Kenwood Eleven GX speaker relay issue

[ddrjboo]

I am trying to repair a Kenwood Eleven GX. When powered on, the speaker relay does not engage to allow the stereo to play. When the relays are closed manually, the stereo appears to play very well.
I have tested the voltage at diode D20 which seems to me to be in parallel with the relay.
The schematic says is should have 25 Volts on the negative side of the diode, but it reads 56 Volts instead.
I have tested the diode, and replaced the diode, and the voltage does not change.
I have tested the voltage of resistor R79 and it is getting 59 volts on the "upstream" side and 56 volts on the "downstream" side. I have also removed the resistor and tested its resistance and it is with spec (1Kohm).
I am wondering if it is possible that the speaker relay is shorted and causing this problem.
If there is anyone that can help me diagnose the problem, I would appreciate the support.

 

[petehall347]

disconnect the speakers before something bad happens .
close the relay contacts and and measure voltages across the speaker terminals .
p.s this is not the way to do this but am just making it easier to follow on from what you started .
ppp.s welcome to AK

 

[ddrjboo]

Thanks for the welcome!
I checked the voltage across the two channels and get about 40 mV on the left channel and about 70 mV on the right.
Oddly, if I leave the speaker relay closed when I turn off the system, the voltage increases to about -4 V. I know if the relay is working properly the speakers will never see that, but I don't know if it "normal" or indicative of what my problem is.
Thanks for your advice.

 

[petehall347]

it appears the fault is in the relay circuit .

 

[ddrjboo]

When you say the fault is in the relay circuit, do you mean within the relay itself, or is it possible that there is a problem with the voltage coming into the relay?

 

[petehall347]

i should have been more precise and said fault in the protect circuit . first check the protect circuit is getting its correct voltages from the power supply .

 

[ddrjboo]

I hadn't looked at this post for a long time, but just noticed that you're the guy that helped me with the Sansui 8080 today!
As an update to this discussion, I just wanted to let you know you were right about this Kenwood Eleven GX. I ended up changing the five transistors Qe31 to Qe35 in the protection circuit after your post last July, and the receiver has been great ever since.
Thanks again!