41–50 of 87 posts
I've not used 6N3P tubes before but looking at the circuit it seems to me a 12AT7 (an old favorite of mine) would substitute in that circuit almost without alteration. Then again with a tweak or two either the higher gain 12AX7 or its lower gain cousin the 12AU7 would do.
> 200 amps Something I’ve been curious about: is the current actually required for the thermionic effect, or just the heat? Could you lower the current requirement by thermally insulating the tubes?
They are insulated really well - by vacuum! I'm actually surprised by the figure, though. A small tube requires about 300 mA at 6 V, and the trick is that you can connect the heaters in series instead of doing it all in parallel and pumping out a ton of amps at a very low voltage. They could've done 10 tubes in series at a reasonably safe 60 VDC, and they'd only need 20 amps. Back in that era, because both valves and…
Thermionic vacuum tubes of this type usually have a specified maximum heater/cathode voltage rating which varies considerably according to design. Exceeding that rating and one risks a short between the heater and cathode. For these types of tubes heaters can safely operate up to 200V negative with respect to the cathode and about 100V positive.
In my post I suggested substituting a tube that's more common in the West—the 12AT7, it has the advantage of having a 'tapped' heater which means it can be wired in parallel mode to operate at 6.3V or in series mode at 12.6V. At 12.6V the current would be halved: https://en.wikipedia.org/wiki/12AT7 (pins 4 and 5, the tap on pin 9).
Earlier quoted context omitted.
> Hold out for the partner that cheers you on when you're doing what you love. If only it were that easy. Those kinds of people are few and far between. I’m almost 50 and I don’t think I’ve ever even met a woman who has actively encouraged me about a single thing. I’ve been married twice and have 4 daughters.
Hence the hold out. I (50m) didn’t meet her until I was 30: until that time I dated and had few months relationships with a lot but it never felt quite right. Which became blatantly obvious when I met my wife.
One piece of advice I do have, though: hold out for someone who's a great partner who you really enjoy spending time with. Don't settle for someone who obviously isn't just because other people are pressuring you to "find someone".
> 200 amps Something I’ve been curious about: is the current actually required for the thermionic effect, or just the heat? Could you lower the current requirement by thermally insulating the tubes?
The thermionic effect is very interesting, if the right material is used to coat the cathode then very large emissions can be had. Combinations of oxides such as barium, strontium and others can have both low work functions and high emissions. Currents in the region of over 100A/sq cm can be achieved.
Thus, valves/tubes could be designed to be much smaller and have much smaller currents. For a digital application such as this only a very small cathode current would be needed, this then would mean a much smaller heater could be used.
In the past, miniaturizing vacuum tubes was desirable but wasn't a major priority and further development was stopped when the transistor became available.
That said, in the 1950s portable tube radios were available that used much less heater power than their mains-operated counterparts, for example tubes like the 3V4. It has a directly-heated cathode and a filament/ heater voltage of 1.4V and current of only 100mA (in series mode it operates at 2.8V at only 50mA).
"But most important of all, is to have a lovely wife, who knows you're daft as a brush, and that life together is brilliant." Hold out for the partner that cheers you on when you're doing what you love.
> Hold out for the partner that cheers you on when you're doing what you love. If only it were that easy. Those kinds of people are few and far between. I’m almost 50 and I don’t think I’ve ever even met a woman who has actively encouraged me about a single thing. I’ve been married twice and have 4 daughters.
> Every one agrees that the Turner Prize is much more than just a display of virtue signalling by the cultural elite, and I have decided to enter the Valve.Computer for the prize. Uh, what? Where did this sudden "virtue signaling" by the "cultural elite" stuff come from?
"But most important of all, is to have a lovely wife, who knows you're daft as a brush, and that life together is brilliant." Hold out for the partner that cheers you on when you're doing what you love.
> When all the valves are glowing, I check the fire extinguisher is full, and run the code. It wasn't until working with valve hardware that I finally grokked the original difference between a cold boot and a warm one.
Silicone hardware generates heat.
Neither silicone hardware nor tube hardware goes literally cold in a cold boot; just the power is cut for a moment, usually not long enough to lose a lot of heat.
> When all the valves are glowing, I check the fire extinguisher is full, and run the code. It wasn't until working with valve hardware that I finally grokked the original difference between a cold boot and a warm one.
What? Silicone hardware generates heat. Neither silicone hardware nor tube hardware goes literally cold in a cold boot; just the power is cut for a moment, usually not long enough to lose a lot of heat.
One difference is that the valves have more chance of burning out on a cold boot due to the temperature change.