Little Christmans Holidays Project

Today my friends Paul and Jacob talked me into helping complete the first step toward converting an OS-8 scope into a NTSC monitor. I did not really want to do it because the candidate scope there made it wrong on so many levels!

But you have to help your friends. For some reason Jacob had promised this to a cousin of his for Christmas, but ran into difficulties trying to do it. In a way the situation was like Derb's recently, where unexpected company was coming and there was nothing to do but put down the screwdriver and pick up the vacuum and pitch in to help. See, this kind of "non-preferred project" thing happens to us single guys too, just in a different way.

Today the job was to copy the 6J6 multivibrator "time base" and get this additional one wired in and going as the vertical oscillator at about 60Hz and sync-able. Well, that was after replacing several capacitors, fixing bad connections, and whatnot to get the instrument working properly in the first place. I got the lucky draw on doing this part.

The vertical osc. tube and socket now lie sideways under the CRT shield up against the selenium rectifiers. The cluster of parts are ugly-style on the bottom of the socket and were wrapped in a layer of 3M self bonding rubber tape, pre-stretched very thin so it can be removed easily if necessary. I wanted to get a picture but maybe later.

The sync separator and video amplifier still need done and there now is a nice square 525i raster which is best viewed with the lights out as the total accelerating voltage in there is only about 750V.

Another thing is - the CRT is a 2BP1 someone has stuck in there years ago, not the correct 3RP1 which we do not have and are not about to buy. We are looking for a big magnifying lens to put on the front of the CRT mounting tube (extendable escutcheon is missing) so it can be viewed more easily.

Impractical as this project may be, it turned out to be very pleasant to work on it with friends. Who gets to do the sync separator? - not decided yet.. Probably the one who thought it was very funny to bring over a bag of non-6.3V series-string compactrons.

The sync sep. will have to be 1/2 of a 6GH8 or something, the pentode half being the video amp. There is no more room inside that little scope and the power budget is not too fat either! We might SS the 6X4 rectifier to save filament power and boost the B+ a little.

For a small and old scope the OS-8 isn't bad at all. It is DC-2MHz, and has balanced amplifiers for delfection. Also has the customary terminals on the rear panel for use as a mod scope etc. I'd have rather defiled an old heathkit scope or something with a little more room!