I need to buy or build a bench power supply to test & design various tube
equipment (audio & ham). I would like it to be something like a Heathkit
HP-23 with voltage & current meters. The major problem with the supplies
I've come across such as the HP-23, is that the B+ current is appx. 100ma.
The bias & filament supplies are OK, but at times I need around 400ma for
the B+ out. Is there such a PS available, perhaps with tube regulation &
rectification or do I need to build from scratch? Any answers will be most
appreciated.

Cordially,
west
AF4GC

"west" wrote in message
news
I need to buy or build a bench power supply to test & design various tube
equipment (audio & ham). I would like it to be something like a Heathkit
HP-23 with voltage & current meters. The major problem with the supplies
I've come across such as the HP-23, is that the B+ current is appx. 100ma.
The bias & filament supplies are OK, but at times I need around 400ma for
the B+ out. Is there such a PS available, perhaps with tube regulation &
rectification or do I need to build from scratch? Any answers will be most
appreciated.
======================
An excellent design for a HV power supply unit can be found in QEX July
/August 1999 pages 50 -55
"A regulated 2400V power supply" ,by Al Williams VE6AWX

Even if you don't need such a high DC voltage ,the design is universal and
the output voltage is adjustable.
The design includes 2 SCRs in the transformer's primary winding circuit ,
with DC feedback resulting in a very stable DC supply voltage under large
load variations . Another feature is the 'soft' start preventing large
surge currents.
The author uses the unit to supply 2x813 tubes in a RF amp. requiring up to
1kW of power , with the no-load voltage of 2400V-DC dropping to 2397V when
load is 1kW.

Frank GM0CSZ / KN6WH

If you don't want to DIY it, consider using a Sorensen -- some of their HV
switching supplies are incredibly inexpensive on EBay. You can also look
for the older Lambda and Kepco supplies with 6550 or 6L6 pass elements --
the one pictured on the link below will do 300 ma -- voltage is controlled
by a variac -- you have to look both at the Business+Industrial section of
the Bay as well as "Vintage Electronics".

http://www.tech-diy.com/images/lambda2.jpg

I use this microprocessor controlled power supply modification for the Heath
IP-17 -- but I figured out the compensation network so it is now beautifully
regulated:
http://www.tech-diy.com/MCTracer_no_...webversion.htm

you can (and should) increase the current capacity for the big IRFPG40's by
paralleling several units (with appropriate modifications) so that they
operate in the SOA. One is not enough for your application.



"west" wrote in message
news
I need to buy or build a bench power supply to test & design various tube
equipment (audio & ham). I would like it to be something like a Heathkit
HP-23 with voltage & current meters. The major problem with the supplies
I've come across such as the HP-23, is that the B+ current is appx. 100ma.
The bias & filament supplies are OK, but at times I need around 400ma for
the B+ out. Is there such a PS available, perhaps with tube regulation &
rectification or do I need to build from scratch? Any answers will be most
appreciated.

Cordially,
west
AF4GC

Johnson posted:

http://www.tech-diy.com/images/lambda2.jpg

Ummm... Nice work!

Harry C.

I own a Heathkit IP-17 which had identical rating to the HP-23 that you
have. For higher amounts of current, I cobbled together the combination
of a Variac, a salvaged TV set power transformer, bridge rectifier, and
filter capacitors to do the job.

Although unregulated, it performed its job well for many years.

Sorenson and other firms manufacture large, regulated power supplies
that will do arguably better work, but even used these generally
command a price of several hundred dollar, compared to the $30 or so
that I invested in my home built variable voltage supply.

Try periodically checking on eBay.

Good luck. Harry C.

) writes:
I own a Heathkit IP-17 which had identical rating to the HP-23 that you
have. For higher amounts of current, I cobbled together the combination
of a Variac, a salvaged TV set power transformer, bridge rectifier, and
filter capacitors to do the job.

Although unregulated, it performed its job well for many years.

There have been a few threads recently about regulated tube supplies,
and each time I see them, I keep wanting to post "but most supplies in
the days of tubes were not regulated".

It's almost as if people have lost that fact, so used to solid state
where regulation is the norm, though regulation there often means
a different thing. Now it's used to get a low impedance out of the power
supply, or because the devices are finicky over a wide range of voltages (or
outright can be damaged by too much voltage, as in the case of ttl). Of
course, three terminal regulators made it easy to add regulation to
just about any sold state design decades ago.

But of course, for most consumer equipment there were no regulators (though
that may mean little since there was little consumer electronics around
the house up till about forty years ago) If there was regulation it
was a VR tube, and for a specific stage or stages, liked an oscillator
stage that would change frequency with voltage variation, rather than making
the whole supply regulated.

It was in the lab that most regulated supplies were seen. All that
test equipment is a prime example. You wanted reproduceability for
that DC coupled scope, so you'd want it well regulated.

I guess in the lab you'd see variable voltage regulated supplies but
that would have been the key place.

Michael VE2BVW

Michael, excellent point all.

Years back I used Lambda regulated H.V. supplies in the workplace, but
only for critical application in experimental physics apparatus where
the accuracy and stability of the voltage had an important impact on
our research. (I still own a comercially produced 0-5 Kv regulated
supply, whose use is largely limited to powering photomultiplier tubes
used in nuclear research applications.)

Like you, I don't recall voltage regulation ever playing a significant
role in vacuum tube electronics, except for those instance that you
mention using VR tubes (as in my Hallicrafters SX-71 receiver to
stabilize the local oscillator). Still, stabilizing that sucker
required much more effort than simpy a VR tube!

Sadly, I gave away the original Variac adjustable power supply to a
student that had greater need for it than myslef. Then too, very little
of the vacuum tube work I do today requires more than a few mils which
My Heatkit IP-17 supplies.

Kindest regards, Harry C.

wrote in message
ups.com...
Michael, excellent point all.

Years back I used Lambda regulated H.V. supplies in the workplace, but
only for critical application in experimental physics apparatus where
the accuracy and stability of the voltage had an important impact on
our research. (I still own a comercially produced 0-5 Kv regulated
supply, whose use is largely limited to powering photomultiplier tubes
used in nuclear research applications.)

Like you, I don't recall voltage regulation ever playing a significant
role in vacuum tube electronics, except for those instance that you
mention using VR tubes (as in my Hallicrafters SX-71 receiver to
stabilize the local oscillator). Still, stabilizing that sucker
required much more effort than simpy a VR tube!

Sadly, I gave away the original Variac adjustable power supply to a
student that had greater need for it than myslef. Then too, very little
of the vacuum tube work I do today requires more than a few mils which
My Heatkit IP-17 supplies.

Kindest regards, Harry C.

What a small world, Harry. I was a field engineer for 25 years working
mostly on Gamma Cameras. I sold a business a few years ago that primarily
retrofitted Nuclear Medicine Gamma Cameras. I heard that there was a man in
the Chicago area who set up a photomultiplier tube to track the moon for
EME. I never found out his name, but probably could, if I made an effort.
Are you a physics professor?

Cordially,
west
AF4GC