AMSCO Medical Lighting VARIAC: Don't Turn it On - Tear it Down! - Page 1
Forum section: electronics / testgear

author: mnementh
author_rank: Super Contributor
timestamp: June 13, 2019, 07:10:42 pm
content: Sorting through two lifetimes of accumulated junk to reduce for a move, I found this beast lurking in a box of power supplies and felt to share, as it is the sort of old-school precision tech that just warms your soul. And your body on a cold winter's night in tool shed.In keeping with Dave's mantra, let's just jump straight to the juicy bits inside. Classic Bakelite barrier strip provides connection to the flowing electrons; and still lurking inside are the provided grommets for alternate installation method. And instructions on the once-ubiquitous wired toe-tag!Here you can see the internal wiring and split-pole circuit-breaker. Wiring is a bit crusty and stiff, but I guess that's to be expected. If that toe-tag is indicative, this thing is older than me; I'm stiff and crusty too.With AMSCO being a premiere medical manufacturer, of course it contains a delicious GenRad 720VA VARIAC. This one is in excellent condition, and has the double-insulated shaft for use with a metal knob even though the one equipped is plastic.Here's a nice shot of the huge aluminum disc that carries the wiper on this beast; Manualzz.com has aninteresting article from a 1955 issue ofGenRad Experimenterwhen they first released the Type W5.Nifty.The back shows this beast's age considerably more than the front; amazingly, the vintage natural rubber lamp-cord and Rodale/Sta-Tite connectors are still in serviceable shape. I still think I'll bring the poor thing into the 21st century with a grounding-compliant rewire before I put it back into service.tzzzzzt.And here's the money shot; all wiped-down and reassembled. Note the UL badge in the lower right corner. She's not exactly a lightweight; bathroom scale puts her at 13 lbs American. But the vertical format makes her very bench-friendly, and 13 lbs is definitely reasonable to handle everyday. Front panel has a slide-plate mount at the top edge; a single #2 Philips screw at the bottom holds it in place. That and a 5/64" (2mm) Allen wrench for the grub-screw in the knob are all you need to get inside. Circuit-breaker is internal common trip; it appears there's supposed to be a tie-pin between the two toggles that is missing.Since the wiring is mostly intact, I figured I'd plug it in (to a breaker-equipped power strip) and take some voltage measurements to close out the article. Unlike some made explicitly for motor speed control and specialty lighting, she does in fact go down to zero volts at minimum.Midpoint is ~72 VAC unloaded. Meter reads considerably low.Max is 142VAC unloaded. Obviously I'll need to tweak the meter, if I don't replace it with something more precise or print up a replacement scale.Alrighty... that pretty much finishes the tour; I need to get back to work sorting for the move. Thanks for looking!mnem

author: mnementh
author_rank: Super Contributor
timestamp: June 14, 2019, 02:53:03 am
content: But wait, there's more! Now how much would you pay?This beast has an ugly sister; she's a bit rustier and has a thin crack in the meter lens in the area above the movement.Once I get a chance to test the internals, I'll be putting ugly sister up in the B/S/T. I'm just keeping the pics here for now.SOLD to a fellow TEA addict who was quick on the draw.And here's the back on ugly sister; someone has drilled and installed grommets. I BELIEVE this is the one I've actually used.Here she is wired for testing with a 1KW Evaporative Heater as a load.Here she is holding and humming a little at 6A/633W.Here she is barely holding at 10.5A/1363W/150% overload - typically this breaker should trip within an hour or so at that loading. It starts to buzz after ~10 seconds and will trip if you just touch it.It trips instantly at any of these loads if I short-circuit the output, so I'm gonna say she's fit as a fiddle & ready for love.Cheers,mnem*Juicy*