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Panasonic CT-27G32V - dead TV with click   Goto page 1, 2, 3, 4, 5, 6, 7, 8, 9  Next  
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chumba



Joined: 01 Jul 2009
Posts: 66

PostPosted: Wed Jul 01, 2009 9:39 am    Post subject: Panasonic CT-27G32V - dead TV with click Reply with quote

Have a Panasonic CT-27G32V TV. Will not power up at all by power button or remote - no video, no audio. When plugged in the 1st time, a faint whine is heard like the CRT is coming up, but still dead. Then I unplug the TV and plug it back in and one click is heard (assuming this is the low V remote Rx circuit relay), but still dead.

When the case was 1st opened I noticed the PC board is cracked at the HOT area and the Collector had no solder connection, but I have repaired the lands and resoldered the HOT.

The fuse is good. Voltage at D1555 HOT is -95V at B & E, & -90V @ C. The junctions read ~0.4v, except C to E which is 0 ohms (but I believe there is a damper diode in this junction??).
The driver xfmrs have continuity. Cannot see any burned or bulged parts.

Please help.... this one is racking by brain!!!
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JTS1957



Joined: 21 Jan 2009
Posts: 2347
Location: Far, Far Away

PostPosted: Wed Jul 01, 2009 11:35 am    Post subject: Reply with quote

1) Remove transistor.
2) Base to emitter (either polarity of test leads) ~.4 on Fluke "diode test."
3) Base to collector infinite on one polarity of test leads and a "reading" with leads reversed.
4) Collector to emitter infinite on one polarity of test leads and a "reading" with leads reversed.
NO "Zero" readings allowed!
chumba



Joined: 01 Jul 2009
Posts: 66

PostPosted: Tue Jul 07, 2009 6:52 am    Post subject: Panasonic CT-27G32V - dead TV with click Reply with quote

Ok, removed the HOT and here are the measurements in diode test mode:

B to C = 0.46 with -ve lead on C and Open with +ve on C.
C to E = 0.45 with +ve on E and Open with +ve on C.
B to E = 0.028 with either polarity on meter and 44 ohms in R mode.

Would B to E be considered shorted? Could that have been caused by the open circuit (when HOT was found unsoldered on C) and full bias flowing through B to E?

Thanks
Wendell1980



Joined: 30 Dec 2007
Posts: 74
Location: Cambridge, Ontario, Canada

PostPosted: Tue Jul 07, 2009 8:18 am    Post subject: Reply with quote

yea the transistor is shorted, usually when one of the legs come loose it will destroy the horiz transistor
JTS1957



Joined: 21 Jan 2009
Posts: 2347
Location: Far, Far Away

PostPosted: Tue Jul 07, 2009 9:39 am    Post subject: Reply with quote

http://pdf1.alldatasheet.com/datasheet-pdf/view/270630/SAVANTIC/2SD1555.html

See anything between base and emitter in this datsheet's symbol? That's what you're reading, a resistor of fairly low value. So transistor is good.

Without the transistor in the TV, What is collector (pad) voltage? Also resistance reading to ground?

Check the whole board for other cracks - use a magnifier - where there's one, there may be more.
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chumba



Joined: 01 Jul 2009
Posts: 66

PostPosted: Wed Jul 08, 2009 11:22 am    Post subject: Panasonic CT-27G32V - dead TV with click Reply with quote

With HOT removed,
Resistance from all lands E, B & C to ground is infinite.
DC Voltages measured to ground (=-ve lead) are:
VC= -88.7 v
VE= -94.3 v
VB= -94.6 v
JTS1957



Joined: 21 Jan 2009
Posts: 2347
Location: Far, Far Away

PostPosted: Wed Jul 08, 2009 12:05 pm    Post subject: Reply with quote

You're doing something wrong (either Not using correct ground or meter not set right).
Resistance from base or emitter to HOT (as opposed to COLD ground) ground should be very low (or the driver transformer is open).
With Black lead of meter on HOT ground (C806 negative terminal "-") and red lead to collector (pad) of Horizontal output transistor should have +130 volts)
chumba



Joined: 01 Jul 2009
Posts: 66

PostPosted: Wed Jul 08, 2009 3:22 pm    Post subject: Panasonic CT-27G32V - dead TV with click Reply with quote

DMM is on DCV - autorange, -ve lead to CRT screw or tuner case for Ground. Could this be a PNP HOT that uses -ve bias V?
JTS1957



Joined: 21 Jan 2009
Posts: 2347
Location: Far, Far Away

PostPosted: Wed Jul 08, 2009 3:47 pm    Post subject: Reply with quote

This chassis uses a HOT ground for the power supply and horizontal deflection areas of the set.
COLD ground for everything else.
chumba



Joined: 01 Jul 2009
Posts: 66

PostPosted: Thu Jul 09, 2009 7:24 am    Post subject: Panasonic CT-27G32V - dead TV with click Reply with quote

With HOT removed,
Resistance from B or E lands to C806 (-ve lead/hot ground) is 0. C is infinite.
DCVolts using C806 as hot ground are:
VC= +9.4 v
VE= 0 v
VB= 0 v

T501: R= 0 Ω between outer 2 terminals, and infinite b/w all its other terminals
T502: R = 0 Ω b/w all terminal combos.
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