PPI 2150 died.. :(

[Marc03]

I have an old school PPI 2150 amplifier. Black case. board says "Rev C"

Anyone have a Schematic for it?

It was playing, but would get noise once in a while. I thought it was a bad gain control, or maybe loose RCA connectors. I opened it up, and wiggled everything while it was playing. Everything seemed OK, so I turned up the volume (that is when I usually hear the noise), and the magic smoke came out!

Nothing looks burned, so I am looking for a schematic so I can figure out what I blew up.

Thanks.

[Perry Babin]

If this amp uses the bottom cover to clamp the transistors to the heatsink, you can't operate it without the bottom cover tightly screwed down, unless you VERY carefully monitor the temperature of all of the transistors.

Which components failed? Give the circuit board designations for each one.

[Marc03]

Already realize where I screwed up.. The bottom of the case keeps all of those TO220 packages against the heat sink!!

I pulled out 2 of the P25N05, and it is for the most part a short (12 ohms from S to G, .7 Ohm from S to D and 240 Ohm from S to G, 230 Ohm from S to D).

Likely that I fried all 10 of them?

Maybe the 2N6486/2N6490 parts are still OK?

Still would love a Schematic.

[Marc03]

Thanks Perry, I saw that (heat sink) too late.. Was posting that, but I think I am being moderated right now, so my posts are delayed.

There is nothing visually obviously failed. I wanted the Schematics to help diagnose.

Strange thing is, the fuse did not blow. I would have expected it to if I cooked all of the MOSFET's.

[Marc03]

Seeing that the P25N05 is disco.. NTE has a replacement (2396), but it is way expensive (as most NTE parts are). I read in another thread that IRFZ44 is a good replacement?

Interesting that NTE lists the xref for Z44 as 2395. This is a 60V part, where the 25N05 is 50V.. More power! (grunt grunt)

Any brand better than another? buying 10 of them, cost becomes important.

Anyone use this outfit? I like the price..

IRFZ44 IRFZ44N MOSFET N-Channel 49A 55V

Newark Electronics has a few options for them.. Even a few with a 150W pd. (50A instead of 25A). Those would be less likely to pop, no?

This looks like the lowest cost in the TO220AB package from Newark;

INTERNATIONAL RECTIFIER|AUIRFZ44Z|MOSFET,N CH,55V,51A,TO220AB | Newark.com


What I am wondering is - if I blew all those MOSFET's would anything else have been taken with it? How likely is it I blew the 6486/6490's from heat too? I tested one of them with the DVM and it did the high/low thing.. so, I guess it is OK? I don't want to pull them all out if I don't have to.

Thanks for the help (and the archives of this forum).

[Marc03]

Kept reading the thread..

PPI amp (power precision) blew out

I need to replace the P25N05 MOSFET's (10 of them), and see that the Z44 or Z48 have been suggested for this purpose. Do I need to change the gate resistors too? Mine look like 650 Ohm. (Blue Green Brown).

Thanks again..

[Perry Babin]

You can use the IRFZ44s if the gate resistors are 100 ohms or less.

I haven't used Tayda but there have been some posts questioning the quality of the FETs sold there. If you're in the US, there are better options.

CLICK

It's possible that you did more damage. You can check most of the transistors in the circuit.

Read the basic amp repair page (link in sig line below).

[1moreamp]

P25N05 fets are used in the older 2150M as I recall, is that the amp your repairing??? If so it is possible to upgrade but you will likely have to also upgrade the gate resistor to make them work.
Try looking for IRFZ-34 as a replacement. PPI used those also without circuit modding the gate resistor.
Just about any 25 to 30 amp fet will work.

[Marc03]

2150M is what it says on the case.. I have no objection to replacing the resistors if that is the preferred solution. Z34, Z44, Z48... Is there any advantage to one over the other? If not, and the Z34 requires the least work, then that seems like the way to go.. no?

[1moreamp]

Z34 's were used by PPI in these very amps when the 25N05's were not available. These amps were built back when fets first hit the car audio market and parts shortages were common.
The no trouble replacement is the Z34, as I recall and the Z42,Z44,Z46, and Z48 all have lower turn on resistance and higher current handling but I don't think you will see any real benefit due the toroid design being what it is.

For me the Z34 is the best no issues choice. Simple drop in place replacement, and no need to worry about gate resistor value.