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Old 23rd March 2004, 11:59 PM   #1
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Location: Iowa
Default Soundcraftsmen RA6501 Troubles

Well, even though I'm new to THIS forum, I'm not new to the world of forums, so I'll preface this by saying that I have already searched the forums and most of the internet to little or no avail on my problem.

I have a Soundcraftsmen RA6501, which is a Class H Amp, 750Wpc 4 Ohms. Weighs around 50 pounds, give or take.

Problem is this. I turn on the unit, and immediately the "Protect" light is lit. About every 3-5 seconds, I see the "clipping" lights for channel A and B flash, which is accompanied by what sounds like a cycling of some sort within the unit. With the cover off, it sounds like the transformer itself is what is cycling, but it's hard to tell without schematics and more knowledge about the unit itself.

That all said, anyone have any experience with Soundcraftsmen Amps other than calling MTX to hear "we don't support that at all"? I'd like to get this beast up and running again soon. Even though it has no vU meters or other fancy lights, it still deserves a new lease on life!
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Old 24th March 2004, 12:37 AM   #2
OMNIFEX is offline OMNIFEX  Jamaica
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Location: Locked Up In The Amp Rack
The Soundcraftsmen RA 6501 is not 750 per channel
@ 4 ohms.

250 watts per channel @ 8 ohms, 20 - 20Khz, 0.09% THD

375 watts per channel @ 4 ohms, 20 - 20Khz, 0.09% THD

750 watts Bridged Mono @ 8 ohm, 20 - 20Khz, 0.09% THD

Sounds like the output transistors are fried.

The RA 5002, 6501, 7501, 7502, and, 7503, are
known for these symptoms. I owned a 7501, 7502,
and, Pro Power Four.

The 7501 spent more time in the shop, than in use.

The 7502 turned into a subwoofer amp for my mother's
Home Theatre. (Was in the shop three times)

The Pro Power Four is in the corner collecting dust.
(Never had a problem)

They are very problematic (The RA Series), and, unstable
under low impedances. I sold mine (7501) on Ebay to this
guy that I believed fixed it. If you want his Email Address,
drop me a PM. He may have the schematic or give you
some leads.

You are better off Doing A Search for the RA 5002, 7501,
or, 7502. They were the more popular ones. Where as
the RA 6501 wasn't appealing to many, due to its lack
of gain controls, pretty green, and red lights.

All the RA Series had the same power. Some offered more
bells and whistles than others............ That's all.
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Old 24th March 2004, 02:32 AM   #3
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Location: Iowa
Ahh, that 'splains it. I was just going by what the front of the amp said, I'm a little new to these amps, as they are older than me...

Not much on the web for 7501 or 7502, I'll look for 5002. Sounds like I delved into the wrong piece of history, unfortunately. A PM is on its way to you. Thanks!
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Old 9th May 2005, 02:57 PM   #4
mhirvon is offline mhirvon  Finland
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I have a Souncraftsmen MA 5002a (with led output power meters, not analog).
Now it seems that the output transistor has burn
Does one of you guys happen to know what could be the transistors type?
I've found that RA 7502 uses MM4003 (substitute would be 2N5415)...
Could it possibly be the same one for a bit smaller AMP of mine?

Thank you
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Old 29th July 2010, 11:30 PM   #5
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Join Date: Jul 2010
Smile Soundcraftsmen RA6501 Troubles

Re: Squall line's comments.


I have used a RA6501 for 4 years now without a single issue. It is by far the best amp and best Soundcraftsmen amp I've ever used! It doesn't have a bunch of silly lights to burn out like others did. No scratchy knobs.
It is truly made with a proffessional set-up in mind. Of course, you must provide a ventilated space as with all amps.

Mine puts out 375WPC @4ohms. 750Watts.

Squall makes it sound like they all have problems, I haven't had any with this amp. I have owned a lot of power amps in the 25 years I've been a musician and this has been my favorite. Just thought I'd share...

I hope this helps!
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Old 29th January 2011, 02:47 AM   #6
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Default Soundcraftsmen RA6501 amp

sorry, my cooment was for omni.
I loved my RA6501. Hated my Ra7501, too many lights that burned out.
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Old 29th January 2011, 02:49 AM   #7
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sorry, my comment was for omni.
I loved my RA6501 and hated my RA7501, it too many lights that burned out.
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Old 10th May 2015, 05:46 PM   #8
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Join Date: May 2015
I have an Ra6501 that I have had since 1981 and it is doing the same thing as soon as I power on the amp the protect light comes on and you hear clicking. I know very little about electronics repair and need to find someone in Riverside ca that can repair this amp
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