Sigh, another dead VESTEL 17PW25-4

[Amjama]

Re: Sigh, another dead VESTEL 17PW25-4

hi,

I have attached the 17pw25-4 board (backside) picture and highlighted in circles the components I am interested in. Does anyone know the name/part number of these components, I cant really see the printed name on the psu board.

Black :IC903?
Red:
Green:
Yellow942?
Blue: D941?

Thank you

[Amjama]

Re: Sigh, another dead VESTEL 17PW25-4

Anyone? Just missing the green highlighted circle.
Blue:. D941
Black: Ic903
Red: D945
Yellow: D942
Green:???

Thanks

[tom66]

Re: Sigh, another dead VESTEL 17PW25-4

Here?
http://www.toms-service-manuals.com/...25-4&typekey=0

[Amjama]

Re: Sigh, another dead VESTEL 17PW25-4

Thanks tom66, I was after the part number c10v sod123, what does the "c" stand for? Is it equivalent to ZENER DIODE, 0.5W, 10V, SOD-123? Thanks

[tom66]

Re: Sigh, another dead VESTEL 17PW25-4

Yes, that looks like an acceptable substitution to me.
Although, SOD123 may be too big, so consider SOD323 option.

[Amjama]

Re: Sigh, another dead VESTEL 17PW25-4

Hi,

Update, so I replaced all the defected components associated with short diode. However when I check my 5v, 12, 24v they all fluctuate a lot. From 5v to 17v for the 12v and 24v is 30v? Basically all my values are all over the place.. I get the blue n red flashing led indicating possible short? But can't find it! When measuring diode mode D941 I get 0.041 both ways however when i remove R923 I get my normal value of 0.540 one way indicating that the diode d941 is ok. Any advice? Thanks

[Agent24]

Re: Sigh, another dead VESTEL 17PW25-4

Why can't they just use one diode with a higher rating instead of several small ones?

[Amjama]

Re: Sigh, another dead VESTEL 17PW25-4

Well, what can cause all my voltages (5,12,24v) all fluctuate that much, for example the 12v is all over the place from 10v to 15 sometimes even from 0.2 to 17v.

[Agent24]

Re: Sigh, another dead VESTEL 17PW25-4

Hi,

Update, so I replaced all the defected components associated with short diode. However when I check my 5v, 12, 24v they all fluctuate a lot. From 5v to 17v for the 12v and 24v is 30v? Basically all my values are all over the place.. I get the blue n red flashing led indicating possible short? But can't find it! When measuring diode mode D941 I get 0.041 both ways however when i remove R923 I get my normal value of 0.540 one way indicating that the diode d941 is ok. Any advice? Thanks

That makes sense, since the other side of R923 has two 0.22R resistors in parallel to GND. D941 is probably OK.

But with so many things blown around IC900, it may also be bad. I also see a black spot on it in the photo. Could be a hole?

Well, what can cause all my voltages (5,12,24v) all fluctuate that much, for example the 12v is all over the place from 10v to 15 sometimes even from 0.2 to 17v.

Power supply controller is power cycling. This can be caused by several things. One of them is shorted components. I suspect there is still something shorted you have not found yet.

[Amjama]

Re: Sigh, another dead VESTEL 17PW25-4

Yes, I have replaced the ic900 as it also got damaged when diode it shorted. Yeah still looking for that possible short somewhere by the ic900 area. But why would all my reference voltages be fluctuating, the something is shorted in the ic900 area surely the only one or possible 2 of the reference voltages should be unstable the rest should be stable. Does anyone have the reference point of what voltages around diodes n ic should be? Thanks for your respond by the way much appreciated

[Agent24]

Re: Sigh, another dead VESTEL 17PW25-4

What is the condition of the standby rails? Are they OK? Where did you measure the 5v rail that was fluctuating? Are you talking of the +5v rail or the 5v standby rail?



I don't consider myself a PSU expert, and it's late at night, so is it just me - or was this PSU (and schematic for that matter) apparently designed by madmen?

It looks like the mains gets rectified and sent to C803 as the primary filter capacitor, which in turn powers IC800, and that creates the 3.3v and 5v Standby rails. Fair enough so far...

But when the mainboard sends STBY_ON\OFF to the PSU, they switch on IC900, a FAN7529 PFC controller IC. Except it's not being used to do PFC, it seems. Rather, it drives TR900 as the main 12v/24v rail PWM controller. Insane or clever? I don't know. Why on earth they use a million diodes in parallel instead of using the already-designed-in board layout for proper heatsink-mounted recifier pairs I don't know. Unless they want the thing to blow up... HMMM....

[Amjama]

Re: Sigh, another dead VESTEL 17PW25-4

Hi,

Well, I think is design to blow or they just trying to save money. Clever I don't know, risky for sure!

My 5v and 5v standby (3.3v I think)are all fluctuating from 0.1 to 5v.

Is been a fun project to tackle from the start now it just 1 more
Min and I will throw that p** of s** out! But got to stay strong. But good learning experience. If I could at least get the 5, and the 12v stable I can look into the 24v which is flicking to 32V! Sad days

Don't want to spend 25-39£ for a new board! But might have to....

[Agent24]

Re: Sigh, another dead VESTEL 17PW25-4

Sounds like something could be bad in the standby circuit then. Check for shorts on the standby rails and any rails derived from them.

Also, IC800 has UVLO of 10.5v on the Vcc pin, so check that its voltage is not dropping below that.

[tom66]

Re: Sigh, another dead VESTEL 17PW25-4

This PSU has OVP/UVP/etc circuit which will cause 5V standby to fluctuate if any of the other rails are bad.
I never did figure out how to fix one of my 17PW25-4s with this fault.
Multiple parallel diodes are a cost saving method but one of the major downfalls of this PSU design. They fail all the time.
They truly are terrible power supplies...

[Amjama]

Re: Sigh, another dead VESTEL 17PW25-4

Oh no, if tom66 can't figure out to fix this my hopes has just ended... Will have to order new power supply or scrap the tv. Buying a new power supply would have been ideal but with so many versions of this power supply the risk are that it might now work at all.. Spend £37 or scrap it.....

Sad days

But thanks guys for the advise n support.

[Agent24]

Re: Sigh, another dead VESTEL 17PW25-4

It's not impossible, just not economically sensible.

If you remove and test all the passive parts and basic semiconductors, replace any bad ones, replace all the ICs, you will fix it unless the transformers are bad. After that time it would have been cheaper to buy a new PSU of course.

But if you wanted to take the time I think you could. It should be possible to go with a process of elimination. Divide the sub-circuits up and verify each one individually. Disconnect each from the other and test with external supply etc.

[Amjama]

Re: Sigh, another dead VESTEL 17PW25-4

Thanks Agent24. I will give it another go, at the moment the suspect fault component is ic901, but for now every component in that psu is a suspect! should be fun. But I still have to think, is it worth repairing the hitachi tv... I will try and relax for few days no point at staring at something that doesn't want to work.

[Amjama]

Re: Sigh, another dead VESTEL 17PW25-4

Is 17PW82-3 a improved version of 17pw25-4? Have they finally figured out that the 17pw25-4 is not good enough!?

[Amjama]

Re: Sigh, another dead VESTEL 17PW25-4

??? 17pw82-3 compatible with 17pw25-4?

[tom66]

Re: Sigh, another dead VESTEL 17PW25-4

That's a variant of 17PW26-4
Without significant modifications, 17PW26-4 and its bretherin will not fit in place of 17PW25-4
It IS possible, but you have to do a lot of trace cutting and add a few parts (ask me how I know how...)