New Microvitec CUB Monitor Tripler

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1024MAK
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Re: New Microvitec CUB Monitor Tripler

Post by 1024MAK » Mon Nov 05, 2018 9:38 am

Back when servicing CRT displays was common, some engineers and some companies used a purpose made discharge probe. Or in some TV repair shops they made their own.

It is basically just a suitable high voltage resistor, a metal probe with an insulated handle and a wire with a croc clip on the end.

But most engineers just used one of the two methods described in the posts above.

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Re: New Microvitec CUB Monitor Tripler

Post by Kazzie » Mon Nov 05, 2018 9:39 am

SmellyGeekBoy wrote:
Mon Nov 05, 2018 8:40 am
I think I'm getting some of my terminology confused - I'm fairly new to CRTs and was under the impression that the "tripler" was usually integrated into the same unit as the LOPT. It seems they're separate things in my CUB. I'll do some more reading on the subject.
Don't worry. Until you reopened this thread I didn't know about separate "triplers": my CM8833 has it integrated in to the LOPT. So we're both new. :)
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Re: New Microvitec CUB Monitor Tripler

Post by SmellyGeekBoy » Mon Nov 05, 2018 10:01 am

paulv wrote:
Sun Nov 04, 2018 8:51 am
Slightly OT but still in the back of a CRT unit that I remember from BITD was the guy that was teaching me about TV repair took a screwdriver and placed it a short distance from the top of a few of the vacuum tubes whilst the TV was on. He was attempting to show me that the High Voltage was "real" by demonstrating the purple/violet arcs from the tips of the tubes to the driver shaft. At the time, I'd been studying physics at GCSE for a year or two and had by then, seen and tinkered with a Jacobs Ladder so I was thinking to myself that he was a nutter doing what he was doing to illustrate the point :-o
It always bothers me when people play with this kind of stuff, a friend of mine is into building big Tesla coils and I won't go anywhere near them. Perhaps I just need to man up :lol:
Last edited by SmellyGeekBoy on Mon Nov 05, 2018 10:01 am, edited 1 time in total.
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Re: New Microvitec CUB Monitor Tripler

Post by guddler » Mon Nov 05, 2018 12:40 pm

It never hurts to be wary of these things. My father was a TV engineer so I learnt at the age of about 6 what the "funny looking sucker thing" can feel like when you stick your fingers in it :lol:

That said, unless you have a dodgy heart or some other medical condition then really the only things to remember are not to shove your fingers onto anything when it's on and never go in to something live with both hands at once. If you do that then any shock you get is going to go straight across your heart and that, for obvious reasons is dangerous! In theory* with one hand it'll just hurt and you're more likely to do yourself some serious damage jerking your hand away and cutting yourself or knocking something off / over.

* I say, "in theory" but obviously, like I said at the start, it never hurts to err on the side of caution and I cannot be held responsible if you decide to be more adventurous and do yourself some damage.

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Re: New Microvitec CUB Monitor Tripler

Post by Kazzie » Mon Nov 05, 2018 1:12 pm

There's a lot to be said for a healthy dose of caution. When I need to jack up the car and do some work underneath, I wait until there'll be someone else at home too, just in case. (As well as the proper use of chocks and axle stands, and putting the wheels under the bodywork to catch the car if something went wrong.)
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Re: New Microvitec CUB Monitor Tripler

Post by SmellyGeekBoy » Mon Nov 05, 2018 1:59 pm

Image

As it was sunny out and this thing was full of a thick layer of grime I decided to do the de-energising thing and stripdown outside. Completely uneventful - not even a "crack". I was a bit disappointed after all the build up :lol:

Image

I did make a pretty interesting discovery - I knew the bottom of the case was bent but didn't realise it was actually putting pressure on the main PCB. One component (labelled R12) had actually completely broken free from 3 of its 4 solder joints and was flapping around. It had obviously been leaning on another component (labelled C17) at some point and scorched it! :shock:

Image

So glad I decided to strip this thing down... The scary part is it was actually working in this state!

Thankfully the PCB traces all look fine and it was just the solder that had cracked. These old electronics are pretty tough. I ordered the new LOPT from Donberg in the end so I'm waiting for that to arrive now, I think R12 is some kind of radial ceramic power resistor and C17 is an MKP1841 film capacitor so I'll have to hunt those down too.
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Re: New Microvitec CUB Monitor Tripler

Post by SmellyGeekBoy » Mon Nov 19, 2018 11:39 am

I just wanted to add that I've now finally replaced the tripler as well as the LOPT and that scorched capacitor from my previous post. It turned out that the capacitor was the wrong value so I replaced it with the correct one as per the service manual.

What a difference!

The monitor is now pin sharp and stable right from initial switch-on, with the high pitched whine massively reduced (it's still there, although it does fade after about 10 mins - or maybe I just get used to it). The picture quality is night-and-day. Will try to get some pics but the ones I took with my phone last night don't really do it justice.

For anyone not wanting to wade through the various threads on this topic, here are the links to the tripler and LOPT on Donberg:

LOPT
Tripler

I'd say my first foray into the HV side of CRTs was well worth the effort. Hopefully she'll be good for another 30 years!
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Re: New Microvitec CUB Monitor Tripler

Post by vanpeebles » Mon Nov 19, 2018 12:20 pm

Threads like this always terrify me, great stuff! :lol:

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