Rockford Fosgate T500-1bd

[cajones65]

Across the speaker terminals I am getting -1.5vdc on both. I didn't understand where you wanted me to put the black probe and measure the resistor and the cap that I jumped. However by putting the black probe on power grd, I was getting no voltage

 

[cajones65]

Actually Perry I am getting -0.095 on the resistor and 0 on the cap

 

[Perry Babin]

Has any work ever been done to this amp.

I wanted the black probe on the negative speaker terminal when measuring the voltage on the driver board.

 

[cajones65]

With the voltages I gave you the second time was from the speaker grd. It doesn't look like it. I looks like factory soldering.

 

[Perry Babin]

Do you have or can you make a probe like the one attached to get the voltages off of U205 on that board?

 

[cajones65]

What is that a tooth brush and meter lead? Don't know what the hook is.

 

[Perry Babin]

It's a dental pick. It an other options are shown near the bottom of the 'know your meter' page.

 

[cajones65]

Looking at that now

 

[cajones65]

I am going to make one, what do I need to measure when I get it made?

 

[Perry Babin]

I need accurate DC voltage readings from all pins of U205 on the driver board.USe the negative speaker terminal for the black probe. Clamp it down. Touching the screw head can be intermittent.

 

[cajones65]

U205 LM6172im
1. -0.100
2. 0
3. 0
4. -5.175
5. -2.241
6. -0.108
7. .451
8. 5.905

Neg speaker terminal as grd ref

 

[Perry Babin]

There seems to be a couple of problems.

If those numbers are good, the IC appears to be defective. With the non-inverting input below the inverting input, the output should also be negative.

That said, pin 5 should be VERY near 0v.

Can you do the same on U208?

 

[cajones65]

U208
1. -.238
2. 0
3. 0
4.- 5.163
5. -.159
6. 0
7. -.005
8. 5.901

 

[cajones65]

Perry I rechecked U205 and you were right, I miss printed and and shouldn't have placed the 2 in front of the decimal. Voltage on pin 5 in -.238

 

[Perry Babin]

Did you remove the board and connect to the main board with wires?

 

[cajones65]

No sir, what I did was bend a meter lead tip, and put heat shrink on it and measured the op amps in board

 

[Perry Babin]

Post a photo of the waveform on pin 5 of U205. Scope, center trace on reference, dc coupling, 2v/div and 10us.

 

[cajones65]

I will do that this afternoon, when I get home. Thanks

 

[cajones65]

Here is the waveform Perry

 

[Perry Babin]

Are you sure you were on the right point? I don't think the amplitude would have been more than about ±5v.