• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Realistic STA-2000 inbalance

The Fuxtor

The Fuxtor

Addicted Member
Checking on a friend's Realistic sta-2000 , seems to need to be one notch to the left on the balance control to keep the channels balanced. I have it up on the scope and with the knob one click to left side the sinewaves are almost one when set on top of each other.... Is there a way to counter this back to the center indent on the balance control??
 
Register to hide this ad
Go through it with the scope and see if the imbalance is due to the balance control, volume control or some failed component.
 
dr*audio said:
Go through it with the scope and see if the imbalance is due to the balance control, volume control or some failed component.
Click to expand...
Ok. I will do that tonight! I know on these units the volume controls are getting worn out but this unit seems good. I'll check out what the scope shows me...
 
Wrong info.... Deleted
Signal is good at volume pot and good at balance pot.
Think I'm gonna replace the caps while I have access...there's a bunch of blue sanyos on the board. Scoping the waves around the output of the board starts showing the imbalance.
 
Last edited:
Ok.. preamp board is scoping perfect now. Output still showing imbalance. It's on the driver boards.... Trying to narrow down the culprit
 
Might be worthwhile checking waveform at power amp outputs to confirm it is symmetrical, check at pin 10 on power amp board.
Also helpful to check waveform at bias transistor c&e pins 4&8.
Thinking maybe a VAS issue (ie, after the differential pair)
 
mbz said:
Might be worthwhile checking waveform at power amp outputs to confirm it is symmetrical, check at pin 10 on power amp board.
Also helpful to check waveform at bias transistor c&e pins 4&8.
Thinking maybe a VAS issue (ie, after the differential pair)
Click to expand...
I'll do that. Thanks!
 
mbz said:
Might be worthwhile checking waveform at power amp outputs to confirm it is symmetrical, check at pin 10 on power amp board.
Also helpful to check waveform at bias transistor c&e pins 4&8.
Thinking maybe a VAS issue (ie, after the differential pair)
Click to expand...
All show a slight imbalance.
 
Check waveform at the base of the VAS(?) transistor, it connects to R517 (don't see transistor designation, TR505??)
If spkr waveforms were symmetrical then can rule out +ve and -ve halves of the amp, also since bias transistor pins 4&8 showed inbalance, so somewhere between pins 4&8 and the main-in...
 
I pulled tr05/06 to test and they were measuring very close, but for shits and giggles I swapped them channel to channel. Now on output test the imbalance is a bit less??
 
  • Like
Reactions: mbz
mbz said:
Check waveform at the base of the VAS(?) transistor, it connects to R517 (don't see transistor designation, TR505??)
If spkr waveforms were symmetrical then can rule out +ve and -ve halves of the amp, also since bias transistor pins 4&8 showed inbalance, so somewhere between pins 4&8 and the main-in...
Click to expand...
The base shows me no sinewaves on this? The collector does . It is slight unbalanced still
 
Silly question, and I'm sure you verified by pulling the knob and verifying the slot was at 0 and 180.

Could the knob be installed one tooth off?
 
You must log in or register to reply here.
Back
Top Bottom