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Old 7th Mar 2024, 9:44 pm   #1
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Default Sony Trinitron KV-M2120U wobbly vertical deflection

Hi all,

Me again with another Trinny that needs some love.

The picture is fairly randomly jumping about in a way that looks like the vertical deflection is about to fail but never does, just flickers in a random way.

I've changed all the caps in that area and reflowed it too, still happily doing it's riverdance.

Just wondered if anyone had seen this before on a BE-1 chassis?

I did have a lovely list of various Trinitron repair logs once but have sadly lost it.
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Old 8th Mar 2024, 1:48 am   #2
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Default Re: Sony Trinitron KV-M2120U wobbly vertical deflection

Well the image looked like it was getting better, then it started expanding vertically and kept going until all it will now display is the attached. Still jumping about and I've really no idea what to look at. I've also now replaced the upc1488h (v deflection ic) and it's not helped
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Old 8th Mar 2024, 3:53 am   #3
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Default Re: Sony Trinitron KV-M2120U wobbly vertical deflection

Hello Retrorepair,
Yes Sony one my favorite All time Tv's I own and collect their stuf and was a factory warranty and sales and service shop for them .

Do you have a Schematic diagram ? if not here is a link for that set

https://elektrotanya.com/sony_kv-m21.../download.html

Sincerely Richard
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Old 8th Mar 2024, 11:48 am   #4
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Default Re: Sony Trinitron KV-M2120U wobbly vertical deflection

A coincidence - just been to an elderly customer who not only has one but uses it daily!

To get to the fault. I'm not sure if it was the BE-1, but there was a small capacitor near the jungle chip that could leak and damage the board causing conduction and odd faults. Might be worth a look?
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Old 8th Mar 2024, 1:19 pm   #5
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Default Re: Sony Trinitron KV-M2120U wobbly vertical deflection

C808 47nf 250v comes to mind
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Old 9th Mar 2024, 10:04 am   #6
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Default Re: Sony Trinitron KV-M2120U wobbly vertical deflection

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Originally Posted by Welsh Anorak View Post
A coincidence - just been to an elderly customer who not only has one but uses it daily!

To get to the fault. I'm not sure if it was the BE-1, but there was a small capacitor near the jungle chip that could leak and damage the board causing conduction and odd faults. Might be worth a look?
Never seen this model before and I'm also in Wales so yes, I'd call that a big coincidence!

There was a 1uf 250v that had previously blown it's top, removed that and cleaned the area around it, it didn't seem to make any difference at all but then that looks to be part of the horizontal deflection anyway.
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Old 9th Mar 2024, 10:05 am   #7
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Default Re: Sony Trinitron KV-M2120U wobbly vertical deflection

Quote:
Originally Posted by FIXITNOW View Post
C808 47nf 250v comes to mind
C808 appears to be 0.068uf 250v on my schematic, I'll check it out anyway. I happen to have one handy if it tests bad.
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Old 9th Mar 2024, 6:34 pm   #8
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Default Re: Sony Trinitron KV-M2120U wobbly vertical deflection

Well C808 is in fact 47nf, appears to read fine though.

Really struggling with this one, whatever has failed did so gradually but I can't find the culprit or even anything that looks different to what I'd expect. Starting to wondernif this poor old set may be headed for the scrap heap
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Old 9th Mar 2024, 6:55 pm   #9
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Default Re: Sony Trinitron KV-M2120U wobbly vertical deflection

I'm thinking there's two issues here. The vertical deflection issue and the G2 is unstable. It'll turn on and show the image above, then it'll settle down and the deflection issue is the only problem, then it'll come back, some times it flickers between the two. It's maddening.

For giggles, I tried a LA7830 in place of the upc1488h and deflection was the same but the picture was green, not red. Why that happened I can't tell you.

Have to say though, it's really weird, partial vertical collapse in my experience has always folded the top over itself. This seems to be folding the top over the BOTTOM. When the G2 calms down, you can see the RGB lines usually at the top on the bottom? Also no change of input seems to make any difference to the image.
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Old 10th Mar 2024, 8:07 am   #10
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Default Re: Sony Trinitron KV-M2120U wobbly vertical deflection

Ok so small update, I have a hunch.

I don't actually think the issue is to do with the vertical deflection IC at all, I think it relates to the jungle IC. A TDA2579A. This is what handles vertical height on this set as well as H/V sync. Now that the jumpy picture has failed all the way, sync seems to have followed as in this video (sorry, no idea how to embed links):

https://youtu.be/zjcX5YHnYP4?si=rmE5dV3dTbTYPxn0

So my attention will now be focussed on this IC and it's driving components.
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Old 10th Mar 2024, 10:24 am   #11
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Default Re: Sony Trinitron KV-M2120U wobbly vertical deflection

As I mentioned earlier, there are some low value electrolytic capacitors around the jungle chip (ones you wouldn't expect to fail) that can leak and cause mayhem.
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Old 10th Mar 2024, 11:25 am   #12
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Default Re: Sony Trinitron KV-M2120U wobbly vertical deflection

Yeah there's definitely some leakage around there, I've cleaned it up as much as I can, just now checking values are correct and if still the same I may just replace the TDA and go from there
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Old 10th Mar 2024, 11:53 am   #13
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Default Re: Sony Trinitron KV-M2120U wobbly vertical deflection

Quote:
Originally Posted by Welsh Anorak View Post
As I mentioned earlier, there are some low value electrolytic capacitors around the jungle chip (ones you wouldn't expect to fail) that can leak and cause mayhem.
You know I'm only in Denbigh, wondering how much it might cost me to get your expert eyes on this thing.
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Old 10th Mar 2024, 1:08 pm   #14
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Default Re: Sony Trinitron KV-M2120U wobbly vertical deflection

Your forum profile says you're in Essex?
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Old 10th Mar 2024, 2:19 pm   #15
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Default Re: Sony Trinitron KV-M2120U wobbly vertical deflection

Yeah I've not updated it, moved here about 2 odd years ago (and not looked back to be honest).
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Old 10th Mar 2024, 2:21 pm   #16
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Default Re: Sony Trinitron KV-M2120U wobbly vertical deflection

Had another quick look, the yellow area is where I think I should be looking, feel free to correct me.

I can't see anything short or open here, resistors read differently but not read them out of circuit. Maybe it'd be worth doing that.

After that I think the TDA will be getting swapped out.
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Old 11th Mar 2024, 9:40 am   #17
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Default Re: Sony Trinitron KV-M2120U wobbly vertical deflection

I seem to remember when at Redifusion, we had one with a similar issue.
Pretty sure the issue was solved after checking the frame feedback loop; pins 1 & 2 of the jungle chip. Pin 2 was receiving spikey noise from what I recall. Can't recall if it was the jungle chip or a related component, sorry.
Hopefully I am not having another "Senior Moment".
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Old 11th Mar 2024, 2:12 pm   #18
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Default Re: Sony Trinitron KV-M2120U wobbly vertical deflection

That would seem to indicate the vertical frame IC was the issue if the problem was on pin 2. I've ruled that out but there are a couple of resistors in that path I can check out. I'd expect no deflection if the TDA was failed but it could just have failed in part of the die. As Glyn mentioned, these small caps leaking in that area could cause all sorts of headaches, I need to get methodical in my approach I think.
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Old 14th Mar 2024, 3:57 pm   #19
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Default Re: Sony Trinitron KV-M2120U wobbly vertical deflection

I'm at a loss. Changed the TDA2579A, can't find any shorts or bad resistors, all caps in the deflection area changed, it's different.. but not really.

This is one that's eating my soul, it's driving me mad.
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Old 21st Apr 2024, 2:06 pm   #20
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Default Re: Sony Trinitron KV-M2120U wobbly vertical deflection

Still stuck with this one. Anyone have any ideas or even better a spare BE-1 chassis?
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