6.3V heaters with 5 volt supply?
Andrew Farkas
What would be the result of driving 6.3volt heaters with only 5
volts?
I just got a bunch of surplus computer PS's and as we all know they
only have 5 volt and 12 volt leads. 5 volt with lots of amps (10 -
17) and the 12 with only about 2+ amps.
Any ideas?
Seems like a good cheap way to have regulated heater supply.
Andy
SBench
Hi Andy,
The emission will be much lower than you'd like to see, possibly
leading to cathode contamination. Some device types work OK
on these lower voltages, some don't. I've had no problem
running 'DJ8's on 5.0 volts, but others may have contrary
experience.
You can also attempt to find the regulation mechanism on those
supplies. Sometimes there's a pot you can adjust to raise the
output, and still maintain regulation.
I stumbled across some 5V 3A Power One (I think) devices that
would adjust up to 5.6 volts. I had to change the overvoltage
protection circuitry, and one of the pot series resistors, but
was able to raise the output to 6.3 volts. Maintained regulation
to 105V and 3 amps.
Of course, if the regulator is a fixed IC, it's a little harder (you
have to raise the "ground" of the regulator by 2 diode
drops), but it can still be done.
Regards,
Steve
Sheldon D. Stokes
In article <34f32583....@news.worldlinx.com>, afa...@wchat.on.ca
(Andrew Farkas) wrote:
> What would be the result of driving 6.3volt heaters with only 5
> volts?
>
> I just got a bunch of surplus computer PS's and as we all know they
> only have 5 volt and 12 volt leads. 5 volt with lots of amps (10 -
> 17) and the 12 with only about 2+ amps.
I wouldn't use them, switching supplies are noisey nasty beasts. I
wouldn't want that noise and EMI/RFI anywhere near my fragile little audio
signals.
Sheldon
--
Remove SPAM_BE_GONE. from my address to reply to me.
Paul Gustafson
Hi Guys,
I made an amp with a single ended EL84 using 5vdc on the heater because
the power tranny I was using was 12v ct and I didn't think it would have
enough oomph to run the el84 and all the rest of the 12v tubes
(12ax7,12au7,12x4) the original pentode was a 12ab5 in the machine I
ravaged for this project (old webcor mono reel to reel) and drew a lot
less heater current. Point is the EL84 worked fine on 5v. I tried it on
a variable supply I have first to see what the diff would be. There was
no perceptible difference using 5 or 6.3 v IN THIS CASE. This was a
telefunken el84.
Might work...
Paul G.
Andrew Farkas wrote:
> What would be the result of driving 6.3volt heaters with only 5
> volts?
>
> I just got a bunch of surplus computer PS's and as we all know they
> only have 5 volt and 12 volt leads. 5 volt with lots of amps (10 -
> 17) and the 12 with only about 2+ amps.
>
Multi-Volti Devices
UGH----
Noisy switching supplies...
and tubes would run way too cool...not enough emission...some tubes
suffer 'cathode stripping' ruining them.
Uncool...
Murray
Andy Moss
Paul Gustafson wrote:
>
> Hi Guys,
> I made an amp with a single ended EL84 using 5vdc on the heater because
> the power tranny I was using was 12v ct and I didn't think it would have
> enough oomph to run the el84 and all the rest of the 12v tubes
> (12ax7,12au7,12x4) the original pentode was a 12ab5 in the machine I
> ravaged for this project (old webcor mono reel to reel) and drew a lot
> less heater current. Point is the EL84 worked fine on 5v. I tried it on
> a variable supply I have first to see what the diff would be. There was
> no perceptible difference using 5 or 6.3 v IN THIS CASE. This was a
> telefunken el84.
> Might work...
> Paul G.
>
>
> > What would be the result of driving 6.3volt heaters with only 5
> > volts?
> >
> > I just got a bunch of surplus computer PS's and as we all know they
> > only have 5 volt and 12 volt leads. 5 volt with lots of amps (10 -
> > 17) and the 12 with only about 2+ amps.
> >
> > Any ideas?
> >
> > Seems like a good cheap way to have regulated heater supply.
I'm certain that the computer power supply could be easily modified for
a regulated 6.3Vdc.
If you are trying to run an EL34 off of a 5V rectifier winding, I just
put in a voltage doubler and then run the filament through a dropping
resistor. I've even seen aplications where the small tubes have their
filaments used as the cathode resitor in the output stage - now this is
economizing!
If you don't have the right voltage on the filament, the emmission could
be too low. It would aggravate "sleeping sickness" and shorten the life
of the tube substatially.
Cheers!
Andy
--
No audiophile - just a music lover.......
Anthony Cirella
In article <34f32583....@news.worldlinx.com>,
afa...@wchat.on.ca (Andrew Farkas) wrote:
>
>
> What would be the result of driving 6.3volt heaters with only 5
>volts?
>
>I just got a bunch of surplus computer PS's and as we all know they
>only have 5 volt and 12 volt leads. 5 volt with lots of amps (10 -
>17) and the 12 with only about 2+ amps.
>
>Any ideas?
>
>Seems like a good cheap way to have regulated heater supply.
>
>
>
gm shows a fairly dramatic drop off with voltages less than
6.0ac on 6.3vac filament tubes.
A.Cirella
email: hand...@ix.netcom.com
http://www2.netcom.com/~handmade/
first.htm
George R. Gonzalez
>In article <34f32583....@news.worldlinx.com>,
> afa...@wchat.on.ca (Andrew Farkas) wrote:
>>
>>
>> What would be the result of driving 6.3volt heaters with only 5
>>volts?
>>
>>I just got a bunch of surplus computer PS's and as we all know they
>>only have 5 volt and 12 volt leads. 5 volt with lots of amps (10 -
>>17) and the 12 with only about 2+ amps.
>>
>>Any ideas?
>>
>>Seems like a good cheap way to have regulated heater supply.
5V is way too low for a 6.3V tube. But there's nothing sacred about the
5V output, its just set by a switching-mode regulator. There should be a
little screwdriver-adjustable pot somewhere in the power supply labeled
"5V ADJ". Crank this puppy up to 6.3 volts, or as close as you can get.
The output filter caps are often rated at 6.3 volts, so you're okay
there.
BTW switching-mode power supplies can put out measureable amounts of
hash. You might want to add some more filtering to the output.
Regards,
George
Sheldon D. Stokes
> I've even seen aplications where the small tubes have their
> filaments used as the cathode resitor in the output stage - now this is
> economizing!
I think that's a really neat idea. Fisher X-100's do that. You have a
nice source of low voltage DC that you were going to just throw away
anyway. It really threw me for a loop the first time I saw that. It was
one of the first tube circuits I tried to reverse engineer from the unit
(I didn't have a schematic).
I wouldn't say it's a good idea for a cost no object unit, but you got to
admit, it's a nice way to economize and reduce hum.