Alpine MRP-M350

[RiLoWa]

I get 4.4mV there

 

[Perry Babin]

What is the DC Voltage on TP608 and TP541?

 

[RiLoWa]

TP608 = 4.98V
TP541 = 2.6mV

 

[Perry Babin]

It appears that the ucom is shutting down the IC. There are too many inputs to justify troubleshooting every possible fault. I'd suggest replacing the outputs. If it doesn't power up, we'll troubleshoot it more.

 

[RiLoWa]

Alright, they are on order. As a reminder, all of these measurements were taken with the outputs and rectifiers removed.
Thanks again for your assistance.

 

[RiLoWa]

New parts finally arrived today.
I re-installed the original rectifiers and installed two new IRFZ44NPBF and two new IRF5305PBF on the outputs. The amp is still not happy. The power LED pulses but it does not make the "sqeaking" sound like originally posted.
UPC494 Pin #3 behaves the same as before ~80.5mV to ~87.5mV
UPC494 Pin #9 & #10 behaving the same as before also
UPC494 Pin #12 pulses between ~3.5V to ~11.8V

 

[Perry Babin]

Is the amp drawing excessive current as it tries to power up?

Is there any DC pulse on either the positive or negative speaker terminals? Place the black meter probe on the amplifier's ground terminal. Place the red meter probe on the point where you need to measure the voltage.

 

[RiLoWa]

Amp is drawing between 0A to .5A during it's pulsing.
DC pulses on both positive and negative terminals from zero to ~155mV.

 

[Perry Babin]

Are the gate resistors for the output transistors within tolerance?

 

[RiLoWa]

My meter only has resolution of .1 Ohm, these are .01 Ohm so they are not open or shorted and read as .1 Ohm on my meter.

 

[Perry Babin]

The 0.01 ohm resistors are for the over-current protection. The gate resistors are R315, R316, R415 and R416.

 

[RiLoWa]

R315 = 22.0 Ohm
R316 = 26.7 Ohm
R415 = 22.2 Ohm
R416 = 26.9 Ohm
They appear to be in tolerace.

 

[Perry Babin]

The driver IC may have failed but I don't know how to test it. If you remove the outputs and drive a strong signal into the amp, the driver IC may produce drive pulses at the gates of the output FETs. If one or more gates have no drive signal, the IC may be defective.

 

[swordfish689]

Usually when the outputs go, it takes the tda 7571 with it.

 

[RiLoWa]

That is pretty much the conclusion I have drawn on this one. Anyone know where the TDA7570 or TDA7571 can be obtained? I have found a few companies that buy up excess inventory that may have them, but I have not yet been able to make contact with any of them, probably due to the holiday weekend.

 

[Perry Babin]

PacParts has it but they want $42 for it.

 

[RiLoWa]

True, I saw that earlier. I'll try these other outfits again tomorrow and see if anything turns up and report back. Its hard for me to pay $42 for a $10-$15 part. The amp isn't worth that much, when perfectly working ones can be had for $50.

 

[RiLoWa]

Unfortunately, I have not found another domestic source for one TDA7570 other than Pac Parts or Herman Electronics which are both at about $45 each.

I did find one source that will sell a minimum of ten for $15 each. I doubt that I will ever need the other 9, so I will not be buying any. Some of you may see enough amps for repair that use this part so here is the info as promised.

V&C Technology, Inc.
15250 Flight Path Dr.
Brooksville, FL 34604
vctechnologyinc.com
352-796-0060

I spoke with a very nice & helpful lady named Jessica at ext. 245

PS. To those that may have a use for ten, I know where you can sell one.