the price of 673's and 575A's

The merchant, radiodaze.com that advertised them for $12 cannot find a trace of one anywyhere. They recently moved. I would hate to think they lost them or pitched them. Maybe the listing was a mistake. He's asking $85 for NOS 575A's which are more desirable. Anyway I now have a deal to buy some good used 673's from a gentleman at a fair price, and that will do fine.

I know that for less than what most online places charge, I could build a rectifier stack that would be just about indestructible and people have told me to do that. But I like the MV tubes for the pleasing glow that varies with modulation. You have to run alot of current through a 673 to see the glow but this transmitter can do it.

Most of the 673's glow is up inside the plate which is shaped like an inverted saucepan and the saucepan covers the snout of the filament shield. I wish I could take an X-ray of one to show.

The 575A on the other hand has the glow very visible from the side and is more desirable. With the 673's, I can still lie on my back behind the transmitter with its rear doors off and speak in the mike and watch the glow flicker way up inside the tops of the tubes.

I found two over the weekend, at "the Gainesville hoard" in a barn with 1/8" of dust on them. It took me all day to find them, but it was fun digging through all the junk. No chance to clean them and warm them up them yet. Those were free since I am removing "toxic waste". But I think I better try to buy some more spares as there are no others there.

The bad one I found seems to be gassy. The plate cap is loose. I cooked it with filament on for a week, same thing. The outside surface of the plate glows violet (not the blue of mercury rectification) when just 200VAC or so is applied to the anode. I should get a picture of this but I have to be very careful setting the variac because the transmitter considers this activity a short. not that it will hurt the transmitter - just cook the relay again. So it will be a rare picture I would like to share.

update FEB 6:
Of the two I found in the old barn, I cleaned and installed one and it seems to be working.
The bad one will soon have its experimental "shorting out in the transmitter" picture taken, then be honored by taking its turn in the youtube microwave, then be given to my apprentice as he asked for it to top his tesla coil with. Old MVR tubes don't die, they just glow differently.