Rockford Fosgate Power 5006

[barber02]

I’m not sure about the identity of this Fosgate amp. The back cover says power 5006, the board says bd15001. PC3065 J

Anywho. I am wondering what D19 was. Kinda hard to identify it in it’s current state. Was also kinda curious as to what you think might have caused it to fail.

Picture is attached. D19 is located in between the two heat sinks.

Thanks,

David

 

[barber02]

Here is another angle at it. I take it, that the gum drop cap on the right is bad as well. The casing is cracked.

The power supply has drive but the red protection LED is dimly lit and there is no audio output.

David

 

[Perry Babin]

That's a diode that connects between the RCA shield and the primary ground. It fails when voltage shorts to the RCA shields.

 

[barber02]

Thanks Perry. Have you ever seen one get naked like that? Weird.

David

 

[Perry Babin]

Yes. They go almost like a firecracker when a high-current source contacts the shields.

 

[barber02]

Wow. Almost wish I could have seen that. Blew the casing right off of it.

Thanks again.

 

[barber02]

I replaced the two bad components and fired up the amp. I still have a red protection LED on.

I have 80vdc at the +HV test point and 0.00vdc at the -HV test point.

IC U14 is UC3526N. I have zero experience with this chip.
The pin voltages are as follows:

1. 5v +E
2. 4.21v -E
3. 4.24v Comp
4. 4.72v SS
5. 4.99v Reset
6. 0.00v. -CS. Connected to ground
7. 0.00v. +CS Connected to ground
8. 4.46v. SD
9. 3.70v. RT
10. 1.94v. CT
11. 0.00v. RD
12. 4.62v. SYNC
13. 7.50v. Out A
14. 17.42v. VC
15. 0.00v. GND
16. 7.50v. Out B
17. 17.46v. VCC
18. 5.01v. Vert

I’m not sure what to make of it. I would be thankful for any guidance.

David

 

[Perry Babin]

That IC is functioning normally. You have rail voltage.

U21 and beyond that IC is the part of the circuit you need to check.

Go to the BD1500 page.
repair_tutorial/miscellaneousstuff/rockford/punchbd1500/repairnotesrockfordbdamplifiers.htm

and search for:
waveforms on the SG3526 power supply driver IC

Open the graphic in a new widow. Maximize it and zoom in on all of the waveforms. You'll find them to be about what you have. The scope is set to DC coupling so you can see the DC offset for pins with no waveforms.

 

[barber02]

Ok. Thanks Perry.

David

 

[barber02]

Ok. It turns out that U21 was the problem. After replacing I got oscillation in the output section.

Then I discovered that the RCA jacks have an intermittent connection to the board so I’ll work on that next and run some tests tomorrow.

Thanks for the help Perry. I thought you had a section in your tutorial on these Rockford amps. I remember seeing it when I went through the tutorial when I read it initially and I even checked the misc stuff folder but didn’t see it in there for some reason. Thanks for directing me to it again. It was very helpful.

David

 

[Perry Babin]

Section 11 on the Audio Troubleshooting page will show you a temporary fix if the ground is broken.

Ask if you need help finding something.