rca wo-33a o-scope. ?questions?

[deth502]

first, i bit of background.i was a bit into electronics in my 20's. i havent done anything in a loooong time. im 35 now and starting to get back into it. id prob. put my education level right now at the avg early teen.

back in the day, i never got much further than multimeters and breadboards, but i did pick up 2 "vintage" scopes to mess with. i never did. lately, ive dug them back out again, looking to pick it up where i left off.

that leads up to today. as the title says, the older one is an rca wo-33a. looking on the web, i see a lot of complaints about the old machines, afa caps leaking down, bad resistors, ect... and the general widespread dislike of anything with a tube.

i was thinking, for a project, of updating this unit. this would have the advantages of possibly making it a bit more reliable and/or accurate, allow me to get a more intimate knowledge of it to facilitate the learning, and be a project to get my feet wet, as it were.

so my questions are twofold. ive been looking around the net, and i see these things going for $25 up to over $100, and everyone i see is missing parts and/or non-functional, compared to other scopes of the era that go for as low as $5 in working order. does the fact that, other than 2 of the original 10 knobs are missing, this is a fairly good shape piece with all of the nessicary parts and fully functional make it more of a "collectible" that id be best not screwing with?

secondly,if not, and i do tear into this. other than replacing the caps and other solid state components, would it even be possible to determine the ratings and purposes of the tubes and retrofit suitable solid state components into it in their place? (making small "plug and play" units to replace the tubes without dismantling the original tube sockets)

tia

 

[JimB]

so my questions are twofold. ive been looking around the net, and i see these things going for $25 up to over $100, and everyone i see is missing parts and/or non-functional, compared to other scopes of the era that go for as low as $5 in working order. does the fact that, other than 2 of the original 10 knobs are missing, this is a fairly good shape piece with all of the nessicary parts and fully functional make it more of a "collectible" that id be best not screwing with?

Never heared of an RCA WO33A before now!
Just had a quick google session and found one for sale for $100,, the guy must be joking!
Must be worth $5 absolute maximum.
I would say that these scopes have no great monetary value, and technically are truely obsolete.

secondly,if not, and i do tear into this. other than replacing the caps and other solid state components, would it even be possible to determine the ratings and purposes of the tubes and retrofit suitable solid state components into it in their place? (making small "plug and play" units to replace the tubes without dismantling the original tube sockets)

The manual is available for download from the BAMA Archive, the circuit is quite simple and would make a good learning exercise for an intermediate level novice.

Replacing the tubes with transistors etc is a complete non-starter in my opinion.

So, play with it, rip it apart, try and get it working if you want you will not be destroying a valuable museum piece.

Beware there are some high voltages inside when it is working.
A quick look at the schematic shows 680 volts.
That will give you a nasty nip if you get it on your fingers!

JimB

 

[deth502]

thanks for the reply. thats what i thought, i just couldnt figure out why they were asking so much for these. thought i might be missing something.

i did already find the manual searching for info on it.

i read this the other night and wasnt afraid to start taking the screwdriver to it. i dont think im going to do anything to it now. what looked like a case wanting a new paint job just turned out to be 60+yrs of dirt over a fairly well preserved hammer finish paint job after some dish detergent and a wet sponge got to it. as far as the inside of it, it looks like someone beat me to it. there is one capacitor in the back that i dont like the looks of ( a HUGE one!) but other than that, it appears that someone already changed out most of the old caps and resistors with new ones. there were 2 tubes that were labled "original" so im assuming that the rest of those were likely replaced as well.

seeing as this thing cleaned up so easily, and looks to have been extensively gone over, i think im going to leave it at that. 2 mods i was going for, that, imo, it could still use, was to replace teh permanent lamp cord with a plug for a modern pc type power cord, and replace the unknown probe jack with a bnc one, but since im not really tearing into it, i think ill live with the cord, and try to find an adapter for the probe hookup.

 

[deth502]

btw, i do realize that the uses are limited, and it is pretty much obsolete, i just like the antiques. i do a lot of metal working too, i have a new power band saw with auto feed and coolant flood that will cut through a 4" solid chunk of steel in under a minute, but i still have an old power hacksaw in the corner too, that takes about 7 min to cut through 1" of steel. its not as useful, but its just fun sometimes to watch the old machinery move and work. this scope is something like that.

i recently got a tectronics 2246 to be the "workhorse", just waiting on some ebay probes to actually be able to use it.

 

[JimB]

what looked like a case wanting a new paint job just turned out to be 60+yrs of dirt over a fairly well preserved hammer finish paint job after some dish detergent and a wet sponge got to it.

It is surprising what a bit of soap and water will do to a scabby looking old case!

If you are a metalworking enthusiast (so am I), you could use the case from this old scope to house some new project.
Make a new front panel and away you go.

JimB

 

[deth502]

oh yes, the case is very well made. i was surprised at all of the weight still there once i removed the "guts" from it. its VERY solid! they dont make them like that anymore.

 

[Jaguarjoe]

Don't beat up those old 0-scopes too badly. I cut my eye them on them. My fav was an AB DuMont 502 dual BEAM scope. 2 vert's, 2 horizontals, 1 CRT.
An RCA Voltohmyst was our keystone instrument.