Mulja tv repair portal
Equipment Repairs => LCD TV forum => Topic started by: Turnip on September 26, 2014,10:51:47
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Hi folks,
Had a couple of these in, where the Blue LED might flash or not, but set wouldn't start.
Latest one has always 5v present but nothing else. Was suspicious of Brown'ish rubber glue on the Dongyang PW607D P/S (bit like a Sammy) so scraped it off B4 it cremated.
Replaced F9222L as they can be a pain but still no go.
Wonder about the 2 main boards, as perhaps no 'turn on' signal, but notice 'Flea' is full of main boards and screens but not a single P/S board in sight.
Any advice - Thanks, Chris.
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I don't know the telly, but what saved my day a few times when 'no power up' and the 5V is OK and hash free, I scrapped a 'El very cheapo' digicam and kept it's 3.7 V battery, I use the battery and lob it on the 'power ON' rail, negative to ground, indicating to me the power supply is raring to go or not... done the same trick with inverters, for protection I add either a diode or low value resistor in series with the +Ve lead depending on nearest to hand, the 'power ON' signal usually sits around 3V or so.
Could point towards, no 'power ON' supply, CPU corrupted and wanting a reflash, one of the inputs kaputted causing a no boot situation, backlights or even the coupling caps to the tubes as well as inverter faults.... this is all after I've checked the CPU clocking oscillator is OK.
Dunno what that brown gunge is made off but sure had it causing problems in almost everything electronics from way back.
Best I can do.
Dave
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Check-change
RS-5 (4,7KR)
RS-7 (4,7KR)
RS-4 (10KR)
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Check-change
RS-5 (4,7KR)
RS-7 (4,7KR)
RS-4 (10KR)
yes I have had 2 of these with this fault resistors sorted it for me
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Thanks Jordan and Vince,
Notice those resistors had been covered in Brown gunge, bottom centre of power board - one 4k7 was O/C.
Thanks Davy, wouldn't mind the brown gunge if it didn't cause P/S boards to become terminal, as with most old LCD Sammies. Like the idea using a lithium cell as a starting handle, will give it a go in future.
Thanks again - set sorted - Chris.
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Hi folks,
After a couple of days, picture flickered for a few initial minutes, then perfectly OK. Suspected T-con connections, so cleaned then tapped main panels as problem didn't clear.
Backlight then cut for some reason with 24v present. Fuses for both inverters were OK, and trannie secondaries were 130 Ohms with a digital meter though the AVO suggested differences with polarity change.
Inverters - cheap as chips, think get a pair to try though suspect the law of diminishing returns will rule. Guess will be duff tubes on such an old set.
Admit never taken this screen apart before, but curious as how the tubes are connected with just a couple of feeds. Guess will find out - Chris.