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Old 8th December 2011, 08:09 AM   #391
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Default SR50 SR200

This is my SR50 and SR200
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Old 8th December 2011, 10:39 AM   #392
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Quote:
Originally Posted by leonatax View Post
Apex I need your help, the BF421 is geting hot on idle on my RS50 what can be the problem?
Nice work, BF421 must be hot, but you can replace BF421 with resistor like in SR200.
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Old 8th December 2011, 01:27 PM   #393
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Thanks
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Old 8th December 2011, 01:34 PM   #394
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Quote:
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Nice work, BF421 must be hot, but you can replace BF421 with resistor like in SR200.
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Q7 on SR50 is BF420 not BF421.
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Old 8th December 2011, 01:49 PM   #395
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The problem is that q10 BF421 is geting hot not q7
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Old 8th December 2011, 06:32 PM   #396
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Originally Posted by leonatax View Post
The problem is that q10 BF421 is geting hot not q7
Ok, all BF420/421 must be hot 12mA x U rail is about 600mW per BF. Replace R16 and R17, use 2k2 instead 3k3 for 6mA thru BFs or 2k7 for 8mA and temperature of BFs will decrease.
What is PSU rail voltage for your SR50?
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Old 9th December 2011, 05:02 PM   #397
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Rail voltage is +-40 vdc 6amps and BF421 is hot even if nothing is conected to amp
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Old 9th December 2011, 05:05 PM   #398
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I use regulated psu with 2 pairs of tranis
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Old 9th December 2011, 07:58 PM   #399
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12mA @ 40V is almost half a Watt. That is hot!
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Old 9th December 2011, 09:41 PM   #400
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Quote:
Originally Posted by leonatax View Post
Rail voltage is +-40 vdc 6amps and BF421 is hot even if nothing is conected to amp
It's OK VAS work in class A, all BFs must be hot without input signal and output load, and you can measure voltages on 100R resistor (about 1,2V for 12mA) and measure offset on amp out (about 1mV) if not something is wrong.
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