Vintage mosfet for a Rauch DVT 250S PA amp - diyAudio
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Old 11th May 2008, 08:51 AM   #1
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Default Vintage mosfet for a Rauch DVT 250S PA amp

Hi everybody!

I've got a Rauch DVT 250S PA amp that needs some repair; several of the mosfets are damaged, and I have problems finding new ones.

The text on the mosfet says: "K227 4M1".

I've found a datasheet (se attachment) that might identify the chip as a SILICON N-CHANNEL ENHANCEMENT MOSFET Toshiba 2SK227. It seems its out of production and I'm struggling to find a replacement. Could please anyone help me?

Thanks in advance!

Regards
Joakim
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Old 12th May 2008, 10:04 AM   #2
Mooly is offline Mooly  United Kingdom
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Not in this package ? Have you contacted the manufacturer ? for suggestions.
There are some wierd older parts around, are these a lateral as can be obtained today, albeit in a different package.
Regards Karl
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Old 12th May 2008, 01:49 PM   #3
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Thanks for the reply.

I've made some more research and it seems like this schematic a370 thread might help me.

I'm not 100% sure, but it seems like the K227 is similar to the SK227. If that's right the SK227 could be replaced by 2SK1058.

The board also has a chip named "J83" which I believe is similar to 2SJ83 and then could be replaced by 2SJ162.

The 2SJ162 and the 2SK1058 are for sale on eBay
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Old 12th May 2008, 02:15 PM   #4
Mooly is offline Mooly  United Kingdom
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Hi,
The 2SK1058 and 2SJ62 are what I was thinking of, BUT they are physically very different. You would have to fit new insulating washers and possibly drill the heatsink as well !
Regards Karl
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Old 12th May 2008, 04:01 PM   #5
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I would consider the IRFP240 and IRFP9240 devices.
Thye dont look too far away from the devices you mention.

I use them extensively in amps I build and they are good solid devices.

If you do use them you might have to fiddle with the bias voltage to get it right.
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Old 12th May 2008, 04:47 PM   #6
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DO NOT try to use IR transistors. Use the aforementioned 2SK1058 and its sibling. The Vgs of your older transistors match the 2SK1058. The pinout also. The IR Vgs are about 4V. They can not be used without redesigning the Vbe bias string. Also, the pinout on the IR are different.

Regards
Roar
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Old 12th May 2008, 04:57 PM   #7
Mooly is offline Mooly  United Kingdom
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Hi,
There is a lot of confusion with some of the early FET's as to just what type they are, vertical or lateral. The IRFP type are HEXFET's and these must NOT under any circumstances be used where a lateral is specified. The gate/source voltage is much higher and MOST important of all they have a positive temperature coefficient, which put simply means the amp will self destruct.
Regards Karl
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Old 12th May 2008, 04:59 PM   #8
Mooly is offline Mooly  United Kingdom
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Think we both posted together then I would stick my neck out and say the 1058/62 are fine .
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Old 12th May 2008, 05:01 PM   #9
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Quote:
Originally posted by Mooly
Hi,
There is a lot of confusion with some of the early FET's as to just what type they are, vertical or lateral. The IRFP type are HEXFET's and these must NOT under any circumstances be used where a lateral is specified. The gate/source voltage is much higher and MOST important of all they have a positive temperature coefficient, which put simply means the amp will self destruct.
Regards Karl

What absolute nonsense !!!!

I use IRFP extensively and they certainly dont run away thermally ! I have one 300 watts RMS amp, a 100 watts RMS amp and a 600 Watts RMS amp which get flogged to death in disco work.

If the gate voltages are different then the bias needs altering accordingly.
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Old 12th May 2008, 05:10 PM   #10
Mooly is offline Mooly  United Kingdom
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Hi,
They dont run away thermally because the amp will have the equivalent of a VBE multiplier. Laterals due to the negative tempco don't require this. It's one of the great features.
Try running a HEXFET with fixed bias and see what happens
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