Rockford Fosgate Punch 400a4

[Perry Babin]

Remove Q408. Do you lose the DC?

Check the 9540 that you removed. Is it leaking from the gate to either of the other legs? It should read OL on ohms from the gate to either of the other legs.

 

[seankane]

Remove Q408. Do you lose the DC?

Check the 9540 that you removed. Is it leaking from the gate to either of the other legs? It should read OL on ohms from the gate to either of the other legs.

The dc goes away when Q408 is removed. I cant check the 9540 I removed, pulled it apart. Bad habbit should stop doing that I guess. Shall I replace the 540 while Im at it?

 

[seankane]

Q408 is an A56

 

[seankane]

The 540 I removed was leaking terribly alot of resistance on both legs.

 

[Perry Babin]

According to the diagram, Q408 is an A06. Q409 is an A56. Compare to other channels.

 

[seankane]

You are correct, whoever repaired installed wrong part. I will install A06 and replace IRF540 and post my result.

 

[seankane]

Installed A06 dc returned to terminal, reinstalled Irf 540 and current draw returned. Checked 540 for leakage before soldering to MESHA and it had none. I dont get it????

 

[Perry Babin]

Is it still positive voltage?

Is there any DC across R430 or R431?

Is Q409 an MPSA56?

 

[seankane]

Is it still positive voltage?

Is there any DC across R430 or R431?

Is Q409 an MPSA56?

Voltage on terminal is + (YES)

R430: 0.000vdc

R431: 0.000vdc

Q409 IS AN MPSA56

 

[seankane]

Q410 IRF 540 is getting super hot, super fast again, and as I said had NO leakage before soldering to MESHA.

 

[Perry Babin]

Is Q405 shorted?

 

[seankane]

Is Q405 shorted?

Replaced Q405 with MMBT 3906 original was marked 2A

Same result, current draw and IRF540 (Q410) gets hot fast

Funny it almost sounds like Q410 is making the clicking noise then begins to heat very fast. Am I missing something???

 

[Perry Babin]

It's heating quickly because the amp is trying to pull the DC down but it can't.

Did you (or anyone else) replace any components other than the ones listed in this thread?

Are the 0.1 ohm resistors within tolerance?

 

[seankane]

It's heating quickly because the amp is trying to pull the DC down but it can't.

Did you (or anyone else) replace any components other than the ones listed in this thread?

Are the 0.1 ohm resistors within tolerance?

Yes the emitters are within tolerance

Parts I replaced in this channel are as follows:

Q310
Q311
Q410
Q411
Q401
Q403
Q405
Q408
Q409

Other than the Q408 originally having the MPSA56 when it should have had the A06 thats the only thing someone else has replaced along with whoever put the IRF540N and IRF9540N in the output fet locations.

 

[Perry Babin]

Q401 and Q402 must match. If you didn't replace it, replace both Q401 and Q401. If you replaced Q401 and have transistors from the same batch, replace Q402.

The same goes for Q403 and Q404.

 

[seankane]

Q401 and Q402 must match. If you didn't replace it, replace both Q401 and Q401. If you replaced Q401 and have transistors from the same batch, replace Q402.

The same goes for Q403 and Q404.

I made a mistake in my parts list.

I replaced D401 not Q401, sorry for the confusion. Its been a long night. I repaired 4 other amps tonight, my brain needs a rest.

 

[seankane]

I will replace Q404 tomorrow and get back to you, need some sleep. Thanks for all your help Perry, I really appreciate it. Most repairs are simple with Rockford amps but these butt kicking ones I could not do without you. Thank you.............TTYS

 

[seankane]

Ok I am back let me know when you are ready.

 

[seankane]

It's heating quickly because the amp is trying to pull the DC down but it can't.

Did you (or anyone else) replace any components other than the ones listed in this thread?

Are the 0.1 ohm resistors within tolerance?

Not sure if this is a valid question, but what components are "in charge of pulling the dc down" ? You think I may have an open resistor somewhere or a blown BJT ?

 

[seankane]

Maybe one of the emitters is testing ok on the meter but under a load is failing? I have hundreds of them, I could change them just for the heck of it.