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Old 3rd June 2012, 06:31 PM   #1
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Default DIY upgrading Meitner MTR-101

Hello all,

I wanted to upgrade my MTR-101 power amplifier. On Museatex website, there is mention to SCR power switch as a first upgrade to the amplifier:

"The power switch, which was previously a triac in the primary side of the power transformer, has been replaced by a Scritch. The Scritch, an SCR - based circuit, is positioned in the power supply after the diode bridge. This provides for soft turn on and better long-term reliability. "

Is this a mod which can be performed with some general circuit? How could I obtain the same?

Then, they add: "The pre-drive transistors have been upgraded to a new Motorola device. This part is faster and shows less variation from the manufacturer."

I was wondering, here, if I could use other kinds of transistors to obtain similar improvements, and what my best chances would be.

Thanks for helping!!
Tony
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Old 4th June 2012, 04:24 AM   #2
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I don't think many will have schematics or even good references to this monobloc from an absorbed manufacturer. Perhaps all we can offer is general advice.

Assuming you are familiar with electronics and are competent to work safely on mains power supplies, you can install any soft-start kit as are available retail or on the net. As long as the switching current and voltage ratings are sufficient, any add-on soft start kit will work and they have nothing to do with the performance of your amp, when switched out. i.e. the type is irrelevant. The main issue is to protect yourself and others exposed to high voltage by fitting proper covers and insulation over exposed wiring and connectors.

I will take a guess that the "pre-driver" referred to is actually a driver transistor and is pointing to one of the MJE15028-35 series of driver transistors. These have been commented on everywhere since their introduction by Motorola/On-semi. Actual pre-driver speed would have been a trivial choice of almost any 5 cent standard part on your amp, if the designe required them. Either that, or the designer (unlikely) boo-booed.
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Old 11th June 2012, 06:02 PM   #3
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Meitner power amps have Hitachi MOSFET output stages.

MJE15029 and up makes little sense, TO220's are in the Vas/driver stage, the Motorola line more likely referred to a switch from MPSU10 & MPSU60 to MPSW42 & MPSW92
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Last edited by jacco vermeulen; 11th June 2012 at 06:06 PM.
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Old 14th June 2012, 12:51 PM   #4
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Thanks for the reply. Would such an upgrade bring a significant improvement?
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Old 14th June 2012, 05:13 PM   #5
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Why not post the lineup inside there as it stands. Without a schematic or a list of the semiconductors, we can't really guess whether a substitution would upgrade or even degrade.
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Old 14th June 2012, 06:20 PM   #6
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Quote:
Originally Posted by antonyfirst View Post
Thanks for the reply. Would such an upgrade bring a significant improvement?
If you're referring to my line, no, the latter are just easier to match/select.
I've still got a lot of MPS10/MPSU60, nice devices, but parameter spread isn't that great.

Eer, mate, how about some nudy pics ?

(lovely amps, btw, me envious. most beautiful heatsinks ever thought up)
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