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Toshiba SA-775 Problem - Relay clicks then.........

ecluser said:
Check again if you have low DC voltages at the coils L601 and L602

If your offset voltage is low try to adjust the bias. Can you adjust the bias close to the values on the schematic (16mV between the emitters of the oower transistors)?

If you have a low offset and the correct bias, it's about time to consider a possible fault in the protection circuit itself, because the protection circuit responds to three possible faults in the amp:

1- high offset voltage, detected by Q803 and Q805
2- high current in the emitter resistors, detected by Q801 and Q802
3- loss of AC voltage, detected by D802

You can confirm that the amp is running well if you have a good signal at the coils L601 and L602. I don't remember if you have a scope but if you don't have one, you can can touch the coil with the positive wire going to a (test) speaker, and the negative wire from the speaker connected to the negative speaker terminal at the back of the receiver (which are grounded all the time anyway)
Click to expand...

Hi ecluser,
Low voltages at the coils L601 and L602, around 2.vdc. I now have NO voltage at the idle test points. I did the speaker wire to the coils test, and I had static / noise, So I feel you are correct in your statements, that the problem lies in the protection circuit. I'll check the resistors around Q801 & Q802, & surrounding area. Any other suggestions are greatly appreciated. I feel so close to hearing this baby sing. Thank You Again,
TubeJunkie
 
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sorry to jump in . but no idle current .both channels ? . do you still have correct voltages at output transistors ?
 
ecluser said:
For me, 2.vdc is not a low voltage. It is a very high offset voltage.

You have this voltage on both channels?
Click to expand...

Q907 has normal voltages. I get around 1.2 volts on the two lugs of the output transtors. But nothing on the top lug test points that are used to adjust idle voltage I followed the S.M. instructions on how to adjust idle. Nothing. Strange.

Thank You all for your time and effort. I think this problem is over my head. I'm going to give this receiver back to my buddy, next week. I hate to see it go to waste. Any other ideas in the meantime, let me know.
TubeJunkie
 
check voltages on outputs q601 to q604 with black lead on ground . collectors should be either + or- 54v . collector is the lead that goes to the case . we know the emitters are high at 2v . what does the base read ? . should be 0.6v .
 
petehall347 said:
check voltages on outputs q601 to q604 with black lead on ground . collectors should be either + or- 54v . collector is the lead that goes to the case . we know the emitters are high at 2v . what does the base read ? . should be 0.6v .
Click to expand...

Hey Pete, Thanks for your patience. Done as you said. The two on the left, in the pic' holds pretty steady at 2.1 volts, but the other two, on the right, starts at 2 volts and drops (cycles). Took some pics of the output transistors, to verify that I'm checking the right thing. Duh........ huh....... What does this mean? Thanks Again.
 

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means voltage isn't correct ..no where near as it happens . check again at big caps black lead on chassis ground red on brown then orange . if its still not around 54v try black lead on centre connection on big caps. red on brown then on orange .
your meter is set on dc volts yes ?
will let you check that ..i will have to sleep on it its late here ..
by the way what did the base read on them ?
 
Pete,
On the big caps, I have +51.4 vdc on orange, & -51.7 on brown. Yes, meter is set on DC. Open to suggestions. Thanks.
 
Hey, I don't want to hijack this thread but I have this same receiver but I get NO click when I power on. The sound just quit yesterday while we were watching tv. ( we use the receiver instead of tv speakers.) Now when I turn it on the familial click of the relay is gone. I hope it's ok to ask for help in here but if not let me know and I will post new thread or search for old thread info.

Cheers.
 
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