Question: Power Supply for Vacuum Tube

[Metropolitian]

For those that thrived in the pre-hybrid age full on with vacuum tubes;   what is your experience/expertise on powering the tubes.

 

I have two tubes that I need to feed with 6.3v and 250v (DC).

Now I have checked at here and there. It's hard to find a transformer that has 6.3v output, and the one that has it are very beefy.

The 250v and to be isolated, depending on the current, theoretically should be easy made by two smallish transformers or an 1:1 (but hasn't seen those, only big isolation transformers) with a diode and resistor in series.

 

Practically I would end up with an transformer with multiple output (I need 2x18v anyway) which has 6.3 ^* (hopefully but ain't seen them much) and a smaller one to push up one of the output to 200v (which is sufficient for the tube).

 

^*Instead of the 6.3v, any other value near this is it accepted? (5v..)

 

Tube is 6e2.

[Metropolitian]

One example use for the tube.

 

Tube is happy when supplied with 180V-250V 8mA for the electrons and 6.3V 0.3A for heating.

[Jan Dietz]

Something like this should be a good start.

No need to rectify the 6.3V, AC will be fine for the heater

 

https://www.aliexpress.com/item/4001160060073.html?spm=a2g0o.productlist.0.0.2db5713cUhZqnf&algo_pvid=ab35a9c3-5e35-47c4-9896-0b377e802872&algo_expid=ab35a9c3-5e35-47c4-9896-0b377e802872-28&btsid=0ab6f82215933730237695573e5c81&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_

[Jan Dietz]

This one might suit you even better, a little smaller, and more of your requested voltages:

https://www.aliexpress.com/item/32919273039.html?spm=a2g0o.productlist.0.0.51bd707eiR824C&algo_pvid=b2307040-f8ef-4e1c-80b2-fbcaab792842&algo_expid=b2307040-f8ef-4e1c-80b2-fbcaab792842-14&btsid=0ab6d59515933733158348887ee766&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_

 

Input voltage:AC220V(red, red)

Output high voltage:AC230V-0-230V 40MA

Two groups of output filament voltage

①Single group AC6.3v 1a:  

② Single group AC13V 0.6A 

[Metropolitian]

^^ Splendid comments.

 

Although I wouldn't order those at Ali, shipping 30usd and above that all it are THOSE that i am finding in the store nearby (NPE/Nattapong) and they are right for big tube amps but too oversized/overkill for the project that I want do with the tubes here.

I only need 3mA with the HV.

 

The HV part I probably can make myself with a 555 ic, another vibrating trans (547) , winded core and fets. (DC-DC boost).

Or ordered, like this one:

 

But the big question for now is for the 6.3v. 

 

If that exact voltage is really needed, then I will go for the transformer as @Jan Dietz already mentioned, they cost around the 500thb and a ride to the store.

But I will be more happy if I can use one of the transformers that I have laying around here in the 'parts-drawer', but no 6.3v. in there.

 

[impulse]

If you're in BKK, stop by the Bang Mo area of Chinatown and peruse the hundreds of shops to ogle everything you'd need.  Lots of hi-fi shops and tons of electronics shops.  Lots of them are buried deep in the bowels of the buildings between the main alleys.  I had some great full days wandering around the rabbit holes.  Best if you speak Thai or have someone with you that does, but a lot of them have good English skills.

 

 Start right here on your GPS...   13.745811°  100.498365°  That's deep inside one of the rabbit holes.

[Jan Dietz]

BTW 6.3V is not critical, it's just where it will have the longest life / correct heating. 

But as tubes are quite resilient you can get away with probably anything between 5 and 8 volts or so.

 

Edited June 29, 2020 by Jan Dietz

[Metropolitian]

1 hour ago, Jan Dietz said:

BTW 6.3V is not critical, it's just where it will have the longest life / correct heating. 

But as tubes are quite resilient you can get away with probably anything between 5 and 8 volts or so.

 

That's good to hear.

The one that I am using is 24-18-0-18-24 and 0-6-9-12. 

Using the 2x18 for another board in the same project and was hoping that I could use the 6 for the tube heater.

Just didn't try it as I wasn't sure if that voltage has to be precise, thanks to the decimal with tenths value.

 

I will try the 6 volt ac first, otherwise I can try to get the value near to the 6.3v by rectifying it with a few diodes.

[Metropolitian]

Dropping Heater Voltage
The heater voltage should be kept within +/-10% of its nominal value for optimum valve performance. For 6.3V heaters that means 5.7V to 6.9V, though it is even better to stay within +/-5% if you can (6V to 6.6V). Many guitar amps suffer from rather excessive heater voltages. This is sometimes because mains voltages are higher today than they were when the transformer was orignally designed (this is common in the US where wall voltages have risen from around 110V to 117V today). Sometimes it is because the transformer is more powerful than it needs to be, i.e. it is not fully loaded so the voltages are not pulled down to their nominal values.

 

A nice page :  Link to Valvewizard site

 

 

And who are to blame?

 

Why 6.3 Volts?

In the early 1930s the Americans wanted to make in car radio possible, this also would have helped the military. The standard for car electrics at the time was a 6 Volt lead acid battery, and a freshly charged battery would have had a terminal voltage of 6.3 Volts. As mains transformers could generate any wanted voltage it was decided to standardise on a voltage that would also allow the valve to be heated from a vehicle battery.

6.3 Volts was adopted as the American standard for filaments and heaters in 1934.

The UK standard for mains valves had been 4 Volts, this too can be related to the lead acid battery as two accumulators in series would be 4 Volts. The accumulator used in the home would be run to near exhaustion prior to being taken to the local shop for recharging and therefore for most of its service live would give the 2 Volt terminal voltage associated with the lead acid cell.

In 1937 MOV went American, introducing 6.3V valves with International Octal (IO) base caps.

Mazda's response was to remain staunchly British but to reissue its range of 4V valves with Mazda Octal (MO) base caps, similar to but not interchangeable with IO.

The main move to 6.3V valves for British domestic receivers was essentially a 1940s phenomenon, spurred by the widespread manufacture, importation and use of improved 6.3V American types during WWII.

 

source: National Valve Musem , link.

 

[Crossy]

All this talk of heater accumulators (A) and HT batteries (B), who remembers these (C) :-

 

 

 

 

[faraday]

Long ago & far away, I used to work in a Faraday cage using Nagard Oscilloscopes.

 

Damn great big things with a ginormous seperate power supply, containing ELS 63 Valves.

 

 

[Metropolitian]

6 hours ago, Crossy said:

who remembers these (C) :-

 

I don't but it reminds me of the 4.5v batteries that has 3 cells in it and with a little hack you was then able to use the 1.5v and 3v from it.

In our country we had the brand 'White Cat'  , long gone.

But these 4.5v batteries are still available here and there.

I do still have one in a classic pocket torch (the one with colored slides) , still working after 25 years. Never replaced the battery.

 

I do remember another battery, which resemble very much the same size as one of the cell from this pack. With the height of a 'D' battery and width between the 'C' (not C as in radiobattery) and 'AA'.

Bit like the size of a cylindrical Lion cell but a tat bit longer.  Who know those?

 

And the 6v pack with springs on the top and 9v pack which was square (squared, not rectangle) with the same connection as the 9v still in use now.

 

[Crossy]

A veritable cornucopia of battery sizes here https://www.wikiwand.com/en/List_of_battery_sizes#/overview

 

 

 

[Metropolitian]

28 minutes ago, Metropolitian said:

do remember another battery, which resemble very much the same size as one of the cell from this pack. With the height of a 'D' battery and width between the 'C' (not C as in radiobattery) and 'AA'.

Bit like the size of a cylindrical Lion cell but a tat bit longer.  Who know those?

That must be the LR12 (which makes sense as the 4.5v is the 3LR12) , in the UK called U10

Source: Wikiwand, check Crossy's post above

 

Amazingly Ali has it, here.

 

I had the LR12 for these torches.

 

41 minutes ago, Metropolitian said:

I do still have one in a classic pocket torch (the one with colored slides) , still working after 25 years. Never replaced the battery.

Exactly this one, mine has still the leather straps and cords.

[Metropolitian]

To continue on battery beauties from the past ????
 

The U10 1.5v battery from the UK and another one from Netherlands the 3v.