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Old 12th January 2008, 05:00 AM   #1
zigo3 is offline zigo3  Italy
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Default Melos triode 200+ looking for spare parts

Hello

I own a melos triode 200+ stereo who had burned a transistor, probably because some old capacitors who altered the values, that now we replaced with some new ones. Unfortunately the data on the transistor are unreadables. We tried to replace the old transistor with other similar values, but with bad results (the sinusoid results cutted in low).

Please, somebody have the originals or can read the data on the originals to try to find them? Or can tell us the address of somebody who can know it?
We obviously can pay for spare parts and correct informations.
Thankyou very much in advance.
my email is zigozigo3@hotmail.com

The transistor is the one in the yellow circle.
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Old 12th January 2008, 05:03 AM   #2
zigo3 is offline zigo3  Italy
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This is the position in the pcb
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Old 12th January 2008, 07:36 PM   #3
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This may not be much help but my memory says that Melos used screen grid drive on this amplifier. So you may be needing a mos-fet in that position. (4 tubes=4 fets)

Victor
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Old 13th January 2008, 04:11 PM   #4
zigo3 is offline zigo3  Italy
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Thankyou for your reply HollowState.
Now there are 2 hypothesis:
- it is a mosfet, ok but what mosfet? There are thousands of mosfets.
- it is a regulator LM317 or LM337.
Tomorrow we will try to understand something more with instruments.
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Old 14th January 2008, 07:35 PM   #5
zigo3 is offline zigo3  Italy
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Quote:
Originally posted by HollowState
This may not be much help but my memory says that Melos used screen grid drive on this amplifier. So you may be needing a mos-fet in that position. (4 tubes=4 fets)

Victor
Seems that it's a mosfet, like you told Victor. But what mosfet?
And now seems that there could be a problem to one of the output transformer.

PLEASE, SOMEBODY HAVE A MELOS TRIODE 200+ STEREO OUTPUT TRANSFORMER?
it is the plus version, then the toroidal.
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Old 14th January 2008, 10:34 PM   #6
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This is only a guess. I would try a general high voltage N-channel mosfet. Perhaps something like an IRF820 (500v-40watt) or an IRF830 (500v-75watt) These units are cheap and easily available. And they are the correct mounting type (TO220 or Y220b)

These are not the only choices by any means. And remember, it's only my best guess.

Also, check the condition of any clamping diodes used around the source-gate junction (if any).

Victor
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Old 17th January 2008, 05:26 AM   #7
zigo3 is offline zigo3  Italy
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Thankyou Victor.
I try them by sure and I will tell you the result.
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Old 2nd March 2008, 06:40 AM   #8
zigo3 is offline zigo3  Italy
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Quote:
Originally posted by zigo3
Thankyou Victor.
I try them by sure and I will tell you the result.
I found that on another Melos triode 200 are mounted 2 identical transistors who are marked "ST D01111 - MOROCCO - P3NB100 - FP".Click the image to open in full size. I don't know if they are originals, all the powamp have some original parts substituted and only 2 of the 4 driver transistors was readables.
I did searched them with google but I did'nt find them. Please somebody can help?
Thankyou very much in advance.
Rob
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Old 2nd March 2008, 10:32 AM   #9
zigo3 is offline zigo3  Italy
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Quote:
Originally posted by zigo3


I found that on another Melos triode 200 are mounted 2 identical transistors who are marked "ST D01111 - MOROCCO - P3NB100 - FP".Click the image to open in full size. I don't know if they are originals, all the powamp have some original parts substituted and only 2 of the 4 driver transistors was readables.
I did searched them with google but I did'nt find them. Please somebody can help?
Thankyou very much in advance.
Rob
A friend from this thread http://www.audiokarma.org/forums/sho...d.php?t=145708 found them.
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Old 3rd March 2008, 11:43 PM   #10
Lorne is offline Lorne  Japan
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In the power supply module of my Melos GK-1 there was a transistor mounted in a similar heat sink. If you think it is worthwhile pulling the cover and so on, I'll look and see what it is. I believe that I replaced it when I rebuilt the PS.

Another thing Melos under-engineered the heat management in my pre-amp. Could it be true of your amp as well? I vastly increased the size of some heat sinks in accordance with some advice I received from a professional. Perhaps heat was the cause of your transistor failure in the first place. The transistor in question was finally mounted vertically on a massive, finned aluminum sink.
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