Soundcraftsmen MA5002 power output type? Help! - diyAudio
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Old 21st June 2003, 03:16 PM   #1
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Question Soundcraftsmen MA5002 power output type? Help!

Power transistor cross-reference help!
For Soundcraftsmen. MA5002. Channel B, Q11-Q16. Labelled over, "Power transistor 8" original p/n 419 222 00. Later changed to 419 221 08.
Don't think MTX (they bought Soundcraftsmen around 1992) will help identify.
The local tech is baffled. It *seems* that the label is over the lettering 'power transistor 4'.
This is a BIG, handsome amplifier. Gotta get those VU meters swingin' again!
HELP

It's like the original number(s) were scratched out, and the Soundcraftsmen p/n label stuck on.
SM didn't help, either.
Anyone identified the proper make/part?
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Old 21st June 2003, 03:44 PM   #2
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Like this? :http://www.diyaudio.com/forums/showt...248#post194248

http://www.sound-smith.com/fets/
Mailing or calling the guys might help.

/Hugo
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Old 21st June 2003, 05:02 PM   #3
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Default yup, like those

what are they? which ones to get, or doesn't it matter if ya replace 'em all?
Bit of a newbie with this Class H amp. Sure is good-looking. Would like to get the bum channel repaired.
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Old 21st June 2003, 05:14 PM   #4
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Sorry, I wasn’t clear enough.
There seems to be no info regarding the numbered transistors.
Its unlikely Soundraftsmen used the same transistors in all there amps.
The link was provided so you could just try to get some more info from Sound-smith regarding which transistors to use in your amp.
Maybe they know.

Hope this helps.
BTW, where did you get the info you have at present? Part numbers? What is MTX? What is SN?
/Hugo
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Old 21st June 2003, 05:45 PM   #5
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Default in doubt output devices broken

rather look for bad contacts in those bordeaux/white plugs between main boards and output device-board. They tend to crack if you touch them after all these years.

That's the vulnerable spot I found on my ma5002 anyway.

Also replaced a resistor somewhere in the power-on circuit if I remember.
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Old 21st June 2003, 07:10 PM   #6
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MTX is Mitek Corp., who bought the financially floundering Soundcraftsmen around 1990.
SM=Service Manual

Actually, it is very likely they used the same transistors. I have two others, the PA5001 and A5002, and the differences are cosmetic. They are all three big, 50-lbs., 250 wpc amps.

I have emailed Peter at Sound-Smith, can't remember getting a reply. MTX says 'we don't support that model anymore.'

Believe me, I have been searching for a long time trying to get this big MA5002 up and running.
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Old 21st June 2003, 08:14 PM   #7
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[IMG]C:\My Documents\a2j_amp1.jpg[/IMG]
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File Type: jpg a2j_amp1.jpg (21.3 KB, 707 views)
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Old 21st June 2003, 10:32 PM   #8
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Yeah, that's the A5002 with the LED's. I have mine currently paired with a Kenwood Basic C-2 preamp driving my Pioneer HPM-900 speaker systems. Pure, simple clean sound. Mine is even usually set with the gain at the same as in the picture!

The PA5001 is a simple big box with power switch and two LED's, one for indicating it is on, the other to indicate clipping. Otherwise pretty much the same inside.

They are sweet, strong amplifiers that easily exceed their specs.
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Old 21st June 2003, 10:57 PM   #9
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after a quick look inside, I have replaced the rectifier bridges also.

The resistor in the power on cicuit that i replaced was the big one, now a wirewound 20w.

I once wired some bigger capacities in paralel with the originals (wich still are in) and found out that there was a hearable enhancement in the lows.
Since I don't use the amp very often, it's more like a collectors item, I don't want to alter too much on the original.
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Old 22nd June 2003, 02:52 AM   #10
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Default Costly Hitachis

Wow! For those who clicked upon the above link advertising replacement NOS Hitachi power MOSFETS (I saw that a few months ago)...

These devices are unique in that the source is connected to the case. I have 24 of the 2SK/2SJ devices in my amplifier...at $62 apiece...$1,488 worth of output devices alone!

Or, if that were a big Pass style amplifier...80 devices would be $4,960!!! Kind of a humbling thought, especially if one thinks of matching them (you'd need a few more devices, wouldn't you??)


I just LOVE the look of the venerable massive TO-3 case.

I met Bob (Brain fart at the moment, I'm terrible with names!), the designer of the monster Soundcraftsmens, back in 1990-1, at the Vegas CES. He had a schematic for the PM1600/PR1800/Pro-Power Eight in his briefcase...how's that for pride? He had just made the transfer to MTX.
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