Amplifier Distortion, DC-Offset, and You!

Thing is despite the very low readings, the amp truly is bpc and sounds like crap.

I started out with a Technics integrated amp from 1984, I cannot recall which one. It was low power, and would shut-down anytime I tried to crank with the Cerwin Vega D-7E s. A barracks-mate across the hall had a Sansui integrated-amp combined with a pair of Heresy's, and I was so damn jealous!
 
After reading your results on your bpc technics I decided to try my su-v9, one of their better integrateds. Wouldn't you know it I got the same readings you got the first time.
Weird.
 
Sony TA-1055, 90mV on left channel, 10mV on the right. Transistors are found to be unsuitable replacements, a swap and some recapping is in order.
 
I think I just ruined my amplifier,
I was measuring center voltage because right channel was a bit weaker, and everything was fine,
0mv for left and -0.5mv for right, then bump a smoke, bad smell, protection kicked in, now it stays in protection mode,
I was careful not to short the pins, I even put some tape on multimeter clamps, but maybe I was not careful enough..
I remember doing this some years ago when I found this thread, and I shorted some pins with the multimeter, protection kicked in and nothing happened, but it seems now is trouble,
It's a beautiful JVC AX-1100, I even have the schematics but not the knowledge to fix anything..

I measured the current with the protection on, and now L is 67v, R is 0.6v, still can't believe this..
 
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Even though there was a pretty strong smell and smoke, I can't find anything burnt on the pcb,
but I can't see front panel..
 
You blew the power transistors and maybe more. You know this thread has nothing to do with measuring idle current but DC offset at the speaker terminals. BTW if you have 67V at the speaker terminals, the protection circuit is not working either!
 
You blew the power transistors and maybe more. You know this thread has nothing to do with measuring idle current but DC offset at the speaker terminals. BTW if you have 67V at the speaker terminals, the protection circuit is not working either!
In fact I was measuring dc offset, but the pins for the idle current are next to them, the amplifier stays in protection, with the light blinking, I dont know if measuring dc offset at this point has any value at all, and didnt check speaker terminals,
I'm not complaining about the thread, this is my fault!
 
You should have measured DC offset at the speaker terminals. If you would have shorted the leads (or whatever happened), your amps protection most likely would have kicked in and saved the day. I'm no tech, but this doesn't look like a simple amp. You should start by checking the output transistors for being shorted and work your way back. I looked at the schematic and it has the outputs paralleled. So it is 4 transistors per channel. These must be matched to share their workload evenly. I don't know if just buying them in the same lot is OK or if they actually need to be matched by selecting them out of a lot. Anyway, unplug it and start ohming out the outputs, emitter resistors, driver transistors, etc. Hopefully the damage isn't too deep.
 
I think 2 pairs of output transistors have gone, probably the left channel, because I don't have any reading with the multimeter, while the other 4 seem ok,
but I haven't removed them from the pcb, is it ok to test them on the pcb?
I hoped any burnt resistor could have saved them, but ..
Components are B863 (Toshiba) and D1148
 
I was expecting them to be shorted, not open. You can get an idea in circuit. obviously if you use ohm or diode test and it is shorted, thay would be a red flag to pull them and test out of circuit. If they are open, they won't get any better when removed.

You should start a new thread in the Solid State forum. This is kind of off topic here and is buried in over 4200 posts and 200 pages!
 
Today I performed a DC offset reading on my preamp/amp combo.

Classe CP-50 Preamp
Classe CA-200 Power Amp

The set the meter to DC Voltage and 200mv. After placing the probes on the speaker terminals, the meter's digital LCD display was moving all over the place negative to positive back and forth. I placed the probes on the terminals and held them as steady as I could. It never went past +/- 2.5mv. The service manual says it should be set to 0.0mv with a tolerance of +/- 1mv. The left channel seemed to deviate the most over the right channel. I'm not sure why the readings were not exact. I still haven't decided if it's worth it getting inside the amp and adjusting the trimpot to exactly 0.0mv.
 
HELLO EVERYONE >
Here thousands of measurements, and how to fix if there is a problem?
I need HELP.
Pioneer SX 3700
L channel - 178mV
R Channel- 148mV

What should be done to fix it?
Do I need to replace the parts ?
What parts need to gage?
Where can I read on this model, if that was written on this issue?
Is it possible adjust without replacement parts?
Thank you in advance.

Pioneer SX-3700 Idle Current Adjustment
2.5mV on both channels
 
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I have a question for Echowars...why, in your avatar do you have a large caliber revolver laying across a plate of vegetables ? Just curious......
 
Zevon was a firearms enthusiast and a friend of Hunter S. Thompson. The pic, taken by Warren's girlfriend, is entitled 'Willy on the Plate', and was used as the inner sleeve for the 1978 album 'Excitable Boy'.
 
I tried my 1977 Sansui 7070 today, which I bought new in 1977, and it read 3.4 right and 14.7 left. Goody. Then I tried my Marantz 2230 and got no reading on either channel, so it's a capacitor output?
 
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