Is it possible to use regulated DC for a rectifier tube?

jarthel · 14th June 2006, 12:33 AM

my main transformer's 5V line is limited to 2A which limits the tubes that I can use. I have a 5V4G (5V@2A) now but it would be nice to have other options like 5U4G (5V@3A).

I have a 2nd transformer (that has 2 secondaries) which will be used to heat up 8CG7 (8.4V@450mA). I am hoping I can use the other secondary to heat up rectifier tubes using 5V.

Thanks for the help

ps. I know that tube data mentions AC/DC heaters can be used. but my experience with tubes amps is very limited and most schematics I've seen uses AC heaters. thanks again

showdown · 14th June 2006, 01:18 AM

You can use a GZ34/5AR4 with a 2A winding, it only draws about 1.9A. It will also give you the lowest voltage drop of all tube rectifiers.

Geek · 14th June 2006, 02:51 AM

I've used regulated DC for DH tubes and have yet killed one.....

OK, I did blow up a 45 before I realized the meaning of soft-start

jarthel · 14th June 2006, 03:10 AM

Quote:

Originally posted by Geek
I've used regulated DC for DH tubes and have yet killed one.....

OK, I did blow up a 45 before I realized the meaning of soft-start

I am planning to use one of the regulator chips from the LM317 family (higher current rating). would this be suitable? if not, can you share your schematic?

thank you

dsavitsk · 14th June 2006, 03:23 AM

Quote:

Originally posted by jarthel
I am planning to use one of the regulator chips from the LM317 family (higher current rating). would this be suitable? if not, can you share your schematic?

It can work, but you'll need lots of caps before the regulator, probably large heatsinks on the diodes, and a large heatsink on the regulator. How about just using a resistor in series with the filament to drop a few volts?

jarthel · 14th June 2006, 03:48 AM

Quote:

Originally posted by dsavitsk

It can work, but you'll need lots of caps before the regulator, probably large heatsinks on the diodes, and a large heatsink on the regulator. How about just using a resistor in series with the filament to drop a few volts?

thinking of doing that and but no more DC. just use resistors to bring 9VAC to 5VAC.

Geek · 14th June 2006, 04:18 AM

Resistors is all I use. Chose the value for warm running, as the filaments are lower in R when cold.

jarthel · 14th June 2006, 04:28 AM

I have a 9V secondary.

so I need to drop 4V from it.

4V / 3A (current rating for 5U4G) = 1.33ohms (5x 6.8ohms 5W in parallel)

4V / 2A (current rating for 5V4G) = 2ohms (5x 10ohm 5W in parallel)

Is my calculation correct? thank you

jlsem · 14th June 2006, 05:08 AM

Quote:

Is it possible to use regulated DC for a rectifier tube?

Only if the heater is not tied to the cathode - a damper diode, e.g.

John

Tube Overdrive · 15th June 2006, 01:25 AM

Also, keep an eye on the insulation rating of your 9V transformer. It may not be rated for safe operation with a winding floating at B+ voltage.

14th June 2006, 12:33 AM	#1
jarthel diyAudio Member Join Date: Jan 2002 Location: somewhere in Australia	Is it possible to use regulated DC for a rectifier tube? my main transformer's 5V line is limited to 2A which limits the tubes that I can use. I have a 5V4G (5V@2A) now but it would be nice to have other options like 5U4G (5V@3A). I have a 2nd transformer (that has 2 secondaries) which will be used to heat up 8CG7 (8.4V@450mA). I am hoping I can use the other secondary to heat up rectifier tubes using 5V. Thanks for the help ps. I know that tube data mentions AC/DC heaters can be used. but my experience with tubes amps is very limited and most schematics I've seen uses AC heaters. thanks again

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14th June 2006, 01:18 AM	#2
showdown diyAudio Member Join Date: Jun 2005 Location: Norway	You can use a GZ34/5AR4 with a 2A winding, it only draws about 1.9A. It will also give you the lowest voltage drop of all tube rectifiers.

14th June 2006, 02:51 AM	#3
Geek diyAudio Member Join Date: Sep 2004	I've used regulated DC for DH tubes and have yet killed one..... OK, I did blow up a 45 before I realized the meaning of soft-start

14th June 2006, 04:18 AM	#7
Geek diyAudio Member Join Date: Sep 2004	Resistors is all I use. Chose the value for warm running, as the filaments are lower in R when cold.

14th June 2006, 04:28 AM	#8
jarthel diyAudio Member Join Date: Jan 2002 Location: somewhere in Australia	I have a 9V secondary. so I need to drop 4V from it. 4V / 3A (current rating for 5U4G) = 1.33ohms (5x 6.8ohms 5W in parallel) 4V / 2A (current rating for 5V4G) = 2ohms (5x 10ohm 5W in parallel) Is my calculation correct? thank you

15th June 2006, 01:25 AM	#10
Tube Overdrive diyAudio Member Join Date: Apr 2005 Location: Quebec	Also, keep an eye on the insulation rating of your 9V transformer. It may not be rated for safe operation with a winding floating at B+ voltage.

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