Alpine MRV-1505

[seankane]

Have this amp for repair.

When the phase switch is at 0 channel 1 works great channel 2 is dead, when the phase switch is at 180 channel 2 works great and channel 1 is dead.

Any ideas?

 

[Perry Babin]

Do you have audio on pin 8 of IC106 and IC206?

 

[seankane]

I have audio on #8 of 206, but no audio on #8 of 106.

 

[Perry Babin]

Do you have audio on any of these points?

IC103 - pin 8
IC103 - pin 2
IC102 - pin 8
IC106 - pin 2

 

[seankane]

Do you have audio on any of these points?

IC103 - pin 8
IC103 - pin 2
IC102 - pin 8
IC106 - pin 2

I have audio on all the pins except for pin #2 of IC106.

 

[Perry Babin]

Check the crossover, stereo/mono and phase switches for the defective channels with a multimeter to confirm that all contacts ion all positions are making proper contact. Attached is a photo of the 3-position switches. I'm assuming that you know how the 2-position switches work.

 

[seankane]

OK the switches do not operate the channels seperately, the switches control both channels at once. I am not 100% how to check the switches with the multimeter.

The phase switch is the only switch that has any effect on the audio signal and its a 2 position switch.

I have posted a pic of the output section.

 

[Perry Babin]

Look at the image. The slider moves between the contacts. You should read 0 ohms between the two contacts with the slider touching them. Check all 3 switches.

 

[seankane]

OK one more question, what are the 2 red LED lights that are lit up on the board in the output section?

 

[Perry Babin]

They are used as a voltage reference for a constant current source.

 

[seankane]

OK not sure if it matters but one was out when I got the amp and I replaced all the outputs and now they are both lit.

 

[Perry Babin]

The voltage across the LED may be important. Measure the DC voltage across the terminals of both LEDs to confirm that they are not significantly different.

 

[seankane]

They are both identical sitting at -1.736 vdc.

 

[Perry Babin]

Measure across the terminals of each LED.

 

[seankane]

I did.

 

[Perry Babin]

Did you replace both of them?

 

[seankane]

Did you replace both of them?

Both of them as in the LED'S?

I replaced the outputs in this amp and thats all so far.

 

[Perry Babin]

If you still have the originals, I'd suggest reinstalling the good one to see what the voltage was across it. According to the service manual, Rx48 and Rx52 shouldn't have more than about 0.5v across them. With the LEDs you used, I'd expect that it is significantly more.

 

[seankane]

I didnt replace the LED'S I only replaced the outputs in this amp.

Everything else is exactly how it came to me. In a previous post I metioned that one was out when I received the amp. I replaced the outputs in the amp and then they were both lit.

The amp has the original LED'S still installed.

 

[Perry Babin]

I misread post #10.