My first image on my first NBTV monitor

Forum for discussion of electronic television. Generally, stuff to do with CRTs and not using mechanical displays.

My first image on my first NBTV monitor

Postby tubefriend » Fri May 24, 2013 11:54 pm

I got an soviet 8LO39B tube, that is the equivalent of an american 3JP7, and built an first crude monitor circuit for it.

The deflection is done by 2* EF80, each one of them connected as an transitron oscillator with miller integtrator and delivering an approximate sawtooth with about 100Vpp. Both are currently directly syncronized from an fraction of the video signal and need permanently very fine adjustment to hold the picture.

The video amplifier is currently an half ECC83 and will be replaced in the next step by some kind of differential amplifier that can accept positive or negative input and both polarities output for CRT drive as well as an true sync separator that i very need.

An switch allows to run this either as an monitor with X and Y from the sawtooth generators and video coupled to the CRT grid, or as an scope with the video signal coupled to the Y plates.

The next thing that i need is an chassi to mount everything onto and add some basic screening, then i can begin to optimize the circuit into an first useful monitor.

The tube was deliberately out of focus to get an more pleasant image, mostly because of smoothing out the jittering from stray fields.
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Postby Steve Anderson » Sat May 25, 2013 12:19 am

Well done and welcome to the forum, good to see another tube-head here.

My first attempts at using CRTs for NBTV looked much the same with the same problems of getting things locked-up. Slowly (perhaps quickly) ypu'll get there. Keep it up.

Steva A.
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