- 2024
- Mar
- 17
An Eico 145 Signal Tracer - Part 0
I sat down with an Eico 145 Signal tracer this weekend, evaluating what it would need to put it back into daily service. The answer? Pretty much everything. Leaky wax capacitors, carbon comp resistors that are 50% off of their marked value, and a few “doesn’t appear to ever have been installed” parts complete the list of this thing’s issues. It’s amazing that it’s still working, but I would bet that continued operation would destroy the tubes in short order.
The large 470Ω resistor in the foreground was of interest. A quick shout out to a friend confirmed that this was a 2W part, not a high-voltage device. This makes sense, as the resistor could potentially dissipate 600mW at maximum plate current. It’s also interesting because there’s supposed to be a 10uF bypass capacitor across that part, but it looks like it was never installed!
Right under that, of course, is the across the line capacitor. That ’splodey boi gets replaced first.
A quick trip to mouser for components is in my future.
Next part of this series: https://wereboar.com … ignal-tracer-part-1/
Previous part of this series: https://wereboar.com … o-145-signal-tracer/
- 2024
- Mar
- 12
An unusual 115VAC demand meter.
I picked this unusual device up from an antique store in rural Pennsylvania, near where the groundhog works one day a year. It’s a fairly large place and prices vary, but it’s worth a couple hours of your time if you’re into that sort of thing, see the link below.
(The place seems to only have a facebook presence, and I’m not going to post one of those dirty links here - but here is the local chamber’s page for Yoder’s Antique Mall in Punxsutawney: https://punxsutawney … 73c05f142052452104c6.)
It’s a toolbox! Yeah, right on! Well…no, unless you’re interested in old toolboxes. It’s a fairly nice example of something from when Sears used to make things worth more than the metal it was stamped from. It’s what’s inside that I was interested in.
It’s a demand meter! Yeah, right on! Well…yes, but there’s something unusual about this one. It’s a 2-wire, 115VAC unit. While this is similar to what you would have on your house (or would have had before the electronic switchover,) those are usually wired for 230VAC instead.
This one appears to have been meant for sub-branch metering at some point, as evidenced by the easy-to-remove wiring compartment at the bottom of the meter’s housing. Whomever had this before me took advantage of that in that they wired a plug and outlet in line with the device - perhaps as a jobsite meter to pay the site owner for power consumed? Not really sure here save that all of the cable is pretty stiff and in need of replacement if it was going to be used.
Overall age of the device is in question as well - it looks to be 1930s, but Westinghouse probably made these things for decades. I suppose I could try and track it down by serial number, but who knows if those records still exist?
I tried it out by hooking it to a kitchen appliance with a heating element. It works as expected.
I’d like to get it out of it’s silicone covered metal box for a good cleaning, but that’s a project for another day.
- 2024
- Jan
- 21
An IMD-202-2 for parts…but let’s take a quick look anyway!
SO…here’s another one of these piece of crap meters. Why? This one was cheap, and was purchased non-working - primarily for parts, as in the NIXIE tubes. ZM1000 tubes aren’t exactly common these days, so having a few spares laying around seems to be a good idea.
I decided to at least take a look inside to see what’s broken. It doesn’t power up because the fuse is blown. That never bodes well, so I jumpered the fuse temporarily and turned it on quickly.
Yep, it’s got some problems. All segments of the tubes are lit, and the tab on the +5 regulator transistor got pretty warm being on for 5 seconds. Turned it on again to get some quick voltage measurements:
+5V Output (Emitter) = +0.8V
+6V (Base) = +2.6V
Measuring the resistance to ground:
E = 2.8 Ohms.
That’s not good.
A good unit measures (to ground):
E = 1.4MOhms.
+5 primarily powers chips, so I pulled all the ICs to start. Things changed, but not necessarily completely back to normal.
Good unit:
E = 1.4M
B = > 8.5k (charging)
C = Open
Bad unit:
E = 2.5k
B = 1.9k
C = Open
I started putting chips back in, the very first one I replaced (IC5) took the Emitter of the regulator transistor down to 3 Ohms. So that chip is bad.
However, there’s something else wrong. With all the chips gone, the +5 load should be negligible. I did a quick scrape on the transistors to see if one was shorted but didn’t find anything obvious. That leaves old capacitors that could be leaky. This thing is full of Tantalum drops and cheap-ass film caps, any one of those could be partially shorted and there’s no real way to know except to start lifting parts.
Since this is just a parts unit, and the tubes and driver ICs appear good, I think it’s just going in the parts bin as intended. Maybe if I have some snowy Saturday, I’ll pull it out and start lifting parts to see what’s going on. But for now - parts is parts, and parts is what it is.
- 2024
- Jan
- 15
The Sunday Creek ARF Hamfest 2024
I’d never attended this show, but was pleasantly pleased with the turnout. There were perhaps a few dozen vendors and a packed house of visitors in the old gymnasium of the converted school. Quite a bit to look at, and prices were really good. I managed to bring home some good things for a total of $10, almost spending more on drinks and snacks on the way home! I didn’t think the weather was going to cooperate, but it turned out to be just a bit slushy, cold, and windy.
We wandered the aisles for about an hour, taking some time to stop and look at the old photos on the walls from the building’s time as a school, talking to some of the vendors, and digging through boxes of stuff. Since this is so close and easy to get to, I’ll probably attend next year as well - weather permitting of course!
- 2024
- Jan
- 14
The Sunday Creek Hamfest has come and gone,
And I have to say it was a pretty good little show. The weather wasn’t planning on agreeing on the ride down, but it turned out to be just a skiff of snow and cold, windy weather. There were maybe a couple dozen vendors, and a packed house full of guests to the point where cars had to shuffle so others could leave.
While I only spent an hour there, I walked out with some good stuff as did my fellow show-goer. I’m working on processing pictures, and will post those soon. In the meantime, bask in the green glow of a magic eye from one of the devices I went home with.
- 2024
- Jan
- 8
Stabilizing the oscillator in the IM-1212 Meter, part 2
One of the issues with the IM-1212 and it’s clones is that it drifts all over the place, and part of that is the oscillator that actually does the counting for the display. This is an attempt to replace that section with better parts to see if it’s any more stable. I started this with this previous post, and present my findings here.
We start by identifying the components of interest and removing the board:
In the oscillator circuit, other than the transistors, are the following passives:
15k
8.2k
3.3k
3.3k
0.0022uF
0.0022uF
15k Potentiometer
We’re not going to replace the pot, but all of the other components are going to be replaced by film and/or temperature stable to 25ppm components.
The sharper-eyed among you will have already seen an issue. There’s no 15k resistor identified here, and I’ll talk about this a bit later in the process.
Before taking the board out, I let it warm up and preset the oscillator to it’s suggested 85 count.
Getting the board out isn’t too bad. There are 6 screws, three solders, and a clamp.
The screws are the ground lug for the power cord on the back panel, the two screws that hold the transformer down, and one screw each in the remaining corners. One of the screws is under the switch assembly and can just be seen by the red input jack, so you’ll need something relatively thin and long for this one. They all appear to be the same size.
Next are the three jacks on the input. I unsoldered these at the front panel itself, but the white wire was long and flopped around and broke because it is solid wire. Not a big deal there.
Last, is the clamp for the power cord on the back panel. This is just squeeze it with pliers and work it out. I left the power cord attached to the unit and just pulled it through the bottom case so I had enough room to work, and used the ground lug screw and nut to temporarily hold the transformer down as not to break the relatively fragile connections to the PCB.
Before getting started, I did an inspection of the board. There were a number of bad solders on some of the components - mostly things with thick leads like the potentiometers. I took a minute to clean those up before getting started.
Removing the parts is relatively easy, this being a single sided board. A soldapult and some wick made short work of the old solder, and that’s when I noticed the 15k resistor wasn’t.
The schematic indicates 15k, as does the board - and another unit I have has the correct 15k part in it. I have to wonder why this was there - did the original builder not get the correct part, or was it broken during assembly? Who knows - but it didn’t really matter as the device worked.
Interesting.
The rest of the parts are replaced without issue, and the correct 15k is placed where indicated.
There’s not a lot of current or voltage here, so I wasn’t particularly concerned with the size of the resistors.
After doing a precursory check of parts, solders, and whatnot, I powered the device up on the bench. The oscillator count was quite different, so my replacements had some effect.
Some warmup time later and I adjusted the oscillator to the correct value:
Putting it back together and:
It’s already drifting. I set it back to 85 and let it set until the next day.
It didn’t do a thing. I will say, however, that it seems easier to adjust it back - there’s not as much play in the overall adjustment - you can set it and it generally stays there until the temperature changes.
So, my conclusions? This whole thing probably would need rebuilt with modern components in order to maintain any stability in measurement. For now, it’s just going to be sitting in a rack on all the time measuring the 12V rail of a power supply so … it is what it is, I guess.
- 2024
- Jan
- 3
Mistakes were made - a long long time ago.
2024 brings this device from years ago, which I opened to find a mistake in assembly. This Bell & Howell IMD-202-2 NIXIE meter has a 10k resistor in the oscillator circuit, where the board and schematic specified a 15k.
The carbon resistor used was so sloppy that it didn’t really matter what went in there, of course, as long as it was close enough to the value specified. The part had long since drifted out of tolerance, the upper limit being 11k - this one read 11.64k!
I have to wonder if the person building this kit did that accidentally, or on purpose because they didn’t have the correct part, or maybe they chose it to correct something else. I’ll never know, but a 15k precision went in to the circuit and seems to be working without issue. I have to assume it was simply an honest mistake, as I didn’t see any evidence of rework on the bottom of the board.
Stay tuned for my findings on trying to fix some of this device’s drift.
- 2023
- Dec
- 23
An odd little part - single plate selenium rectifier.
Here’s a weird little part I picked up at a show, it was in a “Take as many as you want” box. It’s a single plate selenium rectifier. These components were widely used in the time between tube rectification and silicon rectification, but fell out of service because silicon diodes are simply much more efficient at rectifying AC voltages and providing other diode services.
It’s marked as Federal 179545. It has a forward DC resistance of about 88k, and a reverse resistance of 792k. So what would this have been used for? Bias voltages maybe? Or a diode that would blow if the current went higher than anticipated? I’m not sure.
It’s just a cool piece of yesterday’s technology at this point.
- 2023
- Dec
- 22
Stabilizing the oscillator in the IM-1212 Meter
One of the problems with the Heathkit IM-1212 / Bell&Howell IMD-202-2 meter is the oscillator is made of crap-tier parts, and has a problem drifting all over the place. 10% carbon comp resistors and who knows what capacitors make up the parts complement. While that was probably fine for the age, a few dollars more could have made this at least a decent instrument for it’s time.
The main problem here is the parts are not temperature stable. For example, the meter I just recently acquired (see https://wereboar.com … ter-for-some-reason/) came in to the shop cold from being in a delivery van. It was allowed to warm up a little and plugged in. Oscillator was sitting at 94. It drifted down to 79 as it warmed up, and then back up to 88 - all in the course of an hour. That’s not good when you’re relying on that signal to generate the timing for your counts!
There’s not much to the oscillator. A couple of transistors for the oscillator itself, an inhibit transistor to start and stop the counter, and the passives that make up the oscillator circuit itself.
Here’s what we’re interested in:
There are two 3.3k 5% resistors, a 15k 10% resistor, an 8.2k 5% resistor, and two 0.0022uF capacitors. What’s the PPM drift for temperature on any of these parts? “Yes.”
So, off to Mouser we go!
Are these parts overkill? You bet. These are “Parts exceed value of device.” But they’re not really that expensive these days. So…why not? It’s mostly to satisfy my own curiosity to see if it really does make a difference in how the unit operates. If not…oh well, I learn something either way.
(The 15k pot may get replaced with something better - I was thinking of bringing it out to the back panel somehow, since it’s the main pain point.)
I do have some lesser quality (but still better than what’s in there!) parts, if I get ambitious I may replace some stuff before the actual parts arrive. Stay tuned!
- 2023
- Dec
- 17
December 2023’s Scott Antique Market.
There wasn’t quite as much at the December show as opposed to the November show, but there was still a lot to look at. I picked up an oil lamp to match one I already have, and took the Humble Oil tiger with the horse pee stickers home. The stickers came off with some coaxing from a heat gun, so I’m pleased with that. My fellow show-goer bought some cheesy Christmas LPs because you can’t have Christmas without random “Why the eff is that?” records playing on the turntable. A Stoneman Christmas, anyone?
The next show is in January. There’s a small hamfest happening about the same time, so I will probably go to that instead, unless they are happening on different weekends (which they are!)
