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P68 300w sub amp problem
P68 300w sub amp problem
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Old 8th October 2003, 09:50 PM   #1
flashback is offline flashback  Macedonia
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Join Date: Oct 2003
Location: Macedonia
Question P68 300w sub amp problem

Hi everybody!!!
I`m new to this forum and i`m well surprised how people try to help one to each other!
I have built Rod`s 300w sub amp but i have a small problem-quiescent current! As described it should be arround 55mv(55ma)on R16,or R17.My result n R16-50ma;on R17-100ma,and i have a lot of heat on R17!!! No other problems.Can anybody help!!!
I have built a sealed sub encosure using Infinity Kappa 120.3se and this amp is part of that enclosure so it really matters to me to correct this problem before bursting some output device (2SA1943 and 2SC5200)
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Old 9th October 2003, 06:06 AM   #2
DieterD is offline DieterD
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Join Date: Dec 2001
Location: Howick South Africa
I have built four of these amps and they have all worked first time.

Carefully check every component and make sure its correct, especially resistor values, often we grab a 22 ohm instead of a 220 ohm.

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Old 9th October 2003, 07:12 AM   #3
Vigier is offline Vigier  Netherlands
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Join Date: Nov 2002
Location: Netherlands

indeed: check the values of all components around the transistors.

2nd idea: did you match the transistors? There could be a really big difference between them in their properties (hmm...bad english ) .
In 9 of my amps I use Toshiba's GT20D101 and GT20D201. When parallelling those I measured a quiscent current of 184mA and 346mA for the other transistor. I had to match them, and now the problems have been solved (339mA/346mA).

Grtz, Joris
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Old 10th October 2003, 09:58 AM   #4
Tazzy is offline Tazzy
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Join Date: Jul 2002
Location: Netherlands
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Flashback, any luck in fixing your amp?
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Old 12th October 2003, 08:37 AM   #5
flashback is offline flashback  Macedonia
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Join Date: Oct 2003
Location: Macedonia
Talking No result

Hi guys!!!
No success at all.I`ve removed the kse350 transistors which were mounted as a replace for the mje350 at the beginning. Now with the mje`s the result is even worse!!!
At the point where i had a normal quiescent current, now i have only 10-20ma(measured with analog multimetter).I just can understand what is happening??!!??!!
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