I was given these today. One is an RCA WO-91c and the other is an Eico model 406.
http://www.flickr.com/photos/48878097@N02/5770065628/in/photostream/
The Eico has some pretty waxy caps. The pilot light doesn’t come on when you plug it in. Truth be told I think I took a pretty nice risk plugging these in considering the age of the caps.
The RCA I believe just might work, though some of the joints are tarnished.
So what…did I get junk or can these actually be beneficial?
I have one of those Eico’s. They work good for lisijous (sp?) figures. The pilot won’t come on if it isn’t grounded.
Thanks,
I will surely keep that in mind about the grounding.
The fuse loks good, the tubes all have silverish grey in the tops, all the joints look decent. THe caps look very waxy on that unit like at some point one liquified to the point where it started to drip, but never did drip.
The RCA though actually works, I got a seatdy horizontal trace and I just need to rig up a probe so that I can see if it will display a waveform. Im going to check in the manual to see if the Voyager or Freqbox puts out 3v p-p.
How do you like yours; do you actually use it for anything?
Eric
Any voltages out wil display, you use the vert gain to attenuate if needed. You don’t need any fancy probe for audio level signals. Just a signal ground wire and a lead from the Vert input.
I use mine on the test bench for DIY stuff. I’ve also got a nice dual trace that I use in the studio to check levels and balance. I also use it to visualize waveforms and it helps figure out what new modules are doing.
Those old scopes are probably somewhat adequate for tracing audio and control signals through op amps and transistors, but for troubleshooting digital circuits they may not be much help. Even antique microprocessor designs have clock oscillators running at several megahertz which is likely past the bandwidth range of these instruments. Especially if you are using a wire lead in place of a frequency compensated scope probe. Also, accurate triggering and a dual trace display is mandatory for viewing many events in digital circuits. I have not looked, but I would speculate that their may be an abundance of used scopes on the market now since anyone keeping up with technology would have to update their test equipment every few years. If you have an interest in learning to use the scope, it might be beneficial to look for one with dual trace and delayed sweep that has some usable sweep trigger control. Scopes like those in your post that I’ve looked at do not hardly trigger a stable display even under the best of circumstances.
It would be good to learn what you can with these however. Any exposure to using a scope as test equipment will likely inspire you to learn more. When I worked at Tektronix I acquired a 454 scope chassis and several boxes full of reject circuit boards that were set aside from when this unit was still in production. The boards were all of the dogs that the production line technicians gave up on trying to fix. I learned a great deal about how the scope works in the process of getting that scope running. I used it for some time with a display that bloomed with intensity control changes. Finally the CRT (cathode ray tube for you youngsters out there) gave out. Tek still supported this model, and I was able to buy a new CRT at employee price. When replacing the display, I decided to look into that blooming problem. Turns out there was a wrong resistor in the high voltage regulator circuit that resulted in no high voltage regulation. That was the last of about 150 problems I fixed on that scope.
I mention this because I was nervous about getting into that high voltage circuit. If you are inside your scopes probing for answers, remember there is a CRT with some serious high voltage bias. 1800 volts on my 454 if I remember correctly. Best to use a high voltage probe here.
As foolish young technicians on the production line of the Tek 4010 series graphic terminals, (see old Battlestar Galatica TV series) we used to think it was real funny to draw a pencil line from the probe tip up the handle so that the next time 4KV was measured, the operator would get a good jolt. Another good trick was to insert a 10 ohm, 1/4 watt resistor into an AC outlet after hours when the bench power was turned off. The guy on that bench would turn on the power in the morning and that resistor would explode sounding like a .22 caliber gun shot. Lucky nobody got hurt.
One of the scariest things I saw happen was when the guy at the next bench from me was trouble shooting deflection amplifiers on a test jig. He heard an odd sizzling sound coming from somewhere on the board. In an attempt to understand what was happening he had his ear right next to the board listening for the source of the sound. About that time an electrolytic capacitor that had been installed backwards blew out the end seal spewing the insides in Tim’s face. It sounded like a 12 gauge shotgun going off. Luckily he wore glasses and there was no permanent hearing loss. I think he took the rest of the day off though.
Believe it or not, I have a former Tektronix employee coming to look at these units this week.
Eric
I used to have an old tube 5xx Tektronix scope (I don’t remember the exact model, it was many moons ago). It was obvious that is needed calibration because that the trace displacement was not linear. So it was for observation only. Hey it was my first 'scope and it was $50 at a hamfest. Those tubes cost a lot of $$$ to replace and the solder joints were silver solder not the 60/40 commonly used today, and the manual warned against using anything but.
I eventually sold the scope because the tubes made today are nowhere near as good back then, and I wasn’t about to gamble $$$ trying to bring it back into calibration through tube selection.
The guy who gave the scopes to me is a fellow ham and he actually has a pretty substantial tube inventory and said I can have whatever tubes I need to replace any that may be blown out, and for the RCA he does have some duplicates.
Eric