TV won't turn on, PSU issue?

yoyo

Hi folks,

Complete electronics noob here so excuse the ignorance . Parents have an LED telly (Nordmende brand) and it won't turn on. no LED light or nothing. Dad was watching TV and it suddenly went off.
Checked another fuse in the plug-no difference. I opened it up and found the PSU board (Vestel 17PW80 v2) and no signs of burning or popped caps at first. I do notice that one of the ceramic capacitors (picture attached) is leaking.TH701.
I also notice what looks like leakage from the large yellow component (pictured, not sure what it's called). Could this be causing any issues?
I have found a spare parts site here with the psu for €27 delivered, doesn't seem like that bad a deal if I'm sure the board is gone . Do you think the PSU is gone and this would sort it?

Many thanks,

Nick

yoyo

Looking on Badcaps it appears diodes failing is a common issue with these PSUs. Time to dust off the soldering iron and I'll replace the 5 of them and see if it helps. Should be a much cheaper repair job if this is the case. Don't think the ceramic cap is gone, looking at it again it looks like the epoxy glue stuff they used to glue the lying down caps.

Nick

whizbang

Did you check fuses F700, F701. - they have to be checked from behind the board.

TH70x, is a Thyristor or voltage dependent resistor, and the big yellow one is R100, which is a current dependent resistor.
It would be very rare that these cause trouble.

The big rectangular thing is the transformer, the pic shows the protective varnish has been overheated, but probably only during assembly.

good luck with the diodes.

yoyo

whizbang wrote: »

Did you check fuses F700, F701. - they have to be checked from behind the board.

TH70x, is a Thyristor or voltage dependent resistor, and the big yellow one is R100, which is a current dependent resistor.
It would be very rare that these cause trouble.

The big rectangular thing is the transformer, the pic shows the protective varnish has been overheated, but probably only during assembly.

good luck with the diodes.

Thanks for the advise . Everything behind the board looks good, nothing charred or cracked joints. Cannot get my soldering iron to melt the solder on the diodes! It's 40w so should be up to the challenge. The tip has seen better days so I'll have to try it with a new one. It's completely oxidized. The wine and beer not helping in the adventure also I'm sure!
I'll report back when I get around to working on this, prob be a few weeks as very busy these days!

Nick

Chet T16

Check the diodes with a multimeter first, if they're short/open circuit you can cut them at the legs and desolder one at a time which should help get the heat into them.

Or bring it down to me with the aforementioned wine and beer and i'll do it

yoyo

Chet T16 wrote: »

Check the diodes with a multimeter first, if they're short/open circuit you can cut them at the legs and desolder one at a time which should help get the heat into them.

Or bring it down to me with the aforementioned wine and beer and i'll do it

Cheers man. Have a multimeter but been a while since I've used it. Bit ignorant now and don't particularly want to be playing about with the board carrying 240 volts :P . i'll prob just buy 5 diodes, should be under a fiver. Cutting them is a good idea alright, should get the solder melting . The tip is in pretty poor shape as not used in a few years, so I'll look to replacing that before hand. Thanks for the offer its appreciated .

Nick

ZENER

F700 looks like it has a crack in it ? If you run your fingernail over it is it a crack or a ridge ? C714 in the second photo also looks like it's damaged.

First stop for me would be the 2 fuses without doubt and the varistor TH70x looks the worst for wear. My guess is that TH70x is the kickstart for the circuit, the initial surge through it will fire the circuit which then self sustains.

Ken

yoyo

Hi folks,

a few more pics, this time including the board underneath. The damage I suggested in op is not actually cracks. It is the epoxy/glue stuff that has been used to glue the long capacitors down on the board. I've cleaned them off and created several new pictures.
I would preferably not like to power the thing up and use a multimeter because being honest I do not know much about circuitry and don't want to end up killing myself!
Thanks again for all the help folks! Btw I took a soldering iron to a few of the diodes, so if the soldering looks dodgy in the last pic top right that is why!

Nick

raspberrypi67

I do this kind of thing for a living if you need a hand or want it fixed.

brendan bowe

I am looking for a p.s.u. for a phiips 42 pf 7320/10
anyone out there who can help.
BB