Phoenix Gold ms 2125 "Disaster" Help !!!! - Page 2 - diyAudio
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Old 7th July 2010, 05:26 PM   #11
Fenice is offline Fenice  Italy
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Join Date: Jul 2010
Location: Vittorio Veneto
Information for everyone :

Thermal sensors are :

PTC 100 ohm

like this :

Epcos | Passivi | Resistori | Termistori | Termistori - PTC (positive temperature coefficient) |B59901D130A40

Hope this information could be useful foe someone....

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Old 7th July 2010, 10:44 PM   #12
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Location: Northern California
Quote:
Originally Posted by Fenice View Post
I envy your knowledge and where you live too !



I'll try to search components....

Using a 100 ohm resistor in place of thermal res yellow led go off and

power green led light on !!!!!!!!!



....but amp "eat" a ton of current !!! (4-5 ampere)

Have tested all resistors on both channel and are all ok !

Leds are ok

Transistors seems to be ok.....

UFF !!!! so if all components ok...why right channel CLIP and left channel DEAD ?



This evening will make other tests....

WOW !! an 2250 !!!!

I hope you repair it !!!!

Thank U very much....

Good afternoon Fenice...
So the amp now turns on with the 100 ohm resistors in place. This is good. Now you can please replace the two bad clip driver transistors I spoke about earlier. This should relieve you of the permanent clip indication your seeing all the time.

I suggest you turn both of the channel bias adjustments back to a off position. This should reduce current draw at idle to a minimum level. You can reset these later on anyway as part of the final alignment and test procedure for the amp.

I am not so sure your thermal sensor is a PTC device. My good friend Perry has also brought this to my attention that he believes it should be a NTC sensor. Which I agree makes sense. As I said earlier this is the first time I have ever seen a need to replace one of these so my info is limited and you should consult PG either thru email of phone conversation about this. I know they have them as spares, but I have lost track of them since their sell-off and move to Florida. I suggest you contact them thru the PG web-site, or look for a referral on the RODIN web-site.

The only reason I have ever seen the red LEDs in the channels out are 1 they were blown open or 2 they has open fuse resistors in that channel. Although they serve a simple voltage drop service in the circuitry, they are also a fairly good indicator that one or both of the rails are not present in that area of the channel.
So they are a tell tale sign of open fuse resistors, and bad transistors in that stage of the amp. I would go back over all the resistors and realize that in circuit testing can lie to you on a DVM. You might have to pull one leg out of circuit not to get a false reading.


From personal experience on this amp, and I do own one of these also. I have seen all of the things I am telling you about first hand. The amp your restoring has been abused badly, so it will be a headache to bring back. I have seen worse, so don't give up.

There are a few other things that could be wrong, like blown op-amps in the frontend. I isolate the input by lifting the 33 ufd 16 vdc caps on the input of each main channel. < just after the third op-amp stage > This decouples the input op-amp buffer circuitry so I can diagnose and repair the main amp channels without added headaches. Once the amp is operating properly you can diagnose and repair and frontend damage as needed and then test with signals and music. But here again this is my method of madness when dealing with any car amp, yours might be different.

These amps are fairly straight forward once you have seen a few of them. I have seen then since 1992 so after 18 years of them I guess I might appear intelligent LOL LOL LOL...

Please check your DC rails inside the amp channels for both channels. There will be the routine +&- 16 volt rails for the op-amps, and there will be two different rails of each amp channel. One rails set feeds the outputs at about 7 volts less then the raw rail feeding the stage prior to the drivers. The voltage on the large rail caps in the higher of the two and the voltage to the outputs should be 7 to 8 volts lower then that feeding the transistors near the red leds,

You should see +&- 42 volts feeding the 2sc3423 and 2sa1360 devices, and +&- 36 volts feeding the outputs and the drivers just in front of them. There may be some minor variations depending on what voltage your supply is outing to the amp, but nothing too majorly different should be seen. Balance is the key objective if the rails are out of balance by more then 1 volt start looking for leaky transistors. You have them and they must be replaced.

I also have seen the input diff pairs damaged by clipping so don't overlook that a new matched set of input tranny's might make the amp perform like new.
....Ciao...

Last edited by 1moreamp; 7th July 2010 at 11:06 PM. Reason: spelling missed a keystroke and general guidance
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Old 8th July 2010, 08:05 AM   #13
Fenice is offline Fenice  Italy
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Join Date: Jul 2010
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AAAAAAAAAAAAAAAAAAAHHHHH !!!!!!!

So many things to do.....

Your help is really crucial !

My best difficult is find new components....here in Italy is impossible...

When I found one I must wait at least two weeks to have it in my hand...

UPGRADE:

Found malfunction on SG2525 on dead channel.....no signal out on pin 11 and 14....so mosfets Q300 - Q303 doesn't work...

May this cause right channel dead and red led off ??

Thank U very much....

Another question.... :

May you have complete schematics of this amp ?

I have only a partial one....only power side.....need amp side too...

Ciao e grazie !!!!
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Old 8th July 2010, 06:32 PM   #14
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Quote:
Originally Posted by Fenice View Post
AAAAAAAAAAAAAAAAAAAHHHHH !!!!!!!

UPGRADE:

Found malfunction on SG2525 on dead channel.....no signal out on pin 11 and 14....so mosfets Q300 - Q303 doesn't work...

May this cause right channel dead and red led off ??

Thank U very much....

Ciao e grazie !!!!

Well now your cooking with gas my friend. Yes this would cause a dead channel since there would be no drive the gates of the mosfets in that power supply, there would be no secondary voltages also. Please replace the PWM chip and let me know what you get then.

.....Ciao...

Last edited by 1moreamp; 8th July 2010 at 06:47 PM.
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Old 9th July 2010, 08:53 AM   #15
Fenice is offline Fenice  Italy
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Join Date: Jul 2010
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Uff..another component hard to find......

let's try !

Thank U again !!!!
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Old 11th July 2010, 10:50 AM   #16
Fenice is offline Fenice  Italy
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Join Date: Jul 2010
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Dear friends....

UPDATE :

I placed two 100 ohm resistors at place of thermal res and replaced SG2525 IC on left channel :

Now both channel turns on but leds on board in the left channel are really less bright than others.....an both channel clip leds are on...
Green power led now is on !

Help !!!!!

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Old 11th July 2010, 07:53 PM   #17
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Quote:
Originally Posted by Fenice View Post
Dear friends....

UPDATE :

I placed two 100 ohm resistors at place of thermal res and replaced SG2525 IC on left channel :

Now both channel turns on but leds on board in the left channel are really less bright than others.....an both channel clip leds are on...
Green power led now is on !

Help !!!!!


Ok lets get some voltage readings between the two channels. Start with rail voltages at the fuses just after the caps, and also check for DC offset on the speaker terminals < DC offset being any DC voltage present on the speaker terminals while the amp is turned on >.
And what is the current draw on the 12 volt supply with the amp on now ?
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Old 12th July 2010, 09:08 AM   #18
Fenice is offline Fenice  Italy
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Hy 1moreamp !!



this evening I'll do this measurements.....

The amp "eat" 1,5 amps in idle state now...

Thank U !
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Old 12th July 2010, 09:10 AM   #19
Fenice is offline Fenice  Italy
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...excuse me...

1,5 amp when power is on !

Bye !
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Old 12th July 2010, 07:33 PM   #20
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Idle current is a bit low but acceptable for further testing and repair work. Good work !
Now you can proceed with final repairs and then test alignment of the amp. Your doing great !

I would still continue to check out DC offset output and all rail supplies to each channel next. Pending what you find there Bias alignment could be the next step.
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