Phoenix Gold ms 2125 "Disaster" Help !!!! - Page 3 - diyAudio
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Old 13th July 2010, 06:40 AM   #21
Fenice is offline Fenice  Italy
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Join Date: Jul 2010
Location: Vittorio Veneto


Hy !

it is your merit !!!

I'm worry about red clip led on....!!!

Can't find new transistors....uff.....

The center legs of rectifiers give me 35-36 volt

This evening I will test out DC offset !!!

but....

I'm worry about leds on board in left channel....

they are REALLY less bright than other side !!!!!!!!!!!

other measurement to do ???

Thank U again !!!!!!
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Old 13th July 2010, 07:13 AM   #22
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Evening Fenice,
LMK what the two sets of high voltage rails are for each channel. The 10 amp fuses in front of the large caps are the +&- 36 volt set. Look for the small rectifier set for the VAS stage supply that is 7 volts higher then the outputs.

You should see four diodes in each supply that supply the VAS stage +&- 42 volts.
If this is all good and the leds are dim, its time to look at leaky VAS stage transistors, and work forward towards the outputs. I agree brightness should be about the same, so something is pulling this areas supply rails down < it is current limited by the extra few windings on the power toroid by design.

Again the clip indicator is either those two transistors I listed before or the channel has some other problem as not yet found....Let me know what you find...and congratulations on making it this far, Your almost home now. Keep up the effort, the light is at the end of the tunnel....
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Old 13th July 2010, 09:27 AM   #23
Fenice is offline Fenice  Italy
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Quote:
Originally Posted by 1moreamp View Post
Evening Fenice,
LMK what the two sets of high voltage rails are for each channel. The 10 amp fuses in front of the large caps are the +&- 36 volt set. Look for the small rectifier set for the VAS stage supply that is 7 volts higher then the outputs.

You should see four diodes in each supply that supply the VAS stage +&- 42 volts.
If this is all good and the leds are dim, its time to look at leaky VAS stage transistors, and work forward towards the outputs. I agree brightness should be about the same, so something is pulling this areas supply rails down < it is current limited by the extra few windings on the power toroid by design.

Again the clip indicator is either those two transistors I listed before or the channel has some other problem as not yet found....Let me know what you find...and congratulations on making it this far, Your almost home now. Keep up the effort, the light is at the end of the tunnel....

Dear 1moreamp your help is really good !!!!!

If this piece of history will reborn will be your merit !!!!

I will search again bad comp....but my fear is that new components are really hard to find !!!!!!!

I'll do measurement and tell you what I'll find !

Thank U very much !

Ciao !
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Old 16th July 2010, 07:55 AM   #24
Fenice is offline Fenice  Italy
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Hy !!!!

UPDATE :

With fuses F3 - F4 - F5 - F6 OUT amp eat 1,5A and clip led are both ON


With fuses F5 and F6 IN :

amp eat 1,7A, related clip led off !!! the channel seems work perfect !!
...but power consuption increase fast...after 1 minute the current became 2 ampere...and mosfets, and Toshibas too, start became hot ! Is it normal ?



With fuses F3 and F4 IN :

amp eat 5 Ampere !!!!!!!!, related clip led off !!!
the mosfets became really hot immediatly !!!
the problem is after fuses !!!!!! may be a short ???


DC offset at output is about 0,006 V


Hope this information can tell you something !!!!!

UFF !!!!
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Old 16th July 2010, 08:34 AM   #25
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Fenice this amp will need to be sinked properly at this point, if you continue to power it up with the rail fuses in place.

The second channel has issues and is drawing way too much current. Both channels must be turned on for the amps safety circuitry to not trigger.

I suggest you go thru the second "bad" channel again. Please set all bias pots back to zero for any further power testing. This should keep the amp at about 1.5 amps with no output bias. Again the 5 amp channel has issues. I generally find the stage just after the diff input is defective < 2SA1360 and 2SC3423 pairs are in question IMO.
I replace these in sets to bring back like new operation. They tend to run warm to the touch, only in the 2250 did PG sink them.I have seen these fail before.

Let me know what you find...
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Old 16th July 2010, 08:58 AM   #26
Fenice is offline Fenice  Italy
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Dear 1moreamp....the problem is that I can't find replacement for
SA1360 and 2SC3423....



do you know if exists equivalent components ?

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Old 16th July 2010, 06:05 PM   #27
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Quote:
Originally Posted by Fenice View Post
Dear 1moreamp....the problem is that I can't find replacement for
SA1360 and 2SC3423....



do you know if exists equivalent components ?


I use only the exact parts for these, they are still available over here. In later models using the same basic amp design PG used a plastic cased TO-220 device numbered 2SA1964E and 2SC5248E. These were used in the ZX and TI lines. These will not match the looks of the existing transistors since they are in a different case style TO-220. < much larger case
These would most likely be my consideration if the original parts were not available locally. Notice they use the E designation for these, I believe the original transistors were O designation for gain characteristics.....
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Old 21st July 2010, 03:03 PM   #28
Fenice is offline Fenice  Italy
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Hy !!!

Another questions.......

Can I use 35V railcaps instead of 40V railcaps ????



Thanks to everyone !
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Old 21st July 2010, 07:35 PM   #29
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Quote:
Originally Posted by Fenice View Post
Hy !!!

Another questions.......

Can I use 35V railcaps instead of 40V railcaps ????



Thanks to everyone !

I would not vary down from the DC rating on the caps. PG did not allow the normal 15% voltage margins of other amps companies engineering wise. The large caps should be riding around +&- 36 volts DC typically and the input diff stages at +&-42 volts DC for the amp to run correctly.
35 volt caps is pushing it too close IMO...no margin room left
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Old 30th August 2010, 06:06 AM   #30
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Cecil I lost your phone # and other contact info,please send me a private message I would like to talk to you again.

On the subject of this MS2125 I have replaced my rail caps with 50vdc caps as recommended by others that have 2125's that came with 50v rail caps it is ok to go up in volts but not down I was told.
Now I also have a copy of the schematics for this amp if you would like a copy I am pretty sure Cecil would.
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