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 Post subject: Sony BVM 14G5E with 149,761+ hours needs some TLC
PostPosted: Tue Oct 20, 2020 9:28 pm 


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Joined: 04 Oct 2020
Posts: 10
Location: London
Hello,

I got hold of Sony BVM 14G5E at an auction of a broadcast studio that was closing down. These auction can be a bit of a gamble. I guess I got a bit unlucky with this one: The BVM has 149,761 hours (that's 17 years!) of flight and according to a sticker on the back the tube was replaced in Feb 2007.

To my surprise the caps looked in very good shape and had no sign of having been replaced or having leaked. I checked the power supply module, the deflector board and the neck board.

After a couple of minutes of turning the monitor ON and using it it overloads: https://www.youtube.com/watch?v=xL3Vwqdcbxc
On the plus side, the image seemed fine and there is no image burnt into the tube.

I though it would be worth trying recapping G, E and D boards, hopefully this would fix the overload issue.
102 caps later: I tried turning the beast back on and it now exhibits strange symptoms: the tube draws an extremely "zoomed up" image, to the point you only see around 12 lines at a weird angle plus and oblique one (the return of the electrons beam?).
There is also a weird low frequency brightness oscillation: https://www.youtube.com/watch?v=nafXPEzFSrs

It's not in a very happy place right now.

I have already double checked all the caps were inserted the with the right polarity and that the values are correct...
When I have a couple of hours ahead of me, I'll check again and also inspect all solder joints to see if I shorted anything...

If those symptoms ring any bells to anyone, please let me know your thoughts!

I'll update this thread if I make any progress.

Thanks!


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 Post subject: Re: Sony BVM 14G5E with 149,761+ hours needs some TLC
PostPosted: Wed Oct 21, 2020 2:48 am 



Joined: 03 Mar 2005
Posts: 475
Just throwing out a thought:

Do you think it's possible that you removed a cap but forgot to replace it? In addition to shorts, that's something I'd look for.


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 Post subject: Re: Sony BVM 14G5E with 149,761+ hours needs some TLC
PostPosted: Tue Feb 23, 2021 9:10 am 


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Joined: 04 Oct 2020
Posts: 10
Location: London
It turns out while recapping I must have applied pressure on a surface mount resistor with the tip of my soldering iron and snapped it, breaking a circuit controlling the yoke (hence the very spacing between each line on displayed on the tube).

The resistor in question was R034. I managed to salvage a similar resistor from a donor board and now that issue is solved.

The next issue is the image was very noisy for a few minutes, then once "warmed up" the image would become clean.

This took me a while to sort out. It took a phone conversation with "savon pat" to put me in the right direction...

I knew it was something with BK (the input board that takes RGB + sync and connects to the neck board) since I had a spare one from another BVM of the same range...

Patrick recommended I get an ESR meter to check the surface mount resistors on that board. Turns out most resistors will probably need replacing as they mostly all test to have high ESR.
A few around the voltage regulators failed the test completely or had a really really high ESR (8 Ohm and more). I replaced those three and now the image is no longer noisy when the monitor is "cold"!

Hope this helps.


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 Post subject: Re: Sony BVM 14G5E with 149,761+ hours needs some TLC
PostPosted: Tue Feb 23, 2021 11:53 am 


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Joined: 16 Jan 2014
Posts: 1137
Curious as to why you would use an ESR meter (used for capacitive/inductive ESR measurement) on a resistor. That doesnt make sense- a resistors "ESR" will never be higher than its actual DC resistance.


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