The AM Forum

China used to sell a 3-500 socket and chimney for dirt cheap, around $20. Looking at eBay now, that same tube socket is scarce and they don't sell the glass chimneys anymore. The few out there are very expensive. I've seen a pair go for $150. RFparts is sold out of them.

These Coleman kerosene lantern globes are pretty close and sell for $14 each. There's enough curve at the top and at the right height to cool the plate cap.

Jon

Good find, Jon!

That is a much better solution than no chimney or paying thru the nose.

There is also an 813 tube version that I use.  There is an optimum design glass curve, but being off a little will still work FB. Use a finned plate cap and keep an eye on the plate seal cooling area, and especially watch the fil pins for dripping solder. (worst case)   As you know, the fils need good flow.

T

I hear you on the finned plate caps. There's lots of CNC guys out there who sell custom ones. You still need to be picky though.

I saw one version that looked good, but they attached to the factory skimpy plate attachment that goes to the pin. I'm only guessing that's a compromise heat transfer situation since the heat is being pulled off essentially now two screw attachments.

I like the ones where you pull off the factory plate attachment to leave the plate rod just sticking through the tube. Attach the custom plate fin to that.

Then there's the ones that were built so large that now you need to worry about mechanical stresses on the tube. I'm guessing that one I saw was a CB'er CNC guy. Bigger is better...'cmon...

Jon

And just in case someone wants dimensions.

I spent forever Googling information about Coleman products. Every retailer had conflicting dimensions about every product, but I bought this version hoping for the best. It seems to be pretty good.

Jon

PLAN B:


http://www.bearlabsusa.com/ARCH/HENRYWEB/HENRY4.html (http://www.bearlabsusa.com/ARCH/HENRYWEB/HENRY4.html)

I have been told that there is a way to temper glass in a home oven, but
I am not sure.

The above is the DIY mayonnaise jar method...

Nice!

It would’ve been a nice touch to be able to leave the Hellman’s Mayonnaise label on there.

Jon

Good luck with that we anneal glass at 900 degrees Fahrenheit. You have to get it to at least 600 degrees to temper. you might get that on a clean cycle.

Johnathan N8QPC

I used to tease Rich Measure AG6K (sk) that was the only reason to have nichrome in an amplifier.

To be honest, I used a nichrome suppressor in my first 'big' amp.  On the direction of Rich.

--Shane
KD6VXI

So I can send them out to you??
What line of work are you in that does this with glass?

But I expect someone with a ceramics kiln could melt the suckers... if you needed real heat??

I have seen untempered, cut off pickle jars as chimneys on 4-1000s  they are still working...evidently don't get hot enough to matter

On one of my previous 3-500 amps, I had plexiglass about 1 inch away from one of the tubes with no chimneys. Over time a small spot on the plexiglass started deforming. It was one of my early amps and didn't consider heat too much. I thought I'd be smart and double the size of the plexiglass on that side. That too melted...

I watched an episode of Jay Leno's Garage on YouTube where he was showing one of his vintage steam powered cars. To keep an eye on the boiler fire, there was a small viewing window about an inch wide so you could look in. He paid a company to laser etch a film on the inside of the glass as a heat retardant. It was good to literally like 2000 degrees. That could also be done to mayonnaise jars.

https://www.youtube.com/watch?v=rUg_ukBwsyo (https://www.youtube.com/watch?v=rUg_ukBwsyo)

The company might've been based out of Atlanta. Here's their billboard...

Jon

If you ever see a tiny "dimple" develop on the tube glass, watch out.  

I ran a pressurized 4-1000A with a chimney in the 70's and noticed that the tube glass wasn't perfect - there was a tiny glass dimple growing bigger and bigger.  It started as a tiny pinprick, barely noticeable. I had bought it as a used tube at a flea market.

I owned a house with another ham who also had a 4X1 rig. We decided to heat the place with just our 4X1s and let the expensive oil burner lie dormant. (it was during the 70's gas crisis.)   We both ran our 4X1s idling at 4KV at  200 MA = 800W heat for a few weeks. The rig was in my bedroom.   One night I was awakened by a big BANG!  The dimple in the tube that had slowly grown to a walnut-sized stress area had imploded the tube. There was glass everywhere inside the rig.   That was the end of our heating the joint with 4X1 rigs.

As a fitting epitaph, when we finally turned the oil burner on, water came pouring out of the ceiling near the outside door. Seems we didn't realize the pipes would freeze with such little heat. That cost us far more to repair than what we saved running the 4X1s....  ::)

T

I took a couple of classes on glass blowing at an art studio in Detroit. I don't have access to the equipment. It was fun to do.

Johnathan N8QPC