Alpine MRV-M500

[Jason Smith 616]

Does anyone have a schematic for this amp?

Or can tell me the value of R9908 ? It is right in front of the 494

 

[Perry Babin]

68k ohm

 

[Jason Smith 616]

Do you know what might cause this resistor to burn?

And would this cause the amp to protect?

 

[Perry Babin]

It's part of the regulator circuit. I would not expect it to get hot unless the negative rail is far from what it should be. Replace it and monitor the voltage on the rails as you drive a signal into the amp with a load on the amp.

I don't know if it can cause the amp to go into protect.

 

[Jason Smith 616]

replaced it amp is still in protection.

I will check the regulators

 

[Jason Smith 616]

replaced the Regulators and the 68K ohm resistor amp is still stuck in protection

The outputs test fine any idea what to check next?

 

[Perry Babin]

I'm sorry I wasn't more specific. The resistor is part of the rail voltage regulator.

Were there any wire strands in the amp?

Did you check the outputs across all legs and not just 2-3?

 

[Jason Smith 616]

no wire strands were found inside the amp.

I pulled the outputs and amp is still in protection

 

[Perry Babin]

If you jump Q2201 collector to emitter, will the supply power up?

Be careful. Without knowing the fault, I don't know what will happen if it does power up.

 

[Jason Smith 616]

If i jump Q2201 amp is still in protection

 

[Perry Babin]

Did the power supply IC produce output pulses?

Did the power supply IC have 12v on pin 12?

 

[Jason Smith 616]

This is what i get on the 494

Pin 1:0.00
Pin 2:0.10
Pin 3:0.03
Pin 4:3.60
Pin 5:1.53
Pin 6:3.37
Pin 7:0.00
Pin 8:13.88
Pin 9:0.00
Pin 10:0.00
Pin 11:13.88
Pin 12 :13.88
Pin 13:4.98
Pin 14:4.98
Pin 15:4.98
Pin 16: 0.00

Here's what i get on the Power supply fets

Gate:0.00
Drain: 13.88
Source: 0.00

The IC isnt producing pulse's

 

[Perry Babin]

Remove R9903 from the circuit.

 

[Jason Smith 616]

After removing R9903 the IC produces pulses but amp is still in protection mode and doesn't produce rail or regulated voltages

 

[Perry Babin]

Do you have drive pulses on the gate legs of the 3205s?

Do you have a signal that swings from ground to 25v on the drains?

 

[Jason Smith 616]

I get drive pulses on the 3205's

I also get signal that swings about 25 volts volts from ground on drains

 

[Perry Babin]

How can it not have rail voltage if the transformer is being driven?

Are the rectifiers in the circuit?

 

[Jason Smith 616]

The rectifiers are in circuit.

The rail voltage in this amp right now is only positive 2 volts and negative 2 volts thats all i get

I just noticed R9903 is missing it sits by the 494 do you happen to know the value ?

 

[Perry Babin]

What voltage do you read if you read between the center terminals of the rectifiers?

820 ohms

 

[Jason Smith 616]

0.28 volts