Rockford Fosgate Punch 250M2

[caraudioguy2100]

Just checking them to see if I have any shorted since all of the fosgayebamps I’ve worked on if a channel is distorted and won’t bias it’s usually a and transistor that’s bad .

And i’m ohming then out to see if I get any low readings

 

[Perry Babin]

At a most basic level, transistors can be shorted, open or leaky.

You have to check for all. Open/shorted are best checked on diode-check. Leakage checks are done on ohms.

 

[caraudioguy2100]

Is D305 and 306 the same diode or is 305 an 1n4148 ?

 

[Perry Babin]

MMBD914LT3 from a different amp so that's likely the original. The MMBD4148 is essentially the same.

 

[caraudioguy2100]

I replaced all of the transistors and diodes in the channel 300 series parts .

I still bet very distorted audio . At least I got the channel to bias .

Any ideas on what to check since the audio is still very distorted

 

[Perry Babin]

Post a photo of the distorted waveform.

 

[caraudioguy2100]

The scope will lock on bit when trying to take a pic with my phone o only get part of the waveform.

The top edge of the waveform is squared

 

[Perry Babin]

What frequency are you using?

 

[caraudioguy2100]

250hz is where the wave form starts to distort at 100hz the wave form looks perfectly fine

 

[Perry Babin]

Is the crossover set to flat/off?

 

[caraudioguy2100]

With the crossover switch set to bypass I bet a perfect sone wave no matter the frequency . Only when the cross over switch is set to on is when I get the problem

 

[Perry Babin]

What about with a load?

 

[caraudioguy2100]

I’m going back through the channel now checking resistors ect .

 

[Perry Babin]

Did you see post 32?

 

[caraudioguy2100]

It is sill fine with a load until I get up to around the 250hz range then the waveform is bad again

 

[Perry Babin]

Even with the crossover set flat?

It would save a lot of time if you posted more than the absolute minimum possible.

 

[caraudioguy2100]

I can’t think today .

In the schematic it says D308 is a MMBZ5231

D307 it just says SS-803SM

Does the mean D307 is also a 5231?

 

[Perry Babin]

Rockford Fosgate Punch 250M2

 

[caraudioguy2100]

I understand that the 4148 is the same as the 914 .

But the original diode that’s in this amp is a 5231 marked 8F so is the 4158 pretty much the same as that also ?

If not that’s why i’m asking what the SS number is on the schematic is for

 

[Perry Babin]

The components in the top half and the bottom half of this part of the circuit are the same. The diodes linked by the arrows are the same.

What am I missing?