Wharfedale LT26K1CB

[6BW6]

Wharefdale LT26K1CB
Stuck on power 'ON' no back lights, No sound.

I know it's a cheapo.... no bulging caps. in psu, I changed them all the same using low ESR 105deg.C types. Voltages are up and running and appears 'hash free'.

I disconnected the keyboard in case of a sticky or leaky button to no avail. I can force the back lights on by the 'Bon' terminal and they look pretty healthy. Anyone know how to apply a CPU reset.

Thanks Dave.

[ReeceyBurger123]

Re: Wharfedale LT26K1CB

What Psu does it have ?

[dick_barton]

Re: Wharfedale LT26K1CB

Just repaired a Wharfdale LT37K1CB model.

Power supply board JSK 422B-050A

The fault was identical to your description and was traced to C22 on the power supply. 47uF 35V capacitor had gone high ESR.

[6BW6]

Re: Wharfedale LT26K1CB

The power board is a PSM143-310-1-R.
I did change the larger caps. but not the smaller ones, the supply appears to be 'hash free' when checking on scope. The voltages are within spec the last time I measured, was casting my eye's on the Eprom.

Might be worth my while swapping all the 47uF..... at least I'll have a recapped psu.

Dave

[dick_barton]

Re: Wharfedale LT26K1CB

So are all your supplies from the power supply within spec?
You say you can force your backlights on.
What do you have on Power_ON pin when you attempt to switch the set out of standby?

[6BW6]

Re: Wharfedale LT26K1CB

The power ON terminal is stuck 'ON', the back lights are stuck OFF irrespective of any button or remote action being issued. The psu voltages are within spec. plus a couple of 100mV either way, I couldn't see any ripple or hash that caused me to worry, I did change the 'usual' high value caps. in the power supply to be sure but not the 47uF as been suggested but will do at the next opportunity.

For curiosity I tried with the Tcon disconnected, CPU crystal is OK and all the regulators on the main board appears to be up and running (Haier MSD109CL-V400), seems it's all down to CPU, Eprom or a bus line clogged up.

Thank you for your interest, Dave.

[ReeceyBurger123]

Re: Wharfedale LT26K1CB

Probably epprom fault common on them Haier junk boards.

[CapLeaker]

Re: Wharfedale LT26K1CB

Probably epprom fault common on them Haier junk boards.

I think so too.

[dick_barton]

Re: Wharfedale LT26K1CB

Have you tried freezing the EEprom as suggested when considering an EEprom fault to see if you can boot up the TV?

[6BW6]

Re: Wharfedale LT26K1CB

Eprom was the next thing I was casting evil eyes on. No, not tried freezing, I'll give it a try when I get a new can of the stuff..... think I'll gamble on swapping it, I'll let you know how it goes in a day or two. Dave

[dick_barton]

Re: Wharfedale LT26K1CB

Have you solved the problem?

[6BW6]

Re: Wharfedale LT26K1CB

I fitted a eprom and got the dump files.... I could now switch it off and on and now the backlight flickered faintly just before tripping to stand by..... I replaced the SMD zener on the Tcon board marked 'CCD KE' which was s/c, I got one from a scrap Samsung Tcon board.... from what I can find out this is a 5V zener.

Before fitting the SMD zener I thought go on lob a 5V wire ended zener in to see what happens, I was expecting to see a puff of smoke and a load of Indians with their tomahawks doing a war dance .... the telly burst into life all I had to do was retune, so to keep things nice and orderly I fitted the SMD device I robbed..... all I had to do was a retune.

Nice picture but pity about the sound, I've heard worse though.

Thank you all, any problems with these Tcons check the smd zener near the ribbon connector - sorry didn't make a note of the component number, there's only one and it's easily seen.

Dave

[dick_barton]

Re: Wharfedale LT26K1CB

Glad you sorted it out. Another successful repair.