Musical Fidelity e300 power amp trannys help :( - diyAudio
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Old 25th November 2008, 10:19 PM   #1
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Default Musical Fidelity e300 power amp trannys help :(

hi folks,

well ive got the above amp which i have repaired a few times. however i'ts now popped one of the o/p trannys, they are craftily labelled f15n/f15p. obviously these are mf's own codes, a habit they are fond of so they can rip you off when you need replacements.
there's a total of 4 per channel.
i've no idea if they are mosfet or bipolar. circuit consists of (input to output ) - 5534 and 5532 , then x2 of each mps a92/a42 (which ive changed a few times), followed by 2sd649/669 pair then the big TO3 f15n/f15p pairs. there is a bias pot too.
amp always sounded good but is terribly designed from an engineering point. originally had x4 50V 10000uf smoothing caps, running at , u guessed it, over 50v (53ish). changed them for 63v while ago.
i actually wrote to MF 1st time those caps dried out, pointing out the problem. Engineering director wrote back claiming the caps were rated at +10% so 55v . pah! the cheek of it.
also the mpsa92/42's literally cook, along with two 1/4 1k0 metal film resistors which should def have been 1/2 watt.
anyway, im flat broke at the minute and need to revive this beast.

if anyone can help with any info i'd be extremely grateful.

many thanks

raymond
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Old 25th November 2008, 10:37 PM   #2
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post a picture of amp inside , so we can compare it with some schematics we have ......

("we" - any of us )
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Old 25th November 2008, 11:06 PM   #3
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god damn photo too big, will resize at work tommorow and pst then.! thanks
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Old 26th November 2008, 06:59 AM   #4
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ok not so clear due to the 100k restriction .....here u go
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Old 26th November 2008, 07:02 AM   #5
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another
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Old 26th November 2008, 09:38 AM   #6
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send few full res pics to >choky@neobee.net<

try at least to measure one output transistor - on good channel - is it bjt , with simple diode test on DVM
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Old 26th November 2008, 09:54 AM   #7
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hi , i will send you some full res images when i get home later, thanks for the interest greatly appreciated.
will measure one tonight , one channel definately ok .
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Old 26th November 2008, 11:50 AM   #8
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ok i sent you some pics :-)
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Old 26th November 2008, 12:32 PM   #9
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Old 26th November 2008, 12:50 PM   #10
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Default reallly!?

any numbers andy? thanks a lot
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