Atec AV420D No Standby

[matyka]

Re: Atec AV420D No Standby

Hello,I have a similar problem just I have a standby light on all the time ,could you help me to fix the board ,thank you in advance .

[tom66]

Re: Atec AV420D No Standby

Glad to hear. Have a good Xmas.

[anotherdude]

Re: Atec AV420D No Standby

You don't have to replace the 450V cap though.

tom just a quick one to say thanks again

got the new caps today fitted and tv works as it should now

have a good christmas and a even better new year all the best

[anotherdude]

Re: Atec AV420D No Standby

You don't have to replace the 450V cap though.

oh right my mistake, think i've narrowed it down to 2 100uf 50v caps

[tom66]

Re: Atec AV420D No Standby

You don't have to replace the 450V cap though.

[anotherdude]

Re: Atec AV420D No Standby

I really wouldn't advise that. Old capacitors can "form" to a voltage, which means they can fail to work correctly in a new circuit, even if they worked in the old one. Just wait a few days for those caps -- it shouldn't cost more than a few pounds and surely all the time soldering/resoldering caps is not worth it.

i'll wait then, i do have some new caps already but there all big ones so guess there not the right ones

i'll check for colder solder joints at least anyway

[tom66]

Re: Atec AV420D No Standby

I really wouldn't advise that. Old capacitors can "form" to a voltage, which means they can fail to work correctly in a new circuit, even if they worked in the old one. Some capacitors can also dry out if they are left for a long time which may mean they fail too. Just wait a few days for those caps -- it shouldn't cost more than a few pounds and surely all the time soldering/resoldering caps is not worth it.

[anotherdude]

Re: Atec AV420D No Standby

i've got a fair few cable boxes and old boards laying round, might see if i can match the caps and replace to test at least then order some pannys at a later date

tom once again you've been more than helpful, top guy!

[tom66]

Re: Atec AV420D No Standby

A FET would not fail intermittently.
You can still do a check for cold solder joints.

[anotherdude]

Re: Atec AV420D No Standby

so it's more than likely caps rather than fets?

[tom66]

Re: Atec AV420D No Standby

I would replace all the small caps in that area. In fact I'd also replace the two near IC6, too.

Now CPC offers free delivery from £0.01 and stocks Panasonic caps, I'd not order anywhere else:
http://cpc.farnell.com/

Won't arrive before Xmas though.

[anotherdude]

Re: Atec AV420D No Standby

ok tom i've narrowed it down to this

[tom66]

Re: Atec AV420D No Standby

No, that's the secondary. Primary has the mains voltage on it. i.e. do not touch, hurty electric side.

[anotherdude]

Re: Atec AV420D No Standby

I'd try focusing heat on the capacitors on the primary side, over the ones on the secondary.

so the side with the majority of the caps?

[tom66]

Re: Atec AV420D No Standby

I'd try focusing heat on the capacitors on the primary side, over the ones on the secondary.

[anotherdude]

Re: Atec AV420D No Standby

ok tom your on to something

gave it some heat at first i was hearing popping from the speakers and the voltage on 12v was rising i continued with the heat until it hit 12v and the screen turned on and the popping disappeared

assuming bad caps now from previous experience?

also the screen flickering has gone

[tom66]

Re: Atec AV420D No Standby

Try warming up the PS board with a hairdryer to see if that increases; also try isolating all connections from the PSU board.

[anotherdude]

Re: Atec AV420D No Standby

12v still sits a 0.63v with a 100ohm resistor connected to 5v stby and d5 on

[tom66]

Re: Atec AV420D No Standby

That is bad, then. On the power supply.
Take a 100 to 470 ohm resistor and connect it between 5V standby and D5 ON, do the main voltages rise?

[anotherdude]

Re: Atec AV420D No Standby

from power on D5V gets to 2.20-2.40v and continues to drop to 1.20v and slowly continues to drop

D12V after the standby light disappears sits at 0.63v