Aiwa CDC-MP32 Headunit Unresponsive

[Perry Babin]

How much?

 

[D132]

.5v both sides

 

[Perry Babin]

Are your probes on 10x or 1x?

Measure with a multimeter.

 

[D132]

I forgot I had it on 10x sorry, that would be 5v
Multimeter says .028v on DCV 2

 

[Perry Babin]

DCV 2?

What if you reverse the probes?

Make/model meter?

Black probe on ground?

 

[D132]

Reversed probes read -.028v
Black on ground reads about 4.9v both sides

 

[Perry Babin]

Try this with only one ribbon plugged in at a time and with no ribbons connected.

With your probe on 10x, do you see any oscillation on the crystal oscillator terminals for the MCU?

 

[D132]

Still reads 5v with one ribbon at a time and without either

Where would those be? The big pads on either side of it?

 

[Perry Babin]

X901. Metal can (stadium/pill shaped) on the top of the board, terminals on bottom.

Probe must be on 10x (unless you have a 100x probe). The oscillation is fragile and the loading of the scope is sometimes enough to stop it from oscillating. This is inconclusive but there aren't many tests left.

 

[D132]

Goes from picture one to sine wave shown in about half a second after probing, both terminals

 

[Perry Babin]

That generally means that the processor still functions. I'm not sure why you're only getting DC on the pins of the IC.

What DCV do you have on pin 58 of the MCU?

 

[D132]

Just under 4v

 

[Perry Babin]

What's the DC voltage on the battery and acc lines on the power connector?

 

[D132]

This? Or do you mean the terminals on the board where this connects
If it’s the connector, accessory and power both have 12.07v
Corresponding terminals on the board have 12.05v

 

[Perry Babin]

DCV measured directly across D716?

Black on ground, DCV on each terminal of R715?

 

[D132]

5.79v on D716

I’m not sure which of these resistors are R715

 

[Perry Babin]

The one on the left.

 

[D132]

(Pov from previous picture)
Left terminal 3.6v, right 6.3v

 

[Perry Babin]

It appears that the diode D712 is leaking. Lift one terminal and check it for leakage. Don't power the head unit up with it out of the circuit.

 

[D132]

I don’t see anything visually wrong with it, are there any tests I can do to double check?