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Chassis swap between 21" and 28" CRT Beovisions

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tournedos
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tournedos posted on Fri, Sep 25 2020 10:38 PM

TL, DR: is it possible to swap the chassis between the smaller and larger MX/LX models? I'm fully aware all picture geometry settings etc will be completely off, but will it work otherwise?

I've been reading through the service manuals, and the only difference I can find is some components at the deflection coil, and those are mounted on the tube neck anyway.

The reason I'm asking is that I have a nice LX6000 at the summer cottage, and it has failed in the usual way (turns itself off after a short or a longer while). Taking the whole set home for repair is too much work, so I have taken just the chassis with me to do the infamous cap replacements and so on blindly. After three round trips, it still does not like to stay on. I have an MX4000 at home, also due the same repairs, and it occured to me that perhaps I could use the MX4000 tube + frame to test the LX6000 chassis?

--mika

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solderon29
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Yes indeed,you should be able to do this,although as you have noticed,there are some subtle differences in the deflection circuits between the two screen sizes.

However,It might be worth trying the "official" test procedure too?

In my own experience,blanket "re-capping"is not often the solution.

There are several "usual suspects"when this problem presents.This was/is a very reliable chassis,and the problem you have is the very sophisticated protection system preventing the set from powering up.

Nick

tournedos
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Thanks Nick - can you believe it took me a month to notice your reply Laughing

This certainly helps. I'll probably start with repairing the MX4000, the summer house can wait six months now... The LX6000 chassis is annoying to work on - the plastic frames are very brittle and something keeps breaking all the time. I might even consider finding a donor.

I fixed my MX6000 with similar problems more than 10 years ago and it is still going strong. In that, the final culprit was one of the small transistors driving the BUT12.

Trying the test rig is probably the next step. I tried the test mode with protection circuit disabled, and the set stayed on for a long time without any apparent problems. Might be a tricky one to find.

--mika

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