Sony multisystem KV k29MF1 to rescue

[Benyamin39]

Hi,

I recently purchased a Multisystem CRT TV Sony KV k29MF1. This TV is great as it is PAL / SECAM and NTCS and therefore allow me to do retrogaming on european computer systems (PAL COmmodore Amiga, Oric, Amstrad, ...) as well as north american videogame systems (SNES. Genesis, ...).

I tested the TV and the picture is horrible. it needs a lot of work to adjust convergence and geometry but that is not the issue for the moment.

I modded the TV to get RGB, tested with a Mister FPGA and it works great. Either PAL or NTSC systems works automatically.

The problem is that I messed up the TV when I reopened it to do a thorough compressed air cleaning and fix the Red signal that was not soldered properly.

Note that the TV has 2 electronic board : One for the 120V and above (Board D, see schematics) and one for the signal processing (Board A). The design of this TV is pretty neat compared to other TVs I opened (Toshiba, JVC, SAnyo, ...)

I did not not touch the 120V Board, I only worked on the “signal” board. When I reconnected the board I did not properly attached the jumpers. I don’t know if this mistake or the cleaning is the reason I certainly blew up a component.

When I restarted the TV, I got erratic behavior. The picture was heavily skewed like the figure below
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_/xxxxxxxxxxxxxx\
/xxxxxxxxxxxxxxx\

I also got some gentle but prolonged static electricity noise (say 30 seconds to a minute). I can’t say if it is because of the cleaning some dust got stuck on some sensitive parts of the tube or whether a component was already dying somewhere.
Then I got more erratic picture and then no more picture at all.

The TV start. And I can hear the starting buzz as well as relay switch. The IR LED work when I hit keys on the remote control. But I got absolutely no picture at all. The tube has not even any static electricity on its surface.

I am very keen on trying to fix this TV, spending the necessary time and tools (oscilloscope or others) to get it back to life as there are not many of those TVs around. I also have a keen interested in learning this stuff.

I started to measure some voltages using my multimeter.
The power board (board F2) is working fine, giving the required 136V and 12V where needed.
Then I checked straight to the neck board (see my markup)
I got 135V on one of the pin as well as 12 volt on another, which is as expected, I believe.
On H1 and H2 I could barely read 0.1V using my multimeter (not sure how meaningful this measure is)
I could not measure 1000V as I have no tools for that. I believe the issue is on the HV side, but I don’t know exactly where at the moment.

Attached are the diagrams with some markup on voltage measurement I made so far.

My questions are as follows:
1. Is it possible to blew up the HV side by omitting connecting the signal board?
2. How can I check the 1000V? There is a testpoint 8 near the transistor Q2591 that generates 1000V.
3. Could it be the flyback wheel. How can I test this component?
4. Do I need to buy an oscilloscope for this repair?
5. Any other insights are welcome on where to look at for diagnostic

Thx for the help.

https://drive.google.com/file/d/1qOq...ew?usp=sharing

[zeno]

The picture you drew shows a "PIN" or pin cushion problem.

Sony & others had cold solder joints in the following areas.
Horz drive, horz drive transformer, horz output, vert output IC, Small 3 legged regulator IC's also the main power supply board. I would check the HV, CRT & power supply boards for cold joints first.

HV can be detected by checking the 200 VDC at the CRT socket.
If you have 200 V you have HV. Also the H1 & H2 run off the HV.
They are the heaters. If no HV the filaments will not light.

Hope that helps, good luck

Zeno
LFOD !

[Benyamin39]

Thanks that is much helpful,

I looked at the PCB and found 2 locations where soldering points turned yellow, probably due to heat (whether excessive or not).

https://drive.google.com/file/d/1Sbl...ew?usp=sharing

One is the HOT. I need to remove the HOT to test it, which I have not done yet. I will order a replacement part anyway.

The other part is the primary side of the horizontal drive transformer (T2502). The primary side is open. So I need to replace that part for sure.

the part number is 437-195 14 (T?)M

The issue is that I googled on the web and it is very difficult to find replacement horizontal drive transformer. All I found is a close reference
1-437-195-11 Sony Transformer Hori.drive.
I could not find any store where to buy the part. Is the only solution to salvage an existing Sony television?

https://drive.google.com/file/d/1SYq...ew?usp=sharing

[zeno]

The 2nd number looks correct. Most Sony small parts start
with 1- or 8-. Often a partial part number is printed on the part.

Opens are rare on these so look at where the wires hook to the
terminals, may be broken off.

Zeno

[Benyamin39]

Thx Zeno.

You are correct, I retested again the transformer and it is ok! (I get very often false readings when I do this troubleshoot work, I need to practice more I guess).

Silly thing one of the connector between boards was not plugged properly. I realised it after disassembling all the board and reassembling them. I prayed and ... the TV went back to life! Pretty cool and also my RGB modding is working perfectly. I won't touch anything anymore.

Now I need to calibrate the tube.

Thx again

[zeno]

Glad you made progress. If you are doing the PIN problem
next watch the diodes around the Hoz output. Also electrolytics
in the PIN circuit. Its best to use OEM semi's if you can find them.

Adjustments are often done through an OSD service menu. If you
change anything there ALWAYS write down the old number so you
can go back if needed. Also when you exit the menu it wont
save the settings if you dont follow the manual.

C U Later
Zeno
LFOD !