a high pitched whine that only disappears when I brigde the R76 resistor on the board.

I would be grateful for any help or advice as I hope to modify this once I have it fully working again.

I know it is probably an easy fix but at the moment I can not see the wood for the trees.
Logged

Gordonjcp

  • This person is dangerously insane.
  • *******
  • Karma: 78
  • Offline Offline
  • Posts: 1005
    • http://www.nekosynth.co.uk
Re: Korg kpr-77 High pitched whine on output - HELP!
« Reply #1 on: September 18, 2010, 06:51:17 PM »

What's the value of R76?  Has it gone high in value?
Logged
If at first you don't succeed, stick it through a fuzzbox.

Matt the Modulator

  • Kicks like the DADDY!
  • ****
  • Karma: 14
  • Offline Offline
  • Posts: 197
  • 8Bit Brain Analog Heart
    • THE MAGIC MESS
Re: Korg kpr-77 High pitched whine on output - HELP!
« Reply #2 on: September 18, 2010, 06:56:23 PM »

i had the same problem with the toms i replaced the volume slider and that sorted it
Logged
8Bit Brain Analog Heart

davethedoobie

  • Newbie
  • *
  • Karma: 3
  • Offline Offline
  • Posts: 36
Re: Korg kpr-77 High pitched whine on output - HELP!
« Reply #3 on: September 18, 2010, 09:12:06 PM »

Thanks Gordon and Matt appreciate the response.

The resistor value is 220kohms +/- 5%. 

I gave the pot a good clean inside and managed to get the Hi tom sounding but I have noticed that the volume fades after a few minutes then, when I switch it off and turn it back on the hi tom sounds again.



Logged