1965 RCA Oscilloscope….what to do with it

[Ben79]

I just bought this for a fiver.



Brought it home and it seems to work (it's 50 years old! How is that possible??). I've never used a scope before so I don't really know what I'm doing but I can make all kinds of patterns that change when I play the guitar into it.

It's a lovely thing but I'm not sure it's worth keeping as a scope since it's 50 years old, valve powered and is bound to fail soon. I'm thinking about gutting it and turning into a preamp or something….

What do you guys and girls (are there any girls here?) reckon?

[lordgalvar]

Trogotronic did stuff with old test equipment (check out the valkyrie) and it was how their business started. A good preamp would be fun, as would some kind of tube vibrato or something. There may be a possiblility to turn it into some kind of waveshaper like the Metasonix TM-1.

From what trogotronic has said in the past it is easier to rip everything out and start over to just use the case rather than circuit bending, but I don't know.

Soaring Toartise and RMA should probably have better suggestions. Keeping that tube screen working would be awesome though.

It's going to be neat whatever you come up with!

[Ben79]

20 minute video demo from some guy who understands it…

https://www.youtube.com/watch?v=emWeZEeQQtg

[crochambeau]

Hard to tell from your pic, is that a WO-33a? If so, here's a manual.

http://bama.edebris.com/manuals/rca/wo33a/

Are you familiar with tubed stuff at all? A couple CHEAP (if you self perform) prevention tips and you needn't worry too much about it going up in flames, namely: RECAP the power supply electrolytics and change that godawful fucking two prong plug out for a proper three wire ground referenced power cable.

Then have a look at V1 & V2, which probably comprise more voltage gain than most any self respecting creep would need, this is the stuff that just winds up sounding like hershey squirts. Loads of fun, but watch out, CRTs can fucking BITE and there's a thousand volts in there between your B+ standard tube supply and the B- charge on the CRT itself (could be worse though, some CRT tubes were rated to like 30KV, which is just stupid).

I wouldn't trust it for measurement, as is it would make a cool light show. Sadly, I'd probably fall in with the gut it and build something camp, I don't think RCA really made it to true lab grade test gear status (like Tek or HP) so it's no great historical loss.

[crochambeau]

...all that said, slap a couple hefty DC blocking caps (say 0.5 uf @ 600V) branching OUT from where C19 & C20 connect to their respective inductors and you've got yourself a balanced (or two opposite polarity) signal reference that could probably do with a little attenuation and then just wired to the front panel or a discrete connector plugged into the side.

Again, exercise caution - the 12 year old kids building kit TVs in the 1950s could do it, no reason we can't either.

[Ben79]

Thanks for the replies.

It is a WO-33A.

Recapping it looks simple enough but I can't see I'm going to get much use out of it. It would pain me to do so, but I think the sensible thing to do is to gut it and turn it into something more creative. I'd like to keep the fascia intact and work with the holes that are there, just to dignify all the work that went in to designing and building this beautiful thing. The screen I think I will replace with an image of some kind and a backlight.

I'm not as expert at electronics as most of you guys - I've just built a load of fuzzes in the last year and am getting into making my own simple mods but I would love to build a valve pre and I know the basics and the safety measures involved so I might head down that route. Or I could go the whole hog and build a Champ or a Deluxe in there - I've got an old Hammond AO-63 organ amp sitting waiting to be chopped into something.