TideLog Posts Tagged “Vestel”

Some Vestel TV’s have combined PSU and inverter in the same board, as did a Polaroid branded ProView chassis I did a year ago. Common faults include:

  • Red tinge on screen, which gradually goes to normal white, but then the backlight(s) go out. Known-good backlights connected up work fine
  • Backlight(s) flickers briefly and goes out again, but TV still operates with dim picture under bright light, known good backlights do the same
  • Backlight(s) shows no life at all, neither does a known good one connected up, but TV stays running

The red tinge issue is mostly a failing backlight(s), because the anodes of the lamp are wearing out it doesn’t warm up fast enough, causing the inverter protection circuit to shut it off. The other two are faults with the inverter section of the supply itself. On a combined PSU & inverter unit the backlight supply is fed with 24v directly from the secondary side of the SMPS circuit, where it is stepped up to 1000v lamp start current by the inverter transformer. Once the lamp has lit (usually within a few milliseconds for a good lamp) the voltage drops to between 300 and 800v depending on the brightness. One such PSU I recently reconditioned was a Vestel 17IPS01, we often replace faulty supplies with new ones, then recondition the old ones for re-use.

The backlight flickered momentarily and went out. We connected two known-working laptop screen backlights to it, and the same occurred. Note that on a two lamp inverter two lamps MUST be connected, if only one is used this isn’t enough of a load and the protection circuit will trigger. On this supply it turned out to be the output capacitors directly before the backlight output sockets. These act as soft-start filters to prevent damage to the backlights from sudden current inrush as they light, if the 1000v ignition current was suddenly applied without a few milliseconds delay the anodes would be damaged:

Vestel-17IPS01-2-high-voltage-capacitors-faulty

To fix the issue, replace the three caps C355, C356 (12pf 3kv) and C354 (4.7pf 3kv) that I’ve labelled above. The capacitors will check out as normal with a multimeter when power is off, however they break down when put under load, hence the reason why they come on then go off again as the inverter protection circuit shuts the circuit down. Faulty backlight lamps can also stress them out causing them to fail. This repair is good for most Vestel and other make combined PSU/Inverter boards.

Unlike TV’s with separate inverter boards, a TV with combined PSU/Inverter supply will always boot up and work even if the inverter section shuts down, there is no fault feedback to the main TV processor in these variants. This makes diagnosing faults with them easier, whereas a TV with independent inverter will often cause the TV to not start correctly in the event of a fault, sometimes causing confusion with inexperienced people.

 

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Techwood are another “faceless” brand of TV that are Vestel made, they are sold at Morrisons, we have done a few of them. Recently a customer brought her 32″ Techwood TV to our workshop, saying there was power, but no picture or sound, and the LED blinks. Normally on a Vestel mainboard the LED only blinks during Over-The-Air firmware update, so she left it with us, and we took a look under the bonnet.

Techwood-32832-under-the-bonnet

It uses a Vestel 17MB25-3 mainboard, similar to my 16″ Linsar 16LVD4.ย Another common cause of a blinking LED on a Vestel can also be the inverter. Often on these separate inverter TV’s, if the inverter chip, a MOSFET, or indeed the coil (some have 1 some have 2), are faulty, the error reporting circuit built into the main chip on the inverter relays this info to the processor and the software goes into protection mode, preventing the set from booting up, causing the flashing LED.

A blinking LED in any other case than firmware update is mostly a power supply issue, but here’s our checklist:

  • Check microfuse FS105 on main board, near CAM module.
  • Check SMD fuse FS106 (4A) for open-circuit. Check diodes D881 and D893 (UF5402) for short-circuit.
  • 24V rail might be short-circuit, disconnect inverter board supply to prove. Check and replace dual N-channel MOSFETs IC803 and IC804.
  • Replace IC830 (FAN7711 and SMD capacitor C925 (1nF).
  • Check for short-circuit between pin 6 and pin 8 of IC830 (FAN7711). Replace IC830 and SMD capacitor C833 (100nF).
  • Check and replace SMD transistor Q839 (BC859).
  • Check D893 and D891 (UF5402) in centre of PSU for short-circuit.
  • Voltage at regulator U122 varies between 4V and 9V instead of being stable at 8V. Replace U122 (LM1117ADJ) on main board.
  • Check C961 (470uF/35V) at top of PSU.
  • Check D893 and R1036 (2.2K) on PSU.
  • Replace IC830 (FAN7711).
  • Check D893 and its feed resistor. Replace MOSFETs Q813 and Q814 and IC830. Replace C828.
  • Replace C892 (100uF), C801 (33uF), C840 (33uF).

In our case, the voltages coming out of the power supply were fluctuating badly, so we knew the mainboard wasn’t the original fault. The power supply is a Vestel 17 PW26-3. So, out came our service manual and power supply schematics, and we set to work.

Vestel 17pw26-3 PSUNo obvious bulging capacitors, no burst vents, and no burn marks anywhere. The PSU microcontroller was operating, and the clock waveforms were fine. The bridge rectifier system and components were OK. The problem was the output capacitors just before the output sockets, their voltages were up and down.

Replacing C802, C934, Q828, D882 & D883 and some various resistors fixed the problem, and the TV was back up and running. The power supply even emitted less no-load whine than it did before! A lot of people might say Vestel are junk, but the thing I love about them is they’re off the shelf parts and components, fixing them is a joy. You’ll often find a lot of Vestel TV’s with all manner of screen sizes, big and small, being driven by the same boards and power supplies. The ProView panels can also be replaced with dual lamp screens from a Sony Vaio laptop if you need a 15.4″, 16″, or 17″ panel ๐Ÿ˜‰

Here’s a fun fact: The 17MB25 board can drive panels from 12″ all the way to 36″ full HD, even if the TV is marketed as just HD Ready, that’s often just because the panel is a small one, so the board software goes into HD Ready mode to drive it. Connect a 32″ to it and the multiplexer goes into full steam 1920×1080 ๐Ÿ™‚

Vestel? Turkish? Delight? Yeah, I would say so, cheap, cheerful, and easily fixed. Take note, Sony ๐Ÿ˜‰ Funnily enough Greg has a Luxor branded Vestel lined up for me with similar symptoms, I suspect it’s going to be the same routine as this one.

 

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Many Vestel TV’s are often rebadged with another company’s branding, and their own model number. This makes finding service literature for engineers like me really difficult. I have a tip that works on many rebadged Vestels to bring up a service menu that will reveal its true chassis number.

My Linsar 16LVD4 16″ HDTV is one example. There are Alba and Goodmans branded versions of it, with and without Freeview & DVD player, all with different model numbers, so putting “Linsar 16LVD4” into Google never reveals service literature, only replacement parts that are used in other TV’s.

I service a lot of Vestel TV’s, and their main method of getting into service mode is as below:

  1. Enter the TV’s main menu, by pressing either a Menu button, or an M button as it is on my Linsar.
  2. When the user menu appears, press the digits 4-7-2-5. This code works across almost all their LCD chassis, and a lot of older CRT chassis from Vestel.
  3. The user menu disappears, and a service menu appears.

It works for most of their chassis, and depending on the chassis model and S/W version, your menu may look different:

Down in the lower right is the TV’s true chassis number. As you can see, my Linsar is actually a Vestel 17MB25 chassis. CAUTION: This menu IS NOT intended for USERS, only engineers. Using features such as NVM Edit or the Programming function will DAMAGE the EEPROM settings, resulting in a dead TV that will need rescuing by a guy like me. The EEPROM chip will need to be desoldered and reprogrammed, or a new chip soldered.

The MB25 motherboard does not need the EEPROM to be preprogrammed before soldering, as the software is automatically flashed by a control chip on the board. This board is used in variants with a DVD module and USB port.

A few rebadged Vestel makes I’m aware of are Goodmans, Techwood (Morrisons stores), Alba, Grundig, Hitachi and Technika from Tesco. Just look for shiny glossy black plastic, as this is what most Vestels are made of! Note that not all models of the above makes are Vestel, it’d take up too much space in this article for me to list all makes and models that are rebadged Vestels!

 

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