RF Power 1001bd Dead... but how??

[jlind54]

I've had this amp for a while, hasn't been used in a while because I pulled it out of a car I traded in. Its been sitting on a shelf collecting dust. The amp worked perfectly when it was removed from the car. However looking to get back into installing some gear in my current car and was testing out amps and this one seems to magically be dead now. Was hoping to get some ideas on where to start troubleshooting.

upon hooking up to 12v source the amp has a short spike of current draw (i'm guessing this is internal caps charging up)
once the remote wire is connected to 12v the amp has a current draw of .02 amps...

Its like the amp forgot how to turn on or something

any input would be great

 

[Perry Babin]

It's relatively common for amps to fail while in storage. If the protect LED is remaining on, U21 may be defective. You'd need to post the DC voltage on all legs of the IC. If you need more information to do that, let us know.

 

[jlind54]

How do I know which pin is pin one on the U21 chip? Also, protect light does not come on and the power light on the top does not come on.

 

[Perry Babin]

I've attached the layout but if the protect LED never comes on, it's probably not U21. Is the remote terminal loos where it goes into the amp?

 

[jlind54]

that was the first thing I checked, when I first got this amp it had a bad connection there so I resoldered it.

Pin1 :0v
Pin2 :0v
Pin3 :0v
Pin4 :0v
Pin5 :5.04v
Pin6 :9.80v
Pin7 :0v
Pin8 :0v

following the trace from the remote on it appears to end up at pin6. with the remote not connected there is 0v on all pins

 

[Perry Babin]

Pick any of the power supply FETs (the ones near the remote terminal). What is the DC voltage on all 3 legs. Don't let your probes slip while doing this. I'd suggest inserting a 10 amp fuse In the B+ line before measuring.

 

[jlind54]

0, 12.6 (same as battery voltage), 0

 

[Perry Babin]

DC voltage on LM339 and SG3526?

lm339
Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
Pin 9:
Pin 10:
Pin 11:
Pin 12:
Pin 13:
Pin 14:


3526
Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
Pin 9:
Pin 10:
Pin 11:
Pin 12:
Pin 13:
Pin 14:
Pin 15:
Pin 16:
Pin 17:
Pin 18:

 

[jlind54]

Hey just wanted to tell you thanks for you knowledge and time before we go much further!

 

[jlind54]

does the lm339 refer to the chip in U13 and the 3526 U14?

 

[Perry Babin]

Yes but both should have those numbers printed on their faces.

 

[jlind54]

DC voltage on LM339 and SG3526?

lm339
Pin 1: 0
Pin 2: 0
Pin 3: 17.5
Pin 4: .08
Pin 5: 1.73
Pin 6: 5.72
Pin 7: 5.04
Pin 8: .01
Pin 9: .01
Pin 10: 5.04
Pin 11: 10.79
Pin 12: 0
Pin 13: 0
Pin 14: 0


3526
Pin 1: 4.99
Pin 2: 0
Pin 3: .91
Pin 4: .24
Pin 5: 4.83
Pin 6: 0
Pin 7: 0
Pin 8: 0
Pin 9: 3.68
Pin 10: 2.12
Pin 11: 0
Pin 12: 4.94
Pin 13: 0
Pin 14: 17.6
Pin 15: 0
Pin 16: 0
Pin 17: 17.6
Pin 18: 5.04

 

[jlind54]

The chip numbers were pretty much the same, the LM339 was a LM339D and SG3526 was a UC3526N not sure if that will make much of a difference or not.

 

[Perry Babin]

Are you running the amp off of a battery charger?

The voltage is too high causing it to shut down.

You also should have had high voltage on the center legs of the power supply FETs.

 

[jlind54]

it got dark outside so I came in away from the car battery so yes I hooked up the charger, didn't figure it would hurt it any worse at this point. the voltage at the amp terminals is 15.4. Should I hook back up to the battery and take the measurements again?

 

[jlind54]

ok back outside and took some readings hooked up to the battery things have changed around a little bit
m339
Pin 1: 4.53
Pin 2: 4.53
Pin 3: 11.84
Pin 4: .06
Pin 5: 2.34
Pin 6: 3.93
Pin 7: 5.04
Pin 8: .01
Pin 9: .01
Pin 10: 5.04
Pin 11: 7.42
Pin 12: 0
Pin 13: 4.53
Pin 14: 0


3526
Pin 1: 4.99
Pin 2: 0
Pin 3: .91
Pin 4: .24
Pin 5: 4.83
Pin 6: 0
Pin 7: 0
Pin 8: 4.53
Pin 9: 3.68
Pin 10: 2.12
Pin 11: 0
Pin 12: 4.94
Pin 13: 0
Pin 14: 17.6
Pin 15: 0
Pin 16: 0
Pin 17: 11.84
Pin 18: 5.04

 

[Perry Babin]

With no power applied, what's the resistance from pin 4 to pin 15?

Some of the voltages are better but pin 14 is still high. Where are you getting the remote voltage and where are you getting the B+ voltage? They should be about the same but are significantly different.

 

[jlind54]

sorry, pin 14 should have been 11.84 like pin 17. The remote wire is jumped over to the B+ terminal. B+ is coming off the battery through a 10 amp fuse as suggested. for the resistance if my multimeter is set to 2000 it reads 584 with the neg. probe on pin 4 and positive on pin 15.
However if i hook it the other way, I have to set the multimeter to 2000k and it reads 1660 and keeps climbing.

 

[Perry Babin]

It appears that the 3526 is defective. I don't see anything preventing the soft-start capacitor from charging. It doesn't appear to be shorted. That would leave the 3526.

Connecting a jumper from pin 18 to pin 4 'may' force the IC to function but you'd have to have a relatively small fuse (15 amp) in the B+ line before applying power to help prevent serious damage if the IC doesn't produce the right output.

 

[jlind54]

I will give it a try and report back shortly, you have been great help!