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Old 30th April 2013, 08:56 AM   #1
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Default upgrading a threshold 4000 : PLEASE need a courtesy

HI,

Unfortunately my 4000 amp is 100% dead ,so I have to recicle cabinet and PSU.
I have +/- 75 volt B+ ()MONO).

I like the Series, so I have asked in france ( see treshold lovers website) to a lab that restore Threshold amps, but they have responded that the amp is not compatible with more modern type.!!

So I ask if some kind good guy here,
can make physycally two plates of alluminim of 6 mm thick ( to screwing to my heatskins that are 340 per 145 mm) with attached the entires channel of SOMETHING good ( if threshold or Pass better of course because I am alovers of the brand of mister Pass) of about 200 watt / 8 ohms.

My power transformer is 1000 VA ,SQUARED - not toroidal - and the capacitors are 4 Cornell Dubiler 15000 microfarad /80 volt still working!

I hope To have some good news from someone here...
Obviouslly I0' ll pay money bank or paypall the value of the work plus materials.

P.S. I love AB class with little % of clas A operation because thae amp is only for bass zone ( 20 - 350 Hz) and I would save heat.

Thanks for reading!

Cheers

Paolo Pontello - Phaseless High end Speakers
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Old 4th May 2013, 07:42 PM   #2
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Quote:
Originally Posted by inertial View Post
I like the Series, so I have asked in france ( see treshold lovers website) to a lab that restore Threshold amps, but they have responded that the amp is not compatible with more modern type.!!
The way I interpret this: The amp uses TO-3 case transistors, but the modern case is TO-247 (aka TO-3P), so you want to make an adapter so a new amplifier can fit your heat sink?
More info, please?
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Old 5th May 2013, 10:22 AM   #3
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Yes, you are right.
I have two heatsinks 340x345mm with a lot of holes, so I have to attach over it a plate of 6mm of alluminium, where to fix the new plastic transistors and all the components & circuits, PSU excluded.
I think it's possible, because 99% of amplifiers class AB works with a dual B+ of, in my case, 75 + or - Volts. So I don't see any difficults.
In facts, I have asked to AussieAmplifiers and they have suggested me their modules NX300 that it's beautiful modern amp but I'am nostalgic and would like to put a Threshold amp in a Threshold cabinet!

Thanks for reading.
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Old 5th May 2013, 04:46 PM   #4
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You can still get TO-3's through distribution. Digikey and Mouser have parts
like STMicro BUX48, BUX 98 and 2ST2121 in stock.

Also, when you say 100% dead, what do you mean. Have you tested the devices?


Last edited by Nelson Pass; 5th May 2013 at 04:52 PM.
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Old 6th May 2013, 09:56 AM   #5
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Dear Mr. Pass,

I have taken my 4000 in laboratory, and they have said that all transistors (power and signal) are destroyed.
In addition, they can't guarantee a repair, even at about 600 Euro cost.
At this point, my interest is in more musical and modern, IMHO, S350 or S450.
Do you think it's possible?
Do you know some kind guy, maybe in Europe, that can do the work?

Thank you very much!
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Old 6th May 2013, 12:45 PM   #6
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pictures can't do any harm
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Old 6th May 2013, 01:20 PM   #7
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Pictures please. To loose all the transistors and not have a lot of magic smoke let out and a blown transformer is very unique .
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Old 6th May 2013, 04:57 PM   #8
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Hi all!
I can send the pictures, but I don't understand the reason. I have specified as the technician of the lab that repair amps have said that all 24 power transistors for channell are dead. And also all the signal transistors.
From the photo nothing useful can be seen - the transistors appears normal.
There's no sign of fire, or melted components, etc.

Thanks for reading.
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Old 6th May 2013, 08:33 PM   #9
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You said they said "all transistors (power and signal) are destroyed".

I doubt that this statement is true.

Now it is possible that all power devices are destroyed, but I have never seen
such a case. I have met technicians who would say such a thing without doing
the amount of work necessary to confirm that.

Since you would have to take every transistor out anyway, I suggest you
do so carefully and test each one.

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Old 6th May 2013, 09:08 PM   #10
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally Posted by inertial View Post
.........but I don't understand the reason.......
last time when Witch Hunters were cohorting my little place , I was forced to hide my crystal ball

later , when they ( WH) goes away , I spotted that price for hiding my crystal ball in hurry was scratches all around

unfortunately - masters these days aren't so good in crystal polishing , as they are good in simple swapping of LCDs , so my (crystal) ball is waiting for some ole master , to make it useful , again

that's the reason why I need pictures to see posted - here - my remote device for remote observing of ooked remote devices is ooked

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