- 2024
- Nov
- 3
An EICO 242 FET VOM
This device came to me from the Columbus Hamfest, another piece from an estate sale. It’s part of my “I can’t go home without a voltmeter” thing, and I figured it’s small enough that it would make a nice bench “no tubes” meter.
It’s built on EICO’s late model transistor chassis, and features everything you’d expect from a FET VOM. High impedance, a big face, and multiple ranges. Oddly absent is a mirror for parallax error resolution, which seems like it would have been a cheap thing to have. Also odd is EICO’s choice of a phone jack for input. There’s some muttering in the manual about that, but it’s just a gimmick from what I can see. Kind of locks you in to their probes. What’s not good about that is the tip is hot, so if your probe gets pulled out live (or inserted live) you can can hit the ring, which is ground. I need to figure out how to re-make this and make it safe(r).
Some of the parts are quite well made. Take these 10-turn ball-bearing pots. These things turn so smooth.
The device can either run on AC line, or 3 9V batteries and 1 1.5V D-Cell. Sort of.
The D-Cell had been removed, but the 9V batteries were still there.
How long has it been since Mallory made batteries? Long enough that these were coated with carbon-zinc rust. Some of the terminals were corroded into the snaps, which is not a big deal. I don’t expect to use this thing on batteries.
The unit consists of a single board and some parts on strips. It’s really pretty simple, just some differential amps and the FET on the input.
After removing the batteries, I powered it on. DC measurement is off - but there are cal pots inside.
Ohms…that didn’t work. The device stayed on zero and the ohms control did nothing, whereas the zero control slammed the needle to the left. A quick check of the schematic showed something interesting - a 1.5V battery! Turns out this thing NEEDS the 1.5V D-Cell, even when operating off line. I just happened to have one, in it went, and…yep. That works now.
There’s nothing wrong with this save it needs a good warm-up and cal. I’ll probably do that sometime in the next few weeks and get this thing installed on the bench - after I make a probe adapter, of course!
- 2024
- Nov
- 3
A PACO G-30 RF Signal Generator
As with a lot of other things, I picked this signal generator up a few years ago at the Cuyahoga Falls hamfest. I seem to remember the person telling me they were using it up until it was sold, as they were trying to clean out some of the redundant equipment.
(Yes, it’s on. I had already opened it at this point to check on things.}
The device itself looks to consist of an oscillator and an amplifier tube. I assume the amp is on top, and the osc is on the bottom (w/shield) but I won’t know until I check the schematics.
Note the selenium stack. It looks like this device has been rebuilt somewhat recently. I don’t think I would have done the capacitors up like that, but it works well enough.
The person didn’t replace two of the most important things, however:
The first being the power cord, which is just as hard as can be. The second is that little disc thing with three legs. This is a safety capacitor, and is two .01µF capacitors back to back. These tend to blow open, as they physically separate, but it’s still a potential problem. Not sure why this didn’t get replaced, but I have two .01µF film caps @ 630V that would work here. If I decide to put it in service, that is. The output isn’t really pretty.
Before you go “That ain’t right” - it may be. I’ve had other generators of this vintage that had a very similar output. It’s going to require some testing to see if there’s something that can be corrected - if not, then you just have to remember that antique devices don’t necessarily perform the same as newer devices. This is probably fine for an old AA5 radio. I did note that the frequency per the scope is dead on, so that’s a good start.
(I did see a video on this unit, it should put out a sine wave. There’s something going on here.)
Stay tuned, this will probably show up again later as a fix it or forget it post.
Next part of this series: Coming sometime…
- 2024
- Nov
- 2
A Westinghouse H-636T6 AA5+1 Radio - It lives*
This one was a nice example of a 6 tube AA5 - it has a tuned RF front end which amplifies the RF before it’s brought down to it’s IF signal that the radio demodulates the audio from. That gives it the ability to hear more stations - without any further tuning I was listening to a station 115 miles away during the day, something other radios have a hard time doing during the quieter night period.
Radio came to me not working, seller said “Won’t warm up.” I think the guy just didn’t know that the power was pull on, not turn on. Plugged it in, and bad filters - the characteristic loud 60Hz buzz said that immediately. The replacements are the two cylinders standing up in the upper right corner. Two 47μF @ 160V replaced the 40/40@150 there previously. That device was dead, high ESR and loss, and cracked potting.
That brought the radio back to life, but the across-the-line capacitor had to be changed as well. That’s a .047μF @ 630V that literally sits across the AC line, and helps reduce noise in the system. That’s the orange-red rectangle in the middle, a brand new film cap with it’s leads covered in spaghetti to keep it off of the AC below.
These go bad just because they have a lot of voltage on them, and age - the part in there was a type of capacitor called a bumblebee. They’re BumbleBombs now because they like to pop. Fine for the time, but they crack and leak and get moisture in the paper capacitor material, and go boom.
The radio with all of its new parts. I tried to not disturb anything else. (That recent spaghetti purchase has been used a lot!)
Here’s the old parts. The bumblebee measured ok, but I didn’t do leakage. The electrolytic was dead, however. Notice how the leads on the ‘bee are bent weird? That’s how it was in the circuit. Someone hand-inserted the part decades ago and said “eh…good enough!”
The only thing it really needs at this point is a little bit of penetrating oil on the tuner, as it’s gritty - a flush clean with DeOxit helped, but some Kroil is in order here. It probably needs an alignment, not a big deal but that’s after the tuner is cleaned, and it needs the dial lamps replaced. Power cord could be changed as well, but since it’s one of those in-the-case style it’s going to need a bit of doing. I may just solder a new cord in the board and run it out the hole.
In all, it was a good find in my opinion, a nice clean example of a AA5, late enough that silver mica disease hasn’t taken over yet. It’s getting harder to find this kind of radio in good shape, so as soon as the lubricant arrives and I get it tuned up, it goes on the shelf in the living room for use.
I don’t know that there will be much for a third part, except to talk about how far off the alignment is. We’ll see, stay tuned!
Next part of this series: Coming evenutally.
Previous part of this series: https://wereboar.com … -h-636t6-aa51-radio/
- 2024
- Nov
- 2
The Aerovox Model 97 LC-Checker
This interesting piece came from the 2024 Cleveland Hamfest for $5. The vendor was selling an estate - that seems to be happening a lot lately - and was just looking to return some cash to the estate itself. He knew nothing about the unit, but I took a chance and picked it up.
Aerovox, of course, is a name you’ll probably see on capacitors in older devices. The name Aerovox is still out there, but it seems to be more of an industrial player instead of a consumer devices company.
The device seems to be fairly standard at first glance, with your normal ranges and dial to tune to the unit under test.
Nothing special about the case.
The back does have a nice cord wrap area, and the cord seems to be still soft.
The probe is the most unusual part of this device, and is a deal-breaker for using the thing.
Its an inductive probe - there was another piece that went inside this loop of copper, so you could make a part connection without actually connecting the electronics of the tester to the part itself. This is kind of cool because it avoids hitting a live or charged device, but it’s also missing the business end of the probe, so the device can’t read anything. I’m sure it could be modified to work, but I have enough checkers already…
The inside is pretty sparse. A big selenium stack, some capacitors, and the oscillator section for actually checking parts. The big banana slicer in the middle dominates everything.
The device does come alive, and switching things makes the eye open and close.
But…that’s about it. Without the probe, it’s nothing more than a shelf queen - or parts. Fortunately, I have someone who would like a display piece, so it goes to them instead of the parts bin.
- 2024
- Oct
- 31
The 2024 Fort Wayne hamfest
The Fort Wayne hamfest is happening in a couple of weeks. This is a two day event happening November 16th and 17th 2024, and opens at 9AM each day. Admission is $8, and the venue charges a parking fee (this does not go to the show.)
I’ve been to this show many times, it’s all indoors so it doesn’t get snowed out. Prices seem to run average at this one, but there always seems to be a great selection of unusual stuff.
This is the last hamfest I attend for the year, and it makes a nice bookend to the year’s shows.
Fort Wayne Hamfest
Allen Country War Memorial Coliseum
4000 Parnell Ave
Fort Wayne, IN 46805
November 16, 17 2024
Hours vary by day, opens at 9AM
https://www.acarts.com/hfmain.htm
Photos may be delayed a bit due to some obligations the week after, but will be posted as soon as I can get to them.
See you there!
- 2024
- Oct
- 30
A Waterman OCA-11A “industrial / pocket” oscilloscope.
This little scope came from the recent MARC hamfest, and was sold as not working - the previous owner stated that someone had removed tubes, and all he did was verify the heater in the CRT was lighting up. He was right, someone removed all of the 12AX7 tubes as well as a 6U10 compactron, leaving only a 6AG11 compactron in place. All of these devices are triode amplifiers, with the 6AG11 having two diodes in addition to the triodes.
The device appears to have a solid-state power supply with solitary diode. There’s some small evidence of repairs being made over the years, but for the most part it seems to be fairly original.
Tube compliment for this device is:
4x 12AX7 dual triode
1X 6U10 triple triode
1X 6AG11 dual diode/dual triode
The device is capable of operating on 50-400Hz @ 115VAC
The front offers all the controls, and uses pin jacks for input on a strip at the bottom. That’s kind of unusual. The metal under the paint appears to be oxidized, and the enamel with the lettering is flaking off. The potentiometers are brought out to the front by long internal shafts, some of which are bent. This could be an easy fix, as they’re just connected internally with nylon unions.
The back offers a cord wrap and some screw terminals, presumably for grounds. It also offers a badly exiting cord from the previous owner.
The device is relatively clean inside with the transformer, power supply, and high voltage all riding in the back.
The bottom is well packed, but there’s no wax paper stuff as far as I can see. Looks like films and other decent capacitors, but I bet some of those carbon comp resistors are drifting. There’s an electrolytic that’s probably baked out, and some neon bulbs of unknown type probably being used as regulators that would need to be replaced, but that’s about it.
You can see where the previous owner removed all of the “good” tubes. The 6AG11 is also a triode pair, so I’m not sure why they didn’t remove it as well. Fortunately, if you’re not concerned about the make of the tubes, all of them can be relatively cheap - there’s about $25 worth needed for this device.
It’s an interesting little scope, and would be perfect for a benchtop radio repair station - tube scope with tube inputs doesn’t care if you hit B+ for a second.
I think I may give it a shot and see if it will live again. If someone out there has a schematic for this unit, I’d appreciate a copy.
Next part of this series: https://wereboar.com … oscope-part-2-tubes/
- 2024
- Oct
- 29
A Heathkit IG-72 Signal Generator Part 5 - We’re not done yet.
I was warming the device up for final cal. I had just completed it, and put it back in the case. Back on and SNAP.
I did some measurements. Nothing much of note. Removed the tubes, applied power. ZZZZZZZ right on the socket for the 6X4 cathode. WTF???
I removed the wire from the cathode to the filter capacitor. Nothing. I reconnected it to the choke. A nice spark was jumping from one of the plates to the cathode. Removed the wire on the cathode and did a measurement from cathode to plate pins.
There’s nothing connected to this pin other than my meter. 60Ω is not a good measurement. It came and went as the pin was moved around.
It looks like this double-wafer socket may have some carbon tracking inside of it. Oh fun! That means trying to figure out something to replace it. I have some sockets in stock, we’ll see if there’s one that can be used here.
Of course I don’t have the correct socket - these are 1” mounting centers, which is an oddball size. Most are 7/8”. Off to eBay for the rescue!
Stay tuned!
Next part of this series: https://wereboar.com … back-up-and-running/
Previous part of this series: https://wereboar.com … no-need-for-repairs/
- 2024
- Oct
- 29
Pictures from the MARC 2024 Hamfest
This is a show that I’d never been to, but it was a double treat. The show itself had a decent array of vendors and stuff, and the show was being held at the Military Air Preservation Society hanger, so we were able to tour the grounds as part of our show admission.
I highly suggest you check out the air museum portion, there’s a lot to see. Pictures of that coming soon.
We browsed the aisles for a couple hours, wandering through a few times. I brought home a few books and a small scope, my friend brought home some older high-end audio gear. There were a few other things that caught my eye, but I’ve got enough anchors working right now that I’m good - and the few remaining ones I’d like didn’t show up here.
Regardless, we had a good time and will probably come back next year, time and circumstances permitting.
.
Next (and last hamfest of the year) show is Fort Wayne on the 16th of November. See you there!
- 2024
- Oct
- 29
I hit 1000 views on a post - Thank you!
I keep track of views on my project page - not because I get anything from it, as there’s no ads or monetization (and never will be!) - but because it tells me what people like, and it’s just interesting. Data like this is fun, I don’t know why.
For some time, a post about the Findlay hashtag#hamfest was the most popular thing, but recently a general tech post about not overlooking the power cords on a device during rework has reached the top spot. This morning, it hit 1000 views.
The post: https://wereboar.com … look-the-power-cord/
What does that mean? Not a lot, but I appreciate everyone that’s looked at that post - it means you’re finding things here interesting enough to do a direct click on it, as hitting the post in the feed doesn’t increment the view counter.
Thank you for hanging out and spending some of your time with me. If there’s something you’d like to see more of, I’d love to hear from you. Connect with me on LinkedIn, or catch me on Mastodon.
- 2024
- Oct
- 28
A Heathkit IG-72 Signal Generator Part 4 - Final - No need for repairs.
This is probably one of the easiest devices I’ve had to fix - there was really nothing wrong with it beyond needing a new power cord and a tuneup.
A tuneup, in this case, consisted of some Deoxit in the controls, and a new power cord:
There are three reasons I’m replacing the power cord. First is the fact that the old one is about that close to being hard plastic. Since I have it open, it may as well get a new one. Second, I can replace it with a polarized device. This isn’t a hot-chassis set, but I’d rather have the hot on a switch. Third, this just doesn’t look good to me:
I’m also going to replace the tubes. The old ones aren’t bad, but I bought new ones, just in case. There’s no need to not use them, and the old ones will go in the boxes as spares. I’ll probably pick up another new set, but I can’t imagine these will go bad in my lifetime.
You can also see the new power cord exiting the back of the chassis.
There were two of the original Mullard tubes, and one RCA. The getter flash on the RCA tube looks a little baked compared to the new one, which is a nice, shiny RCA device.
In order to calibrate this, I basically ignored the manual. Since we have DVMs with more than 500 ohms/volt impedance, we can calibrate the device directly. Take note, however, that the device needs to be good and hot before doing this. Let it warm up for a long time to stabilize. I’d suggest taking it out of the case and putting a cardboard box over it. Also note this device was designed to run on 110VAC, so you may need to variac it down a bit.
But, to start, I did a quick beginning cal on it. I set the frequency to 1Khz, and attenuators to minimum. A scope was connected, as was a digital meter. Frequency was set to 1KHz, course attenuator (switch) and fine attenuator (pot) to minimum. Meter and Oscillator controls were set to about the middle of their range.
You’re going to adjust the osc and meter controls on the chassis. Oscillator is the one closest to the transformer, and mine had a slot in the top. Meter was closest to the edge, and has no slot on mine.
Power was applied and the tubes warmed up. I turned the course attenuator to maximum, and adjusted fine to about 2/5 of max. The unit wasn’t oscillating well, so I turned the oscillator control CCW until I got a sine. I adjusted this until the bottom wasn’t clipped, and then turned it down a bit more.
For the meter, I adjusted the fine control until my digital meter read ~5.0V, and then adjusted the meter control on the chassis until the analog meter agreed. It’s not a terribly linear meter, so don’t be surprised if it’s off some at other points on the reading.
I did notice the signal levels drifted as it warmed up - therefore, let it warm up before adjusting.
I didn’t notice the load switch doing anything. Normally, you would calibrate at load, but I’m not sure why this didn’t do much. I’m not terribly worried about it, the thing makes audio and it’s close enough for what I need to do.
So…that’s it! I’m going to get a box and cover it this weekend while on, let it get nice and hot, and do a calibration - but the device is working with little to no effort.
I have an RF generator to accompany this, I think that may be the next project. Stay tuned!
(Something went wrong during final cal…looks like we do have a problem!)
Next part of this series: https://wereboar.com … 5-were-not-done-yet/
Previous part of this series: https://wereboar.com … t-3-do-i-need-parts/