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Old 20th January 2012, 03:13 AM   #11
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I see a few sources for Z34.. I guess I will go with those..

Also need to go through the link Perry sent to see if I need other parts too.. (too tired to do it now, it is past my bed time.. LOL!)

Thanks guys!
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Old 20th January 2012, 03:32 PM   #12
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Had time to read through the the link Perry sent out. Very comprehensive, nice work.

I do have experience in working with electronics, testing components, using an oscilloscope (I have a digital storage scope), so I think I have what I need to do this myself. I have repaired audio amplifiers before, so although I may be rusty- I think I got the basics- Ignoring the fact that it is my own DUMB fault this amplifier is broken (running it with the cover off, so the heat sink did not have good contact).

I can't be the first idiot to do this, right? At this point, I'd like to place an order for the parts I will likely need. Without a schematic, frankly, I was looking for someone with experience on this particular model to suggest what else I may have blown out by running it without the cover... So I only have to place one order for parts.

10 of the Z34's will cost me only $3. But it is $8 to ship! So, if I need more parts I'd like to get them to begin with.

Thanks again.
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Old 20th January 2012, 04:09 PM   #13
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Post a picture of the amp board. Most of us go by that when the amp is as old as yours just to jog our memory a bit about what it looks like. I have not seen one of these for at least 10 years now myself.
For what its worth always check the fet gate drivers if that amp has them. And also ohm out all your output transistors to make sure you won't power the amp back up into a dead short. Also check the rectifiers near the toroid they like to go shorted as I remember especially when you find no bad output transistors...

Other then that these amps were very simple to repair in most cases and I am thinking you will likely find it to be the same if you follow the few steps above and Perry's excellent tutorial....
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Old 20th January 2012, 04:24 PM   #14
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If it is cheap enough, maybe I should just order all of the parts that would likely blow out??

Even if I bought replacements for all of the TO220 parts on the heat sink, what other parts may have gone with it?

I don't mind the shotgun approach, if the cost is low enough.
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Old 20th January 2012, 05:07 PM   #15
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I advocate shotgunning sometimes myself but only when its just plain cheaper to completely rebuild, then second guess and waste time testing individual parts, and when its financially prudent.

In your case though I would test and check prior to replacement of the power supply, and not shot gun because you might create an unknown situation where you replaced everything and now it has a new set of symptoms. I have seen this enough over the years and if I were you I would stick with getting it running and then test some of the signal thru put to judge if you need anymore intervention.

Build a set of clamps out of some plain old bar stock or tube steel to clamp the amp together while you operate on it. Some simple bar stock with holes drilled in the right place to accept hold down screws will do fine. Just make sure it is ridge and NOT flexing as you tighten it down on the transistors. The screws are 9/16 as i recall and just use some plain hardware on hand to clamp the bars and transistors to the sink. Perry describes this in many of his posts and it makes very good sense. I don't work on any PPI amps without a set of home made clamps...

A: Tests would include DC offset on the speaker terminals < this helps to decide if you have left leaky components in the channel under test. High DC output usually means there are weakened or damaged components left in the channel then you find them and replace them < very time consuming

B: Bias Idle voltage drop across each emitter resistor< this decides if all the output will current share evenly. If the V drop across each emitter is different by more then say 10% you looking at possibly having a early failure of the output transistors due to uneven current sharing. < the higher reading devices will likely be the point of failure as they are generally weakened inside.

These and just a few simple tests you can do to verify how well your amp is doing before you make a decision to shot gun / intervene anymore or not. Replacing perfectly good working components will gain you next to nothing except expense, time sink, and if other symptoms arise a huge headache trying to figure out where it all went wrong....

As I recall your already on the big three for this type of amp, 1: the fets in the supply, 2: the diodes near the toroid, 3; and the outputs. These were the big three for this series of amp as I remember. Oh and please do not use replacement parts try to find original part numbers. Generic replacement parts are often very unsuitable for the demands this amp will see...
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Old 20th January 2012, 05:16 PM   #16
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Well, I am pretty sure all of the P25N05's are dead.. I don't think I can do much else until I replace those. At this point, it was more about ordering everything I will need instead of paying 2X the shipping (since the shipping is more expensive than the parts themselves!).
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Old 20th January 2012, 05:26 PM   #17
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Oh I forgot the gain pots on these are usually trashed < scratchy and have fall outs in their spans> A suitable replacement that fits the PCB might be a bit tough to locate but a worthwhile investment IMHO...

I did dozens of these years ago, along with Fosgate's and Orion's. It was a long time ago but I doubt they have improved with age lol...
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Old 20th January 2012, 05:42 PM   #18
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Those gain pots always suck, on all amplifiers. If there is a replacement, I'd do it.. But don't want to spend too much effort on trying to find one. I have the same issue with lots of "external" pars on Car Amplifiers. I am looking for the wire harness for a HiFonics amplifier. Also have a Infinity RSA250 in the stack that has a broken speaker terminal. And, my favorite amplifier a Harman Kardon CA260 with a broken RCA input. I have been unable to find suitable replacement parts. If the time comes that I want to use this equipment but have not found anything, I will just modify them to as needed.

A few sound stream units in the collection too. Most of them I have picked up broken, and fixed. They seem to be the least damaged by physical abuse.

I was reading about gluing the transformer on these PPI units but can't figure out what the purpose of it is?

I will post photos of the board when I get home tonight. Hopefully Perry with jump back on this t some point, he seems to have a lot of experience with this vintage PPI item.
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Old 20th January 2012, 06:52 PM   #19
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I didn't see any questions that were not answered.

I don't know what you mean by gluing the transformers.

The large white pots can be removed, disassembled, cleaned and reassembled. #2-64 screws can be used to close them back up. You'll have to drill out the holes with a #49 drill bit.
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Old 20th January 2012, 07:08 PM   #20
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Thanks Perry. I will try to clean mine out.

I guess I was hoping that you had a better idea of what parts I should order based on how this unit failed (running with the cover off).

Thanks again.
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