- 2023
- Apr
- 28
My haul from the Cuyahoga Falls Hamfest.
As usual, there was a lot of good stuff to be seen at the show. I had to force myself to not bring it all home because a lot of it isn’t useful (to me) past a “Wow, that’s neat!”
Boxes of relays from the “Pay what you want table.” This is all donations for the club, and was the estate of a now silent key.
Hayes 56k modems that were part of a BBS. Yeah, I don’t know why except that they’re a matched pair.
An interesting Ethernet to Serial gateway. Vendor said it was from a friend who was doing some odd project. It was free, with the caveat that it’s a project case if it doesn’t work.
Jacks from Rat Shack of the past. Nothing more to say about this.
Adventureland is the game that’s credited as defining the Interactive Fiction genre. While the original release was for the TRS-80, the VIC-20 version wasn’t far behind. I don’t have a VIC, so this cartridge is more as a piece of computer history than as a useful item.
Of note here is this Regency counter. This device is kind of unusual for something Regency produced. It’s a fairly competent piece of test equipment with a crystal oven and a known ppm deviation. Apparently, it was designed for FCC compliance checks (at the time of manufacture.) It works, but needs an alignment. If I can find some service data, that will be it’s own post.
I kind of wish I’d got that phase corrector device, I found out later that it went for $5 - that’s a steal and a shame, but I have no use for it.
Next post(s) will be the TUSCO Hamfest. That one was small, but excellent. Stay tuned!
- 2023
- Apr
- 23
Returning a Kaypro 2 to it’s original owner… but,
I’ve had this Kaypro 2 Luggable Computer since about 1993, I believe. I purchased it from a fellow college student with the disclaimer that if I ever needed to get rid of it, he would like it back. Since it’s been 30 years, I figure it’s time for it to go back home since it’s not doing anything here at the pygg pen.
A little history…
Kaypro, aka Non-Linear Systems, is credited with manufacturing one of the first widely available DVMs in the world. Using a relay driven wheatstone bridge, it was a concept that would have been difficult earlier, but transistors made it easy enough (if expensive) to make. NLS continued the test equipment line, making voltmeters, panel meters, scopes, and other items. Non-Linear Systems still exists as an entity, making panel voltmeters as usual. Find them here https://nonlinearsystems.com/.
In the 80s, however, NLS decided to get into the nascent home computing market with their entry, the Kaycomp. Named after the founder Alan Kay, these Ferguson Big Board clones rapidly gained a following due to their simple robustness and the fact that you received an entire library of software with them - OS (CP/M), Word processing, spreadsheet, programming, games - the machine was ready to go out of the box. Businesses loved them, and they were reasonable enough that home users bought them. Kaypro went on to make several offerings including hard drive models, and even a PC based model on the luggable form factor.
Kaypro eventually succumbed to that which kills all PC makers. PCs became commodity devices, and their IBM-PC based offerings weren’t any different (but they did manage to get a 286 machine out the door before IBM released the AT!) - and they released some machines that had crippling issues. The 90s saw bankruptcy and closure of the computer manufacturing, with test equipment continuing.
The Kaypro name has been resurrected a few times over the years, but has never stuck, and has faded to legends of a world before the IBM compatible devices took over.
And now, the main(board) feature.
This machine suffered a failure some years ago where the 8048 keyboard decoder went bad, got hot, and destroyed the relatively narrow +5V supply line. I, um, fixed it (yeah) years ago, but did a terrible job. The first order of business was to fix what younger me did. That was as easy as removing the wire fix, cleaning everything up, and re-placing it with some hot glue to keep things in place. Easy enough, and that’s done.
(Just as a note, the 8048 was a common microcontroller used as a keyboard decoder, and often had a mask-program ROM onboard for the decoder portion. Replacing it was impossible unless you had a pull from another machine handy.)
Next thing was to give things a good cleaning. The connectors that I could access got a squirt of DeOxit for metal-to-metal contacts, and the scratchy brightness control got a squirt of DeOxit for controls. All good, and the brightness pot now feels nice and smooth. A dust removal and the inside looks good.
Of note here is the mainboard ROM is populated with a Micro Cornucopia Pro-Monitor ROM. Micro C, as it was fondly called, was a magazine/tech house dedicated to the Big Board machines, and later it’s clones like the Kaypro and Xerox devices. Micro Cornucopia manufactured several enhanced ROMs for these machines, and this one is no different. I believe this one allows the use of DSDD drives (instead of SSDD,) as well as provides the ability for 4 floppies. While it looks like I or someone may have modified it to do such, I can’t remember if this had the ROM onboard when I got it, or if I put it there from one of my other machines. It will simply remain lost to the mysteries of time.
Also of note: There’s a keyboard in here. I do not remember putting that in, but again, it must have come from one of the many junkers I purchased over the years. Another mystery.
But now, the but…
A quick inspection didn’t show any noticeable physical damage.
A few quick checks didn’t reveal any shorts or other electrical problems. So, plug into a fused outlet and…
The Kaypro “Grrrrrrk!” of the drives spinning up greets me. All LEDs are lit. The drives are running. That’s good - the drives on this spin constantly and load the head on and off the disk during access. It’s a way of getting quicker access, but you’re spinning the disks all the time.
However, there’s a problem. Not surprising after sitting for 20+ years.
I know it’s hard to see, and I apologize. The screen has multiple issues. The first, that of the characters are partially formed. The second, and the problem which prevented me from troubleshooting the first is the screen is dim and goes dark.
Since the brightness is controlled by an analog pot, this is probably indicative of something in the power supply failing. I turned it off immediately so as not to destroy potentially unobtainable parts.
We can theorize about the malformed characters without power.
For a bigger copy of this, click here: https://files.catbox.moe/pgldav.png
Video is generated with some RAM, a character EPROM, and a bunch of TTL glue. There are several things that strike me as potentially being bad here. Those are (but, not limited to of course!):
- A bad character EPROM. These can fade over the years.
- Bad RAM.
- A bad TTL part.
- One of the socketed chips just needs pulled and reseated.
- Data from the monitor EPROM is bad, for the same reason as above.
- An interconnect problem between the mainboard and CRT.
To be fair, this would probably be easy enough to track down with a logic probe or scope, but I’m unwilling to run it for any length of time because of the screen going black. I don’t have any CRT device troubleshooting tools left, and I don’t want to destroy the device to a point where I can’t get a part.
I’m not sure how the original owner wants to use if (if at all,) so it stays in the state it’s in.
- 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
- Apr
- 13
The Tusco ARC Hamfest
I’ve never been to this show, but it’s close enough that I’ll check it out. They claim this is the first one since the world decided that a runny nose was cause for martial law, hopefully some good stuff will show up. See you there, and as always, stay tuned for pictures of the event.
When:
Saturday April 22nd, 2023 8A-??
Where:
Tuscarawas County Fair Grounds
259 S Tuscarawas Ave
Dover, OH 44622
(Must Enter Through the Tuscarawas Ave Gate)
Admission is $5.00 per person.
https://www.w8zx.net/hamfest
- 2023
- Apr
- 13
The 67th Cuyahoga Falls ARC Hamfest
This show was excellent last year, and I’m looking forward to attending this year. Unless something major comes up, I’ll see you there!
When:
Saturday April 15th 2023, 8A-1P
Where:
Emidio & Sons Party Center
48 E. Bath Road
Cuyahoga Falls, Ohio 44221
Admission is $7.00 per person.
Stay tuned for pictures of the event.
https://sites.google.com/cfarc.org/cfarc/hamfest
- 2023
- Mar
- 19
The TMRA Hamfest Haul
I was kind of disappointed, nothing really stuck out at me and I didn’t see anything picture worthy. The only real item, other than some parts, was a nice old Hickock DVM with VFD tubes, but someone picked it up and put it on their own table for resale (at a higher price of course.) I don’t need another meter but eh…
I don’t know if it’s because of the area, because what I’m looking for didn’t show up, or because there didn’t seem to be as much general electronics as I’d expect, I only came home with trinkets.
A sleeve of 35W4, because you always need more of those, a couple of books, some insulated drivers, and some parts are all I took home. There are more shows coming up, so we’ll see what happens.
- 2023
- Mar
- 19
Random board shot - a commercial weather radio.
It’s always interesting to open a device and see ancient chips you’ve never run across before. The LM389 is a LM386 with three transistors for RF, IF, and 2nd IF on the substrate. This ancient commercial weather radio uses one for it’s audio final, if I want to keep it in operation it’s probably best to find a couple of spares along with the MC3357 IF chip next door. This device was made in the USA, even the circuit board was made right here in Ohio as evidenced by the GE Textolite “T” in the substrate of the board.
It’s well built, but the electrolytic capacitors with the long leads surprise me. I would think for a device with RF floating around inside, you’d want to keep those short.
It needs a new power cord, the old one is short and worn, as well as some DeOxit sprayed in the controls and switches. I may also replace the power supply filter capacitor, but that’s only because it was laying against the regulator for untold years and has a nice discolored spot on it.
More on this device later…
- 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
The Breezeshooter’s Hamfest 2023
I just noticed that the Breezeshooter’s club in PA is holding their annual hamfest again this year, after several years of everyone’s television saying we were all going to die.
While the details are scarce, it appears to be happening the first weekend in June (3rd and ?4th?) - this has always been a good show when I’ve attended, and has a lot of good deals and eye candy. I’ll post more details as they become available.
- 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.