[Heathkit] HP-23(*) differences - voltage readings.

[Kenneth G. Gordon]

First some history:

I bought both of these power supplies off that auction site. 

One is an HP-23, the first model, with a connection for 6.3 vac and 
adjustable bias, but with no external switch for 250/300 VDC LV. 
This one looked practically brand new. I "re-kitted" it, since the 
wiring looked pretty bad, and replaced the electrolytics with NIB 
ones, and all the diodes with new 2KV at 2 amp jobs. I also added 
a 250/300 VDC switch so that I could more easily use it when 
working on the single-banders, and a new, panel-mounted fuse 
holder. It has been in nearly constant use since I rebuilt it. I have 
used it with my HW-101, and it is seldom turned off. It runs at 
normal temperatures and is very reliable.

The other one is an HP-23B with the original 250/300 VDC switch, 
a panel-mounted breaker, no connection for adjustable bias or for 
6.3 VAC. I have also replaced all the electrolytics with the 
indentical ones I used in the HP-23, and the same new diodes.

This power supply looks pretty ratty, but works just as reliably as 
the other one. I have only been using this one for the past two 
months.

The measured output voltages for these two supplies, no-load, 
sitting side by side on the bench, are as follows:

HP-23				HP-23B
793 VDC			846 VDC
364/275 VDC			373/294 VDC
-131 VDC			-140.5 VDC
13.56 VAC			14.67 VAC

All voltages are noticeably higher in every case with the HP-23B, 
indicating to me that it is capable of higher power output. Perhaps 
the primary winding is made of larger wire, therefore of lower 
resistance, or there are one or two fewer turns in the primary.

I will check the voltages under load, and report back, but to me this 
indicates that Heathkit DID upgrade the power transformers 
somewhere between the two models.

I repeat: both power supplies run at normal temperatures.

Ken Gordon W7EKB