Rockford T10001bd

[seankane]

Board number: PC-5445-B


This amp powers up blue light but the yellow protection light is lit. Its not dimly lit but seems like its on. The amp is only drawing about 1 amp idle current which is to low.


Its making rail and regulated. The drive signal on the power supply is good.


Seems the amp is not fully operating, no audio, and around 2-3vdc on the output terminals.


U4 and U9 have the exact same readings.


pin1: 1.884
pin2: 1.884
pin3: 13.70
pin4: 4.30
pin5: 4.98
pin6: 4.98
pin7: 8.11
pin8: 0.015
pin9: 1.040
pin10: 0.016
pin11: 1.040
pin12: 0.003
pin13: 0.764
pin14: 0.749


U10 is a little different


pin1: -0.311
pin2: 13.42
Pin3: 13.88
pin4: 0.086
pin5: 1.501
pin6: -0.237
pin7: 0.002
pin8: -0.245
pin9: 0.002
pin10: 0.021
pin11: 0.822
pin12: 0.002
pin13: 0.447
pin14: -0.248


So far haven't found anything shorted.

 

[Perry Babin]

It looks like you measured U9 twice.

I wouldn't expect any negative voltages.

 

[seankane]

U4 and U9 have the exact same readings on all pins, so I only posted one set of readings.


U10 reads as posted.

 

[Perry Babin]

According to the diagram, that's not possible.

 

[seankane]

I checked all 3 again and U4 was causing some issue while checking it. Some pins would make the protect light go out and some would make it super bright.


I replaced U4 and retested all 3 lm339, here is what I read.


U4


Pin1: 4.97
Pin2: 0.042
pin3: 13.70
pin4: 10.95
pin5: 1.381
pin6: 0.587
pin7: 1.647
pin8: 2.492
pin9: 2.321
pin10: 10.95
pin11: 1.381
pin12: 0.002
pin13: 0.043
pin14: 0.267


U9


pin1: 1.868
pin2: 1.868
pin3: 13.70
pin4: 4.29
pin5: 4.98
pin6: 4.98
pin7: 8.10
pin8: 0.008
pin9: 1.039
pin10: 0.008
pin11: 1.039
pin12: 0.002
pin13: 0.738
pin14: 0.738


U10


pin1: 0.119
pin2: 13.44
pin3: 13.89
pin4: 0.043
pin5: 1.501
pin6: 0.019
pin7: 0.001
pin8: 0.365
pin9: 0.001
pin10: 0.001
pin11: 0.822
pin12: 0.001
pin13: 0.456
pin14: 0.002


The led protect light is on but not real dim or super bright if that makes sense. Its in between. Still no audio.

 

[Perry Babin]

Do you have rail-rail oscillation on the output transistors?

 

[seankane]

Yes I do.

 

[Perry Babin]

Dirty switch or pot?

Broken inductor?

Do you see modulation of the r-r square wave when you drive signal into it?

 

[seankane]

The switches and pots are fine, inductor is fine.


Why does U204 have 5.50 vdc on pin 2 and U202 does not? Its the only reading between the two that differs.


If I short pins 2 and 3 together of either driver I can hear audio but it does not increase with the volume.


I have a square wave on pin 1 of U200 and U203. Pin 7 of U200 and U203 has a square wave but its not correct at the top half.


I'm missing something here.

 

[Perry Babin]

How can there be a problem with the drivers if you have rail-rail oscillation on the output FETs?

 

[seankane]

I don't think there is a problem with the drivers. I think the problem lies within U201 and U290 area.


U290 has almost 3vdc on pin1 and nothing on pin7.


U201 has significant voltage on all pins especially pin 7 that has 11.50vdc.


I was thinking they may be defective. I removed both of them and out of the circuit the amp powers up fully and draws the correct idle current.


I installed new and same issue. Pin 7 of U201 latches to pin 4 of U4?


Sometimes I have a hard time following the schematic from page to page.

 

[seankane]

Q10 has a small burn spot on top.

 

[seankane]

Q10 was shorted and burned. Replacing it lowered the voltages on the 2 72's but the amp will still not fully power up.

 

[Perry Babin]

Solder a bridge between terminals 1 and 2 of U200. Does that give you audio out of U200 pin 1?

 

[seankane]

No.


This amp has square waves at pin1 and 7 of both 6172's. When I use a 100hz sine wave it kills the square wave on pin 1 of U200, and looks like your looking at music with the scope but it does not increase in amplitude with the volume.

 

[Perry Babin]

What's the board number on this amp?

 

[seankane]

PC-5445-B

 

[seankane]

I have this schematic if you want it.

 

[Perry Babin]

I have it but you should not have a square wave that far back The carrier is introduced at the points marked 'carrier'. Beyond that point is where you should have a high-frequency triangle or square wave.

 

[seankane]

U201 and U290 when removed allow the amp to fully power up. I just cant figure out what is dragging them down or where all the voltage on the pins are coming from, mainly U201.


I have tried powering the amp with either removed always leaving one in circuit and the amp wont fully power up. They both have to be removed.


I do not even know if this pertinent but thought I would ask you your thoughts on that.