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  1. alfa88

    Need Help Analyzing Constant Current Source

    Thank you for your analysis it helps my confusion. Attached is a picture of the thing I'm working on. If I'm not mistaken Don Lancaster helped design the line and some of the information was published in Radio Electronics. There was some sort of falling out and further details of the product...
  2. alfa88

    Need Help Analyzing Constant Current Source

    IC1 is a polarity separator and has a transistor stage to drive an LED indicating a negative Voltage. Keep in mind this is a 70's vintage circuit and digital meters were pretty wiz-bang back then. IC2 is a summer. IC3a is an integrator serving as a ramp generator IC3b is a comparator that drives...
  3. alfa88

    Need Help Analyzing Constant Current Source

    Attached is a schematic of a multimeter section of a SWTP Universal Digital Equipment kit (70s vintage). The circuits in violet are what I suspect are the cause of a malfunction. Fortunately I was able to find a functioning unit and found several discrepancies in the original schematic. The...
  4. alfa88

    Sensistor vs Thermistor

    Yea, I saw that Wiki. Since there doesn't seem to be much info on the sensistor's specs other than ambient resistance I guess I'm at the mercy of the thermistor gods
  5. alfa88

    Sensistor vs Thermistor

    I've been remastering a 70s vintage digital multimeter kit and I've managed to find replacements for most of the parts but one of the parts is called a sensistor. I sort of assumed that the part is the same thing as a positive coefficient thermistor. Opinions?, Guidance?
  6. alfa88

    Display Lens Source

    The polyester from Granger turned out to be opaque. Didn't order. Then I had a brain fart. I just bought some tinted CD cases at Office Depot. Thin, transparent and in 5 different colors.
  7. alfa88

    Display Lens Source

    I found paint or dyes not to durable. I looked up polyester and sure enough Granger has something that will work. I guess I just associated polyester with Saturday Night Fever
  8. alfa88

    Display Lens Source

    I've been restoring some old equipment and run into a brick wall trying to replace the damaged front panel display window. One meter uses Nixie displays and has an amber colored window, the other uses a 7 segment led display and would need a red tint. The thickness should be ~ 0.9mm/.035" . I...
  9. alfa88

    Desire datasheets for obsolete Signetics FFs, Nor

    Most excellent. Why didn't I think of that?(head-slap)
  10. alfa88

    Desire datasheets for obsolete Signetics FFs, Nor

    Does anyone have datasheets for LU321A, LU322B and LU380A? I can glean some info from a schematic but some pin-outs are missing and there'll be some tracing to do. Datasheets might be helpful should I need substitutions. They are JK Flipflops w/S-R, JK Flipflops w/R, and Quad Nor respectively.
  11. alfa88

    Southwest Technical Products Corporation

    Got myself the nixie style mainframe w/freq. counter and the final version w/freq. counter using the MK5009 via Ebay so hopefully I can do a little reverse engineering with this info. There is a Yahoo group (manual_exchange) that trades manual info. but results may be hit or miss.
  12. alfa88

    Southwest Technical Products Corporation

    PS I'm going to be in the San Antonio area in a while so Mr. deEd are you aware of any electronic surplus stores nearby?
  13. alfa88

    Southwest Technical Products Corporation

    Thank you Mr. De Ed, It now becomes clear why Mr. Meyer and Mr. Lancaster had later iterations of the digital instrumentation. The nixie version left it up to the readers to either purchase a 3rd party nixie/driver board or glean their own design from previous articles. Plus back then 7 segment...
  14. alfa88

    Southwest Technical Products Corporation

    Digital Multimeter(VOM-2) and Capacity(UC-1) Plug-ins are the ones that seem most useful. There was a time base, and time period(stopwatch) plug-in but they don't seem that useful to me. Sure I could purchase a newer and better modern meter but I"m being nostalgic.
  15. alfa88

    Southwest Technical Products Corporation

    Years back I posted a query regarding SWTPC 's Universal Digital Test Equipment. For all you young bucks this stuff was all the rage and they constantly had diy articles in the electronic magazines. Their prices were way better than Heathkit though their finish was somewhat lacking. Anyhow I...
  16. alfa88

    Conductive Foil

    The first thing that came to mind was reflective mylar film. Can be found at garden supply shops. I'm not sure if you can obtain 500 Ohms per meter, it's pretty conductive. Maybe by playing with width.
  17. alfa88

    Vacuum in a Can

    A future project would be making a simple triode. In what I've read one reason Edison's light bulb succeeded was that he managed to achieve a higher vacuum thus eliminating that pesky oxidation and inadvertently discovered a rectifying effect later on(which didn't seem to impress him too much)...
  18. alfa88

    Vacuum in a Can

    I don't know what you're going for, alfa88. I'm fascinated by H.P. Friedrich's 'McGyver' approach to recreating old technology, i.e., using readily available materials to accomplish said tasks.
  19. alfa88

    Vacuum in a Can

    Not to belabor this subject but I had a brain-fart. A CRT might make a good source of high vacuum if proper plumbing was attached to the neck and a method was devised to rupture said neck in the right place. Walla... Canned vacuum! Sounds dangerous as Heck. I feel stupid even suggesting a gas...
  20. alfa88

    Vacuum in a Can

    Well that's no fun.
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