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What are CR-620 protection voltages when operating?

lowredmoon

lowredmoon

Active Member
Greetings!

I have a CR-620 that turns on and operates but has a flaw in the protection circuit.
At turn on:
0 seconds: As the power button is pressed, the relay is already closed, and there's a loud pop from the speakers.
<1 second: The relay opens.
3 to 4 seconds: The relay closes and receiver operates.
At power down, there are no unwanted noises from the speakers.

I checked all the voltages WRT chassis at TR805 to TR809 when operating.
An image showing measured and published voltages is attached.
TR805 ECB: 0 / 0.067 / -0.023
TR806 ECB: 0 / 0.667 / -4.75
TR807 ECB: 0 / -10.49 / -0.023
TR808 ECB: 0 / 0.028 / 0.667
TR809 ECB: 13.65 / 13.41 / 12.94

TR809 has been replaced with a KSA1013YTA. All other transistors are original. All capacitors have been replaced.

My goal is to figure out why my voltages are incorrect.

As I continue to stare and probe, your insights and ideas are appreciated. Please chime in. Thank you!!!

CR-620 protection circuit - incorrect voltages.jpg
 
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lowredmoon said:
My goal is to figure out why my voltages are incorrect.
Click to expand...
Published voltages are ( in protect mode)
Your voltages are (not in protect mode)
Look at the relay contacts position in the schematic..;)
 
Install your new lamps...And see if the protect circuit still acts the same way. Usually if you have burnt out lamps the receiver will "pop" at power down. The lamps are part of the protect circuits power source.
 
avionic said:
They look OK to me.
Click to expand...
OK. Good. Thanks for that input.
So it looks like my issue is the big SLAP coming through the speakers (or headphones) at power-on.
The relay seems to be closed before power-on, then opens, then closes when it comes out of protect mode. Is that normal? Shouldn't the relay be closed when it is not energized?
EDIT: I meant, "shouldn't the relay be open when not energized?"
 
avionic said:
Install your new lamps...And see if the protect circuit still acts the same way. Usually if you have burnt out lamps the receiver will "pop" at power down. The lamps are part of the protect circuits power source.
Click to expand...
I'll install the new lamps and see if it changes.
 
While I'm reviving this receiver, I'd like to replace the electrolytics in the tuner. Many of the small capacitors on the amp board were faulty.
It looks to me like that shouldn't effect the alignment, but I'm a novice. What is your input on changing them? Thanks again!
 
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