Mulja tv repair portal
Equipment Repairs => LCD TV forum => Topic started by: Turnip on July 18, 2017,11:44:49
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Hi folks,
Got one of these antiques in where no S/by Led lights. Thought check that area of the P/S where the 7 pin S/by supply chip has full HT but nothing the other side of the transformer and no obvious duff diodes. Downloaded manual for the set but it's rather different to mine in that area.
Wonder if there's a common cause for the problem ? - Thanks - Chris.
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Hi Chris,
Check D6903 for s/c and R6304 for o/c. Must use an ultra-fast diode for D6903 like UF4004 or BA159. On the PSU circuit, these are located at 10 o'clock to T6300.
Have uploaded a service manual.....may be the same as yours. The standby control IC may be inert. Have further notes for no standby:-
Replace D6903 and D6905 - diodes may check ok but replace them anyway.
Replace IC6300, D6903, D6904, D6905, C6306, C6308, C6312 and R6301. D6903 (on schematic) may be D6905 (on the board)
Food for thought. Bruce
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Hi Bruce,
Many thanks. Didn't notice I'd printed out the Power board schematic for the small screen version so naturally the part numbers didn't tie up with my 40 inch set.
Eventually got the plot, checked/replaced the bits suggested discovering one of those fast diodes D6903/5 were a bit leaky. Used BA159 and all OK.
Got there in the end, but it's an odd set relying on input to sort video parameters - Having no provision for adjusting contrast or colour saturation in the menu.
Thanks again - Chris.
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Nice trouble-shooting, Chris, and unlike some, you do give feedback. Bruce
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Thanks Bruce,
Mostly always give feedback as suspect some folks have less of a clue than me.
Have noticed that Google tends to direct to Quuq on a given model number for such 'Problems' and suspect it's a much better site than some where no-one has a clue but freely give 'advice' - Chris.
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Hi Chris,
Noticed that with google. This forum is much too public. Should be members only with password access. My tuppence worth. Bruce
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Hi Bruce,
It's a thought and such paid sites exist with tridents to poke folks who spill Beans quoted verbatim on free sites.
Costs a bit though, and you'd miss all the biz of guiding folks who don't have a clue but insist on 'The Answer' without knowing the question.
All a bit Dodgson and Douglas Adams where 42 is always the answer - Chris.
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mmmm I might just dig out one of those power supplies and have another go at it as the 5V standby is missing replaced the IC 6300 but a broken screen unit came up on ebay so bought it for the psu! Flogged the other parts on ebay!
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Hi Cheeky,
Had the same issue a while ago on another old Sony PS where I checked those two diodes in circuit where they seemed OK, being neither S/C or O/C.
Eventually after replacing everything else in the S/by PS, took them out and found one or the other leaky - So it goes - Chris.
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As I recall I checked pretty much everything before so I have a few ba159s so I will give it a go...
I will keep you updated on my progress
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Thanks Bruce and Chris success :13: This one has puzzled me for ages.
Changed D6903 and D6905 and up she came! Both tested ok in and out of circuit. I guess they breakdown under the high voltage. Neither of them were leaky. I did think the transformer T6300 was up the swanny after testing everything.
Have a good weekend and be lucky :)
Regards Anthony