Too true!
AM for the Video, FM for the audio!

But you all know that ;)

Oli

I'm not sure what you mean about "coke bottle"

A common nickname for shouldered tubes.

5AS4 in the photo has getter. If it goes white the tube is likely gassy. Envelope, I believe is the 1930's "ST14.

Although it has getter, I have tried it on one of my sets, and I just didn't get any B+ at all. Oh well. Hopefully I find one, or I might have to go without!

Oli

Is the base loose? If so it may have a broken wire inside. Not easy to repair but it is possible.

Having had a 6D6 envelope fall out of its base, pin soldering can be dodgy.

Checking one of the clothes baskets of Octals; I find one in a GT package and one in a ST-14, both with loose bases which is an easy fix.

As is to be expected here the Poltergeist has hidden the book I want for the VCT, as its not in the original one, however, the Knight 600 seems to tell me they are OK.

"
Although it has getter, I have tried it on one of my sets, and I just didn't get any B+ at all.
"
Yes that happens with some 60 years unused 5AS4s ime. They get hot but don't glow purple or produce more than 2 or 3 volts output. And the getter looks OK.

A broken wire would lose one anode (not a show-stopper) or the filament, which would be obvious.

Go figure!

Just to confirm, I ran the '209c with the pictured coke bottle 5AS4, and just by seeing the valve I could see that it had gone to air. (Filaments didn't even try to warm up!). Set was dead, only the filaments were glowing.

It's funny, I actually got this 5AS4 from a late 50's early 60's set, which - from my understanding - they had all changed over to the more conventional cylindrical envelope.

So I think that someone swapped the valve from that set to another!


The base is rock solid.

Marcc, That's great! Oh, to have clothes baskets of valves. I can barely fill a drawer!

Oli

That is a rather ambiguous description.

The only tube that has filaments is the 5AS4, I would expect the others to be heater tubes and are on a separate winding.
The filament winding cannot be grounded.

If that is the case, I would expect a starting surge that could get close to twice the "B" voltage before the heaters cause the other tubes to conduct. If the filter caps and those exposed to that surge are underrated and cannot handle that voltage, they will be punched through.

EG: If I have a 250V "B" and an #80 / 5Y3 or anything that behaves like them, feeding heater tubes, I will not go below 500V & prefer 600V.

One of the things you had to love about the EHT on some of those old ones was the bias would fail on the horizontal output. That would burn it all out & if a fuse was fitted it might condescend to blow after the event.

Yes, my apologies.

The heaters on all the other valves were lit, apart from the filaments on the 5AS4.

Aka, the valve is bad.

Oli

Hu Oli, does the valve heater measure 'open circuit' ohms on the base pins?

Fred.

You did not, per chance, run that tube sideways? In common with 5Y3 that long filament in an air conditioner duct, will sag & hit /short to a plate. 5AS4 can only be run sideways with pins 1&4 in the vertical plane.

Fred:
Heaters are fine. 0.5Ω

When I had it running, the filaments did glow.

Marcc:
Yes, in the original set it ran sideways, but with the key facing down, so, like you said, with pins 1 and 4 in the vertical plane.


I guess the valve is just weak. And, judging by the black getter, possibly red-plated at some point in its life for an extended period of time, causing the metal to off-gas.

Oli

You would think, AWV valve, AWA TV, you'd think they'd get the orientation right. Looks like they did!

Ollie, one of the two 5AS4s in my Healing is an original 1956 made AWV, still in good condition. It doesn't match the other one so I guess you could have it.

A JJ 5U4 goes in to replace it!