Robyn T-240D Executive

[Shadetree Mechanic]

Chris Do you have a dummy load? One of those 15-20 watt jobie's that screw right on the back of the rig.

Then use the old receiver you have, without antenna connected and use it for a monitor. Use like the 5kc /Am filter on it...should make an acceptable monitor.
Maybe Andy remembers without digging up the manual, but I would guess(swag) that the Robyn needs a Low impedance(600 Ohm) input. I would really have to look to be quite sure.
So you might try that idea. Make sure you use the correct filter and keep the RF and AF gain about half way back on the old receiver,until you get about half scale on the S meter with no feedback thru the speaker from mic, and that should give you a pretty good idea of what it will sounds like "On the Air"...it's not a prefect system, but without a scope it should be pretty damn close.
Drop me a line, if you can't find a tester for the tubes. We may be able to work out packing them and I'll run them thru my two...and get them back your way.
GL
All the Best
Gary

PS:https://www.gordonwestradioschool.com/main/page_w5yi_training_resources.html
FOCUS!!!

Today is the first time in a long while that I have been able to sit down and enjoy my station. Thanks for the tube test offer, BJ. I think one of our locals has a tester, but if I can't arrange something with him I might take you up on your offer. That's a great idea to use the Hammerlund as a monitor, now I just need to figure out how to get 11m on it. I did it once when I first set it up, I will have to play with it again. For now I am going to use a Cobra 29 with headphones and it works good enough to tell if I am overdriving the mic input. I still haven't built a shelf but it is on the list. For now the Robyn is sitting on the filing cabinet. It might end up in the station in my garage this spring. I like fiddling with things and changing things around so it might even end up in my truck. LOL
Thanks again,
Chris

 

[kopcicle]

Still need to find out where to buy the same gauge and alloy aluminum foil. Might be worth having a mold made to shape new diaphragms and rebuild them.

The original diaphragm will never come loose without damaging it.

 

[nomadradio]

Boy, that one doesn't look like any of my MC320s I have on the inside.

Could that one be the ceramic-element model MC-321? The Rochelle-salt element is bigger, rectangular and wrapped in its own metal foil.

Only two diagonally-opposite corners are anchored to the inside of the cup, so that it flexes along the longest axis possible. The Y-shaped yoke that protrudes through the center of the diaphragm is glued to the other two diagonal corners.

73

 

[kopcicle]

The real question is diaphragm dimensions. Regular Renolds foil has enough iron and silicon that it will work harden easily.

 

[nomadradio]

Now THAT looks like the MC-320. The Rochelle-Salt crystal is wrapped in metal foil. Makes me wonder if a tiny dab of super glue to each of the two tiny rubber support blocks wouldn't fix a lot of them.

I'm no metallurgist, but knowing the alloy used for the diaphragm, as well as the thickness would seem to be an important part it it's accoustic properties. Leads me to wonder if I took an old diaphragm to the local scrap-metal yard if they would let me zap it with their handheld metal-identifier gadget and see what it says is in there.

Forming the new diaphragm with a cone-shaped pair of dies seemed obvious enough. Figured a plastic 3D printer might be able to produce that. Never got around to learning how to model it in CAD to feed into one of those. Seems like the #D printers at the local hackerspace are either busy or broken whenever I drop in on them.

Just another project of high hopes and low priority, seems like.

73

 

[Shadetree Mechanic]

If the aluminum diaphragm is unusable after it is removed, then maybe it can be fixed without removing it? Maybe drill a hole in the back or a tiny hole in the diaphragm. Then squirt some glue in with a syringe. Lightly probing for the foil pack and then flood the area around it. I am thinking that maybe the reason mine started working again is that when I had the element out, I laid it on the diaphragm and it sat there for days like that. Maybe it stuck itself back together? Maybe it was pure luck and it would have started working no matter what I did. You guys really got me thinking now.
Chris

 

[kopcicle]

Figured a plastic 3D printer might be able to produce that

Get me the dimensions and I'll save you the CAD /Print time

 

[Rick Hicks]

Is this still an issue on this Robyn radio or has it been solved?

 

[kopcicle]

https://www.ebay.com/itm/CB-Base-Radio-Robyn-T-240D-/183534353177

heh heh

 

[kopcicle]

Is this still an issue on this Robyn radio or has it been solved?

Rick, it's an issue with the D-104 and other aluminum diaphragm microphone elements. Seems like a project within manual machining tolerances.

 

[Shadetree Mechanic]

Is this still an issue on this Robyn radio or has it been solved?

The crystal element in the D104 just started working again and then I fixed it some more with a different mic amp in the tug 8 base but it didn't really need it. The Robyn itself works ok, I just need to make some room for it in the station. Thanks for stopping by and checking it out.
Chris

 

[Shadetree Mechanic]

Hooked it up to the Thunder Bolt 101 today, getting about 150w peak.

 

[nomadradio]

This is pretty much the exact size radio that amplifier was designed to use with. Way cool!

73

 

[Slowmover]

X2

 

[Rick Hicks]

ShadeTree, I don't see many Behringer comps in the audio chain for 10/11 meter. How's that working for you? Money wise those are hard to beat.

Nice radio cabinet btw!