If you’re like me and have a liking for vintage electronics, you’ll know that they turn up in a lot of places. Craigslist tends to be a pretty good spot for radios and even piles of tubes from time to time, but vintage test equipment is a bit harder to find. Occasionally, though, you’ll find something really special like this old Tektronix 519 microwave oscilloscope on Craigslist – and for free, too!
An old tektronics type 519 oscilloscope from 1960s. I don’t have a power cord that fits the plug to test it. No other accessories. Its very big and heavy, you’ll need a car and a couple of strong people to pick it up.
Big and heavy indeed! The Tek 519 was an engineering marvel at the time it was released in 1961 and it stayed in production until 1973.
Coming out at a time when companies like HP were just getting up to the “kilomegacycles” ranges through sampling techniques, or harmonic pre-selectors to shift GHz signals down to the ranges of conventional oscilloscope bandwidths of the time, the Tek 519 was a brute-force, direct-measurement instrument. It wasn’t suitable for most everyday usage (a weird 125-Ohm input with a proprietary connector, and fixed vertical sensitivity of 10V/cm) but if you needed an instrument that would display a GHz signal in real-time, this was the one for you.
It took some hefty power to make it all work, of course. The Tek 519 scope weighed 99 lbs. and uses a whopping 650W to get the job done, a large portion of that powering the 4CX250 horizontal sweep tube (more often found in transmitters and similar) which had to respond incredibly quickly to signals, and a 24,000V CRT voltage. It wasn’t possible to locate a catalog price for this rare instrument, but when new, it could easily have cost as much as a house.
Just goes to show you that, if you’re paying attention, you might find a good deal on something interesting! This particular one is reportedly going to pass through several hands on its way to a Tektronix collector in Germany.
Closer to home, I picked up my Tektronix 575 Mod 122C Curve Tracer on my local Craigslist, for a pretty good deal but not free unfortunately, back last August. These are also pretty rare. The Mod 122C extends the collector and base voltages which makes it, with the addition of a stabilized power supply for screen voltages and a negative-step amplifier, suitable for curve tracing both transistors and vacuum tubes.
It saw a pretty hard life, apparently. A bit of rust inside, and nearly all of the tubes were cracked in their sockets which made removing their shells more interesting than I planned for.
Fortunately, I have a full set of tubes from a scrapped parts unit curve tracer, so it shouldn’t be too bad. These use 36 tubes, plus the CRT, and two transistors.
Ever find anything good on your local Craigslist?
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Looking closer at the storage damage you want to make sure there are no ‘new’ paths to ground. Take time to clean all the mess where all the wiring and Tek ceramic strips, tube sockets, etc. If this was summer, you might be surprised but the generation of ‘scopes at the time were cleaned at Tek field offices with water and a non-ionic detergent then put in a drying booth where warm air was circulated until dry.
Take a very good looks at the switch wafers, if you see stuff in them that looks like the stuff on the lower deck, it is going to be a not fun time. If you can make your self a box to wash and dry everything in do it, if not do everything you can do to make sure the contacts are clean and get some Deoxit, get the stuff in a bottle, not the spay and use a drop oilier. That’s my personal view, many people use the spray.
Check all resistors over say 33K. Even though Tek only used AB’s the moisture is still a killer. No surprise there.
Next is the HV supply, specially the Tek made transformer. I would change the tube diodes in to silicon. It will reduce the load on the transformer not having to light up
filaments. Yours may have the solid state mod, if so .. great.
Make sure the whole HV path is clean all the way to the CRT.
Hmmm .. what else are those rusty diodes seleniums ? If so it is a crap shoot. If it was
me I’d swap them out, being careful of the lower drop of Silicon.
Make sure the fan turns easily, I’d take it apart and re-oil the bearings, it takes time but you don’t want the fan running slow or freezing up. Have the metal mesh filter ? Wash in the sink soak in hot water for an hour, then degrease, Simple Green will do it. I suggest not using Filter Coat again, heck don’t even know if you can get it. No longer have the filter ? For now get some open cell foam. The whole idea is not to restrict air flow.
What else be very careful of those light tan silicon rubber covered resistors. They are made of quite thin glass substrates. We use to call them glass-ohms. And they break
just looking at them. But are very stable and accurate. Don’t use regular solder on the ceramic strips. There should be a small spool of it somewhere inside. If not only use solder that has at least 2% silver. If you don’t the metal to ceramic bond will go away.
Lets see some more pictures !
I’ll take some shortly and make a separate blog post showing a lot of detail!
Agree that a 575 is something worth having. Specially the mod 122C, mine sadly is not but have been keeping my eyes open for one.
Quite interesting how the tubes were broken, quite a bit a vibration/shock to be able to break so many. I’m curious, how does the mounting around the power transformer look ?
-pete Ex Tek
Hey Pete, thanks for your comment! I’ll check out the mounting around the transformer and post a photo. The panel mount rectifier diodes are super rusty on the surface, too. Seeing such damage to the tubes…I’m not optimistic for the CRT, fortunately, I pulled the CRT from my donor unit and have it on the shelf so hopefully at least one of the two is any good.
Any recommendations for firing it up for the first time (once I get there!) beyond just replace the electrolytic and old film/paper caps and fire it up?
In addition to what Pete said, look for broken connections. I had a 531 that wasn’t stored properly, and lots of wires and leads (including some on the 5642 rectifiers) corroded right through. Also, if your manual lists resistances from power supply rails to ground, check those and make sure they are within tolerance.
Thanks! I’m pretty concerned about some of those neon bulbs in the next post I’ve made with a ton of close-ups…not looking great. We’ll see.