Availability of TV valves for Nixie Clock.

[woodchips]

I did a casual search for the 50s/60s valves used in TVs and came up with nothing. This was a surprise, I thought they were two a penny and no one wanted them.

The reason is that I was sorting my valves to start selling them, gave up, put them all back in the loft. Then I was looking at some Nixie tubes and thought "why not a Nixie clock but with valve frequency dividers?".

May be a silly idea but it was chucking it down with rain so either have a think, and a tea, or go outside. It is obvious that a double triode will make a divide by two, just need an awful lot of double triodes. Some thinking around and found a circuit where a pentode would act as a two stable state divider, halving the number of heaters at a stroke.

Still need a lot of pentodes, hence the quick search for the unwanted Uxx valves, but none. Can get EF80, EF91 from places, at £8+ each, which seemed a bit much.

Are old TV valves now extinct?

Further though suggested that it would be nice to make the clock using all sorts of different shape, style and size valves. Could even use worn out EL34s, only need to pass a few mA for the Nixie.

With modern switching regulators that one valve needs 1.4V and another 36V isn't important.

[G6Tanuki]

Go to any radio-rally and you can pick up small-signal series-heater-type TV valves for pennies.

The problem-valves are generally late-40s/1950s line/frame power valves - the likes of the EL37/38 - or stupid "do-everything-in-one-envelope" rectifiers like the U801.

US-style "Sweep-tubes" - 6LF6/6KD6 etc - are sought-after by us amateur-radio types for use in linear-amps, along with the PL519 which can deliver really-good anode currents with only 500-700V of HT.

[Argus25]

If you are going down this road I would recommend using physically small valves or the heater power demands and physical size of the clock will become large very quickly.

Common compact double triodes used in American TV's are the 6J6.

Common small TV pentodes are the 6AG5 or 6AU6, also popular in radios.

Double diodes, you might need for gating; 6AL5.

Many of these TV valves are still cheap and plentiful on US ebay because they have not attracted the attention of the audiophile community yet or had their sonics investigated in controlled scientific studies.

[joebog1]

You are all being engineers again !!!!

Why not use the nixies themselves??
OR just use a divider made from NE2 lamps..
Just my humble suggestion

Joe

[paulsherwin]

There is so little demand for the common TV types that most people don't try to sell them. If you ask here you will probably find someone who will send you some decent pulls for the cost of the postage.

[broadgage]

I recently sold a large box of "pulls" from TV sets for £25, which was more than I expected, but still only about 25 pence each.
A smaller box of NOS TV valves went for another £25, or about £1 each.

(this is not an offer to sell them, all now gone)

This sale was to a neighbour who is a very keen amateur radio fan, He had a particular use for some of the valves but felt that the others might come in handy.
I know that he built a vintage style audio amp with some ex TV valves. Designed for 110 volt DC input, the intention is to exhibit this at a steam fair, powered from a showman's engine.

[high_vacuum_house]

For a cheap double triode you could use a PCC84 which was used as a small signal VHF amplifier valve in 405 line television tuners. 7 volt .3A heater with all electrodes separate from each other, so may be worth experimenting with.

Christopher Capener

[Ed_Dinning]

Hi Woodchips, plenty of PCC types here, yours for the postage, also plenty of 6AL5 etc diodes and assorted other types.
Just let me know how many you want.
I can probably supply the other essential ~valve bases and a big heater transformer

Cheers, Ed

[woodchips]

Thank you to everyone.

Thinking more about the valve clock and the real problem seems to be the binary to decimal decoder, just how do you do that without a 74141? HP used a pile of neons and photo cells in there old counters, I can't come up with anything smaller.

So, looks like a silly idea that has been proved to be a silly idea! Also decided that the valves would have to do something as the time changed, not just glow, boring.

[Peter.N.]

There are usually loads on ebay, I have several boxes full.

Peter

[TonyDuell]

Originally Posted by woodchips

Thank you to everyone.

Thinking more about the valve clock and the real problem seems to be the binary to decimal decoder, just how do you do that without a 74141? HP used a pile of neons and photo cells in there old counters, I can't come up with anything smaller.

The binary flip flops wil give you the bits and their inverses so you could decode that with a diode matrix feeding more valves (a total of 10 more triodes?) to drive the nixie tubes.

Or since it's fairly slow, you could use relays with the coils in the anode circuits of the flip-flop valves and wire the contacts up as the decoder tree network. I've seen a 4 bit binary to 1-of-16 line decoder made that way in a book printed in 1919 so it is clearly 'period'.

Or if you can find some, what about Trochotron valves? They will drive nixie tubes directly. You need one Trochotron and I think a flip-flop per digit.

[woodchips]

I found a circuit where a single pentode would act as a flip flop, so no state and inverse from each stage, just a high and low.

The trigger tubes used in the old Anita calculator might be a possibility, except that are they available other than gutting an Anita, would not be popular! They would also flash on and off making it look far more interesting. Remember the Anita I had decades ago, wonderful to look at.

[Argus25]

Originally Posted by woodchips

So, looks like a silly idea that has been proved to be a silly idea! Also decided that the valves would have to do something as the time changed, not just glow, boring.

There is another way to make counters/dividers not using a valve or transistor, but SCR's instead.

It is a little known arrangement where you use an Alnico core (unmagnetised initially). The sort of small cores used for guitar pickups will work, but Alnico toroids are better with pairs of coils on them.

The SCR's current pulse via one core alters the magnetization of the core which acts as a pulse transformer, thereby allowing the next SCR in the chain to trigger, but not the others. The "logic state" propagates down the magnetic stages, like a magnetic shift register and if the stages are looped around to the beginning to make a ring counter, it makes a frequency divider. It was invented by none other than Lucas in the UK and the data was found on it hidden in the archives at their defunct factory before everything was carted away to the dump. I have yet to see it in a textbook. They appear to have been the masters of electromagnetic techniques.

A while back I restored a Nixie clock. The manufacturers had a very special LSI IC manufactured especially for it. But if you search you will find that there are LSI IC's that will drive nixie driver IC's, like the '141, so it is really easy to make a nixie clock from these vintage parts.

http://worldphaco.com/uploads/THE_19...S_LSI_CHIP.pdf

[Radio_Dave]

This website inspired me to make my neon ring counter nixie clock https://www.dos4ever.com/ring/ring.html#introduction

I made my clock from a load of IN-3 neons which unfortunately didn't stay reliable for long but if you could find neons of better quality, or ones that were specifically made to be used in ring counters, maybe it could be an option?

Regards
David

[G8HQP Dave]

If you are dividing a constant frequency by a smallish ratio then you can use semi-analogue techniques such as a triggered multivibrator. This may reduce the number of valves.

[Cobaltblue]

Cold Cathode trigger tubes can still be bought:

https://www.ebay.co.uk/itm/Z700U-MUL...QAAOSwzthdepi3

I built dividers using them.

Divide by 10 use Dekatrons

Looks pretty!

Cheers

Mike T

[gingpeakin]

Do these still work? I understood they contained tritium to stabalise the trigger voltage. With a half life of 12 years some of those NOS devices will be more than 50 years old. Certainly the ones in my Anita MkV111 (1961 I think) are all a bit random.

Ging

[factory]

They must be OK, I found this website where someone had built a clock using 85 of those Z700U trigger tubes, they did make a few kits with the PCB's (long sold out), they also got the trigger tubes from Langrex.
http://www.sgitheach.org.uk/nixie8.html

Another way of building a clock is with stepper relays, as HP did with the 570A.


I also own another HP clock, but it's just lots of TTL.

David

[GrimJosef]

Originally Posted by gingpeakin

Do these still work? I understood they contained tritium to stabalise the trigger voltage ...

The Z700U has a primer cathode which I suspect does the same job as the radioactive pre-ioniser in other trigger tubes. There's no mention of radioactivity in the data sheet https://frank.pocnet.net/sheets/129/z/Z700U.pdf.

Cheers,

GJ

[turretslug]

Wow, what a lovely thing. Utterly obsolete and completely eclipsed, of course, but still a masterpiece of HP-ism. The stuff of James Bond's nightmares....