Alpine MRV-F307

[seankane]

I recieved this amp with one channel not producing any sound but all the other 3 channels worked great. I replaced 2 output fets that were burnt. I powered up the amp and it powers on and the LED stays lit. The amp pulses on my power supply. It produces sound in all channels but goes on and off. You can see the current draw then nothing. Its like the power supply is turning on and off over and over again. The LED stays lit the whole time and is green.

Does anyone have any clues for me??

 

[Perry Babin]

Is there any pulsing DC on the dead channel?

Did you check the drivers for the outputs?

Are the emitter/source resistors within tolerance?

 

[seankane]

Is there any pulsing DC on the dead channel?

Did you check the drivers for the outputs?

Are the emitter/source resistors within tolerance?

The dead channels produces audio as well as the other 3. The sound goes on for 3 seconds then off for 3 seconds over and over. Its like the power supply is shutting on and off but the LED stays lit green the whole time.

Drivers you mean the little 1/8 watt 220 ohm rsistors?

The emitters you mean the 5 watt 0.1 ohm ceramic/stone looking resistors?

 

[seankane]

All channels produce sound but shut on and off.

I dont see any DC on the channels but they do make a pop when you connect a speaker.

I am not at all familiar with Alpine amps.

 

[seankane]

After re-checking for dc using the terminals inside the amp instead of the screws I do find a pulsing of DC. Channel 3 bridging terminal pulses up to 1.5 vdc and channel 4 bridging terminal pulses up to 14.50 vdc.

 

[seankane]

The emitters and drivers seem to be OK and within tolerance one of the drivers was at 215.5 ohms seems a little low. It looks as if they use one driver and one emitter per pair of fets. Thats seems strange to me. There are 4 drivers and 4 emitters, but 8 output fets.

 

[Perry Babin]

Do the emitter resistors have 3 legs?

Did you lift the transistor to see if it was leaking or if the 215 ohms was from something else on the board?

 

[seankane]

The emitter resistors do have 3 legs. I have not pulled the transistor since they were installed new. I dont know why they would be leaking unless I bought bad ones. I can pull them to be sure if needed. I have not checked anything else yet.

 

[Perry Babin]

If it reads differently than the others on the board, you'll probably have to remove it to determine if it's the transistors or another component on the board.