G-50 Push-To-Talk.

[KD1SH]

   Well, the site's been up and running uninterrupted for a couple of days now; perhaps the dark days are behind us? I certainly hope so. So, while the site is up, I'll take advantage of the opportunity to contribute some fun stuff.
   I've got two Gonset G-50s: My first one, with the metal knobs, bought at Nearfest back in 2018, and my second, with the blue knobs; again, a Nearfest find, but this time in the fall of 2024. A few weeks ago, I slid "Blue" out of its cabinet to look into a modulation problem I'd noted a while back, and discovered, sadly, that one of the decks of the triple-stack T/R rotary switch had broken all to pieces. I'm assuming that it happened during removal or installation into its cabinet.
   What to do? I've got a Gonset G-28, the 10-meter version, that I could use as a parts donor. Or, something I'd thought of in the past but never seriously considered: replacing the rotary switch with an array of relays, for push-to-talk functionality. Okay, great chance to try something new!
   The plan is to replace the original rotary switch with a simpler single-deck switch, mounted right behind the front panel, doing away with the long shaft that turns the rear-mounted switch, and using that switch to simultaneously actuate an array of relays. That way, the original functionality of the front-panel T/R switch can be maintained, while still allowing push-to-talk action via the microphone.
   Fortunately, the interior of the G-50 isn't nearly as densely packed as the Lafayette HA-460, but still, the project required moving some components around, as well as removing the aluminum structure to which the original rotary switch was mounted.
   It's a bit of an endeavor, really, and I wouldn't recommend doing it on a whim; I'm only doing it because the original switch broke. Otherwise, I'd recommend staying with the original T/R operation. Note in the picture that there are 6 relays on my board. Each is double-pole/double-throw, for a total of 12 individual SPDT switches, and I'll be using all of them. When you flip that switch on a G-50, there's a lot going on in there!
It's an ongoing project, and I'll post some more progress soon.

[AG5UM]

Interesting idea,
 I guess your past banana plugs and knife switches...
 I think you might need some of the old Bell System, Western Electric switching network equipment,
It was vacuum tubes and relays, etc...
Also,
Its always great to see the workbench photos, (I think I actually have more interest in test equipment than radios.)
You have some interesting things there, Cool.
Keep us posted and good luck with your project.

[MikeKE0ZUinkcmo]

I agree with your reason for the project, sometimes its simply the challenge that motivates.  I've had a couple projects like that, and you often wind up with a Rube Goldberg radio, but it works well.

[KD1SH]

And then there are those projects that, in the long run, you wish you'd never started. I have a Simplicity riding mower that I inherited from my father; essentially in working order other than a few minor fixes. The first time I used it, I noticed a slight vibration when engaging the mower deck. Feeling what I thought, or imagined to be, a slight run-out in the arbor bearings, I pulled the whole mower deck apart, figuring I'd replace the bearings quite easily. Whether it's a radio, an engine, a piece of machinery, or a bit of household plumbing, inanimate objects laugh at you when you make assumptions like that. It's subtle, almost inaudible, but they laugh. The drive pulley, and the bolt that secures it to the arbor, were rust-welded in place. The only way to get the whole thing apart and removed from the bearing housing was to cut the arbor with my reciprocating saw, but only after I'd first destroyed the pulley in my attempts to remove it, initiating a long and tedious parts search that is still ongoing. Bottom line: it was working fine; the problem was minor, or maybe even imaginary, and I should have left it alone.
The broken rotary switch in my G-50 wasn't imaginary, and the project certainly isn't a waste of time, but I'm careful these days about diving headlong into rabbit holes when sometimes all you find at the bottom of that hole is rabbit poop.

I agree with your reason for the project, sometimes its simply the challenge that motivates.  I've had a couple projects like that, and you often wind up with a Rube Goldberg radio, but it works well.

[MikeKE0ZUinkcmo]

Bill, Thanks for the great laff about the poop.   I've scooped out a few shovels of that myself.    Like you said, it makes you a little cautious.

[AG5UM]

Did your idea work out?
I was'nt completely kidding with Bell system Western electric...relay/tube technology,
Relay logic is at least... as interesting as computer logic..
Fun project,
good luck.

 

[KD1SH]

Still in progress. As of this afternoon, most of the wiring has been traced out and identified with wire markers, and I've made up a chart showing all the switching actions that need to be accomplished. Some terminal strips and such needed to be relocated to make room for the relay board, and while I was in there I noted some work done by previous owners that I want to tidy up a bit, as well. And so it goes.

Did your idea work out?
I was'nt completely kidding with Bell system Western electric...relay/tube technology,
Relay logic is at least... as interesting as computer logic..
Fun project,
good luck.

 

[W3SLK]

KD1SH said:

And then there are those projects that, in the long run, you wish you'd never started. I have a Simplicity riding mower that I inherited from my father; essentially in working order other than a few minor fixes. The first time I used it, I noticed a slight vibration when engaging the mower deck. Feeling what I thought, or imagined to be, a slight run-out in the arbor bearings, I pulled the whole mower deck apart, figuring I'd replace the bearings quite easily. Whether it's a radio, an engine, a piece of machinery, or a bit of household plumbing, inanimate objects laugh at you when you make assumptions like that. It's subtle, almost inaudible, but they laugh. The drive pulley, and the bolt that secures it to the arbor, were rust-welded in place. The only way to get the whole thing apart and removed from the bearing housing was to cut the arbor with my reciprocating saw, but only after I'd first destroyed the pulley in my attempts to remove it, initiating a long and tedious parts search that is still ongoing. Bottom line: it was working fine; the problem was minor, or maybe even imaginary, and I should have left it alone.
The broken rotary switch in my G-50 wasn't imaginary, and the project certainly isn't a waste of time, but I'm careful these days about diving headlong into rabbit holes when sometimes all you find at the bottom of that hole is rabbit poop.

Gawd! I do that all the time and never seem to learn my lesson!
Ugh!

[KD1SH]

I'm also very easily distracted, which probably explains why I have such a backlog of unfinished projects. I'll be working on a project, and then one day something on the back shelf will catch my eye: an old rig, a partially finished project from last year, or maybe an old piece of test equipment that quit working a while back, and the next thing you know both my legs are sticking out of another rabbit hole.

KD1SH said:

And then there are those projects that, in the long run, you wish you'd never started. I have a Simplicity riding mower that I inherited from my father; essentially in working order other than a few minor fixes. The first time I used it, I noticed a slight vibration when engaging the mower deck. Feeling what I thought, or imagined to be, a slight run-out in the arbor bearings, I pulled the whole mower deck apart, figuring I'd replace the bearings quite easily. Whether it's a radio, an engine, a piece of machinery, or a bit of household plumbing, inanimate objects laugh at you when you make assumptions like that. It's subtle, almost inaudible, but they laugh. The drive pulley, and the bolt that secures it to the arbor, were rust-welded in place. The only way to get the whole thing apart and removed from the bearing housing was to cut the arbor with my reciprocating saw, but only after I'd first destroyed the pulley in my attempts to remove it, initiating a long and tedious parts search that is still ongoing. Bottom line: it was working fine; the problem was minor, or maybe even imaginary, and I should have left it alone.
The broken rotary switch in my G-50 wasn't imaginary, and the project certainly isn't a waste of time, but I'm careful these days about diving headlong into rabbit holes when sometimes all you find at the bottom of that hole is rabbit poop.

Gawd! I do that all the time and never seem to learn my lesson!
Ugh!

[WA1LGQ]

Good luck with that Bill. You did mention that project in person before, I hope that it actually works. I wonder if you have any other mods in mind for the G50? Mine is getting closer to one of the benches, but they need to be cleaned of other projects first. You seem to have the same issue. I see that yours is clean, that is a challenge!

[KD1SH]

   Hi, Larry! Yes, I think we were talking about it at the Museum a few weeks ago. Everything's coming along well; all the wires have been traced out and marked, and some original (and some not so original) terminal strips and such have been moved around to make more comfortable room for the relay board.
   Since I solid-stated the high voltage supply, I don't need the 5-volt winding of the transformer to run the filaments of the rectifier tubes, so I'm rectifying that 5 volts to power the coils of the six relays instead. The current drawn by those relay coils totals over half an amp, and rather than have my microphone PTT contacts handling that current, I'm using a PNP power transistor to do the dirty work, so the microphone contacts only see the few milliamps of base current for the transistor.
   The only issue that might pop up is that the B+ voltage is a bit higher than the Omron relays are rated for, but I tested them on the bench first with a high-voltage supply at well above what they'll be seeing, and they worked fine.

Good luck with that Bill. You did mention that project in person before, I hope that it actually works. I wonder if you have any other mods in mind for the G50? Mine is getting closer to one of the benches, but they need to be cleaned of other projects first. You seem to have the same issue. I see that yours is clean, that is a challenge!

[KD1SH]

   My bench is clean? Well, that's a fleeting moment in time; a very temporary state. It's never that way for long! As far as other G-50 mods, I did very briefly consider, and fortunately put out of my mind (because I'd have to be out of my mind to do it), replacing the Heising choke with a real mod transformer and reconnecting the two 6L6's in push pull, for traditional plate modulation. It would sound a bit better, and easily achieve 100% modulation. But, it would pretty much amount to federal highway project level drilling and blasting, and almost certainly not worth it. I've got suitable mod transformers, but in addition to completely rewiring the 6L6's, I would need to either put in a driver transformer or kludge up a phase inverter. Now, if it were a total basket-case G-50, I might consider it, but I'd have a hard time justifying hacking up a good one.
   Actually, if I really wanted to make my G-50 sound better, I could externally modulate it with the external modulator I use with "Ugly Betty." Now there's a thought!

Good luck with that Bill. You did mention that project in person before, I hope that it actually works. I wonder if you have any other mods in mind for the G50? Mine is getting closer to one of the benches, but they need to be cleaned of other projects first. You seem to have the same issue. I see that yours is clean, that is a challenge!

[WA1QHQ]

Bill,

Good luck with that G50 project, I thought about doing the same to my G50 but quickly dismissed the thought when I looked at what would be involved. One thing I wish was provided on the G50 is an extra set of contacts for T/R. I wanted this to turn on and off an external VFO. I am not sure if you have ever checked the TX VFO drift on your G50, but it is terrible on mine, greater than 25KHz in the first hour of warm-up from initial turn-on. You can literally blow on the TX VFO tuning cap and it will drift a few KHz and then come right back. I am not sure if this is normal for the G50 but if you can check it out on yours I would be curious to know if it behaves in the same way. So I am rock bound for now but if I had an extra set of contacts on that T/R switch I could key an external stable solid state VFO.

Mark WA1QHQ

[KD1SH]

Hi, Mark,
    It was great meeting you at the Museum a few weeks ago, and talking about G-50's and such.
    I remember back when I bought my first G-50, thinking that I could use an unassigned set of contacts on that rotary switch for keying external devices, but every contact on that triple-decker is used. But, several of those contacts switch B+ on transmit, so you could probably run that switched B+ to a resistive voltage divider, leaving just enough at the bottom of the string to drive the base of a transistor, or the gate of a FET, and use that to pull in a relay.
   Yes, there's a lot involved in putting PTT into a G-50, and if it hadn't been for this one having a broken switch, I wouldn't be doing it. It's a fun project, but a lot of work.
    I've got my original G-50 on the bench right now, for comparison with the PTT project rig, and next time I'm spending some time at the bench I'll power it up and give you a detailed report on the drift.

Bill,

Good luck with that G50 project, I thought about doing the same to my G50 but quickly dismissed the thought when I looked at what would be involved. One thing I wish was provided on the G50 is an extra set of contacts for T/R. I wanted this to turn on and off an external VFO. I am not sure if you have ever checked the TX VFO drift on your G50, but it is terrible on mine, greater than 25KHz in the first hour of warm-up from initial turn-on. You can literally blow on the TX VFO tuning cap and it will drift a few KHz and then come right back. I am not sure if this is normal for the G50 but if you can check it out on yours I would be curious to know if it behaves in the same way. So I am rock bound for now but if I had an extra set of contacts on that T/R switch I could key an external stable solid state VFO.

Mark WA1QHQ