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Wharfedale L32TA6A lcd tv - trips to standby after a few minutes.

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tv john:
Hi guys,I had similar fault on a Bush LCD37TV016HD , could it be the same chassis ? U8 was hot and cut out to standby after time.It is a TIP31 shape (OLD REGULATOR FROM DONKEYS AGO ) and I bolted it to the chassis with extension leads and an old TIP31 isolating kit. This was ages ago,but I remember I only had to remove the centre section of the back cover.

John.

Contrast John:
Hi John
Think these are two different chassis with different types of regulators.
The AP1501 regulator used in this model is a 5 pin switched mode type. Although in a similar shaped package to a TIP 31 only a short tab with no drill hole was available for mounting, the device being designed for surface mounting on the pcb with the copper print doing the job of a heatsink. I managed to find some spec on the AP1501 and found it rated at 3 amps which ruled out replacing it with a more standard 3pin 7805 type 5 Volt regulator rated around 1.5 amps. Like yourself I considered re-siting the AP1501, but was put off by the likelihood of extension wires introducing an inductance into the circuit and affecting the operating frequency of the IC. This left only the option of soldering a heatsink onto the tab which fortunately worked quite well.
Would be usefull to know if anyone has found or used a better rated device than a 7805 with perhaps a rating of 5 Amps or so, that would be handy to use in these circumstances and would allow re-siting with wires, it not being a switch mode type.
Regards
John.

Turnip:
Hi John,
Considering efficiency of linear compared to buck regulators, a linear might need a considerable heat sink.

Tried it a while ago on some of those 10inch tubed portables when original buck regs became obsolete,  before the noisy replacements became available, needed nearly a square foot of blackened aluminium as the drop was about 5 volts at 3 amps. Never had one back though - Chris.

Contrast John:
Hi Chris
Yeah, that was the basic idea. Attach it to a huge sheet of metal (space permitting) and test with moist finger whilst looking out for steam! It would be nice for once to be able to buy a standard off the shelf part to do the job, instead of spending hours researching and eventually modifying circuit designs.
Always up for the challenge though.
Regards
John.

Turnip:
Well said John,

As both you and I are still in the biz, whilst some others, still awaiting approved mods have taken up more profitable occupations, doubtless requiring little original thought - well, and so on.

Penuary is us, think to invent a radio with rubber bands - again  - Chris.

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