[TechAssist] Fix JVC AV32260am dead
- From: "Wayne Vanaman" <Wayne@xxxxxxxxxxxxxxxxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Tue, 24 Jun 2003 11:50:08 -0500
[NESDAnet]
Model #: JVC av-32260am
Subject: unit shuts down
Reason: Bad Soldering Other
Symptom: Horizontal output transistor shorted. After replacement the set
would run for about 2 sec. and shutdown, or the set would run at 22Khz H and
81Hz V, the Horizontal output transistor and horizontal drive transistor
would get very hot
Cause: Micro ic701p55 had horizontal rate pulses instead of vertical rate
pulses. On the second tuner board, corrosion between W019 and W020 measuring
19 ohms, but would change with temperature, was coupling "HP" onto the "VP"
line, swamping the Vertical pulse on Q701c and into the micro.
Cure: Desoldered, cleaned, resoldered W019 and W020 on the second tuner
board.
NOTE:
The jungle IC is TB1265AN. This is also the jungle IC in the new Thomson
ATC113 Chassis.
At start up this IC outputs the Horizontal at 22KHz and the vertical at
81Hz. After about 2 seconds the frequencies drop to their NTSC standard.
The effect here is a "soft start" in that, due to the tuning of the
horizontal section, the High Voltage will only rise to about 19700v. When
the frequency drops to nominal the high voltage goes on up to 29KV. Viewing
the drive signal when it is running at 22Khz gives the impression that there
is a problem in the drive circuit because there is distortion in the
waveforms.
It appears that, in the JVC chassis, the micro will tell the jungle when to
frequency shift. This may or may not be the same in the Thomson chassis, I
have yet to see one.
Wayne Vanaman
Omega Electronics
6904 W Fairfield Dr
Pensacola, FL 32506-3310
850-456-5995 voice
850-458-6369 fax
Wayne@xxxxxxxxxxxxxxxxxxxxx
www.PensacolaTVRepair.Com
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