[Heath] HP-23 power supplies - an idea and some questions.

[Kenneth G. Gordon]

If one looks closely at the schematic diagrams for the HP-23 series of power supplies, one 
notices an interesting thing:

In the first-model HP-23 supply, the AC winding which feeds the voltage doubler which 
provides the HV is 268 volts, whereas that winding in all subsequent supplies is 282 volts, 
an increase of 14 VAC.

268 * 2.828 = 741 VDC whereas 282 * 2.828 = 798 VDC, an increase of 57 volts. 

ALL HP-23 power supplies are "rated" by Heathkit at 820 VDC output, but as is clear from 
the info above, this cannot possible be so as far as the HP-23 is concerned. 750 VDC 
output is far more likely, and in fact, I have measured it at that voltage when attached to an 
HW-101 and in the transmit condition in CW.

In my experience, it has been almost impossible to realize the full output power of a pair of 
6146s when using the first-model HP-23 power supply, whereas using the later models, full 
power output is easily realizable.

So, I have considered installing a small 110 VAC to 12.6 VAC transformer in the HP-23 with 
the 12.6 Volt winding added in series between the bottom end of the original power 
transformer's HV winding and ground to boost the HV output closer to the "correct" voltage.

What is holding me back is that, as far as I can see, there would be at least 410 VDC 
between that point and the frame of the added transformer.

Now, most modern insulation is rated, according to the National Electric Code, at 600 VDC, 
so, if this is so, then that would, it seems, give me an almost 200 volt safety margin.

Even so, I am still suspicious.

Has anyone here attempted what I am proposing, and if so, what was your result?

If not, I'll go ahead and try this out. I have at least two HP-23s so I can afford to use one as 
a test bench.

Comments?

Ken W7EKB

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