Soniq (australian brand) 32" - screen doesn't always start up

[psmedley]

Re: Soniq (australian brand) 32" - screen doesn't always start up

I had already measured AC DET - 5.04v in both scenarios

[psmedley]

Re: Soniq (australian brand) 32" - screen doesn't always start up

YAY - finally a clue

I had already checked the outputs on the power supply in the working/non working state. I thought I'd also reconfirm the voltages on the YSUS board where the connector is that feeds the ZSUS board.

Much to my surprise, I found that VA and VS on the connector on the YSUS board were essentially 0. VA is about 0.7v compared to 'working' being 62.4V and VS is 0v compared to 'working' being 189.5v

I reconfirmed this on the connector on the power supply.

So that suggests to me a definite power supply problem - my next question is do I replace ALL caps (bar the 2x big fat ones) per my list on page 1, or are the smaller ones less critical?

[psmedley]

Re: Soniq (australian brand) 32" - screen doesn't always start up

remove double post

[tom66]

Re: Soniq (australian brand) 32" - screen doesn't always start up

Hmm. You are getting good Vs and Va on PSU outputs, but nothing on the Ysus?

Damaged wire? Cold joint? Maybe even a blown fuse?

[psmedley]

Re: Soniq (australian brand) 32" - screen doesn't always start up

Sorry for the confusion! When I checked va/vs on the psu initially, they seemed ok.

When I later checked on the ysus board connector, i found them to be low, then checked again on the psu and found then low there as well.

[psmedley]

Re: Soniq (australian brand) 32" - screen doesn't always start up

Just realised this is still a little confusing... it seems that depending WHEN it's tested, VA/VS as measured either on the PSU _or_ the YSUS board can be either GOOD when the TV works, or BAD when it isn't

[psmedley]

Re: Soniq (australian brand) 32" - screen doesn't always start up

Does look reasoable in terms of replacements?

[mariushm]

Re: Soniq (australian brand) 32" - screen doesn't always start up

It looks good to me.

The only one that jumps out is the Nichicon PW but considering the capacitance value and the voltage rating, it's unlikely that one is low esr from the start so PW series is a good enough series for that one.

[tom66]

Re: Soniq (australian brand) 32" - screen doesn't always start up

Hmm. But I don't think it's bad caps. Check VS_ON from main board to PSU.

I encountered an issue with a TV switching off randomly recently - it turned out to be the power button on the side button board was stuck and intermittently firing power-off signals to the TV. (It would also sometimes power on when first plugged in.) I used some contact cleaner on it, and that fixed the problem. Maybe try unplugging the button board and seeing if it will stay on?

[psmedley]

Re: Soniq (australian brand) 32" - screen doesn't always start up

VS_ON is always OK - 5V. In the cases where VA/VS where low/zero - the other supplies to main board, YSUS, etc of 5V and 16V were all on and good.

Assuming it is caps, should I also replace the higher voltage caps? ie

2 x 250V 220uF Samwha PT
1 x 100V 470uF Samwha PT

re: he Nichicon PW - for that voltage/capacitance it was the best I could find

[psmedley]

Re: Soniq (australian brand) 32" - screen doesn't always start up

I encountered an issue with a TV switching off randomly recently - it turned out to be the power button on the side button board was stuck and intermittently firing power-off signals to the TV. (It would also sometimes power on when first plugged in.) I used some contact cleaner on it, and that fixed the problem. Maybe try unplugging the button board and seeing if it will stay on?

I'm turning the TV on/off via the remote - not via any button, so I don't think that's it.

As mentioned - the power supplies to the different boards seem OK, but sometimes there is no VA/VS as measured on the power supply or on the YSUS board.

[psmedley]

Re: Soniq (australian brand) 32" - screen doesn't always start up

Hmm. But I don't think it's bad caps. Check VS_ON from main board to PSU.

I must apologise... I rechecked this evening - and in the scenario where VA/VS are zero, so is VS_ON. AC_DET and RL_ON are 5v and 4.7v respectively, and the 16V & other 5V supplies are ok, so it's partially turned things on??

Any thoughts on why VS_ON wouldn't be activated? A problem with the main board I assume?

[psmedley]

Re: Soniq (australian brand) 32" - screen doesn't always start up

Hi selldoor,

We really need the better pictures and close up of the caps dont recall seeing JAYE on anything. I am assuming that it did go back into fail. Nexy easy thing to try would be to gently heat different parts of the boards with a hairdryer for 2 -3 minutes when in the failed state but still on, to see if it starts up. If that doesnt work then switch off re heat part of a board and re-try. We are looking for either a cap that is failing but when heated works a bit better or a solder joint that has cracked but rejoins when it expands on heating. Its a bit laborious but lot easier than resoldering every joint or replacing every cap. Do not overheat any part.

Going to try this today (hopefully) as it's a holiday here for anzac day.

Now that I know that VS_ON isn't coming on when the tv is turned on, I'll start with heating the main board - I know that if I cycle power a few times, the TV will start up, so heat is definitely a factor.

[psmedley]

Re: Soniq (australian brand) 32" - screen doesn't always start up

didn't have any luck with heating... I had the meter probing VA whilst I was heating different parts of the mainboard - nothing changed I have a ESR meter coming from ebay, so when it arrives, I'll test all the caps on the mainboard - they LOOK ok but ya never know

[psmedley]

Re: Soniq (australian brand) 32" - screen doesn't always start up

I see other posts on other threads requesting photos of the bottom of boards - I'll try get some clear photos of the bottom of the main board and power supply board in the hope that someone can see some clues

[psmedley]

Re: Soniq (australian brand) 32" - screen doesn't always start up

Photos of back of main board and power supply board are attached in the hope they show something

[vinceroger69]

Re: Soniq (australian brand) 32" - screen doesn't always start up

in your pic on power board gp1 2 3 4 all look like they could have dry joints maybe re solder these.

[selldoor]

Re: Soniq (australian brand) 32" - screen doesn't always start up

You could also have a look at the ones marked in red - they look greyer than the others, which is sometimes a sign they are not good.
Its hard to tell in a picture though - they may be ok. Where the yellow dots are, was there never a cap in here.

[psmedley]

Re: Soniq (australian brand) 32" - screen doesn't always start up

Yup - agree. There are also several on the main board that look much duller/greyer than the rest - particularly in the blocks of four larger solder joints in the bottom RH corner.

Will try touching them up when I get back from walking the dogs

[tw2005]

Re: Soniq (australian brand) 32" - screen doesn't always start up

Hi,

just sharing an experience i had yesterday with a friends SAMSUNG PS50C91HD Plasma. Symptoms were random shutdowns, followed by continuous cycling of the SMPS relays attempting to restart pwr supply. TV would work for various periods ranging from not starting up , 5mins, 30mins, several hours, few days etc.

Originally i thought it was the usual dud caps however after checking these all tested ok.

I decided to investigate the possibility of bad joints so i grabbed a wooden and whilst it was on I started to tap components/heatsinks etc hoping to cause a bad joint to fail.

Bam, unit failed and starting cycling after I tapped a cap. The cap was fine however, i then tapped a large transformer and a large heatsink with some transistors on it and it failed again and then with some gentle flexing of the board i could either make it work or fail. I flexed the heatsink and it did the same. I ended up reflowing the solder on the semiconductors attached to the heatsink and the large transformers as a precaution.

I can't be 100% sure which of these it was but I highly suspect the transistors.

Anyway on completion repeated the tapping and flexing of the board and could no longer make it fail.

I'm 100% confident I fixed my issue. Maybe your fault could be similar.