Electronics > Projects, Designs, and Technical Stuff
Planning to build benchtop 500V tube PSU, help needed.
TERRA Operative:
I'm still around. :)
I've just been waiting for parts for multiple other projects, sorting through a cubic meter of electronics junk of mine I had shipped over from storage in Australia, finishing some other stuff, work and real life, etc etc.
I might end up getting that custom transformer I mentioned previously made one day, once a few other things on my todo list are done (SWMBO keeps adding stuff to the top of the todo list, as usual. :D )
KD4CCF:
For vintage stuff, it's often better to buy then recreate.
Check out Heathkit IP-17 and IP-32 power supplies on ebay.
Attached is schematic of IP-32 which uses two 6L6 tubes for regulation.
schmitt trigger:
*Interesting* that the Heatkit design incorporates solid state diodes for the main DC bus, but has an 6X4 to supply the regulator tubes.
Why would they do so? Why not replace the 6X4 with solid state diodes also?
duak:
One possibility why Heathkit used a 6X4 was that it delayed and/or softened the voltage rise on the regulator tubes. This could perhaps prevent the output voltage from going wild or from exceeding some voltage or current spec on some part during startup.
Another is that 6X4s were cheaper than silicon rectifiers. The main rectifier was silicon because it saved power and reduced dissipation. It was cheaper because a separate 5 V winding was not needed for a thermionic rectifier's heater. I see that a voltage doubler was also used, so probably two thermionic rectifiers and two heater windings would have been needed.
Cheers,
schmitt trigger:
I believe that you are correct in both counts.
However, I can see from the schematic that the main power switch has a standby position.
Which presumably would be used to allow for the heaters to warm up prior to applying the main B+.
Still, the slow warm up of the 6X4 would have prevented an incorrect start up procedure.
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