Alpine 3542 no sound

[DeHchik]

There is only TIP107 at hand, can I solder it and check the amplifier's operation?

 

[Perry Babin]

Check it with your meter or tester to see if reads like the one you pulled.

You can try it in the circuit.

 

[DeHchik]

With a faulty Q318, the voltage on the uPC494C was:
1. 0V
2. 4,72V

3. 93,8mV

4. 4.72V

5. 1,62V

6. 3,63V
7. 0V

8. 14.4V

9. 0V

10. 0V

11. 14.4V

12. 14,4V

13. 4,87V
14. 4,87V

15. 4.87V

16. 0V
Power consumption 0A.


When replacing 2SB1076M with TIP107, the voltage on uPC494C became:
1. 0V

2. 4,72V

3. 91,7mV

4. 10,2mV

5. 1,61V

6. 3,61V

7. 0V

8. 14,16V

9. 5,93V

10. 5,92V

11. 14,15V

12. 14,15V

13. 4,87V

14. 4,87V

15. 4,87V

16. 0V

Power consumption 1A.
But there is still no sound.

 

[Perry Babin]

It was driving pin 4 high, shutting the IC down.

Could this transistor have been damaged after your initial post?

Are the 3 muting transistors still out of the circuit?

 

[DeHchik]

Perhaps it was damaged after my first message. Three muting transistors are on the board, I have not tried to solder them all at once, only one by one. Is it worth trying to remove these three transistors and check the sound?

 

[Perry Babin]

Yes

 

[DeHchik]

I wanted to clarify remove transistors Q319, Q101, Q201?

 

[Perry Babin]

Yes.

 

[DeHchik]

I removed the transistors, the situation did not change, there is no sound.

 

[Perry Babin]

Please (and this applies to anyone who needs repair help) use your sig line to list all equipment you have, editing it as equipment changes. Include the model numbers. If you can't do this due to being a new member, make a list in the next post.

Top of page, menu USER CP >> EDIT SIGNATURE

Oscilloscope (yes or no)
Multimeter(s)
Type of signal source (grounded RCA shields preferred).
Soldering iron
Desoldering pump
Power supply
2 ohm current limiting resistor (hollow cylindrical ceramic 100w preferred)

 

[DeHchik]

Added.

 

[Perry Babin]

You will need to try to trace the signal through the amp. This would be easier with a scope or with a signal tracer but you may be able to do this with a multimeter.

Set your meter to 2v AC. Set the volume on the head unit high. Go between mute and normal audio. Be sure that you can see the change at the RCA jacks on your meter. Go from point to point along the circuit path to see where the signal is lost.

 

[DeHchik]

I found a faulty resistor in the -15 volt R328 power supply circuit, after replacing it, the sound appeared in both channels. But I am confused by the voltages on IC101 and IC201, they differ from those indicated in the service manual. Here's what I measured:



IC101
1. 15,15 V
2. 47 mV
3. 5,4 mV
4. 5,2 mV
5. -14,9 V
6. 15,2 V
7. 1,85 V
8. 13,85 V



IC201
1. 15,25 V

2. 0 V

3. 0 V

4. 0 V

5. -15 V

6. 0,5 mV

7. 0,2 mV

8. 0,7 mV



On the rest of the microcircuits, the voltage is normal. It is also necessary to measure the voltage across the transistors according to the service manual.

 

[Perry Babin]

You have the pin configuration wrong. Repost the numbers.
https://datasheet.octopart.com/UPC4570G2-E1-A-Renesas-datasheet-138184105.pdf

 

[DeHchik]

I wrote by the numbering on the board. The figure shows measurements by datasheet.

 

[Perry Babin]

That's the first time that I've seen that sort of error but looking at the diagram again, I can see what you did.

I wouldn't expect the amp to produce audio in this condition. Is the amp in stereo mode?

If so, does the voltage on pin 1 of the 4570 change significantly is you switch from fixed gain to variable gain?

 

[DeHchik]

Found a solder jumper between +15 volts and R103. It's strange that the amplifier worked. But the tension is still not like in the service manual, I will look further.

 

[DeHchik]

The amplifier is in stereo mode, and when I switch the fixed gain to variable gain, the voltage at pin 1 4570 changes from 40,5 mV to 20 mV;

 

[Perry Babin]

I don't think the amp could have had audio on both channels if the amp is in stereo mode with 15v on pin 1.

The numbers on the service manual won't be exactly the same. Which voltages are you concerned with?

 

[DeHchik]

I just thought that the voltages on the 4570 pins should be exactly the same as indicated in the service manual. Do you think the voltages that I measured at 4570 are normal, you can finish the repair?