Ballast in a motorola 8" set
 

i discovered there is a glass tube that looks like a glass ballast tube in the socket , was there such a glass tube that would work in that application?
i don't recall the number on it but it was a long one.
if it is not something that would work is there a way to build a ballast tube with resistors ?
mike

Yes its fine. I have a set with a glass ballast.

Yes, here's one done by Phil Nelson: http://www.antiqueradio.org/motvt73.htm

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http://www.videokarma.org/archive/in...p/t-79834.html

that is what i found doing a search after posting.

There are many discussion threads on this topic.

Here's one of mine where I installed a glass Amperite ballast
http://www.videokarma.org/showthread...=233337&page=4

another about using capacitors rather than resistors in the ballast
http://www.videokarma.org/showthread.php?t=249434

thanks ,now long does a glass ballast tube last ?

:) If never overloaded , pretty close to forever .

:tears: If overloaded , about .0002 seconds ......

IIRC, the glass Amperite ballast, has some kind of an atmosphere in it. I don't remember what gas, could be nitrogen.
The true ballast tubes had an iron alloy wire, that had a higher resistance when cold. It would minimize surge, for longer tube life.
Nichrome wire can't do this, so you have to use a surge limiting resister in series.
My vote is for the capacitive-reactance voltage dropper. A bonus is no wattage losses and a cooler running power supply. :thmbsp:

From the Amperite ballast catalog .PDF:
http://www.amperite.com/assets/Documents/Ballasts.pdf

Amperite still makes glass time delay relays and ballast tubes, just, unfortunately, not the ones used in the Motorolas any longer, I don't believe, though there might still be something close. They also might do a custom job if someone wanted to pay the $$$ for maintaining vintage originality since they will do custom voltages on the glass TDRs.

In about 1998, while I was working on my Dynaco Mk.6 tube amplifiers, I accidentally dropped one of the 6NO30T time delay relays (delays the preamp tube B+) just a few inches to the table I was working on and it shattered. I was horrified and started thinking if I knew anyone with glass blowing equipment and abilities to re-seal it when I found Amperite's number and called them up.

I asked the receptionist something like "This may sound like a silly question but do you still have any of the old glass type time delay relays lying around?" The very helpful woman on the other end said cheerfully, "Oh, yes! We still make those. Not a problem. What model do you need?"

They cost something like $98.50 each but I ordered two and still have them here, NIB, as spares. :) (I also found a few used ones on eBay and I think what I've had in there for the past 15-16 years is a used 45 second one, IIRC. The 6NO45T)

The .PDF for the G (glass) series Time Delay Relays is:
http://www.amperite.com/assets/Documents/g.PDF

The glass Amperite ballasts contain hydrogen gas which reacts with the iron wire to form a type of current regulation.

That's what they mean by Automatic Regulator on the box.

(edit) I just read the pdf link above which explains it nicely :)

https://farm5.staticflickr.com/4018/...85811f65cb.jpg