Precision Power Incorporated A600.2 Repair


PPI A600.2 Amplifier



This is a clean little old school PPI amp. Good sound, draws lots of current, but doesn't necessarily put out alot of power. These amps are known more for their good sound quality I think. For the most part it's a simple Class AB design, but with a more responsive beefier power supply than most amps it's size.

UPDATE 05/2014: Sorry but we no longer service the old PPI amps. Just too old to be able to warranty the repair and/or find parts for these anymore. Try Zed Audio Corp, (google for them) they may still repair these, but most shops no longer service the old school amps because of same reasons, reliability concerns, and/or parts sourcing problems.


Click image to Enlarge the image



This is a good clean example of an old school PPI A600.2.

Even after lots of years, it is still shiny and not all scratched up.

The Art Series amps have this drawing on them, not sure what it is supposed
to mean, has a worm, 3 globes, some rocks and 2 or three triangles. I
would love to hear the story of where this drawing came from and why they
used it.

This one actually doesn't have wires coming out of it... And has a 60 amp Maxi-fuse.

The business end of it. Nice clean layout, similar to lots of newer model
amps, minus the crossovers and other nice additions over the years that
technology and ever decreasing cost of parts has brought us...

The inside of the amp, minus 1 output transistor. It was bad and was
causing the whole amp to shutdown, removed it and now amp works great!
But more work will be done to insure reliability (rather than just
replacing this one part).

Part of the power supply, really old IRFZ44's. But they still work great.

A shot of the missing output (that I removed). This is 1 channel of the
output of the amp, 10 transistors, 5 each of NPN and PNP respectively.
Old School design, small output transistors.

Power supply IC, SG3525AN, protect circuits, mute circuit, and audio
driver boards, the brains of the amp basically. Same exact thing in most
all older model PPI amps.

The bad output transistor just disappeared didn't it? It takes knowledge
and good equipment to narrow down to the exact bad part like we did here.
Without even powering up the amp we found the bad part that fast.

One side of the power supply, notice the excessive heatsink compound. A
common problem with older PPI amps.

The other side of the power supply.

Here you can see where the heatsink compound is thick and so old that it
is beggining to harden and crack. Not good for the amp, it won't transfer
heat from the transistors and FETs very well.

Lots of amps claim to be made in the USA, I think these actually were.
Most that claim they are are full of you know what, they are made in Korea,
I don't care what it says on the amp, or what the manufacturer tells you.

The mainboard removed from the heatsink.

The bottom of the mainboard, lots of yucky white heatsink compound. Got
to clean it all up and replace it.

Despite the fact that this amp only had 1 bad output transistor, in a group
of only five parallel transistors, I talked the owner into replacing them
all with newer parts that are rated for higher voltage. Won't make the amp
put out any more power, but since he was planning on running it bridged,
it needed all new matched outputs to be reliable.

The bottom after removal, all the old parts cleanly removed.

20 new output transistors. These are BiPolar Junction Transistors, or
"BJT's". They are not Mosfets. The only thing Mosfet in this amp are the
power supply mosfets. The outputs are all BJT's. The parts that remain
on the board are Rectifier Diodes, driver transistors and voltage regulator
pass transistors. All output transistors will be replaced with matching
parts.

A closeup of the new parts, they are 1 step up from the original transistors
They put out the same power as the originals, but will handle a higher rail
voltage.

All new parts installed.

Time to take care of the heatsink compound problem before re-assembly.

Here you can see it's pretty nasty.

Hard to tell in these pics, but there are clear Mica insulators here,
mixed in with the gobs of heatsink compound.

I attempted to clean them up, but too much trouble, the compound has
gotten very dry and hard.

All of it is cleaned from the heatsink itself.

New insulating material (Kapton Tape) is layed down on the heatsink, and a
light coat of heatsink compound (clear)is applied.

Mainboard is placed back into the heatsink.

Endplate and bottom cover are placed back on the amp.

Re-assembled and testing.

Green light means go!

How to properly package your amp. Wrap the whole amp in bubble wrap 1-3
times depending on how heavy it is. Then add extra bubble wrap on the ends
of the amp, 1-2 layers.

If you use peanuts the box should be almost full of peanuts, it must be
packed tight. For heavy amps, do not use peanuts at all, just use bubble
wrap and foam.

When you put the amp in the box, it should fit tight like this. If it
doesn't it will get banged up.

If it doesn't fit tight, to where the amp rattles around in the box when you
shake it, the weight will shift when the UPS guy (of whoever) goes to pick
it up and they usually only use one arm because they are in a hurry and
when the weight shifts they will drop your box. Not good at all for your amp.

Tape it up good, use a black marker or something like it if there are old
labels on the box you are going to use. To eliminate confusion of multiples
labels, or your amp delivery may get delayed or sent to the wrong address.

This is my big Marks-A-Lot. It works great, they are about $2. Makes
marking out old labels a breeze. It is a huge marker, the pen laying next
to it is acutally kind of a big pen.



This amp was a fairly easy repair, a classic amp. Good clean example of an older model PPI amp, pretty much in good enough shape for a collector.