Vestel 17PW16-2 PSU low 12V & 24V Help!

[cheeky2]

This psu I have been playing with on a Sanyo CE42LD33-B 42inch TV. The 12V is around 11.6V initially then starts dropping down to 11.2V after warming up for around 10-15 minutes whilst it has been on. All the caps have been checked with ESR meter and are OK. I did notice whilst checking the feedback from the opto's that one of the resistors was higher than expecter 5.5K opossed to 5K within tolerance of 10% of resistor i only had a 4.7K so substituted that. A marginal increase in voltage but not significant 0.1V also replaced at the same time a 16V 1000uf capacitor which was slightly low capacitance around 940uf.
So when the voltage drops to around 11.2V the digital tuner in the TV doesn't respond properly and epg goes out. Also if you shut the TV down it will not always boot up again once its reached around 11.2V. The 24V is around 23.5 and drops to around 22.8V. No problem with powering the inverter and screen displays fine.
The main cap when switched on is around 370V C892 which I am not sure is high enough? All other voltages on the psu are pretty much spot on besides the 12V and 24V.
So any help as to likely culprits would be welcome.
I have attached schematic though some of the resistor values are different to psu (nothing unusual there though!).
So any help with regards rectifying it are welcome.

[cheeky2]

Re: Vestel 17PW16-2 PSU low 12V & 24V Help!

Just been checking the circuit I have found 18V across the 12V zener diode D854 which isn't correct if it is a 12V zener (diagram could be wrong again) as the resistor values are different compared to schematic.

[Shotgun25]

Re: Vestel 17PW16-2 PSU low 12V & 24V Help!

Hi,

I have one of these boards to repair.

A few years ago I bought the following repair kit called MODKIT66A from the following link http://tidmanmailorder.co.uk/index.p...roducts_id=256.

Kit contains the following

Text on accompanying A4 sheet.

"Vestel 17PW16-2 PSU Board. Replacing all the components should cure most known faults and improve reliability of the PSU. Based on Hitachi L42VP01U, Technika TVLCD40 & Wharfdale LCD42F1080P"

Kit Contains
F800 - 2.5A fuse
IC801 - PC817 Opto
IC802 - IC FAN7529
IC806 - IC 01653
IC807 - SG3525
C877/8* - Capacitor 15nFd 1000V
R830 - Resistor 0.22ohm
Q803 - Transistor P10NK80ZFP
Q837 - Transistor Yellow (?)
IC825 - IC STPS5L25B
D824 - Diode STTH12 +Insulation kit
D851 - Programmable Zener Diode TL431 (W19)
D836 - Zener Diode Blue (F2J)
D866 - Diode UF5402
C801 - Electrolytic Capacitor 33mFd 50V
C817 - Electrolytic Capacitor 220mFd
C892 - Electrolytic Capacitor 10mFd 50V
*C878 may be 33nFd without C877 in some versions

March 2009

In the last year I've got a decent soldering iron and I've had enough practice to attempt the repair.

I think the kit includes parts that are not needed for my model or are not direct replacements but are equivalents.

Since this kit is for numerous models could someone review the following and advise me please?

D824 - Diode STTH12 +Insulation kit (data sheet )

The version I removed is B0872 F10L6OU (data sheet )

IC802 - IC FAN7529 (data sheet https://cdn.badcaps-static.com/pdfs/...6fc7b6f5ff.pdf)

The version I removed is EH14 FAN 7529 but the replacement is EA31 FAN 7529. I presume these are like for like but thought I'd ask about it.

IC807 - SG3525 (data sheet https://cdn.badcaps-static.com/pdfs/...eb47ba46d7.pdf)

Do pins 4 and 9 have no connection on this PSU design? The pads lifted while I was wicking the solder up.
I have looked at the data sheet and also the PSU design PDF linked here in another thread (https://www.badcaps.net/forum/attach...3&d=1478727993) it looks like they are optional. Having looked at the traces from the pins, I think they are unused.
Please could someone confirm that.

Just IC802 and IC806 to replace and then re-solder the large cap C819 covering IC807.

[cheeky2]

Re: Vestel 17PW16-2 PSU low 12V & 24V Help!

After looking at all the voltages on the psu and the main board it was found that there was around 0.4V difference on the 3.3V rail between the connectors. This drop in the resistance between the connectors was causing an issue with the TV not operating from the remote control when in the standby. I removed the connectors from the plug cleaned them up and now no issues with turning the TV from standby with the remote control. The voltage drop is now around 0.1V so i guess these connectors just deteriorate over time.

[cadu]

Re: Vestel 17PW16-2 PSU low 12V & 24V Help!

cheeky2, have you solve the problem with voltage drop on 24v and 12v?

BR,
Dusan

[cheeky2]

Re: Vestel 17PW16-2 PSU low 12V & 24V Help!

cheeky2, have you solve the problem with voltage drop on 24v and 12v?

BR,
Dusan

For convenience I replaced the power unit after thinking the issue was related to the low voltages on the power supply. I will at some time look at the old one with a view to repairing it. Though after cleaning the metal connectors on the psu it resolved the issue with the main board not coming out of standby with the remote control.
In short to you answer no!