Tubes tubes tubes!

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Tubes tubes tubes!

Postby Andrew Davie » Fri Jun 16, 2017 2:31 pm

I stopped by the "tip shop" - local recycling centre - just to see how all the old tubes there were doing. Not a lot left, but there were 9 CRTs sitting in boxes, and I hadn't seen one or two before. I decided to see if I could do a bulk purchase and, although I spent more than I really wanted, I came home with them all. One sealed box I have no idea what's in it, and one looks as though the white coating is flaking at the edges. But apart from that I know nothing about them yet - still in boxes (with flaps open). The side of the box is often hard to read, but what I could make out seems to be the following...

AT-56 (maybe AJ-56)
AJ-122
CT-47
DA-331
VCR-139A
1T-70
AW-329
3AP1A

So, quite a haul!
Not sure what I'm going to do with these but wanted to ensure they find good homes.
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Re: Tubes tubes tubes!

Postby Steve Anderson » Fri Jun 16, 2017 4:04 pm

Apart from the 3AP1A and the VCR139A all the others I have no data on and wasn't able to find any online using my usual resources. They may be 'house numbers' where a standard CRT is renumbered to to suit the equipment builder, e.g. a 5CP1 becomes an SA507. Heathkit did this a lot with semiconductors though not tubes or CRTs.

When you have time it may be useful to take a photo of each one alongside a ruler or measuring tape with the measured screen size and overall length. Even so, unless obviously oddball it may be hard to identify what the heck they are.

If there any other numbers on the box or the CRT itself they may yield a clue, especially if they have a CVxxx type number, that's just a military version of a civilian CRT. That can be looked up easily.

Steve A.
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Re: Tubes tubes tubes!

Postby Andrew Davie » Fri Jun 16, 2017 4:06 pm

Steve Anderson wrote:Apart from the 3AP1A and the VCR139A all the others I have no data on and wasn't able to find any online using my usual resources. They may be 'house numbers' where a standard CRT is renumbered to to suit the equipment builder, e.g. a 5CP1 becomes an SA507. Heathkit did this a lot with semiconductors though not tubes or CRTs.

When you have time it may be useful to take a photo of each one alongside a ruler or measuring tape with the measured screen size and overall length. Even so, unless obviously oddball it may be hard to identify what the heck they are.

If there any other numbers on the box or the CRT itself they may yield a clue, especially if they have a CVxxx type number, that's just a military version of a civilian CRT. That can be looked up easily.

Steve A.



I figured as much, too :) I'll have a bit of fun tonight measuring and photographing. I suspect I actually have a batch of very similar if not mostly identical tubes. Still, I'm confident that they were worth "rescuing". I paid about US$10 each.
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Re: Tubes tubes tubes!

Postby Andrew Davie » Fri Jun 16, 2017 6:33 pm

Home and inventory time.
Looks like generic boxes were used - not much of a variety...

I have 7 x 3BP1; most look brand new, one is almost certainly dead.

I have a long thin one about 30cm long marked "RCA RADIOTRON ELECTRON TUBE" with "MADE IN U.S.A." and "648" on the base.
It came in a box with TSH24B on the flap, inside another box with 3AP1A on the front.

I have one marked VCR139A in box, but it might be dead. Black deposit on inside and base slightly loose.

Finally, the DG7-32 previously mentioned.

So, that's it.
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Re: Tubes tubes tubes!

Postby Steve Anderson » Fri Jun 16, 2017 7:30 pm

The 3BP1s are common general purpose scope tubes, their downside is they require around 2000V to operate, but anyone willing to have a go it's quite an easy tube otherwise.

The CRT with the black deposit on the inside could well be OK. This may be the 'getter' which is chemical sprayed into the tube after vacuum pumping and before sealing. It's function is to mop up any residual gas (air) in the tube. As long as it's not white it should be OK, often the getter has a silvery finish, especially true on radio-type valves/tubes. If it is white air has leaked in rendering it useless, usually through the glass/wire or pin seal. When a TV type CRT starts to lose resolution/focus this is what's generally happening, the trade term is the tube has gone 'soft', it's not a hard vacuum any more.

First thing to check is the heater is intact, two pins on the base will have a low resistance between them, though not zero. By low I mean a few ohms, anything from 1-20 ohms. Using a variable power supply gradually (very slowly) wind up the volts until you get that characteristic orange glow from the heater, measure the voltage and current. It will usually be between 300mA and 1A, there are exceptions though. Very few CRTs have heaters over 6.3V. The vast majority are either 4V or 6.3V.

Look for any burn marks on the face of the tube, if there's a straight light-brown line this CRT has already seen considerable service or the burn was the result of some other failure in the equipment it was installed in. (A grid-bias failure).

A very gentle shake should not provide any indication of loose parts rattling around inside, put it base up first, then invert, this will also show up anything not quite mechanically right.

All of these checks can be done as you buy them with the exception of actually applying heater volts. If it passes these then there's a 90%+ chance you have a good CRT.

In this case you want know what the heck they are though!

Steve A.
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Re: Tubes tubes tubes!

Postby Andrew Davie » Fri Jun 16, 2017 9:32 pm

Thanks for the interesting info, Steve. I know that I'll never be doing anything with these tubes. I consider them just temporary possessions and will hand them to anyone who demonstrates a need for them. I have really enjoyed Harry's builds and seeing the progress. Hopefully these will come in handy for him and others in future. Not really a lot of $ tied up here. As to the black spot and possibly dead tube(s) I will revisit each one carefully and respond with pictures, maybe over the weekend.
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Re: Tubes tubes tubes!

Postby Harry Dalek » Sun Jun 18, 2017 7:58 pm

Andrew Davie wrote:Thanks for the interesting info, Steve. I know that I'll never be doing anything with these tubes. I consider them just temporary possessions and will hand them to anyone who demonstrates a need for them. I have really enjoyed Harry's builds and seeing the progress. Hopefully these will come in handy for him and others in future. Not really a lot of $ tied up here. As to the black spot and possibly dead tube(s) I will revisit each one carefully and respond with pictures, maybe over the weekend.


Great finds there Andrew ! i have been away for a few days just got home today .
Sounds like some rarer tubes and the old 3bp1 in this new find.
Yes do post up the pictures of tubes when you can Andrew .
BTW Troys 3pb1 has a rattle init he was worried it was a dud tube got him test stages to try it and all tests seemed fine and he's monitor works ,must be a some loose glass or mica init.
Steve there was the Heathkit IO-4205 Dual Trace Oscilloscope and and at least another model or 2 that was a touch smaller mine was this model and a beast as far as size a lot of wasted space in the case may be just to keep the transformer at a safe distance.
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The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: Tubes tubes tubes!

Postby Harry Dalek » Sun Jun 25, 2017 9:51 pm

i found this on the 3AP1A i think yours is a earlier version may be same pin connections
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The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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