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Old 19th February 2013, 07:23 AM   #11
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The 4558 isn't likely to be used to supply power to the power supply IC. It may drive a transistor that drives voltage to the PS IC but it won't drive it directly. The voltage is likely supplied via the collector of a PNP transistor.
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Old 22nd February 2013, 09:17 PM   #12
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I found a B647 that deliveras the 12 volts to pin 8,11,12..

Is there a good sub for the B647 ?
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Old 22nd February 2013, 09:28 PM   #13
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BD140
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Old 22nd February 2013, 09:39 PM   #14
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Replaced that same problem only 2 volts on pin 8..

There are only 2 other transistors in that area A1015's

If i find 1 to be defective is there a good replacement for thoose?


Also there is a diode connected to pin 8 (ZD1) 1 side has 2 volts other side is 0.00 volts and 2 volts measured directly across it..

I that normal and i need to back track more?
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Old 22nd February 2013, 09:50 PM   #15
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Post the DC voltage on all 3 legs of the transistor.
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Old 22nd February 2013, 09:54 PM   #16
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Leg 1:13.90
Leg 2:13.60
Leg 3:13.10
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Old 22nd February 2013, 09:58 PM   #17
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Either that transistor doesn't go to pin 8 or the voltage you read on pin 8 was wrong.
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Old 22nd February 2013, 10:08 PM   #18
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There is an A1015 transistor the voltage on that is

Leg 1:13.80
Leg 2:0.8
Leg 3:13.90
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Old 22nd February 2013, 11:23 PM   #19
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Do you see a 0 ohm connection to either of these transistors from pin 8, 11 or 12?
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Old 22nd February 2013, 11:59 PM   #20
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The middle leg of the BD140 connects to a 100 ohm resistor then goes to pins 8,11,12..


If i place one probe on pin 8 and the other probe on the middle leg of the BD140 i get 100 ohms on pin 8 ..

So im assuming that the BD140 is connected to pin 8


I get 13.89 volts on 1 side of the 100 ohm resistor but only 2.74 volts on the other side..


Could the 494 possibly be bad?
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