Rockford fosgate power 500bd in protect

[chipper]

Hello everyone I just in for my own collection a rockford fosgate power 500bd. It's in protect (red light on) I checked the output fets (IRF540 & IRF9540) they all test out fine no shorts. If I can get a lil more detailed help on this one that would be cool. I've never had BD series power amp nor have I ever touched one. This is my first time.

This is PC-3066-F board.

 

[Perry Babin]

U21 is likely defective. Post the voltage on all 8 pins.

 

[chipper]

Here's a pic

 

[chipper]

U21 is likely defective. Post the voltage on all 8 pins.

I can't do any voltage testing right now until my dad gets home so I can use his meter. Is Q15 & Q16 suppose to run a little above warm?

May I ask if the outputs aren't shorted then what is making this amp go into protect? And what does U21 do or control?? Thanks

 

[seankane]

Dont have schematic in front of me but Q15 and Q16 are regulators and yes they run hot...totally normal.

I always check the solder joints on those as well since they run so hot.

If U21 is defective the amp will remain in protect. Take one out of your parts boards and throw it in since its your own amp. You can always order new ones and put it in later??

Its a TL072C pretty common op-amp.

 

[chipper]

Dont have schematic in front of me but Q15 and Q16 are regulators and yes they run hot...totally normal.

I always check the solder joints on those as well since they run so hot.

If U21 is defective the amp will remain in protect. Take one out of your parts boards and throw it in since its your own amp. You can always order new ones and put it in later??

Its a TL072C pretty common op-amp.

Alright just thought maybe those where the culprits.

I have a couple parts boards that have those if it works then ill order new ones for extra reliability. I just have to buy some more desolder braid and see what happens.

 

[chipper]

Btw what do you do or how do you remove those small ICs? It's a fairly small chip.

 

[seankane]

You need to purchase chipquik. The stuff is amazing at removing various components without damaging vias or solder pads.

Perry turned me onto it. You should also think of investing a hot air
rework station. I have not yet, but I do have a heat gun used for removing.

 

[seankane]

If you dont have either, use solder.

Heat both sides of the op-amp and apply solder generously back and forth till the chip loosens.

You can suck any extra off with a desoldering tool.

 

[Perry Babin]

I resisted buying a hot air station for a long time due to the limited need and the cost. When I found that they've dropped to $60, I picked one up. I rarely use it (even for SMD components) but it occasionally comes in handy.

 

[chipper]

What does U21 do or control?

 

[Perry Babin]

It latches over-current protection and provides the turn-on delay.

Did you measure the voltage? The voltage on the op-amp can tell you whether it's likely to be defective or not.

 

[chipper]

It was that IC I replaced it from a parts board. Amp will turn on protect will flash for a sec then resume to normal. I played it for 2 hours in the car full tilt didn't skip a beat. I'm going to order a few of these ICs new for mor reliability.

Btw why is the transformer so noisy? Loud hum, when I touch the transformer it stops.

And what is 'subsonic filter' and 0 - 180 degree phase? And is this a class D? Instead of 'BD'?

 

[seankane]

It was that IC I replaced it from a parts board. Amp will turn on protect will flash for a sec then resume to normal. I played it for 2 hours in the car full tilt didn't skip a beat. I'm going to order a few of these ICs new for mor reliability.

Btw why is the transformer so noisy? Loud hum, when I touch the transformer it stops.

And what is 'subsonic filter' and 0 - 180 degree phase? And is this a class D? Instead of 'BD'?

The BD transformers are known to whine or hum sometimes. I usually use a silicone or an epoxy on the transformer. I twist it first to get the noise quiet, then apply the epoxy.

If you do this be 100% sure what ever you use is completely dry before powering up the amp.

The sub sonics switch filters out tones unable to be heard by the human ear, thus focusing the amp on playing tones the ear can hear, thus making a little more efficiency.......I think.....lol

The 180 phase is for phasing the subwoofer. It would be great if you were running an inverted sub. Never really used it and dont know alot about it.

I understand the use of the phase warp as it is used for subs that are firing from different distances so you hear them all at once and not the closest one first.....I think.....lol

This is a class D amp not sure why its called the BD. Perry might know.

 

[Perry Babin]

Generally, if touching the windings stops the noise, you can move the windings to the side a bit and that will solve the problem. If you apply anything to the windings, apply it only where necessary. Don't apply it to the entire transformer. There's a good chance that nothing needs to be done to the transformer, especially if the amp will not be installed in the passenger compartment of the vehicle.

The phase switch is used when bridging two BD amps. One amp is set to 0°. The other is set to 180°. Setting it to 180° inverts the signal.

The BD is a variation of the Class D. Most class D amps are class AD. Instead of using both positive and negative rail voltage, it uses a single rail that driven up (to act as the positive rail) or down (to act as the negative rail) as needed by the output transistors. If you really want to know more about them, read the following patent information.
Click HERE.

The subsonic filter blocks inaudible frequencies so that the amp won't waste energy trying to reproduce them.