- 2023
- Apr
- 16
Cuyahoga Falls Amateur Radio Club Hamfest, 2023 show pictures
This year’s show was about the same number of vendors as last year, so it was pretty good. There seemed to be more general electronics and whatnot this year, and less test equipment and other non-consumer items. Not really a big deal, there was still plenty to look at, including some vendors that I recognized from last year. I didn’t take as many pictures because of that, and missed some opportunities to get more because a friend I hadn’t seen in 18 years showed up and we were chatting the whole time.
In all, it was a decent show and worth the trip. While I only brought home about as much as I did from the TMRA show, it was only because I had to stop myself from dragging home more - there were a number of things I’d have like to had, but just do not have the room.
Enjoy the pictures, and I’ll be posting my haul a little later.. I found an unusual piece of equipment from a manufacturer that you wouldn’t expect to make something like it is, and I’ll be breaking that out into a separate post - if I can find it’s service data, it will be a technical post as well.
- 2023
- Mar
- 12
A General Electric T-125A “All American Five” Radio, Part III
This is part 3, and the final part of working with this radio. It didn’t turn out as good as I’d hoped, some of the other capacitors are leaky - and some of those are in a couplet. The customer just wanted it to make voices come from the air, so I’ve left it at that for now.
The original diagnosis I came up with was bad filters, and that was the case. The original electrolytic capacitors were bad, and were simply acting as opens instead of capacitors. The device in questions was a dual section, wax sealed tubular device, consisting of a 50uF and a 30uF part. I chose to replace them with Cornell-Dublier 47uF capacitors, which should be good for another 50 years. The across-the-line capacitor also got replaced with a Vishay 0.047uF @ 600VDC device. Just as good as the original without the bumblebomb problems.
The parts, fresh from Mouser:
What we’re working with. The black tubular part in front, and the metal cased tube in back are the suspects. If you look in the middle of the board, you’ll see a reddish-brown rectangle That’s the couplet, and was a cost-saving multi-part unit. When they go bad you rebuild what’s in them…
Other problems reared their head as it was being taken apart. The biggest is the age of the plastics. The knob used a metal band on the plastic to tension it on the shaft of the tuning capacitor. Pulling this knob from the shaft left the tension band on the shaft (it had little ears that were probably used during manufacture as an install aid,) and the plastic is so brittle and dried out that it just crumbles to dust. There was enough left to put it back on, so I broke the ears on the band off and replaced the tension band and said “Don’t touch this again” to myself.
The other bad thing, and something I didn’t notice before, is the speaker had a tear. The paper was so rotten it felt like wet tissue and just kept tearing itself. Well, it still works, and this can be replaced easily enough if desired.
So, on to the repair. It was a simple matter to desolder the parts, the heavy copper on the board let it’s old solder go with a 35W iron and some wick. The parts pulled out easily and the board cleaned up well.
You’ll notice the board is discolored. That’s where the 50C5 power amp tube sits, and it gets toasty. The solder joints are exhibiting potential cracks, so they all got touched up.
The parts I installed were much smaller than their vintage counterparts, so they got bent leads to sit down on the board, and were just placed in the board. I wasn’t going for a beauty contest here, they need to be in there solid and electrically correct. You’ll notice the one electrolytic is offset a bit, I realized after I put one in that the banana slicer had one section larger than the other. Oops…that other part goes in the parts bin.
For the filters, I just jumped the two together with a loop, looped a piece of bare wire around the common and soldered it all together. The original capacitor was full of old wax and wasn’t being rebuilt.
It was all back together…but there was still no joy. The filters took care of the buzz, and the output was nice and strong - then it started to fade and get fuzzy as something started leaking. One of the coupling capacitors or other small filters on the plates is probably leaky and drawing things out of tolerance, or a tube is bad. On a whim, I tested a few of the tubes, and they seem ok, so it’s probably one of the capacitors. With some being in that couplet, that’s more of a job that a “I’ll take a look” can cover.
A short clip of the radio playing. When it’s first turned on, it’s nice and strong but fades quickly. Sorry about the download, Youtube has decided that I need to verify my identity once again, and I’m done with that game.
https://privateemail … 9e11/1/8/NjE/NjEvMTA
It goes back the owner this week, if they want more repairs that’s a different proposition. Some of the younger members of that family are starting to get into electronics, perhaps this is a good project 15 years down the road.
Beyond that, it’s really not cost-effective to repair something like this for someone else unless they understand it’s basically a replace everything deal.
- 2023
- Feb
- 28
A General Electric T-125A “All American Five” Radio, Part II
A short update: I decided to just order some good quality parts from Mouser instead of trying to pick through the junk at a show.
While they’d probably be cheaper at a show, the three parts I need to get this radio playing cost less than $7, and that’s just because I decided to go a bit higher in quality than absolutely necessary. I should have them in hand Friday, and it won’t take long at all to get them installed.
Stand by for part 3.
- 2023
- Feb
- 7
A General Electric T-125A “All American Five” Radio
This is a radio a co-worker rescued from a barn sale, and wanted to know if it could be made to work again. The T-125A was manufactured between 1958 and 1962 (or 1963, depending on who you believe.) It still has the civil defense markings on the dial, so this radio was probably one of GE’s last radios to have this marking.
The radio apparently spent the majority of it’s life in a woodshop, and it shows. While the case plastic is in excellent condition with no chips or cracks, it’s stained with various wood coloring products. Back and original cord are present and intact, although the cord is getting stiff. It, however, exhibits no cracking so it will get left as-is for now. The inside of the radio shows you where it was for most of it’s life, being coated with wood dust.
Since these are simple inside, there wasn’t any need to grab an isolation transformer or variac, just plug the thing in. The worst that would happen would be the across-the-line capacitor would pop, so…
It exhibits exactly what you’d expect. A loud 60Hz hum, so the filters are bad. That was completely expected. It’s a dual section filter consisting of a 50uF and a 30uF capacitor, so I’m simply going to get two 47uF @ 150V caps and replace it. The across-the-line cap is .047uF at 600, it will be replaced with something similar. The only other suspect item would be the coupling capacitor between the detector and the power amplifier, so it will probably get replaced as well. The grid capacitors could be eyed with suspicion, but I’m going to leave those alone unless they show problems. One is in a couplet, which would require rebuilding the device if it’s bad.
The owner simply wants it to play long enough to go “Hey, that’s cool.”
A quick cleaning with a paintbrush and some canned air got rid of most of the dirt:
So it’s ready to repair. I’ll pick up some parts at the next few hamfests I attend.
One interesting thing about this radio is the 50C5 power amp tube. It has different color writing, so I assume it’s a (genuine GE) replacement tube. It still has something interesting about it - the getter is black. I can’t say I’ve ever seen one like this without the tube being red-plated. I have to assume this radio was on for most of it’s life. Pretty cool.
Off to a show for parts. Check back later for results on this radio.
The GE T-125A schematic.
Courtesy of radiomuseum.org
https://privateemail … 729ec/1/8/NjQ/NjQvOQ
- 2023
- Jan
- 7
The TechTran 980 standalone 5 1/4” disk drive.
So what is this thing?
One of the devices I’ve had kicking around the shop for years are these TechTran 900 series standalone disk drives. These were the main storage medium for a large test platform at a former employer. They would provide commands to a computerized telco switching frame in the form of responses to a “Read next record” command. When the project finally ended, I asked the project engineer for the drive. Turns out there were 4 units, with manuals and service information.
So, it’s a disk drive?
These have two modes. First is a “File” mode, which works like you’d expect from a mass storage device. You create a file, write to it, then read it back. It also has a “Record” mode - instead of writing files with a directory, these store records, much like a punch card would store a piece of information that may or may not be part of something larger. You would write and read records - bits of text - in sequential order.
The unit does this via a RS-232C interface, using text commands. The device can operate in standalone or passthru mode, and has all the normal serial settings you’d expect - except everything is done via switches that control what is literally a box full of 74LS chips.
How does it work?
Because the device was expected to be continually available while in operation, the manufacturer set these so the disk spins at all times, and the device loads the head on to the media whenever an operation is requested. This has the effect of only requiring the time to drop the head and wait for the record of interest to arrive at the head before the operation is completed. Normally, a drive would spin up, perhaps drop the head on the disk after it was spinning, seek the correct record in the directory, and then move to read it. These spent the majority of their life reading sequences, while the time savings was small it added up to all the years the unit was in operation. File operations, of course, required seeking the record in a directory, but there was still a small time savings in not having to spin the drive up each time.
This made for a very noisy device, as the fan was spinning, the drive was spinning, and the head was being loaded on and off the media surface over and over (with an accompanying clunk of the head load solenoid) each time. Not something you’d want in a quiet space, but the noise of the test frames generally overrode any noise this thing made.
Really?
Kind of. I’m digging into the service manual more because it has a theory of operation. It looks like the record mode does create “files,” but not quite in the same way as file mode. More on that as I understand it.
I have to say I’m somewhat surprised that these things still come up. I figured the belts would have long turned to goo at this point, and the fact they’ve been sitting since about 2000 probably hasn’t done them any good either. They had a long life, being put into operation in the early 1980s and running up to early 2000 or so. But spin up they did, attesting to the fact they were well engineered (aka cost a lot of 1980 dollars) and designed to last for a long time.
The one in the pictures, a Model 980, is going to be the subject of an attempt to make it talk to something modern, which shouldn’t be that difficult as it speaks serial. Set your baud rate to 1200 and stand by for further posts in this series.
Deleted the manuals for now, will package them up again soon!
- 2022
- Aug
- 31
Blonder-Tongue Audio Baton (BT B-9) Schematics
A few months ago, I posted about some Blonder-Tongue Audio Baton (Blonder-Tongue B-9) units that I’d rebuilt some years ago. Those units, unfortunately, are long gone but I knew I still had the Sams Photofacts schematic laying around somewhere, and I thought that if I could find it, I’d scan and post it for anyone else who has an interest in these devices.
I was able to locate that documentation, and you can download a copy of it as a zip file or a 7z file. The 7z is a little smaller than the zip file, the zip being about 58MB. The schematics are 600DPI .bmp files for maximum clarity.
I’m pretty sure I had a scan of the original manual as well, if I can locate that I’ll post it as well.
If you happen to know where the units in the pictures are, I’d love to know.
- 2022
- Aug
- 24
The Hallicrafters S-41G: Found the Sams folder.
While the Riders schematics are useful and have the proper alignment information, the Sams set simple excels in the parts listings for a device. This folder came from a well-known auction site, and is in remarkable shape for something from 1946. I probably paid a bit too much for it, but having this information is simply invaluable.
If you’d like to download the high-res scans of this set, along with the Riders images I posted earlier, you can do so with this link: https://app.box.com/ … 7cuc70d70xnay5dmusuq. This will open a box.com window, and you can either download the entire folder by clicking the “Download” button in the upper right corner, or go through the folders and pick and choose. It’s about 116MB, and contains BMP and PNG images.
You can download a .7z version of the archive here: https://privateemail … 43a07/1/8/NjQ/NjQvMw. This archive is smaller than the .zip version, if you’re trying to save bandwidth and space.
These images are reduced in size and quality so I could fit them without using up my server space. If you’d like the full resolution scans, be sure to use the box.com url above.
Now that I have an accurate parts list, I’m going to make a list of capacitors and resistors. I’ll probably just get them all and replace as needed.
- 2022
- Aug
- 11
The Hallicrafters S-41G: Found a schematic.
While I didn’t expect this to be difficult to find, I was pleasantly surprised to find the Rider’s available on Antique Electronic Supply’s website. AES has a nice selection of components for the radio enthusiast, I highly recommend them for restoration components.
Antique Electronic Supply’s website https://www.tubesandmore.com/
Now to start identifying what I need to make this thing sing again.
- 2022
- Aug
- 7
The Hallicrafters S-41G Skyrider Jr.
I’ve been looking for an AA5 “Shockbox” radio for a while now, but these seem to be getting kind of rare, which is odd considering how many of those things were made. So I’ve decided to instead look for an older multi-band unit. While this one wasn’t exactly what I wanted, it was cheap enough that it will work until I find a better example.
The Hallicrafters S-41G “Skyrider Jr.” was introduced right after WWII as a low-cost entry level receiver, alongside the company’s Echophone EC-1B which is electrically and mechanically identical. This unit lasted for a few years, and was replaced with the more common and more familiar S-38 line, which lasted for 6 models (S-38 through S-38E.)
This unit is in “acceptable” condition, and is complete with original knobs, a usable face, and limited damage to the chassis. It was purchased for $25 on August 6th, 2022 at the Columbus, Ohio hamfest.
When I first saw it, the friend I was with said “That looks like it sat around in a shop for years as the shop radio.” Turns out that was correct, the gentleman that sold it said it was in his father’s shop for years, but his father was unable to answer any questions about it, being in a state of mind that didn’t allow for much these days. That’s kind of sad to know I won’t be able to get any history, but that’s how it usually goes with these things.
First thing I did when I brought it home, of course, was to give it a quick lookover and then plug it in. Unsurprisingly, it came right up, and after getting the crud of the ages out of the switches, I was able to receive one of the strong local AM stations without any antenna connection. It must still be decently aligned.
The radio had the “science fiction squeal” as you turned the dial. Bad AGC capacitor, but that’s expected. Then the volume started dropping. Grid coupling capacitor was leaky and slowly allowing voltage through, cutting off the tube. I was about ready to turn if off, as I don’t want to destroy the tubes when it went POP and smoked. Capacitor blew out. Since the volume didn’t change, I expect it was the one across the line. But I rapidly pulled the plug anyway because it was shown to be working and that’s what I needed to see.
What’s a good initial showing without tearing the bottom off and baring the goods to the world? So that’s what I did next, and probably should have done first.
There were those big orange replacement filters. That was visible from the back, so no surprise. These were 450VDC capacitors with a 1974 date code, and decently installed. The voltage was far too high for the rectified line, but there are multiple schools of thought on this. One says go to the max, others say keep the voltage near the working voltage. The thought behind this is if you don’t give the capacitors their rated voltage, they can lose their ability to be a capacitor, and will try to “reform” and become capacitors again every time you apply voltage. I’ve always followed that rule, so a B+ of 150VDC probably would net a 200WVDC capacitor. In any event, these will go and get replaced with modern (and smaller) capacitors. Since these are nearing 50 years old themselves, it’s probably time regardless.
The other changes were the addition of a new line cord (sans the probably long dried out grommet in the chassis it went through) and a phone jack across the pin terminals originally placed by the factory. Not bad, usually these things are just a mess inside.
What’s going to happen next is the finding of a schematic. While I’d like to get the original Riders or Sams set for the radio, that may be difficult. There are a number of offerings online, so it’s just a matter of finding one that’s not a honeypot and downloading it. Then, the process of determining which parts need to be replaced begins - but that’s probably a job for this winter when the snow flies and the days are short. But check back in a few months for more on this set.
- 2022
- Jul
- 4
Unusual and interesting light sensors
There used to be a place in Dayton, Ohio called Mendelsons. This was a giant surplus house in one of the old Delco buildings on 1st street, near where the current Dayton Dragons field is. In 2021, the store did it’s final sale and closed.
There were several bulk bidders, including a place in Mansfield, Ohio called ESL Surplus. One of the things in the lot they bought was these unique little sensors. I had purchased a number of these years ago from Mendelsons, and I always wanted to get some more - unfortunately, with the world being afraid to open their door for two years, that didn’t happen. When the store went out of business, I figured that was it.
Fortunately, I had the chance to get more this past weekend.
These are tiny solar cells embedded in a plastic bubble, with an output of about 0.5V each - just enough to amplify and detect. I have no idea who made them, or when they were made - the discolored lens suggests they’ve been around for a while, quite possibly the 1970s. There’s no marks or other ID on the plastic housing - perhaps these were made to order and never used?
I’m not really sure what I’m going to do with these devices, but they go in my parts stash as, at minimum, an unusual piece of technology from years past.
ESL Computers (and surplus) URL removed
Mendelsons (archive) https://web.archive. … 30/https://meci.com/
ESL does not appear to exist at this point. Their website is now a malware pot.