MF2500 throwing 68 DCvolt out on right channel

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jahatl513
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MF2500 throwing 68 DCvolt out on right channel

Post by jahatl513 » Thu Dec 21, 2017 12:43 pm

Is there anyone who can help identify if this is possibly a fixable issue; left channel plays fine. I don't mind sending it to Jeff to have it fixed, just wonder what it could be and the amp is not in my hands.

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Re: MF2500 throwing 68 DCvolt out on right channel

Post by admin » Thu Dec 21, 2017 3:57 pm

Unfortunately, we do not have the MF2500 schematic in our database. If you have access to the unit you can try to take measurements backwards along the signal path and try to identify at what component the signals deviate from each other.

However, you would have to be very careful and kind of know what you are doing as working on a live amp can be dangerous.
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Current Conrad Johnson Equipment in System: Evolution 2000, PV-12L, and D/A-2b.

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Re: MF2500 throwing 68 DCvolt out on right channel

Post by ronenash » Fri Dec 22, 2017 3:55 pm

Most likely it's the output transistors failed. It's not unlikely they took out other parts as well. The amp needs to be professionally serviced.
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Power:CJ LP125m SE, Beard P100, McCormack DNA500, Krell FPB300
Pre:CJ ACT2.1, Pr14, Pr15
Analog:VPI Classic/Falcon/SoundSmith Denon 103R, Lenco L75 rebuild
Digital:J.River-->Chord 2Qude
Speakers:SF Amati Futura

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Re: MF2500 throwing 68 DCvolt out on right channel

Post by bambadoo » Wed Jan 03, 2018 4:53 am

Have one that did excactly the same. Many parts are fried including one pair of output transistors.
Look here
viewtopic.php?f=17&t=1118

and here

http://www.diyaudio.com/forums/solid-st ... f2500.html

CJ was kind enough providing schematics.

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Re: MF2500 throwing 68 DCvolt out on right channel

Post by roberto » Tue Jan 09, 2018 3:02 pm

Hola. Bambadoo is right! Follow his instructions.
68 DC Volts can fried your speaker coils. Do not plug any speakers to the output terminal. If you want to load the amp, use a 30 Watt resistor, from 4 to 8 ohms.

My advice is, you must check all the output transistors from emitter to collector leakage. Drives could suffer of leakage too. Do the same thing. Usually at the input, there is a diferential amplifier, you must check here for semiconductor leakage too.

My best advice is, contact Conrad Johnson for help and advice. Mr. Jeff Fisher is a very helpful man. He can guide you better with your problem.
Last edited by roberto on Mon Jan 15, 2018 12:41 am, edited 1 time in total.
ML CLX speakers, BF-210 sub, Classic One Twenty SE amp. ET-7 C-J pre. Exasound E-32DAC, Mac Mini i7, Anthem MCA-3 power amp, Anthem AVM-60, Oppo BDP-103. ML Stage X Center, Motion 4, BPTSignature 3.5 Plus condiciones.

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designing engineer for Evulation 2000?

Post by runner70 » Fri Jan 12, 2018 10:28 am

I have been enjoying the Youtube videos by Stan McGowen from PS Audio. A great deal of information concerning many audiophile topics, but a great interview with both Bascom King and Arnie Nudell. The discussion was great (sorry to see Arnie pass away not long ago). I owned and operated for 13 year a high end audio store in Oshkosh, Wisconsin (Audiophile Specialists). We handled a large number of great products (one of which was Infinity).
I currently have an Evolution 2000 power amp (had it for over 6 years and great sound). But wondered about all the talk about tube front ends and MOSFET outputs on the new PS Audio BHK (Bascom King) designed power amp. He (Bascom) stated that this was one of the first times this application was used. I thought this is the design of my CJ power amp. Bascom became technical when discussing circuit design of outputs, and I am not qualified to be able to understand that, but did Bacom King have any input on the design of the CJ 2000 power amp, and how much is different between the new PS Audio BHK design amp, and my CJ power amp? Stan did mention that Bascom did work with CJ, so just wondering how the two compare? I know my unit is a few years old, and this is a new product from PS Audio, but would like to know how they compare in design and maybe, sound? Love my CJ amp. Is bi-amped with the CJ driving my Acoustat Monitor 4 panels, and a ARC D150 driving my two large subs, with a modified Dahlquist electronic crossover, along with a tube preamp and tube CD player. These are products that I sold for many years, and still lover them after 30 years. Work great and still sound great. Do you recommend any reasonable priced mods for the amp? No mods to date on the unit.

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Re: MF2500 throwing 68 DCvolt out on right channel

Post by admin » Sat Jan 13, 2018 7:59 am

Hi runner70. I also have a 2000 Evolution amp and love it. I, unfortunately, do not know its design history in detail. I too would be interested in the sound comparison of this now "older" amp vs something designed more recently. As for mods, one simple cheap mod that can be done and which my unit has is the addition of an IEC plug so the power cord can be changed. Whether this makes a significant difference in sound,... I don't know?

-sorry about this post being a little off-topic.
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Current Conrad Johnson Equipment in System: Evolution 2000, PV-12L, and D/A-2b.

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