Rockford Fosgate Punch 400.4

[S Merlington]

This amp has a few issues with it..

The left rear channel plays clean audio

The right rear channel plays clean audio but is very low output

Both these channels play but the outputs and mesha board get to hot to touch after a min ..

Any ideas on what to check ?

The front left channel plays clean audio

Right front channel has no output

Since both right channels have no audio or low audio im assuming this may be a dirty switch

Wondering why he rear channels all the outputs and mesha board get vry hot after a min

 

[Perry Babin]

Is the bias set too high?

 

[S Merlington]

Bias pots are fully counterclockwise ..

Amp idles around 1amp

 

[Perry Babin]

Where is the hot spot on the back of the insulator?

 

[S Merlington]

The whole mesha board gets to hot to touch the entire length of it

 

[Perry Babin]

Are you telling me that if you power it up cold that the entire board heats up uniformly along it's entire length with no centralized hot spot?

 

[S Merlington]

Yes

 

[S Merlington]

After replacing some transistors and resistors now I can tell where the hot spot is coming from ..

The mesha board starts getting hot under Q310 -IRF540

 

[Perry Babin]

Do you find anything other than infinite resistance between the back of the MEHSA strip and any of the metal tabs on any component on the strip?

 

[S Merlington]

Meter stays at OL ..

I've replaced the bias transistors on that channel also replaced Q316,315,317,312,314..

Problem is still there

 

[Perry Babin]

Does that channel produce clean audio now?

 

[S Merlington]

Yes it produces clean audio but the outputs still heat up
Quickly and get to hot to touch .

 

[Perry Babin]

What's the board number?

 

[S Merlington]

Board # PC-3084A

 

[Perry Babin]

Measure the DC voltage across the two 0.1 ohm source resistors in that channel. Post the voltage for each one.

 

[S Merlington]

Both of them are at 0.18 measured directly across them
..

 

[Perry Babin]

Short the bias transistor collector to emitter. Does that stop the heating?

 

[S Merlington]

Are you talking about the 2A Q305 or the leaded transistor

 

[Perry Babin]

Q307 is the bias transistor.

 

[S Merlington]

Shorting the bias transistor emitter to collector legs 1 to 3

The outputs still heat up no change