Alpine 3542 no sound

[DeHchik]

Have I measured the DC between the amplifier ground and the RCA pin? it turned out 0.02 V. Did I measure it correctly?

 

[Perry Babin]

I need the voltage between the shield (outer ring) and the primary ground.

 

[DeHchik]

0.03 volt.

 

[Perry Babin]

What is the DC voltage on all 3 terminals of Q319?

Post using the primary ground AND using the negative speaker terminals as reference (two sets of voltages).

What is the resistance between the negative speaker terminals and the primary ground, no RCAs plugged in?

 

[DeHchik]

The power supply voltage is 11.88 volts.
DC voltage at terminals Q319:
between common ground and Q3190:
1. 7.72
2. drops to 0V
3. 8.2
between left speaker:
1. drops to 0V
2. 4,51V
3.Drops to 0V
The resistance between the negative terminals of the speaker and the primary mass is infinity.

 

[Perry Babin]

Connect a jumper between a negative speaker terminal and the primary ground and re-do but you only need to give the measurement from the primary ground.

 

[DeHchik]

Okay, but I'll be able to measure it only the day after tomorrow, I'm going to work for a day.

 

[DeHchik]

The supply voltage is 14.4 volts.
DC voltage at terminals Q319 between common ground and Q319:
1. 9.74 V
2. ≈ 0 V
3. 10.23 V
After installing the jumper between the negative terminals of the speaker and the primary ground, the DC voltage at terminals Q319 between the negative terminal of the speakers and Q319:
1. 9.74 V
2. -6.6 V
3. 10.23 V

 

[Perry Babin]

Remove that transistor. Does audio return?

Those voltages should be identical. If they are not (readings in error), your jumper has a bad connection.

 

[DeHchik]

I deleted Q319, there is still no sound. I also removed the transistors Q101 and Q201, there is no sound. The jumper is connected on screws, so the contact should be good.

 

[Perry Babin]

Have you operated all pots and switches through their entire range while listening for audio to see if it every played through (even just for an instant)?

 

[DeHchik]

Yes, I tried different modes for both channels. I have doubts about the two resistors R353(6,8K), R360(22 K). When measured without soldering them out of the board, they have the following readings:
R353 - 5.15
R360 - 7.9K
Do I need to drink them out to measure them correctly?

 

[Perry Babin]

With the muting transistors out of the circuit, if there is no audio, the problem is in the audio path. You'll have to trace it from the input RCA jacks to the driver ICs to see where it's being lost.

You can pull those and check them later if you still have issues when the three transistors are soldered back into the circuit.

 

[DeHchik]

It is strange that there is no sound in both channels at once.

 

[DeHchik]

I have not tried to turn on an amplifier with three soldered transistors at once (Q101, Q201, Q 319), is it worth a try?

 

[Perry Babin]

I'm not sure I understand the question. If you're asking if you should go back and test pots and switches (signal in and speakers connected) with those transistors all out of the circuit. Yes, that would be a good plan.

 

[DeHchik]

Good afternoon, sorry for not answering for a long time, there was no time. I found one damaged transistor Q318 2SB1076M, but I cannot find them on sale. Tell me what analogue it can be replaced with?

 

[Perry Babin]

Was it open/shorted? It's a darlington so it may seem defective if you're checking with a meter.

https://alltransistors.com/adv/pdfdatasheet_rohm/2sb1076m_2sb1239.pdf

 

[DeHchik]

Is the collector-base junction shorted, cannot be checked with a multimeter?
The Chinese tester also shows that the transistor is defective.

 

[Perry Babin]

Do you have any other darlington transistors on hand that you can test to compare readings?

You can build a darlington from the diagram on the datasheet to see if you get the same results when testing.