PPI PC2350 schematic or service manual?? - diyAudio
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Old 5th November 2009, 04:26 PM   #1
Staykov is offline Staykov  Bulgaria
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Default PPI PC2350 schematic or service manual??

Does anyone know where I can get a schematic or service manual for
Precision Power PC2350?
.... Thanks in advance..
e-mail: staykov1975@abv.bg
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Old 5th November 2009, 05:31 PM   #2
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I don't think any schematic diagrams for that amp were ever released by PPI. What's wrong with the amp?
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Old 5th November 2009, 06:10 PM   #3
Staykov is offline Staykov  Bulgaria
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we replace the defect transistor 2sa1303 with original one.
...but the impulse power supply is noising like bzzzzzzzzz sound(the small power supply).
but all the output transistors are OK.
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Old 5th November 2009, 06:16 PM   #4
Staykov is offline Staykov  Bulgaria
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http://img193.imageshack.us/img193/9430/p1020446t.jpg
may be the problem is somewhere here...
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Old 5th November 2009, 06:28 PM   #5
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How much current is is drawing (no load, no audio)?
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Old 5th November 2009, 06:40 PM   #6
Staykov is offline Staykov  Bulgaria
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we could'n measure that, because of the noise, the transistors will be dead, there is a short connection somewhere...
we have a short connection on the exit , the impulse power is around 1-2 v, the normal is 56 v.
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Old 5th November 2009, 06:45 PM   #7
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There are a couple of 2 pin headers in the audio section near the outputs. Place shunts on them and power up the amp. If it still makes noise or draws excessive, measure the DC voltage across the emitter resistors. If either channel has more than 0.000v across any of the emitter resistors, you have a problem in that channel. If it's drawing enough current to damage the power supply components, insert a 1-2 ohm resistor in series with the B+ line to limit the current. Of course, you should have the power semiconductors tightly clamped to the heatsink when doing this.
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Old 5th November 2009, 07:00 PM   #8
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The whole storry is that:
1. We powered the amp with proper power sypply from 12 v accu, with 60 amp. fuse. We connet then remote pin to 12v DC. No load and input signal at the moment. All was ok. Outputs was 0.0v.
After that I applied 1KHz sine wave with small level, and I saw the output sine wave. The amp was ok in this moment.
2. I swithed off the amp and connect the load resistor 4 ohms 40W cooled by water.
3. Then we powered up again the amp, and slowly rising up input level up to point, when output was clipped. (this was approx. 36v RMS out voltage (around 325W).). This was done for less than 30 second, because we use small accu.).
4. After that we make some other measurements, and suddenly i hear some noise from PSU, and then I stopped immediately the supply from accu.
...(sorry for bad english )
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Old 5th November 2009, 07:22 PM   #9
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... cont..
5. I checked the power transistors, and i found 1 (2SA1303) that was defective. (short between BE and CE I think).
6. I replaced this transistor with new one, and checked everythink I can (All power transistors, incl 2 drivers (2SD2400 and 2SBxxx i think.) and other 2 poewers near ceramic modules. All was ok.
7 I powered Up the amp again for 1-2 secs (with no load), but the same storry. No w burned one transistor from other rail - 2scxxxx.
8. I replaced this transistor, and I checked all transistors again. All was ok.
9 Now, I connedted 1ohm/40W resistor on the positive power from the accu. (I know so the proper place is between PSU an Power Amp, but I don't want to cut some tracks and so...)
10. I powered the Amp again for short time, I hear againg noise from PSU, and swithed off. Now All output transisotrs was Ok, but there is steel some problem.

I think there is something wrong outside output stage. I measured BE resistors, and was ok. I tryed to draw the output part of the schematic to be more easy to find the problem, beacuse you know, without service manual or schematic it's not so easy ... The real problem is, so some stage before power transistors switching on both set output transistors in the same time, and this shorts power supply (and some of power transistors burning then).
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Old 5th November 2009, 07:48 PM   #10
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About the current without load and input, when the amp was ok, I didn't measure is, but I think is was fine. (somewhere I read, that the whole current should be 3 amps...). Now, I can't measure, because the output stage shorts the power supply.
Today, I thinkd to make some other thing... To remove all power transistors from defective channel, and then to see if PSU and other channel is ok. But I thing PSU and other channel are good.
Our mistake was, so we put the amp in max power (around 330W on 4ohms load (one channel only), continous sine wave 1KHz), but this was done when the bottom cover was removed. This cover is not only cover, but it forces the transistors to be connected firmly to the heatsink. I checked transistors before to apply power voltage to be stuck to the heatsink, but probably some of them was not good connected to heatsink, and this was the reason, one of them to burn (thermaly, not by short cirquit ot other stupid thinks).
Tomorrow when I go to work, I'll check that you write (for 2 pin headers), and will try to take other part of scheamtic to see the reason for this problem.
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