Arcam Alpha 8R Amp blowin fuses....... - diyAudio
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Old 20th September 2010, 08:52 PM   #1
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Talking Arcam Alpha 8R Amp blowin fuses.......

Hi All

As it says....the 8R amp (Conf. with an 8P in Bi Amp mode!) is blowing fuses
....2 so far!!

Had a similar problem with a Mission Cyrus 1 recently, and cured it by replacing 4 X rectifier diodes in the PS....am hoping this might be a similar fix....?

I have a decent meter at hand....but have no idea how to test the O/P transistors....
What would members check first??

Ta
Kev/Leeds/UK
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Old 20th September 2010, 09:46 PM   #2
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You need to check for a short from CE or DS on the output transistors.

Sometimes the driver is wiped out as well.
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Old 20th September 2010, 10:03 PM   #3
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....Now then.....what is ....'the driver'...?
Kev
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Old 20th September 2010, 10:31 PM   #4
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Talking ....testing MOSFETS......

With meter set for continuity...
....on LH both semi's show no shorting between pins

....on RH....one semi shorts between all 3 pins, and the other shorts between outer pins.....

Farnell lists several replacements for the IRF540....some with different specs

......

Browse for Products | Farnell United Kingdom

which one would suffice??? (I may as well replace all 4...??!)
Kev
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Old 20th September 2010, 10:47 PM   #5
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Do you know what caused the amp to blow?

Avoid the IRF540N devices as they can't take the heat (literally). Use IRF540PBF or IRF540A. I do have some IRF540 made by ST for sale if you don't have enough to meet Farnell's minimum order.
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Old 20th September 2010, 11:01 PM   #6
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Talking Do I know what caused the amp to blow.....?

....MAY have inadvertently shorted o/p's while re-positioning speakers

(I know I should've turned off the amps before disconnecting and reconnecting)

.......I'll learn in the end.....

Of course....that could all be just couincidental......

Kev
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Old 21st September 2010, 12:14 PM   #7
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Was music playing at the time?
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Old 21st September 2010, 07:43 PM   #8
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...4 X IRF540PBF's (at 1.00 each from local Farnell)....and a 10p fuse later,
and all is well!!

Many thanks for your help....

Kev
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