Yes, he means the gate series resistors between the sg3525 and the FETs, which on my amp are R90-R99. I just happened across this thread while searching google for the 3525 PWM chip since I have a broken PPI 600 watt art series here (PPI-2150AM) that appears to have been made in 1992 according to date codes on parts. My doofus friend had an amp stacked on top of this one, which of course caused thermal failure. Luckily, it appears that the damage is limited to a couple very blown (plastic package melted and soot everwhere) push-pull FETs in the power supply. Everything else visually looks fine. I'm going to replace these 10 fets with some nice low-Rds units from IRF and hopefully that will do the trick. Thank goodness for academic sampling 
Did you ever get your amp working, profuse? Just curious, it's kinda fun working on these badarse old PPI amps.. I'll get a picture of mine this weekend when I have my camera handy. The board says "752162 Rev K", but I assume we have the same amp.
By the way, for those interested in how amps work, here's a great writeup about switch-mode power supplies:
http://sound.westhost.com/project89.htm
It doesn't show the audio stages but the power supply is half the battle in these 12V amps
Did you ever get your amp working, profuse? Just curious, it's kinda fun working on these badarse old PPI amps.. I'll get a picture of mine this weekend when I have my camera handy. The board says "752162 Rev K", but I assume we have the same amp.
By the way, for those interested in how amps work, here's a great writeup about switch-mode power supplies:
http://sound.westhost.com/project89.htm
It doesn't show the audio stages but the power supply is half the battle in these 12V amps
Hey TO-3, what was the reason that PPI went to 22 ohm resistors instead of the original 468 ohm parts? I don't know if you've seen it but I'm having a problem with the gate drive circuitry of my a600 after putting in new FETs and 22 ohm gate resistors. Please give me some input on that thread if you have any since I'm at a loss as to why the gate driver works fine with no FETs in place but craps out with them installed, even though they should theoretically be easier to drive than irz44n's that seem to be the standard replacement part. Thanks 
rth said:Hey TO-3, what was the reason that PPI went to 22 ohm resistors instead of the original 468 ohm parts? I don't know if you've seen it but I'm having a problem with the gate drive circuitry of my a600 after putting in new FETs and 22 ohm gate resistors. Please give me some input on that thread if you have any since I'm at a loss as to why the gate driver works fine with no FETs in place but craps out with them installed, even though they should theoretically be easier to drive than irz44n's that seem to be the standard replacement part. Thanks
I don't recall any of the gate resisitors being 468 ohms. I know that the previous FETs(don't recall the P/N) had 47ohmers on the gates. 468ohms seems way too high to have on a gate. It is possible that the ground resistor may be inappropriate for the 22ohmer and needs to be replaced with another value. I'll look at one of my boards and get back to you.
They might have been 46.8 ohms, I already trashed em so I guess we'll never know. I got the power supply working now, one of the new FETs had its gate shorted to ground already due to high current, which I've now narrowed down to a short in the output stage since the power supply is working great with no rectifiers in there, with +/- 100 volts to boot I should've just replaced all these transistors from the beginning since they're 13 years old and have been abused and then some
I should've just replaced all these transistors from the beginning since they're 13 years old and have been abused and then some
TO-3 said:
its pretty much the same amp as in this thread, ppi 2150am rev I board. Q47 of the power supply is blown out, the lead next to r28 has fried off the switcher and the trace has lifted a little. i WOULD attemped to fix my self, but i dont feel confident enough to monkey around in this piece of hardware on the simple notion that it is the only one i got (for free) and in its day was a top-o-the line amp and i want to use it, unless i have to drop a ton of cash in to it, for after that ill just buy a new amp.
i have some experiance with electronics (resister networks), i do not have an o-scope(wish i did), i do have a DMM, and many computers, a lot of tools: small screw drivers, soldering irons, mini pliers, bla bla bla.
if this was a crappy little jensen and no problem, no loss, i would dive in and try to fix it my self. not this, i love the old ppi amps and i dont want to mess it up trying to fix it. im the kind of person that would do it once the first time and do it right, with this amp i dont feel im ready to take on some thing this complex, i know i dont have the experence to tackle some thing like this just yet, but im willing to learn, just not on my ppi amp. i do have a crappy little pioneer some were, cant find it though
so if any thoughts let me know, i appreciate any help. thanx...
rth said:They might have been 46.8 ohms, I already trashed em so I guess we'll never know. I got the power supply working now, one of the new FETs had its gate shorted to ground already due to high current, which I've now narrowed down to a short in the output stage since the power supply is working great with no rectifiers in there, with +/- 100 volts to boot
Hey man- I looked at one of my PPIs this morning and found I gave out bad info. The gate resistors are supposed to be 47ohms(NOT 22) and the ground-tying resistor(directly on the outputs of the PWM chip Pins 11 & 14 is 2.2kohms) for the Z44s. Maybe it was the other MosFETs, though I don't recall thier P/N that was 22. Although, if your amp is working now, don't fix it. I apologize to all that may have used the 22s due to my info.
Whenever you replace one switcher, you need to replace them all. This is due to the amount of stress that the part inherits due to the higher amount of power it is subjected to.
Glad your amp is stable now.
sid216 said:
its pretty much the same amp as in this thread, ppi 2150am rev I board. Q47 of the power supply is blown out, the lead next to r28 has fried off the switcher and the trace has lifted a little. i WOULD attemped to fix my self, but i dont feel confident enough to monkey around in this piece of hardware on the simple notion that it is the only one i got (for free) and in its day was a top-o-the line amp and i want to use it, unless i have to drop a ton of cash in to it, for after that ill just buy a new amp.
i have some experiance with electronics (resister networks), i do not have an o-scope(wish i did), i do have a DMM, and many computers, a lot of tools: small screw drivers, soldering irons, mini pliers, bla bla bla.
if this was a crappy little jensen and no problem, no loss, i would dive in and try to fix it my self. not this, i love the old ppi amps and i dont want to mess it up trying to fix it. im the kind of person that would do it once the first time and do it right, with this amp i dont feel im ready to take on some thing this complex, i know i dont have the experence to tackle some thing like this just yet, but im willing to learn, just not on my ppi amp. i do have a crappy little pioneer some were, cant find it though
It's really not that difficult. I looked in my trunk, I still haven't unloaded it completely, and saw that I have at least one of my sine-wave generators and I think my soldering iron, but my scope and DC power supplies are still in Denver.
I hope to be able to retrieve them later this summer, but I need to work for awhile and get some cash, I was unemployed for a year. My first week in the Valley, I interviewed for a job, and my third week here, I got offered the job. Much better electronic industry here. If your amp is something you can hold off on for a few months, I can help you out when I do retrieve my test equipment and tools.
well... thats eazy for you to say...TO-3 said:
well its good you got some of your gear, me personally, i couldn't live with out my computer for more than a few days, and thats with the sound system for it. good luck with the job, i know im going to need it in about 7 weeks. any one want to hire an A+ certifided computer nerd?I looked in my trunk, I still haven't unloaded it completely, and saw that I have at least one of my sine-wave generators and I think my soldering iron, but my scope and DC power supplies are still in Denver.
ya, my amp isn't going any where any time soon as with me, so it could wait. besides it will give me some time to work on the design stages of a few projects im tinkering with...
Ti, TO3,
I've got a strange PPI amp. The amp is PCX1400.
When there is a bass in the system, the toroidal smps core is making sound, like ringing, but quite loud. How to eliminate this? Have to glue all the wires+cores with resin?
PS. The smps driver is SG3525, but there is 2 of HIP4081 full bridge driver. I think the SMPS is not pushpull like ordinary for car amps, but it is full bridge mode, the mosfets are divided to 4 sections.
I've got a strange PPI amp. The amp is PCX1400.
When there is a bass in the system, the toroidal smps core is making sound, like ringing, but quite loud. How to eliminate this? Have to glue all the wires+cores with resin?
PS. The smps driver is SG3525, but there is 2 of HIP4081 full bridge driver. I think the SMPS is not pushpull like ordinary for car amps, but it is full bridge mode, the mosfets are divided to 4 sections.
PPI PC2150 Help
I have a PPI amp 2150 that I purchased at a auction , but as soon as i hook it up it blows the fuse on the power line as soon as I turn the radio on. I'll be a bit more specific I hook up the amp then I turn the radio on and the green light on the amp turns on for a split second and then the fuse blows. I tried a higher amperage fuse (assuming the amp might need a bigger fuse) and it does the same thing. Had someone tell me it might be the power supply ? not sure if thats the issue ? has anyone heard on an issue like this on these amps and is the amp worth fixing ? thanks in advance, and any help or comments would be greatly appreciated.
I have a PPI amp 2150 that I purchased at a auction , but as soon as i hook it up it blows the fuse on the power line as soon as I turn the radio on. I'll be a bit more specific I hook up the amp then I turn the radio on and the green light on the amp turns on for a split second and then the fuse blows. I tried a higher amperage fuse (assuming the amp might need a bigger fuse) and it does the same thing. Had someone tell me it might be the power supply ? not sure if thats the issue ? has anyone heard on an issue like this on these amps and is the amp worth fixing ? thanks in advance, and any help or comments would be greatly appreciated.
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