Alpine MRP_M450

[Chuppster]

I have a blown Alpine MRP_M450 and I am trying to get it working. When it was first broken,the LED lit up but there was no output. I replaced the blown IRFZ44N output transistors. Now, no LED and the power transistors (which seem to be working) don't even warm up. Does anybody have the schematics for this model?

 

[seankane]

They might not be switching on.

Have you measured voltage in the power supply fets?

Have you checked the drivers for the power supply fets?

 

[Chuppster]

I figured out why my LED wasn't working, I got the polarity mixed up.

Voltage to PSU FET's (IRF5305's, right?) reads ~300 mA on the gate and ~700 mA on the source and drain, measured between ground and the respective leg. Value constantly drops the longer I hold the probe there.

I am having trouble identifying a driver without any schematics.

 

[Perry Babin]

Assuming that you meant millivolts and not milliamps...

The source leg should read 0v if you have the probe on ground since the source leg is directly connected to ground.

 

[Chuppster]

Okay, I'm assuming the power supply transistors are the IRFZ44N's marked Q601-604. Each has 12 volts going to the center leg. There are 2 more 44N's on the board, as well as 2 IRF5305's. None of these get 12 volts to the middle leg. Sorry about the mix up there.

 

[Perry Babin]

I don't have any specific information on this amp. If no one else can help, you'll need to post a photo of the amp and the components that you're referring to.

 

[Chuppster]

Here are a few pictures of the board. If you want close - up's of any area let me know. One of the photos has the transistors labeled.

 

[Chuppster]

Here are a few pictures of the board. If you want close - up's of any area let me know. One of the photos has the transistors labeled.

Here's the link.

https://drive.google.com/folderview?id=0B50P1QWuuYzcNFJSSHBxVE1LdVE&usp=sharing

 

[Perry Babin]

Is IC601 a TL494?

If so, post the DC voltage on all legs of that IC. Copy and paste the following into your reply.
Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
Pin 9:
Pin 10:
Pin 11:
Pin 12:
Pin 13:
Pin 14:
Pin 15:
Pin 16:

 

[Chuppster]

C494GS.
Pin 1: 0
Pin 2: 4.5
Pin 3: 4.5
Pin 4: 0
Pin 5: 0
Pin 6: 0
Pin 7: 0
Pin 8: .5
Pin 9: 0
Pin 10: 0
Pin 11: .5
Pin 12: 0
Pin 13: 0
Pin 14: 0
Pin 15: 0
Pin 16:0

I checked my multimeter to make sure it was still working. It is.

 

[Perry Babin]

Do you have 5v on pin 40 of IC501?

 

[Chuppster]

Yes, pin 40 on the C847UG reads around 5 volts.

 

[Perry Babin]

If the number on the IC is 847, it doesn't appear the the manual I'm using will be of any use in troubleshooting. You'll need to find the exact service manual for that amp.

 

[Chuppster]

Okay, I'll contact them today and see if they will give it to me.

I pulled 2 of the IRFZ44N's, the multimeter reads open leads unless I have positive on leg 3 and negative on pin 2. I need to replace these again, right? The amp seems to power up.

 

[Perry Babin]

They won't send it to you free of charge. Expect to pay approximately $20 for it.

You should also understand that with complex amps (like this one), having the service manual will not guarantee that you will be able to repair the amplifier.

You need to follow the test procedure on the transistor testing page.
Basic Amplifier Repair - Transistor Test Applet Link

 

[Chuppster]

I found this manual for an M350, how similar do you think they are?
http://dl.dropboxusercontent.com/u/35219914/-Audio Manuals/Alpine/Alpine MRP-M350.pdf

 

[Perry Babin]

That's the manual I have. The control IC is different.

 

[Chuppster]

This is the biggest IC on the board - IC301.
http://www.st.com/web/en/resource/technical/document/datasheet/CD00169483.pdf

This 494 appears to be the controller.
UPC494GS pdf, UPC494GS description, UPC494GS datasheets, UPC494GS view ::: ALLDATASHEET :::

And there is this C847UG microcontroller...
View TMP86C847UG_4107501.PDF datasheet online --- IC-ON-LINE

Is this enough information to go off of? I can trace leads to the best of may ability if need be. Otherwise I'll probably put it up, it isn't worth paying for the service manual.

 

[Perry Babin]

IC501 is programmable. That means that there are some pins that can be programmed to be inputs, outputs or both. Their function is determined entirely by programming and the IC is programmed for the features of the amp that it's used in.

 

[Chuppster]

Okay. Well, how could I verify that the power supply is working?