PPI A200

[S Merlington]

Outputs are defective in this amp..

The are marked

PH
BDT82

PH
BDT81

Anyone know of a good replacement for them??

 

[1moreamp]

2N6488 and 2N6491 were used by PPI after those devices became unavailable. no alterations required they just drop in and play...😉

 

[S Merlington]

Replaced the BDT82's with the 2N6491's

And replaced the BDT81's with 2N6488's

I noticed that one of the diodes on the bottom side of the board was cracked in half..

Anyone know what i can replace it with??

I have a PPI PC1400 scrap board dont know if the diodes are the same or not ??

 

[1moreamp]

can you post a pic? or maybe describe what it connects to circuitry wise? I would be guessing at best without seeing it or knowing its circuitry location to explain its use in the amp... 😉

 

[S Merlington]

I believe its part of the Bias ..

It solders underneath the board and connects between legs 2 and 3 of a MPSA06..

It also connects between the pins of JP2..

The board location is R3

PPI also covers it in about a pound of heatsink compound

 

[1moreamp]

Yeah that is what i was thinking it was. Yes its a temp sensor for the bias tracking. The only info I can find shows its as a Temperature Dependent Resistor R250 and that's on a PC1400 document I found...
So if you borrow one from another PPI amp measure and compare them with a ohm meter at room temp to see if they match resistance at the same temp with a good one from another channel. If so I would feel confident they could be interchanged without issue.
PPI like most car amp makers stuck with the same design over the years just engineering newer transistors into the amp due to availability so I am thinking they are the same for all models and you could borrow one from your other amp without much issue. But test them first to be sure...hope this helps some...

 

[S Merlington]

Not the same resistor..

The 1 in the amp measures 0.952K ohms..

Anyone know where i can get one of theese?

 

[1moreamp]

You have a PM 🙂

 

[S Merlington]

I found a resistor that will work from a scrap PPI board..

There is 2 pots in the amp 1 for each channel is that the bias or DC offset pots or does anyone know what they are being used for??

 

[1moreamp]

there should be four pots. 2 are Dc offset adjustment, and 2 are bias adjustment. The bias pots will be located near the center of each channel and the two pots off by themselves are the dc offset adjustments.....Glad you found a usable spare TDR....😉