(no subject)
Feb. 19th, 2018 11:53 am![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
stormdogI have updates that aren't related to electronics. I really do! Pretty significant ones even! But I haven't had a chance to think about them and write them up.
In the meantime, with apologies for those uninterested, more electronics!
----
I keep ending up with weird hardware. When I had a Suzuki Swift, it was the sedan version, which was far rarer than the hatchback. Super-mechanic Juan continually got the wrong parts when ordering things for it even though the part numbers matched.
My VTVM is an oddball too. A different tube than any I can find anywhere else, and a probe connector that's been described by some folks as "the worst connector ever designed."
Most recently in the annals of Stormdog's strange electronics, on Saturday I bought a regulated DC power supply; a Kepco ABC 200M. It looked like a quality solid-state unit; for $35 it seemed like a bargain. 0-200 VDC with integral ammeter and short-circuit current protection. Positive and negative terminals as well as neutral. It's even programmable remotely via resistance or voltage level. Really nice vernier knob to control the voltage. The indicator on the front slid smoothly along up to 200 volts and back. I bought it.
At home, I put a multimeter on the terminals and found no voltage. When I turn the voltage up or down, a little bit of voltage, maybe half a volt, appears on the meter while the setting is changing, then back to 0. The meter, meanwhile, stays steady at whatever voltage I set it to.. I thought maybe there was an issue with it needing to have a load on it, or it was detecting a short circuit erroneously. The short circuit level detection pot was loose, so I opened up the case to tighten it down.
That was easy enough to do. Before I did though, I was startled to find a vacuum tube inside the beast. Googling further, I learned that this is from a line of hybrid power supplies that are partially transistorized, but incorporate a big pentode tube as well. It also has an extra switch on the front that none of the images of similar power supplies I've found has, and if there was a label for it, it is lost to time.
Of course, I cannot locate any schematics or documentation for this device that might explain it's behavior. I'm going to try emailing the company.
On the other hand, after buying the appropriate screwdrivers while out with Posi, I popped open my other vintage multimeter. It's a nifty old thing with a heavy Bakelite case and a really nifty range indicator on a big cylinder inside it that rotates when changing settings.
This one is non-amplified, and therefore much simpler. The glass protecting the needle indicator had popped out of its window, but all else seemed well. I cleaned the glass and frame off with nail polish remover on the glass and rubbing alcohol on the frame. (I didn't want to potentially damage the Bakelite with something more powerful.) I also very, very carefully straightened the slight bed in the indicator needle and cleaned off the anti-parallax mirror as best I could. It's not perfect, but it all looks far better.
With the glass fixed, and not hanging around loose inside the meter, I plugged the probes in and measured voltage from a D cell. Other than slight stickiness of the movement, which I think I fixed with some compressed air around the coil, it works beautifully. I need to buy new probes to replace the sixty-year old ones with flaky wires that came with it, but after that it may become my go-to volt-ohmmeter.
It's one of these: https://www.youtube.com/watch?v=vjMTq1AxQYo
Made in Chicago! I love having truly local, vintage gear that works! It'll be so neat to use on my made-in-Chicago Sherwood receiver.
Going back to the VTVM, I am continuing slow progress I think. I keep iterating back and forth between poking at it's innards and reading (and re-reading, and re-rereading theory), and the process is moving along. Last night, I connected a voltmeter in place of the VTVM's meter in the thought that I'd backtrace where the too-high voltage was coming from. I didn't get too far along that path before referencing and then getting absorbed in theory again, but it made more sense than last time. I'm going to try to make a simplified, functional map of the rectified DC circuit and ignore the probe circuit for now because, with no device under test, the circuit should balance out for 0 volts at the meter. Since it's not, something is wrong in there, and I think it might be one of the potentiometers.
Of course, all the fancy terminology hides the fact that I really have no clue what I'm doing most of the time. I've managed to avoid major injury or magic smoke, so so far so good.
In the meantime, with apologies for those uninterested, more electronics!
----
I keep ending up with weird hardware. When I had a Suzuki Swift, it was the sedan version, which was far rarer than the hatchback. Super-mechanic Juan continually got the wrong parts when ordering things for it even though the part numbers matched.
My VTVM is an oddball too. A different tube than any I can find anywhere else, and a probe connector that's been described by some folks as "the worst connector ever designed."
Most recently in the annals of Stormdog's strange electronics, on Saturday I bought a regulated DC power supply; a Kepco ABC 200M. It looked like a quality solid-state unit; for $35 it seemed like a bargain. 0-200 VDC with integral ammeter and short-circuit current protection. Positive and negative terminals as well as neutral. It's even programmable remotely via resistance or voltage level. Really nice vernier knob to control the voltage. The indicator on the front slid smoothly along up to 200 volts and back. I bought it.
At home, I put a multimeter on the terminals and found no voltage. When I turn the voltage up or down, a little bit of voltage, maybe half a volt, appears on the meter while the setting is changing, then back to 0. The meter, meanwhile, stays steady at whatever voltage I set it to.. I thought maybe there was an issue with it needing to have a load on it, or it was detecting a short circuit erroneously. The short circuit level detection pot was loose, so I opened up the case to tighten it down.
That was easy enough to do. Before I did though, I was startled to find a vacuum tube inside the beast. Googling further, I learned that this is from a line of hybrid power supplies that are partially transistorized, but incorporate a big pentode tube as well. It also has an extra switch on the front that none of the images of similar power supplies I've found has, and if there was a label for it, it is lost to time.
Of course, I cannot locate any schematics or documentation for this device that might explain it's behavior. I'm going to try emailing the company.
On the other hand, after buying the appropriate screwdrivers while out with Posi, I popped open my other vintage multimeter. It's a nifty old thing with a heavy Bakelite case and a really nifty range indicator on a big cylinder inside it that rotates when changing settings.
This one is non-amplified, and therefore much simpler. The glass protecting the needle indicator had popped out of its window, but all else seemed well. I cleaned the glass and frame off with nail polish remover on the glass and rubbing alcohol on the frame. (I didn't want to potentially damage the Bakelite with something more powerful.) I also very, very carefully straightened the slight bed in the indicator needle and cleaned off the anti-parallax mirror as best I could. It's not perfect, but it all looks far better.
With the glass fixed, and not hanging around loose inside the meter, I plugged the probes in and measured voltage from a D cell. Other than slight stickiness of the movement, which I think I fixed with some compressed air around the coil, it works beautifully. I need to buy new probes to replace the sixty-year old ones with flaky wires that came with it, but after that it may become my go-to volt-ohmmeter.
It's one of these: https://www.youtube.com/watch?v=vjMTq1AxQYo
Made in Chicago! I love having truly local, vintage gear that works! It'll be so neat to use on my made-in-Chicago Sherwood receiver.
Going back to the VTVM, I am continuing slow progress I think. I keep iterating back and forth between poking at it's innards and reading (and re-reading, and re-rereading theory), and the process is moving along. Last night, I connected a voltmeter in place of the VTVM's meter in the thought that I'd backtrace where the too-high voltage was coming from. I didn't get too far along that path before referencing and then getting absorbed in theory again, but it made more sense than last time. I'm going to try to make a simplified, functional map of the rectified DC circuit and ignore the probe circuit for now because, with no device under test, the circuit should balance out for 0 volts at the meter. Since it's not, something is wrong in there, and I think it might be one of the potentiometers.
Of course, all the fancy terminology hides the fact that I really have no clue what I'm doing most of the time. I've managed to avoid major injury or magic smoke, so so far so good.
no subject
Date: 2018-02-19 10:55 pm (UTC)We're watching a cheesy TV miniseries on Tesla, and one aspect of it is a group of guys trying to recreate a "death ray" using very large capacitors. Seems very dangerous!
no subject
Date: 2018-02-20 01:50 pm (UTC)And would probably handily kill someone if they were charged up.