Sony KV-XJ29M31 CRT TV - Very dim image on turn on

[Dreamcazman]

Hi all, I recently picked up a Sony KV-XJ29M31 CRT TV (BG3R chassis, Australian model) cheaply & completed the RGB mux mod on it for some retro gaming. That worked great, however, I have another problem which I hope someone can help me with or at least steer me in the right direction.

Basically, the issue is when it's cold, it takes a while (like 2 mins) for the picture to come up. I think the image is there, it's just very dark or dim. I can hear the degaussing sound & I can change inputs & hear audio but no image.

Once it's running properly, it keeps going fine.

If I put the TV in standby, then turn on the next day, the image comes up straight away. The problem only seems to happen when using the main on/off switch (fully off).

The service manual doesn't mention this specific problem, but I assume it may be a capacitor issue due to the nature of needing to warm/charge up first.

Manual can be found here - https://www.manualslib.com/manual/83...v-Xj29m31.html

I'm relatively knowledgeable with electronics, but I'm a little rusty as I haven't worked on CRT's for a long time. I'm sure someone here is more expert than me.

Any help would be greatly appreciated.

[Dreamcazman]

Re: Sony KV-XJ29M31 CRT TV - Very dim image on turn on

A colleague recommended to swap out a couple of capacitors C558 & C565 which I did & while there is still a delay on turn on, it's a lot better than it used to be.

The image is still very dark first off, but comes good in less than a minute now.

Maybe this is normal for this set, I don't know.

[ducky29]

Re: Sony KV-XJ29M31 CRT TV - Very dim image on turn on

Does the led flash 5 times when you turn it on? If so the crt screen might be dying. In my experience sony crt tvs had only 2 major faults: crt and flyback transformer.

[Dreamcazman]

Re: Sony KV-XJ29M31 CRT TV - Very dim image on turn on

Does the led flash 5 times when you turn it on? If so the crt screen might be dying. In my experience sony crt tvs had only 2 major faults: crt and flyback transformer.

Thanks for the reply. No blinking LED.

After a bit of testing, I think it's something to do with the RGB mux mod I did. I removed it & the TV seems to be 'normal' again. I will have to do some more trial & error to make sure that is what's causing it.

[Dreamcazman]

Re: Sony KV-XJ29M31 CRT TV - Very dim image on turn on

Does the led flash 5 times when you turn it on? If so the crt screen might be dying. In my experience sony crt tvs had only 2 major faults: crt and flyback transformer.

Just an update. I found a number of bad caps on the main board which I replaced. Powered it up, but unfortunately didn't fix the startup delay.

Funny you mentioned the 5x led blinking, it's doing that now.

Incidentally, when I first turned it on, the image was very blurry. I checked all my connections & found the red wire on the flyback transformer which goes to the CRT neck board had come out! I pushed it back in & now the image is fine again.

Still getting the 5 blinking error code, but still have a picture. It doesn't mention the flyback tranny as the cause for the error code, but could be the CRT itself.

EDIT: I fixed the blinking error, the G2 (brightness knob) on the flyback had moved, so I readjusted it & the error code is fixed.

So basically the TV is as it originally was before I replaced the caps. Not sure what else it could be & with my limited knowledge/tools to troubleshoot, I may just leave it as-is, at least I can still use it.

[ducky29]

Re: Sony KV-XJ29M31 CRT TV - Very dim image on turn on

5 times blinking means a dying ctr. Sorry about that. The picture will get better after it gets warms but it will get worse day by day, meaning that each day you have to wait longer to get a better picture.

You can remove a resistor(or lower its value) that supplies the filament so the ctr gets a higher voltage but its a temporary fix.

[Dreamcazman]

Re: Sony KV-XJ29M31 CRT TV - Very dim image on turn on

5 times blinking means a dying ctr.

Did you not read all my post? The CRT itself is fine, the problem was the brightness adjustment on the flyback (my fault). The blinking has since stopped once I corrected it. According to the manual, an improper setting can cause the 5 blinks.

Forget all of that & let's get back to the main issue please.

[Dreamcazman]

Re: Sony KV-XJ29M31 CRT TV - Very dim image on turn on

I'm sure someone here has had the same issue as me or can at least give me some idea what the problem could be.

To recap, when I turn the TV on, after 10 secs or so a picture comes up, but it's dull, like half brightness. After 1-2 mins (always different amounts of time), the full brightness kicks in & is fine from then on.

I thought it was a capacitor problem, so I replaced more than a dozen dodgy electrolytic caps which tested as bad but it did not fix the problem. Any ideas anyone?

[R_J]

Re: Sony KV-XJ29M31 CRT TV - Very dim image on turn on

You say the crt is ok, what did you use to check it? Is the 200v screen voltage ok? Did you replace C565 & C717

[Dreamcazman]

Re: Sony KV-XJ29M31 CRT TV - Very dim image on turn on

You say the crt is ok, what did you use to check it? Is the 200v screen voltage ok? Did you replace C565 & C717

I didn't check it per se, but I assume it's ok due to the 5 blink error code has since gone (caused by something else). Can I check the screen voltage with just a multimeter?

I had replaced C565, but not C717. I don't currently have any of those, but from memory, it was ok. I might pick some up tomorrow & get it changed too just in case. My local supplier only has 4.7uF 450v caps, but higher voltage should be ok. Thanks.

[nomoresonys]

Re: Sony KV-XJ29M31 CRT TV - Very dim image on turn on

The life expectancy of a good electrolytic cap is 10 years, tho it's true that many last a lot longer.

[R_J]

Re: Sony KV-XJ29M31 CRT TV - Very dim image on turn on

When the screen control was misadjusted, the crt cathode current was low triggering the 5 blink error code, You can check that the 200v is there with a meter but it likely is ok. The problem is very likely a weak crt. it takes longer to heat the crt cathodes so they will emit electrons, the cathodes get contaminated over time and this causes the problem of a poor picture. You will likely see some color bleeding to the right of characters which also indicates a weak crt.

[Dreamcazman]

Re: Sony KV-XJ29M31 CRT TV - Very dim image on turn on

You will likely see some color bleeding to the right of characters which also indicates a weak crt.

I don't have any colour bleeding.

For the record, I replaced C717, in fact I replaced all the electro caps on the C6 neck board (for good measure) but it didn't make a difference, still takes a minute or so for the full brightness to kick in. I dunno.

If it is a weak tube, I'll use it till it's dead then throw to the kerb.