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Heathkit variac
Heathkit variac
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Old 2nd April 2008, 02:28 AM   #1
ixe13 is offline ixe13  Canada
diyAudio Member
Join Date: Nov 2006
Default Heathkit variac

Hi all,

I bought a Heathkit regulated power supply model PS-4 on Ebay. It's working good. I want to use it to try different kind of tubes circuits. Put them together
temporarly and compare them to the Quad II I built last year.

If I dont like the sound, i would simply rebuild another one, and so on...
The PS-4 Spec are 0 to 400 volts, 0 to 100 Ma (125 intermittent)

Now, the circuits I'm looking into on the internet using 6L6GC, KT88, EL34, 6B4G and so on, have a B+ of between 300 to 375 Volts , but always around 120 to 150 Ma.

Does this mean that the PS-4 can't do the job? it can supply the voltage but doesnt seem to to be able to supply enough Amperage

I suppose I'm missing something here...

Anyway, any advices would be appreciated

Thanx in advance

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Old 2nd April 2008, 02:46 AM   #2
ArtG is offline ArtG  United States
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Join Date: Nov 2006
Location: Central PA
The power supply seems to be far to small for the job that you describe. 400 volts times the maximum current output (100ma) will deliver a maximum of 40 watts, or 40 VA, to even more precise. I'm unfamiliar with this supply, but I assume it is an AC supply, since you titled it a "variac" Even monoblock power amplifiers using PP output tubes such as KT88s or EL34s will typically draw considerably more than 40 watts, depending upon the exact design.
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Old 3rd April 2008, 12:47 AM   #3
ixe13 is offline ixe13  Canada
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Join Date: Nov 2006
hey ArtG,

Thanx for the reply,

Good thing it was cheap. Anyhow, Anybody has a suggestion of a model that would do the job ?

I'm actually looking around the internet and I'm sure I'll come across something...

I'm even considering building one at this point, all I need is to find the right circuit drawing...
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Old 3rd April 2008, 05:01 AM   #4
kevinkr is offline kevinkr  United States
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Location: Boston, Massachusetts
Heathkit variac
The Heathkit IP-17 and IP-32 can manage 400V continuous at 100mA and 125mA intermittently. (I have both and have deliberately overloaded them short term without difficulty.)

Another option would be to look for an electrophoresis supply, these generally come in a variety of current ratings and in some cases can deliver in excess of 2KV continuously. I have an ISCO 494 which has a 300mA range at up to 600V (max power 150W) and a 90mA range at up to 2KV (max 150W).

It goes without saying that one of these electrophoresis supplies can be lethal, extreme care is required in their use. (This applies to lesser supplies as well.) Be careful regardless of what you are using!

Incidentally the PS-4 appears to be very similar in design to the IP-32 and presumably can source up to 125mA short term. None of these supplies are variacs, but fully regulated adjustable dc supplies.
"To argue with a person who has renounced the use of reason is like administering medicine to the dead." - Thomas Paine
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