PPI 2150 AM Dead! Need help or good repair person!

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Hi all,

I would've emailed a couple local people about this, but can't since I"m a new member here. Tried to IM TO-3 through Yahoo Messenger since he's here in Phoenix, but haven't heard back. So, I'm posting here hoping to find some help with my dead PPI 2150 AM amp. I just finished reinstalling the system in my Cherokee, after not having a working deck for a while, and have no idea why the amp doesn't power up. It worked the last time my system was still running a year or so ago, but now won't even give the slightest hint of life!

I did open the amp up to solder in new power and ground wires, but I'm good at soldering and didn't see any solder bridges or potential problems before closing it up. So if someone could point me in a direction to start troubleshooting, that'd be great! Or even better, I'd like to find someone who's good with old-school PPI amps to repair it for me. :D I'm a bit hesitant about sending it out to someone I don't know though, which is why I'd prefer finding someone local, here in Phoenix (where PPI used to be).

Thanks in advance for any helpful replies!

Peter
 
Sweet! Thanks for the info. I don't suppose you know the name of the store, do you? Or is it just that obvious to find across from Taco Hell? Gonna head up there later today and see if he's open on Saturdays. If I had a name of the store, I could look up the number and save myself a trip, though...:clown:

Anyhoo...thanks again for the info. If not today, I'll definitely be up there on Monday.

Pyro
 
How long ago did you PM me? I have not seen it.

PyroZona said:
Hi all,

I would've emailed a couple local people about this, but can't since I"m a new member here. Tried to IM TO-3 through Yahoo Messenger since he's here in Phoenix, but haven't heard back. So, I'm posting here hoping to find some help with my dead PPI 2150 AM amp. I just finished reinstalling the system in my Cherokee, after not having a working deck for a while, and have no idea why the amp doesn't power up. It worked the last time my system was still running a year or so ago, but now won't even give the slightest hint of life!

I did open the amp up to solder in new power and ground wires, but I'm good at soldering and didn't see any solder bridges or potential problems before closing it up. So if someone could point me in a direction to start troubleshooting, that'd be great! Or even better, I'd like to find someone who's good with old-school PPI amps to repair it for me. :D I'm a bit hesitant about sending it out to someone I don't know though, which is why I'd prefer finding someone local, here in Phoenix (where PPI used to be).

Thanks in advance for any helpful replies!

Peter
 
Hi TO - 3,

Didn't PM you, I sent you an IM at your Yahoo Messenger ID that you have listed in your profile. No biggie. I took my amp over to Tran, as suggested by boxcustom above. Tran said he'd have it ready for me by 5 pm. tomorrow, for a max cost of $75...which sounds good to me!

However...if, for some reason, it still has problems, I'll be back up here looking for you, TO - 3. ;)

Pyro
 
YAY!! I have TUNES again!!

Update: to boxcustom - Thank you SOOOO much for referring me to Tran!!! He's good and he's definitely fast. Took my amp to him Monday afternoon and picked it up working this afternoon. Lickety-split! He even kept to his estimated repair price...which is good business. Needless to say...

I HAVE TUNES IN MY JEEP ONCE AGAIN!!!

After about a four year hiatus with no deck (and hence, no tunes), I can finally once again set off multiple cheap car alarms in parking lots and garages!! :devilr:

Need to do some system tuning and maybe box re-construction, but I at least have the old-school, balanced, clean and full PPI sound that I've been missing for way too long. :D

Thanks again for the help. I'll definitely be frequenting this forum from now on.

Pyro
 
Can someone post a contact number for Tran or the mailing address? I live in TX but I want to get a similar amp repaired. The fuse at the amp blows immediately when it turns on. I'd like to find out if Tran would be willing to repair it and ship it back.

Thanks!
Brian
 
babarche said:
Can someone post a contact number for Tran or the mailing address? I live in TX but I want to get a similar amp repaired. The fuse at the amp blows immediately when it turns on. I'd like to find out if Tran would be willing to repair it and ship it back.


Hope I'm not too late with this follow-up, but I'd suggest looking for another repair person if I were you. I just returned from picking my amp up from Tran...for the THIRD time!! After he "fixed" it the first time, the amp ran ok for almost a month...although it never really sounded as good as i remember it sounding originally. Luckily I still had my repair receipt that had a 30-day warranty written on it. So after taking it back to Tran the second time, I wired it back up and started playing it at a low volume, only to have it last a whopping 3 or 4 minutes, then POP....SNAP.........SMOOOOOOOOOKE. Back to Tran again. After having it for 3 days this time, Tran tells me that my amp won't be able to push the 2 DVC 12's that I had been running for the past 10-12 years. He pointed to the rated specs printed on the top of the amp, saying "150 watt per channel only...no more!"...essentially telling me that running the amp at 2 ohms stereo was not possible without killing it. Not acceptable as far as I'm concerned.

Then, when I went to pick up my amp today, Tran tells me that he replaced lots of things in the power supply and amplification sections, and that I can now safely run it "...at 4 ohm, at 2 ohm - whateva you wan...just no over 150 watt per channel". I just nodded, smiled, thanked him and brought the amp home...straight to my work table. After removing the drywall/sheetmetal screws :bigeyes: that Tran had used to attach the bottom cover plate (thankfully, he did include the original 6-32 machine screws that he, for reasons I'm unaware of, had replaced), I found both banks of fets/transistors now had strips of foam rubber adhered to them and strips of sheet metal had been laid over them...so that the bottom cover could press down harder on the foam-covered banks, according to Tran. WTF!??!!?! I can also tell exactly which parts were replaced due to the extremely sloppy soldering job.

Needless to say, I was appauled. I even grabbed my digital camera and took some shots of Tran's work (I'll try and post 'em if anyone wants) before getting my soldering station ready to clean things up and re-apply a layer of thermal grease, since there is much less of that in there now than before I took it to Tran.

My question now is for TO - 3...Can you help me make sure my amp has the right parts in it so that it'll comfortably run a 2 ohm stereo load??? I realize I'm asking a lot, but if you (or someone who really knows the old AM series PPI's) could tell me what fets/transistors should be where, I'll feel much more confident about installing this once-fabulous amp back into my system. As I said above, I can post pics if that would help.

Thanks in advance,

Pyro
 
Before you clean it up and reassemble it, reinstall the original screws in the bottom cover and make sure they can be tightened. If the holes are stripped so the screws can't be tightened, let me know.

The amp may have an intermittent problem like an intermittently shorted transformer. Sometimes it's difficult to find and may not be apparent even if you check for it.

I'd like to see the photos but I'd prefer that you zip them at full resolution and email them to me if you don't mind.

babin_perry@yahoo.com
 
Wow, that was fast...thanks Perry!

Pics are zipped and on the way to you.

One odd thing I noticed about the amp each time I brought it back from Tran's shop is that the power & ground wires are hot (i.e. - have current in them) and will spark when I wire them back up to my power and ground blocks...or if they're touched together. Am I incorrect in thinking that really shouldn't happen?

Thanks again for your help,

Pyro
 
The filter capacitors will remain charged until they're discharged by some means. They will eventually discharge internally due to leakage (normal) or possibly through some of the circuitry. If you touch the wires together before something else discharges them, you will get a spark. For amplifiers that have wire leads for power and ground, I generally touch them together to discharge the caps. When I forget, I know it because the owner calls back freaked out/concerned because the amp made a spark while they were carrying it.

It appears that he didn't clean out the old compound. I'd suggest that you remove all of the old compound from the heatsink, the transistors and the insulators and reapply new compound. If you use a solvent like acetone, be careful. Many of the PPI finishes (powdercoating) are damaged by acetone.

When you reapply the compound, you don't need much. You only want to apply enough so that a tiny bit is displaced all along the perimeter of the transistor (see attached) when clamping pressure is applied.

Remove the rubber tape and metal strips he used. If the fingers are weak, pull them out so that they're parallel with the bottom of the cover. That will apply enough pressure when the cover is replaced.


Did you check to see if the screw holes were stripped. This is very common and must be repaired before the new compound is applied.
 

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Perry Babin said:
...I generally touch them together to discharge the caps. When I forget, I know it because the owner calls back freaked out/concerned because the amp made a spark while they were carrying it.

:rolleyes: LOL...sounds familiar.

Did you check to see if the screw holes were stripped. This is very common and must be repaired before the new compound is applied.

Yes, that was one of the first things I did. I'm pretty sure I got all of the holes back to a point where they'll provide sufficient grip for the original screws. Luckily I just happened to have a 6-32 tap in my mess of tools. Should be ok.

I'm good on R/R'ing the compound. Just enough to transfer heat, much like one would apply between a computer processor and its heatsink, right?

Perry Babin said:
What are the gate resistor values (the resistors connected to the first leg of the power supply transistors)?

What transistors did he use as replacements?

Not sure if you're asking what they measure now, or what the color codes on them are.

As for the transistors on the power supply side, there are 4 that say MUR810 on them and then 10 (I think) that are 44N, which I think was mentioned as a possible replacement in another PPI repair thread on this forum. Are these adequate, or is there a superior replacement that I should be looking to order?

Thanks again for your help!

Pyro
 

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The gate resistors are connected to the first leg of the IRFZ44s. From the photos, they look like yellow, purple, gold, gold or yellow, purple, brown, gold. If he left the yellow purple brown gold (470 ohms), they are likely the problem (or at least part of it). They should have been changed to 100 ohms or less.

The MUR810s are the rectifiers.
 
Gotcha. Hopefully I can get those at RatShack or Fry's Electronics here in town and won't have to order 'em. I really wanna get this amp rockin' again like it should and make one last trip to Tran's...just to show him that a PPI 2150AM absolutely can push 2 DVC 12's and 4 6 1/2's in stereo at 2 ohms without turning into a small version of a Pink Floyd smoke & laser light show, LOL!

It did it without a problem for at least 12 years without a problem, and his argument of "that was then, this is now" (pretty much) just doesn't fly with me. :whazzat:

OH...one more question about the thermal grease application. Originally, sandwiched between the transistors and the heatsink were strips of clear lexan or plastic. Is there any reason I should or shouldn't be sure to put them back in when I re-apply the thermal grease? Do they serve a functional purpose, or should I not worry about 'em?

Thanks again SO MUCH for all your gracious help!

Pyro
 
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