Atec AV420D No Standby

[anotherdude]

Picked this up yesterday for £30 fault was described as "won't turn on it used to turn on after 20 minutes but now theres no standby light"

So i took the psu out and removed the old fuse near the 250v input and replaced it with another I had off a faulty board.

It now gets a standby light for all of 5 seconds then konks out, no sign of any other damage anywhere

top of caps get low voltages and gradually drop as the standby light dissappears

samxon caps too

[anotherdude]

Re: Atec AV420D No Standby

found this thread that tom66 fixed https://www.badcaps.net/forum/showth...highlight=atec

there not the same psu so not sure it's the same fault

what should i be looking for if standby voltage disappears?

[tom66]

Re: Atec AV420D No Standby

Check if the PSU 5V standby is stable or not.

[anotherdude]

Re: Atec AV420D No Standby

Check if the PSU 5V standby is stable or not.

at the stby 5v pin i get 4.96v so would appear to be stable?

[tom66]

Re: Atec AV420D No Standby

Check what the PSON signal is doing.

[anotherdude]

Re: Atec AV420D No Standby

Check what the PSON signal is doing.

sorry tom i appreciate your help but i can't seem to see anything labelled with PSON

better image of the board

[anotherdude]

Re: Atec AV420D No Standby

ok was going through checking all the pins for voltage to see if they were correct and funnily enough the screen turned on and it worked but theres a flicker to the screen including menus too. turned it off and back on and now no picture again and no standby light

so seems it has to get warmed up so to speak before it will turn on, caps?

[tom66]

Re: Atec AV420D No Standby

D5-ON might be the pin.

[anotherdude]

Re: Atec AV420D No Standby

D5-ON might be the pin.

ok when i power on the standby light comes on at the d5-on pin i read 1.45v and when the standby light disappears it drops to 0.03v

[tom66]

Re: Atec AV420D No Standby

OK, and what do the D5V, D12V do during this?
Seems like main board fault.

[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

[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

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

[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

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

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

[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

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

ok tom i've narrowed it down to this

[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.