Fried my MPS-2500, need schematic please

[interestingfellow]

I had started posting about this in another thread http://phoenixphorum.com/viewtopic.php?f=3&t=18314 but since it is no longer about just recapping my amp, I need the schematic, and to get a little more exposure, here I am posting.

Pretty bad, about 8 of the fets opposite the external hookups either exploded or threw flames. some of my newly installed caps have carbon on them, and I'm sure several of cheaper surrounding components got fried too.

EHHHHH.

The good news is that the best field tech for component level repairs in the world at my disposal (at least, that's what I think of him). He's actually a TV repair guy (now), but he's been doing this for 42+ years. It doesn't hurt that he believes repairing a board on a component level is wayyy better than just swapping the board. He's an honest dude who knows what he's doing, and he said he would "hold my hand" and go over the board with me, if I went ahead and got a copy of the schematic. If I get it, he'll help me for free (I'm still gonna tip'm). I do appriciate all of the help that I've gotten from ya'll and this forum, but I know it would be alot easier for any of you (or anyone) to perform a diagnostic if you had the amp in front of you instead of just photos.

I called AAMP, and once again talked to the ever so helpful Earnie, who informed me that if it's over a year or two old, then they don't have spit beyond the user/install manual.....

So, please, if you have a copy, or know where to get the schematic for an MPS-2500, shoot me a pm, or email me at (myusernameonthisforum) at hotmail (you know the rest).

Thanks again!

PS: I could just drop it off to my guy, and get it fixed for a couple hundred bucks, but I have made a mistake somewhere, and just won't sleep well till I know why the amp failed, and that I fixed it.

[Eric D]

You likely don't need the schematic, if you can even find one. Step one is to remove the bad FETs, and then step two is to remove the resistors driving the FETs. The next step is to put the amp on an o-scope and check the PWM driver signal to make sure it is working right.

Then put new FETs back in, and new driver resistors, then power the amp on through a 12V light bulb to limit the current. If you can get rail voltages, and even play music at low level on 8 ohm speakers, you have the amp back in action.

[interestingfellow]

At the risk of further reducing my rep here, I don't even know what those blown fets are for (power, signal, etc...). If I can get through this amp, I have a feeling I'll be WAYYYYYY better prepared for the next one; but I'd like for this guy to help me, this time, and he says he wants the schema. I told him I'd try to get it.

I have also read over some website I have bookmarked on my laptop, and the guy basically walks you through how to diagnose the amp, and then the basics to fixing it. But, I'm not that good (yet).

[ttocs]

how about a link? I am more curious then anything as I have been amazed at some of the instructional posts online. Found a great one where a software eng from utah showed how to use a 12v flashlight battery just like you would a cap to get extra power to your amp. Of course he had not considered that the battery he choose was not only not rechargable but also not able to handle the current we are talking about.

[00goobs]

bcae1.com is a site I found while trying to repair one of my 2125s. It was pretty informative, but the guys on here are way more familiar with PG amps.

I was bored one day and decided to direct short a AA battery with my Fluke meter on DC amp setting. That battery pulled 10.5 amps on my meter for a quick reading then I disconnected it. I was pretty surprised to see 10.5 amps out of a AA battery.

Mr. fellow, just ask and someone on here only has to look though a plexi to tell you what components you may need or should have. Good luck with your repair! It does get fun when you start buying cheap amps in need of repair at a fraction of regular price...

[interestingfellow]

That's what I keep telling people, this amp was $1200+ back in the day, and (theoretically) it will still do what it did then, but I got it for almost nothin. Then again, it did burn up, so that'll cost me. I always tell my clients, "you are going to pay for "it" one way or another. Either aggravation, repairs, or low quality/short life." And "good, fast, or cheap; you may only pick 2".
One of these amps in good shape is $300+. Repairs would be $150+ parts. I expected this venture to cost me less than that, but not much.

[ttocs]

bcae1.com is a site I found while trying to repair one of my 2125s. It was pretty informative, but the guys on here are way more familiar with PG amps.

I was bored one day and decided to direct short a AA battery with my Fluke meter on DC amp setting. That battery pulled 10.5 amps on my meter for a quick reading then I disconnected it. I was pretty surprised to see 10.5 amps out of a AA battery.

Mr. fellow, just ask and someone on here only has to look though a plexi to tell you what components you may need or should have. Good luck with your repair! It does get fun when you start buying cheap amps in need of repair at a fraction of regular price...

10 amps out of a AA?

What circuit did you put it in to draw 10 amps of current out of a AA?

[Eric D]

In current mode, a DMM is just a wire, so he took the DMM and shorted the battery through it. I would think this could be hard on the DMM, as in theory the battery would do infinite current, but the DMM should have a fuse so it would blow anyway.

[00goobs]

My fluke (most DMMs) has a DC amp reading where there is a shunt and internal fuse. Pretty much causing a direct short internally to measure amperage draw through the leads. I was curious to know why 4-AAs in my RC car was stronger than 5-AA NIMH rechargeables in the same set-up.

I was just thinking that using a battery in place of the caps for the secondary rails would provide a better source for the output voltage in amplifiers in general. It was just a thought or speculation on how that RF 15kw could run on such a lowish input amperage for that much output...

[ttocs]

to test a batteries current output, you would need to set up a circuit that would put a load on the battery, then you would put your meter IN SERIES in the circuit to measure its output. Simply setting our meter to the current setting and then touching it to the battery isn't going to tell you much.

The standard AA's are stronger because they are 1.5 v each, most rechargeable batteries only go to 1.2v, and willing to bet the current output of these would be in the milliamp area

[Eric D]

to test a batteries current output, you would need to set up a circuit that would put a load on the battery, then you would put your meter IN SERIES in the circuit to measure its output. Simply setting our meter to the current setting and then touching it to the battery isn't going to tell you much.

The standard AA's are stronger because they are 1.5 v each, most rechargeable batteries only go to 1.2v, and willing to bet the current output of these would be in the milliamp area

He did do this. When you put your DMM in current mode, it is a wire. You wire it in series. You can use the DMM as a wire, with say a light bulb as a load. However, he just took the load out of the circuit and shorted the battery through the DMM, which would be no different than shorting it with a solid piece of wire.

In the DMM is a shunt to measure current flow, with a small resistance. So the load on the battery became this resistance, and the combination of the resistance in the DMM lead wires. I don't think this is a very accurate way to measure what the battery can do, but if the DMM showed 10A for instance, I do believe there was 10A flowing, just that with a dead short the battery would do more than 10A.

[ttocs]

after a quick search, all I could find is a fairly general rating that they have a max capacity of 2000-3000mAh, and energizer claims a max of 2700mA, or 2.7 amps. Even that sounds high and I would imagine that would be for a VERY short time.

[Kurt Wild]

Sure enough an AA battery pukes out 10+ amps when shorted. I've tried it too. What limits the current is the battery's internal resistance which can be calculated ohms=V/A.
1,5V/10A = 0,15ohms. This resistance rises when the battery goes flat.

But the thing is, shorting a battery is going to harm it unless the short is just brief. At the very least it will get hot.
A rating of 2,7amps or so means the current you can safely draw. If the capacity is 3000mA, you can theoretically draw 2,7 amps for over an hour.