Technika lcd 32-207 intermittently sticking in standby

[tom66]

Re: Technika lcd 32-207 intermittently sticking in standby

I always swap the PSUs on these Vestels, because there are so many PSUs out there they are usually around £20 each (high supply with relatively low demand as most people just throw these TVs out when they fail and don't bother to fix them) and there are so many things that go wrong on them...

[LesWoollam]

Re: Technika lcd 32-207 intermittently sticking in standby

Will a 17PW20 V2 SMPS successfully replace my 17PW20.1?

[tom66]

Re: Technika lcd 32-207 intermittently sticking in standby

Yes, but also a 17PW15-9 is compatible (and cheaper) if the connectors match.

[vinceroger69]

Re: Technika lcd 32-207 intermittently sticking in standby

http://www.ebay.co.uk/itm/32-SIRLING...item416d820246
not a bad price

[LesWoollam]

Re: Technika lcd 32-207 intermittently sticking in standby

Thanks guys, that's useful info!

[vinceroger69]

Re: Technika lcd 32-207 intermittently sticking in standby

of another post
For general purposes, here are the components and values contained in the repair kits for the 17PW20.1:

IC829 - 78L05 (if on board)
Q809 - BC337 (if on board)
C877 - 15nF 1600V
C878 - 15nF 1600V
C817 - 220uF 25V
C892 - 100uF 50V
C801 - 33uF 63V
C901 - 3,3uF 50V
R817 - 330 kOhm
R818 - 330 kOhm
R819 - 330 KOhm

just wonder if its worth you checking all of these parts out on your board

[Techstar]

Re: Technika lcd 32-207 intermittently sticking in standby

The fact it's an intermittent fault means it could be a component thats just drifted out of tolerence. Some are putting these boards with a similar type of fault in a special oven and reflowing the board i heard a lot of vestel boards can be fixed this way thats those with intermittent problems mostly. Thats something i would like to own but expensive no doubt.

[tom66]

Re: Technika lcd 32-207 intermittently sticking in standby

No, that's not the problem.

The PFC booster boosts the 335V DC up to 392V DC and in the process ensures the input current is relatively sinusodial and in phase with the AC line voltage.

When the PFC fails, the bus voltage varies from approx 270V to 335V DC. This may work just about when line voltage is high (245V AC or so.) But UK line voltage can fall, maybe it's just 230V AC. Then you don't have enough voltage to maintain the DC 24V and other outputs, and it won't always start.

[Techstar]

Re: Technika lcd 32-207 intermittently sticking in standby

Well said.

I never thought of that

[LesWoollam]

Re: Technika lcd 32-207 intermittently sticking in standby

That's certainly the problem here - no difference between standby voltage and run voltage (both around 337v). It certainly makes sense that when the mains voltage is slightly high the TV works fine, but when it drops slightly it refuses to come-out of standby. In the meantime I've ordered a 17PW20.2 board for £24 all-in. . . fingers crossed!

[LesWoollam]

Re: Technika lcd 32-207 intermittently sticking in standby

This just gets better. The 17PW20.2 board arrived today. I' put it in and guess what - it won't come out of standby. The 24V rail comes up and then dies back down; likewise the main cap voltage rises from 337V to 390V then dies back down to 337V. The standby trigger voltage goes from 1V7 to 0V3 then climbs back up to 1V7. I really don't want to have to go through the hassle of sending this board back. Any ideas???

[tom66]

Re: Technika lcd 32-207 intermittently sticking in standby

If you force the STBY line low, do the PSU outputs run within tolerance?

[LesWoollam]

Re: Technika lcd 32-207 intermittently sticking in standby

With the standby line forced low the 24V rail fluctuates between approx 14V and 24V and the main cap voltage between approx 382V and 390V. It's as though it tiues to come-up then for some reason shuts-down.

[tom66]

Re: Technika lcd 32-207 intermittently sticking in standby

Was the PSU refurb or pull?

[Techstar]

Re: Technika lcd 32-207 intermittently sticking in standby

Could be heading towards an inverter fault for a change , interesting this.
I am betting lamps / inverter fault.

[Techstar]

Re: Technika lcd 32-207 intermittently sticking in standby

Was the PSU refurb or pull?

Probably a pull most are.

[LesWoollam]

Re: Technika lcd 32-207 intermittently sticking in standby

Pull

[tom66]

Re: Technika lcd 32-207 intermittently sticking in standby

It's unlikely for an inverter to draw too much current, they are usually current controlled.

I think it is faulty, as your original board worked occasionally, it confirms the inverter is not at fault.

[LesWoollam]

Re: Technika lcd 32-207 intermittently sticking in standby

The TV is fine (apart from the SMPS board) as I've tested it with a good SMPS from another TV.

[LesWoollam]

Re: Technika lcd 32-207 intermittently sticking in standby

OK, if I unplug PL804 (12V supply to main board), all voltages on the SMPS come-up. However, the 12V rail measure 11V3. The main board is fine as the TV works perfectly with another SMPS.