Yes, it's only a small signal, if I turn the gain, you can see, that it's working, but the amplification is not enough. It seems also, when I turn the gain full in, that it's clipped. But only 2 v. The amp draws all the time only 0.6 amps
What is the signal level on the op-amps that are in the circuit?
Do any swing to clipping at about ±12v?
Do any swing to clipping at about ±12v?
That's 7v AC. Where are you losing signal up to the input of the differential amplifier?
What's the AC voltage at the input of the differential amplifier and at the speaker output?
What's the AC voltage at the input of the differential amplifier and at the speaker output?
Are you sure that Q117 and the corresponding transistor in the other channel are the muting transistors? Lift both if you are.
Do both channels have the same signals on the input of the differential amplifier and the output of the channel?
Do both channels have the same signals on the input of the differential amplifier and the output of the channel?
The 5.8v on the equivalent of R142/3 if there is only one resistor in each circuit beyond the 100 ohm resistors.
Is the circuit more like the one below where there are two resistors in series, fed from a ±15v supply?
Is the circuit more like the one below where there are two resistors in series, fed from a ±15v supply?
Yes, it's better. R161 2.1k is the one with 5.8v. This resistor goes to audio ground, and the other pin over a cap (+) to sec center. The connection from the resistor to +cap is also connected to resistor r161a. It's a 5.6k. The other end from r161a has 15v.
When you have the signal shown in the right side image in post #26, what is the signal on the right side (inverting side) of the differential amplifier bases?
It's the same, but the half wave is on the opposite side. I lifted all four transistors from the diff. Amp, now I have 15v at the resistor. As soon, I connect one transistor, the voltage drops at this side to 5.8v.. The transistor are ok.
I'm a bit confused.
In post 26, which image (left or right) is the signal on the left side of the differential amplifier input?
In post 26, which image (left or right) is the signal on the left side of the differential amplifier input?
"it goes to the both diff amp transistors."
There are 4 differential amplifier transistors per channel.
Look at this diagram. From the last images you posted (higher resolution), it looks like this may be even closer.
There are 4 differential amplifier transistors per channel.
Look at this diagram. From the last images you posted (higher resolution), it looks like this may be even closer.
Was this amp working perfectly and then both channels just went silent?
Can you find the equivalent of R168 on the last diagram and increase it incrementally to see if you can get the outputs to bias on?
What is the bias voltage (G-S) on the output transistors?
Can you find the equivalent of R168 on the last diagram and increase it incrementally to see if you can get the outputs to bias on?
What is the bias voltage (G-S) on the output transistors?
I bought this amp damaged, the previous owner removed some Parts in the Audio drive stage. So i dont know, what was the problem. The other questions i will chekc out.
G-s has 0v with signal allied. R168 is 1k, I don't have the thermistor in the circuit, only the transistor k115 c3200