I picked up a new shop toy just the other day, a Tektronix 575 Transistor-Curve Tracer. This is a piece of lab gear I’ll use to match transistors for their operating characteristics, and can also be used to analyze and test other kinds of components too. This component tester is a tube-based device from the late ’50s, but tests BJTs, and with some adapters can test tubes and JFETs so I should be able to get some good use out of it.
This came out of a garage where it was stored for several years, so it’ll need a full overhaul, but these are pretty tough to find in any condition. When they’re repaired, they look like so, and produce the curve families shown on the display from the Tek enthusiasts wiki:
The test panel includes two sets of sockets, and a switch to alternate between them, perfect for matching pairs of transistors. I’m excited to get to work on this, although it won’t be for several months at least! I’d really love to find a Tektronix 570 curve tracer, though. It’s a dedicated machine for sweeping tubes.
There’s some trade-offs. The 575 can test both sides of a dual triode at once; the 570 would need have its test sockets re-wired for each, but can more flexibly accommodate multiple sets of tubes, and tubes other than triodes. The Tek 570 was the only professional tube curve tracer ever commercialized, though, so it might not be possible to find one easily or affordably – especially when it’d mostly be for collector value that I’d want both, not a lack of functionality.
The 575 can perform the same sweep, although lacks the heater and screen supplies. Adapters to provide the missing heater voltage for testing triodes on the 575 aren’t that tough to make, although this example tests a fixed pin-out only.
Here’s another which could accommodate changing pin configurations, although is set up only with a single socket.
I’m lucky that I happen to have an external tube power supply already, the Oregon Electronics A3 Regulated Power Supply that I refurbished.
That’s a pretty hefty piece of equipment; it provides a 6.3V filament at 5A, and a variable 0-300 and 400V fixed regulated output, helped along by neon gas regulators:
With this supply, I’ll be able to supply a high quality heater supply to most tubes where it’d be appropriate to match characteristics – octal and loctal dual triodes like the 6SN7 and 7N7, and miniature tubes like the 6AV6 or with a tapped heater like the 12AX7. The Oregon Electronics power supply also has a stiff, clean supply rail for the screen voltage and a meter to measure its output. Since I work on radios from many different age ranges, I’d need to build an adapter box with octal, loctal, 7-pin and 9-pin miniature sockets, but also the 6-pin and 7-pin pre-octal sockets. If I’m building a breakout box, it’s not much more effort to add a couple more sockets to take care of the edge cases like testing a #19 or 6A6 tub. I have a tube tester lying around with a bad meter-read switch that won’t be useful in this application, so I might use the chassis to make the filament supply and socket box.
The Tek 575 can deliver up up to 400V at 0.5A, 1A at 200V, or 20A at 20V; it can be paired with a Tektronix 175 High-Current Adapter which offers up to 200A at 0-20V, or up to 40A at 100V. From what I gather these are even more uncommon, although do turn up from time to time.
This should be a fun project, I’m excited for when I can get a chance to do a restoration.
If you’re around Seattle and do have a 570 or a 175 for sale, or have a replacement for the base step generator repetitive/single family switch, I’d be interested in hearing about it.