[TechAssist] Heads up Toshiba 32A32 FIX
- From: MDileo0000@xxxxxxx
- To: techassist@xxxxxxxxxxxxx
- Date: Mon, 30 Jan 2006 12:49:48 EST
TAC 245 chassis, manufac.Apr 2002.
The customer said the raster bowed in suddenly. The set ran a further 10
minutes and then went into shut down. Initial troubleshooting revealed a
shorted
pincushion diode, D461. After replacement, the set came up but with a bowed
screen. L461 was becoming hot and leads to the pin amp circuit, all of those
components checked good. But there was no drive waveform to this circuit and no
output from pin 23 of the jungle IC, Q501. Bad IC. Not in my stock. By luck, as
I shut down the power I noticed an arc across an smd resistor, R457 (100k
1/20 wt). This ties back to the e/w feedback, PIN 23 of Q501. The resistor was
open, but the arc over was a concern since there was no isolation at this point
to shield the new IC from being knocked out again. The feedback source comes
from the ABL monitoring of pin 8 on the FBT, T461. Looking at pin 8 with the
scope showed a 600 volt spike, C445 (.056ufd@100vdc ) was open. Replacing the
cap eliminated the arc over and replacing the failed components restored this
set to normal operation. This extensive failure may have been preventable had
R457 been a larger resistor, 1/4 wt. I have had other repairs that involved the
failure of these incredibly small components. Good for business.
Dominic DiLeo
Atlantic TV
Freeport, Maine
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