Technics SU 8600 protect problem.

[Lynyrd]

Hello.
Its strange problem of protect mode on TECHNICS SU 8600 Amplifier.
If I desoldered TR506 relay click,and Amplifier works fine.
With TR506 relay not click.
All voltages are ok.
No DC voltage on speakers terminals.
Amplifier works fine without TR506....
THANKS

 

[Lynyrd]

Service manual

https://www.google.com/url?sa=t&sou...cQFnoECA8QAQ&usg=AOvVaw08GQyUd4l_vSYyUggTvM_x

 

[Lynyrd]

Sorry,it's DC +2.8v on speaker terminals on 2 channels.
how can i fix this?

 

[Lynyrd]

No adjustments of DC offset on this Amplifier....

 

[Lynyrd]

What parts are responsible for DC offset?

 

[Lynyrd]

when I turn off the amplifier, the voltage rises to 4 volts and then slowly drops to 0v.

 

[Lynyrd]

BIAS is ok,10mV
+-47v ok

 

[huggygood]

the service manual for the SU 8600 (and this generation of Technics in general) is one of the best written I know.
If you read it in order, you will better understand how this amp works.
Me at first, I will replace the 6V220uF of the protection circuit (accessible, easy and fast)

 

[Lynyrd]

6v 220uf is replaced

 

[Lynyrd]

Its problem of DC voltage +2.8v on speaker terminals

 

[huggygood]

L & R ?

 

[Lynyrd]

Yes

 

[Lynyrd]

Same DC voltage on R&L......+2.8v

 

[huggygood]

ok, so the problem is common to two channels.
So question: what is common to both channels?

 

[Lynyrd]

when I turn off the amplifier, the voltage rises to 4 volts and then slowly drops to 0v.

 

[Lynyrd]

ok, so the problem is common to two channels.
So question: what is common to both channels?

Power supply?

 

[huggygood]

and have you tried separating preamp and amp?

 

[huggygood]

Power supply?

and ground

 

[Lynyrd]

Yes,no results

 

[Lynyrd]

now again measured +3.25v on 2 Channels