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Old 02-18-2018, 09:56 AM   #36
seve91
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Join Date: Oct 2013
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Default Re: Philips FR-740 working but no audio output

Quote:
Originally Posted by R_J View Post
I wonder if 7309 is'nt bad, there should be -34.5 volts on the collector. I guess you could check the 2 100k's 3329 & 3936
-------from other post-------
ok, page 79:
A of 6305: 0V
K of 6305: 3.2V
C of 7309: 0.04V <------------the schematic indicates there should be -34.5 volts here
C of 7304: -41.5V
C of 7310: -41.5V
--------------------
I see from before
STK496-270
11 = 39,5V
14 = -33,5V
10 = -39,5V
3,4,19 = -40V
7,8,9,12,13,15,16,17,18,20 = 0V <------------pin 12 listed as 0 volts
7309: E= 3.4V, B= 3.05V, C= -1.4V
7304: E= -40.3V, B= -39.6V, C= -40.3V
7902: E= -40.3V, B= -39.6V, C= -40.3V <-------7902 (C) listed as -32V
check the voltage on resistor 3918 and then 3935

I checked a data sheet for a STK486-430 and the CCC pin only changes BY 2 volts between amp on and amp off (it uses -50v amp ON -52v amp OFF)
the resistors are all SMD and all are in good conditions.
Voltages:
3329: -39.6V (B of 7304) and -1.44V (C of 7309)
3936: -39.8V (B of 7909) and -38.15V (to 4910)
3918: -40.28V (to 3935) and -40.27V (C of 7902)
3935: -40.16 (C of 7909) and -40.18V (to 3918)

is it possible that one of these transistors is not working good?
I don't know if it can help, but every time i touch the tip of oscilloscope probe to C of 7310 (pin 14 CCC of STK496-270) i can hear a click coming from the speaker (i have connected a speaker, just to test, to the Front L output)

Last edited by seve91; 02-18-2018 at 09:59 AM..
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