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Old 15th May 2008, 02:27 AM   #1
KyferEz is offline KyferEz  United States
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Default PG X200.2 help please

Ok, here is an amp that I think will be a pain to fix, but I would like to start on it... I have to say I hate the color of the PCB: it's really harder to see the copper under the soldermask.

First thing I did was pull the rectifiers to isolate the power supply from the rest of the amp. Now I applied power to the amp and checked the gate signals. A screenshot of the signals is below. I guess the gate driver board has a problem... I put the scope leads on the SG3525's output pins and got what's posted in the next two posts. The first is from pin 11 and the second is from pin 14 of the SG3525.
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File Type: gif smps fet gate signals.gif (24.5 KB, 68 views)
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Old 15th May 2008, 02:29 AM   #2
KyferEz is offline KyferEz  United States
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SG3525 pin11
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Old 15th May 2008, 02:30 AM   #3
KyferEz is offline KyferEz  United States
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SG3525 pin14
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Old 15th May 2008, 02:34 AM   #4
KyferEz is offline KyferEz  United States
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So, would I be correct in thinking that the drivers on the SMPS daughter board are bad, or could the issue be elsewhere? There are 2 that say B1181 and 2 that say D1733.

Also, I've noted some physical damage on the daughter board in the audio output section. A white part with the text: 208 on one line and 339S on the next line. Also part number C100 has exploded off of the board.

Thanks!
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Old 15th May 2008, 03:51 AM   #5
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208 is referring to a MOC208 which is Q113, and Q213. There is also a KTC-3911S located near there also

There are lots of 100 pico-farad caps in this circuit by no C100

B1181 and 2 that say D1733.< these are the Mosfet drivers, and unless the ohm out bad I really don't think these are bad. Were the Mosfets bad ?

This is a fairly different designed amplifier if your unfamiliar with it, PG has a flat rate of repair for these on their web-site, just goggle Rodin and you will find their web page. They list their flat rates under support. If you call the 800 just ask for Phil in service. He can set you up with a RMA# if you have a debit or credit card. The list rate is $95.00 to repair this amp.

These amps produce the exact same power per channel at any load from 4 to 1 ohms with not as much as a single switch for the owner to operate, so there is a bunch of current sense feedback into the power supply to control its output voltage. The current sense is performed on the load and in the channels.
On lower ohm loads the rails drop automatically to keep the magic smoke inside the amp.

I would tend to think, that you have a damaged channel, and its feedback to the power supply is inhibiting the amp from turning on....
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Old 15th May 2008, 05:57 AM   #6
KyferEz is offline KyferEz  United States
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Quote:
There are lots of 100 pico-farad caps in this circuit by no C100
No, the part doesn't say C100, that's the part designator, such as U1 R1 and C1. This is C100 on the daughter board in the audio section (image attached; the C100 part is on the far right). I want to place an order with Mouser and Digikey tomorrow so if you know what value that cap is I'd greatly appreciate it

Quote:
B1181 and 2 that say D1733.< these are the Mosfet drivers, and unless the ohm out bad I really don't think these are bad. Were the Mosfets bad ?
No they don't ohm out. I didn't realize there was feedback controlling the SMPS circuit, but it's good to have. Is there a way to safely disable it and make the SMPS run? I always like to make sure the supply is functioning properly before I move on to the rest of the amp.

Quote:
This is a fairly different designed amplifier if your unfamiliar with it, PG has a flat rate of repair for these on their web-site, just goggle Rodin and you will find their web page.
I am learning of the difference As for having them fixed by a repair center: I need to learn to work on them. Why? Because I have a number of different models of Xenon amps I picked up broken for cheap, from x200.2 to x1200.1 and several others in between. I didn't know at the time that they were quite so different, but I intend to fix them for use in my system. I just need to learn the design and what commonly goes wrong with them, what some of the LEDs mean, if anything, what the check-points are testing for and anything else helpful... I know they are likely going to be challenging.

Quote:
On lower ohm loads the rails drop automatically to keep the magic smoke inside the amp.
I figured it had to work that way, as I knew that they produce the same output for different loads.

Quote:
I would tend to think, that you have a damaged channel, and its feedback to the power supply is inhibiting the amp from turning on....
Well, not me Thanks for the suggestion, that seems likely seeing as how the daughter card for the audio section has visible damage (again, see image attached).

The audio driver boards: Is it common for them to fail? The C3284 and A1303 audio outputs test Ok. I obviously have a damaged driver board, I'm just trying to gauge what is most likely to fail on these amps.

This was a long post, so I'll highlight my questions below:
1) The part designated by C100, do you know it's value?
2) Can I _safely_ bypass the feedback and get the SMPS to run ?
3) What do all those leds mean?
4) What are the check points testing and what should I expect to see on them?
5) What are the common things that fail on these amps?

I greatly appreciate any assistance.
Thank you!
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Old 15th May 2008, 07:48 AM   #7
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The Fairchild MOC208 is a Opto-coupler that is a LED and a transistors in a 8 pin package. It gets a signal from the B+ and the Reference buffer line , so its a connection back to the power supply. Its tied between the 17 volts rails and the bases of two transistors that are connected across the base pathway to the Darlington outputs.

1: C100 is not a valid number to me and my info. But I have placed a cap in circuit there and its 33 Pico-farad.

2: Bypassing safety circuits is not recommended, if the circuitry is triggered it has good reason to be triggered, and is protecting you from more trouble that has not been addressed yet. First find the other issues, and then remove them from the circuit. The safety's should release then. I.E. remove the bad daughter board, and test again.


3: "Most all of the LEDs are used for voltage drop reasons only, so to a tech they mean nothing but a given drop across a diode junction in those circuits." This is straight from A PG staff engineer.

They are tied into each and every feedback circuit from thermal to voltage sense, and references. So they do really mean something when they are on. I am used to seeing only one red led inside and its a reference , LED 3 I believe, and other that that the blue led on the cover must be on constantly not flashing, during normal operation of the amp.

4: The only check points I recall are the Bias set point reading, and the main supply check points but they are in the supply. Other then that there are the normal output check points you would use to scope and check as usual.

The class D amps are different They use PIC micro-controllers to handle power control and safety intervention. They are sort of tamper proof, and work in some very harsh conditions unlike analogue safety overrides. There are tricks to these though, but I can not divulge any work around openly for safety reasons.


5: Common failures are blown outputs, and channel driver cards, and power supplies. and an occasional power toroid. Failures are limited in scope by design limitations inside the circuitry PG designs in stop gaps that limit catastrophic damage in most cases. I.E. current limit resistors, and fuse type resistors, DC offset protection, dis-similar rail supply protection, etc.... among others like thermal protection etc...and they all work. they use simple transistor and LED circuitry in the analogue protection. The references are set by the Zeners in these circuits. It does not get much more straight forward. But the lay-out and scheme of this will seem daunting until your use to them.

If you call PG I think they will sell you a new driver card for that channel, probably for a reasonable price. NO maker uses card like this and does not stock them for quick replacement. Its part of the whole reason behind channel driver cards. Bad channel, OK just drop a new card in and test the outputs and Viola ! fast economical repairs.
If your 3S card in your D class amps are blown then you will need to buy one from PG anyway. As I don't recall a US supplier for the 3S cards in the past, and they build custom cards for everybody that builds D class amps. 3S grinds numbers off their IR chips they use, and without the BOM or call out scheme then your just guessing which IR chip they use.

So to recap, keep looking for the channel troubles, do not bypass the safety's. it will cause you only more headaches, and parts. remove the suspected driver cards, and test again. Pulling diodes might work on other amps, but its probably not going to get you far on a PG amp. You will need the supply to be intact just to keep it operational and latched on.

I hope I have been able to answer some of your questions. I based all my answers on technical data and time spent with these over the last few years. PG's rates are so low, sometimes its just a no brainer to get the factory to fix it. After all time is money...
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Old 15th May 2008, 04:26 PM   #8
KyferEz is offline KyferEz  United States
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2) I'll bow to your recommendations

4) See the attached image.

What's all this about 3S? None of the part numbers are ground off on this amp. Or was that referring to one of the other amps I have?

Thanks, you have helped quite a bit. I'll call about replacement driver boards, if they are economical I'll just get them, otherwise I'll replace parts. It seems like the thermal design of the driver boards may be an issue if they commonly fail while the remain Ok...

Thanks a lot!
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Old 15th May 2008, 05:58 PM   #9
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Quote:
Originally posted by KyferEz


What's all this about 3S? None of the part numbers are ground off on this amp. Or was that referring to one of the other amps I have?

[/B]

the3S boards are used in the D class amps. Lots of other makers use these also. Its like a off shore Tripath card, in simplistic terms. And yes 3S grinds the numbers off the IR fet drivers that they use on these boards.

I own several Xenon amps. For the money they can't be beat for price to performance ratio. SQ is very acceptable when compared to others, and as cheap as these sold for on flea-bay a few years back, its a no brainer to buy and use them. At least the PG design is original and not a Chinese Clone amp, and they deliver to spec, unlike many others that fall short in real testing.

I have talked with you before I believe. Didn't you buy a load of kicker 1000 amps a while back? Let me know if you have more questions. My e-mail is active and I monitor it...
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Old 15th May 2008, 06:17 PM   #10
KyferEz is offline KyferEz  United States
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I have talked with you before I believe. Didn't you buy a load of kicker 1000 amps a while back? Let me know if you have more questions. My e-mail is active and I monitor it...
Yes we did talk before. I haven't had any time until recently to work on the "load", but a several are fixed and 4 are in the works waiting for my parts order today. That "load" was a sweet deal. About 20 amps in all.

I just got crunched for time again, but I intend to fix this PG before I stop!

I'll try to find your email... mine has my screen name in it.

Thanks!
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