17PW20 PSU problems (From Finlux 32FLD760 TV)

[emardee]

Hi,

I have been having intermittent problems with a Finlux 32FLD760 TV, which uses the Vestel 17MB22-2 mainboard with 17PW20v1 PSU.

Thinking it was the power supply at fault because the run voltages were a bit low (although standby volts were spot on), I bought a reconditioned 17PW20v1 off ebay (although they actually sent me a 17PW20v2 but I think this should be OK?)

However the TV still doesn't power on correctly and unfortunately it powers off again too quick to get reliable main voltage readings (other than the standby voltages which are spot on again)

Therefore, I want to test the two PSUs outside the TV so that I can compare the voltages to see if they are comparable when in standby and when in powered on fully.

So does any one know how I can get a 17PW20 PSU to power on under no load outside the TV? Presumably I need to supply them a signal on a particular pin to switch on fully. Which pin? What do I give it?

I have the service manual direct from Finlux if someone can make sense of it. (I'll attach it to this post along with the standard user manual for the same Tv).

The ebay seller has offered to test the PSU and has therefore asked me to return the PSU to him, but since I'm in New Zealand, and he's in the UK, the postage is a lot of money, especially if this new power supply is working correctly (as it should be after being reconditioned). Therefore I might well have another problem on this TV, (maybe with the Backlight inverter or the mainboard), but I want to start with checking the two power supplies side by side, as I can then see if they are giving a similar output under no load, or if they are showing any differences.

So:

Is the 17PW20v2 a drop in replacement for the 17PW20v1?
How trigger the 17PW20 to power up outside the TV?

Thanks in advance for your help.

Mike

ps I found Finlux to be very helpful when I phoned them. They immediately emailed both these manuals to me in response to my phone call.

[tom66]

Re: 17PW20 PSU problems (From Finlux 32FLD760 TV)

17PW20v2 should work for 17PW20v1 if the sockets match.

Also 17PW15-9 is compatible (if sockets match) with 17PW20 for 32" TVs only (you must use 17PW20 for 37") Yours is 32" so no problem.

The problem with these Vestel TVs is that they perform a self-test when first plugged in. They check the PSU can output the right voltages and if it can't in the brief time it gives it to start up, they will go into lock-out mode.

Here's the schematic for your PSU, if it's any help:


To turn on the PSU, you must, I think, pull ST_BY low. However, I am not 100% on this.

On an unrelated note, I wasn't aware Vestel sold TVs out of Europe and possibly Asia or Africa. I did hear on the grapevine that they were planning an expansion into the US, but I didn't know if anything happened to that.

[vinceroger69]

Re: 17PW20 PSU problems (From Finlux 32FLD760 TV)

maybe worth a read through as same psu
https://www.badcaps.net/forum/showthread.php?t=15313

[emardee]

Re: 17PW20 PSU problems (From Finlux 32FLD760 TV)

Tom,

Thanks for the reply. I had already read all 6 pages of this thread of yours about a Goodmans TV which was based on the same psu & mainboard as mine.

This Finlux was brought over to NZ from the UK and as you say Vestel don't appear to be sold over here. Hence no spares available, which is why I bought the psu board on ebay from the UK.

Thanks for the schematic for the 17PW20v1. I just looked again at the service manual Finlux gave me, and realised that it has the schematics for the 17PW15v9 in it... not the 17PW20v1 which was fitted in my TV! So yours will be helpful. Mine has some other useful pages, although a few of the most useful are very low resolution unfortunately!

Glad to hear the 17PW20v2 is drop in replacement, so that is unlikely to be the cause of my problems.

Will have a dabble and see if I can work out how to get the PSU on.

Any idea how to disconnect the inverter? The ebay chap has suggested I try powering up the TV with the inverter disconnected. I tried unplugging PL802, which I assume is what he means, but it still just powers off on its own.

Mike

[emardee]

Re: 17PW20 PSU problems (From Finlux 32FLD760 TV)

maybe worth a read through as same psu
https://www.badcaps.net/forum/showthread.php?t=15313

Thanks Vince. I've already read that one to the end before I posted here!

I kept thinking the thread would reveal a big clue to my own problem, but that missing info seemed elusive.... although now I have Tom from that thread over in my thread, maybe his wisdom will shed some light here!

Mike

[tom66]

Re: 17PW20 PSU problems (From Finlux 32FLD760 TV)

The inverter is the connector with the five red and five black wires. It goes to the underside of the TV.

The most common failure on Vestel 17PW15/20 are the two capacitors, C877 and C878, near the main transformer.

With that Goodmans, I just gave up fixing the power supply. It was an absolute nightmare, as all Vestels are. I had the TV sitting in my room for 3 months and decided to just replace the PSU, which cost £18. That fixed the problem immediately. I have tried to debug this PSU - there are so many things that go wrong with it, I just don't bother any more, considering it is available for relatively little.

The problem with the Goodmans TV was that it would get stuck in standby. Sometimes, it would power up normally, but usually only once or twice an hour. Yours sounds like a development of the fault to the point that the TV won't power up at all - so has it slowly got worse, or did it just die one day?

[emardee]

Re: 17PW20 PSU problems (From Finlux 32FLD760 TV)

Oh. I just tried it again in the TV, and it has powered on and stayed on .

Will record some voltage readings off the replacement psu whilst it is working:

Voltage on C819 = 389V when on.

Then on the socket pins (from left to right)

PL801:
n/c
n/c
n/c
24v0
24v0
GND
GND
n/c
n/c
n/c

PL802:
24v0
24v0
24v0
24v0
GND
GND
GND
n/c
n/c
2v4
2v8

PL804:
GND
GND
11v9
11v9


PL803:
2v8
2v4
?
?
?
etc
etc

Then I can't get it to power on again to get the rest of the readings. Will leave it off a while in case that helps





This actually took me a lot of attempts, as the TV kept powering back off again after a couple of readings (and sometimes many attempts just to get one reading).
I did also manage to test the voltages at the test points marked on the mainboard too though, and all were well within spec (when the TV was powered on). Of course, what I am not seeing is what causes it to turn back off again, and this could still be a wandering voltage somewhere... but you'd have to be reading that voltage at the moment it wandered to know which it was. Almost by definition the voltages must be within specs when the TV is powered on, or it wouldn't be on! (the protection circuits would power it off again).

With the old power supply I was seeing 11v and 22v on the 12v and 24v lines respectively when powered up, which struck me as "fringe", and suspected that it wouldn't take much wobble or extra current drain to take them out of spec and hence take the TV back to standby.

I bought the TV already faulty from another Brit out here in NZ. It used to work for longer than now though. It was always definitely worse on bright scenes. You could watch a whole dark movie just fine, but then when the adverts came it would power off several times during the brightest white scenes (and buzz/crackle the speakers too just before power off). It was highly repeatable and predictable. The longer it had been turned on for, the more fragile it got (the more sensitive to white scenes).

I suspected that the white scenes were drawing more current and tipping the power supply out of spec, hence the powering off.

Of course, it could well be a problem with the mainboard or the inverter, or even still with both PSUs!

Certainly when powered on, this new board so far looks to be closer to spec voltages than the original one, but that doesn't prove that the replacement PSU isn't still the problem. But it has to be less likely, unless I just got unlucky with this replacement psu and it has a residual problem too.

I'll wait a while, and see if I can get the readings finished, and then compare them to the ones in your other thread linked above.

Thanks for the help so far guys. Really useful. Hopefully I'll be able to get enough of an idea about the power supply to know whether to look elsewhere for the problem, or to return the PSU to the UK for further testing by the ebay supplier.

Feeling confident that I'll be able to sort this one way or another...

Mike

[tom66]

Re: 17PW20 PSU problems (From Finlux 32FLD760 TV)

Your original PSU was definitely faulty if it had 22V on the 24V rail.

However it looks like your replacement is too. Was it new, used or refurbished?

Got to go to 1 hr lecture plus 3 hrs lab session now... will be back later.

[emardee]

Re: 17PW20 PSU problems (From Finlux 32FLD760 TV)

It was "refurbished". Clear signs of solder work, and claims to have been "upgraded" in its components to fix the common faults.

The low volts on original was why I bought myself a replacement. I'm hoping the replacement isn't at fault, although if it is, I'll just have to bite the postage and ship it back to the UK. What makes you think this one is faulty too? Something I already posted? Or just the scenario?

The other possibility is that there are two different faults. The original PSU and something else!

If I can figure out how to get them turned on side by side outside the TV, then I can compare the two supplies in detail without the protection circuitry on the main board interfering. If they still power off, then I know it is the psu itself.

I think other than that, I want to finish off my full set of voltage readings.

I'm off to bed now, as it is middle of the night here anyway. Thanks for your help. I really appreciate it.

Mike

[emardee]

Re: 17PW20 PSU problems (From Finlux 32FLD760 TV)

So if I need to "pull stby low" to power psu up outside the TV, what would be the easiest way to do this?

Mike

[tom66]

Re: 17PW20 PSU problems (From Finlux 32FLD760 TV)

It was "refurbished". Clear signs of solder work, and claims to have been "upgraded" in its components to fix the common faults.

The low volts on original was why I bought myself a replacement. I'm hoping the replacement isn't at fault, although if it is, I'll just have to bite the postage and ship it back to the UK. What makes you think this one is faulty too? Something I already posted? Or just the scenario?

You have a very common fault with Vestels - stuck in standby intermittently.

I think the ST_BY needs to go to +3.3V to turn on PSU, not to 0V (my error.) You can do this with a 100-470 ohm resistor connected to the 3.3V standby pins. Do you have one of those available?

Some LCDs require more power to make black, others require more to make white. The variation can be from 1W to as much as 15W, which might explain why it started shutting down on brighter scenes. The most common failure are the poly caps C878 and C877, I still haven't worked out what causes these to fail, but it's definitely temperature sensitive.

[emardee]

Re: 17PW20 PSU problems (From Finlux 32FLD760 TV)

I'll try to get hold of a suitable resistor later today. Most likely pick one up from a store. Any specific Watts or style best, or literally any old resistor that is close?

Presumably I need to short out the wires that go to the push switch too (or leave that connected). I think it was called PL811 or something catchy like that.

I think I'm starting to agree with you that this replacement PSU is probably bad too, as it was making all sorts of clicks and buzzing last night (at one point about 4 per sec, and later approximately 1 per sec), and during the testing last night was the first time I'd ever managed to get it to turn on for more than a second at all. Will see if it behaves for more tests later today, but looks likely I'll need to return it to UK.

Will try and test it out of the TV soon.

Mike

[tom66]

Re: 17PW20 PSU problems (From Finlux 32FLD760 TV)

I'll try to get hold of a suitable resistor later today. Most likely pick one up from a store. Any specific Watts or style best, or literally any old resistor that is close?

Basically any old one you can find.

Presumably I need to short out the wires that go to the push switch too (or leave that connected). I think it was called PL811 or something catchy like that.

I believe... don't quote me on this... that the condition for on is normally open, i.e. that connector disconnected, TV is in standby or on (otherwise, it appears completely dead - but it's an illusion and draws about 0.5W anyway.)

Clicking and buzzing is a sure sign the PSU is on its way out. Many people don't bother testing the PSUs after they pull them from scrap TVs (usually cracked screens.)

[budm]

Re: 17PW20 PSU problems (From Finlux 32FLD760 TV)

OK, I look at the sch from TOM, when the TV does not want to turn on again, please check and see if you still have the
5VSTBY
3.3VSTBY
Power supply on at PL803 PIN 6, it should have >3VDC.
Capacitor C819, TV OFF = 325VDC, TV ON =390~400VDC.

[Lethagized]

Re: 17PW20 PSU problems (From Finlux 32FLD760 TV)

Hello gents, new member here. I have this psu board 17PW20 V2 removed from a JVC tv and the IC chip IC802 on the solder side has a hole in it. Looks like it's overheated and blew the hole. The fuse on this board blew as well. Anyone heard of this happening before on this board

[tom66]

Re: 17PW20 PSU problems (From Finlux 32FLD760 TV)

Yes, more than likely the PFC MOSFET has failed shorted and taken out IC802 in the process, and it's blown the fuse too.

[Lethagized]

Re: 17PW20 PSU problems (From Finlux 32FLD760 TV)

Thanks for the quick reply Tom. You say that the PW15 board will also work providing the sockets are the same as the PW20. I've found a PW15 for sale for half the price of the PW20, so i would like to go with that ideally, but i've noticed that it has an extra socket over the PW20.

This is a pic of the PW15 and i've circled the extra socket in red which my PW20 doesn't have. All the rest of the sockets appear to be the same as mine.


There is someone selling an harness that converts a PW15 to a PW20 HERE, but at £15.50 i think it's way overpriced for what it is, and i would like to know if i can do a simple modification which enables me to use the PW15 board instead of the PW20.

[tom66]

Re: 17PW20 PSU problems (From Finlux 32FLD760 TV)

That's fine -- you simply don't use the extra socket. Remember only 17PW15-9 is compatible. 17PW15-8 is sometimes compatible but it's not guaranteed. You don't need any cable conversion. Just plug in all connectors as usual and leave that one unpopulated.

[Lethagized]

Re: 17PW20 PSU problems (From Finlux 32FLD760 TV)

Fantastic. Thanks for that. I've found a gem of a forum here. Thanks very much for the help tom, much appreciated.

[tom66]

Re: 17PW20 PSU problems (From Finlux 32FLD760 TV)

Out of curiosity what JVC TV was that removed from? Trying to gauge the date they stopped making their own and started badging Vestel rubbish.