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 Post subject: Heathkit HP-23 power supply mod
PostPosted: Oct Tue 22, 2019 3:55 pm 
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Joined: Apr Thu 12, 2007 3:24 am
Posts: 2198
Location: Milwaukee WI
I needed a power supply with lower voltages than the normal 700-800 volt output from the supply's HV side. I have some smaller transmitters that want to see 350-400vdc. So I thought I would remove the original voltage doubler circuit and rewire the supply with a standard full wave bridge circuit. There is nothing new or special here. I'm posting mostly to give the measured voltages under various loads in case anyone else was thinking of doing the same thing with their supply but wasn't sure of the outcome.

I will update this post after I do the same thing to the LV side of the supply. The only difference schematic wise will be the use of a resistor instead of the choke, possibly a larger cap on the output and a switch between the 2 taps on the LV secondary.

ADDED: I forgot to mention that voltages will likely be a bit lower if other windings of the transformer will also be used. I'll post final numbers when I'm done with the rebuild and test with other windings loaded.


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hp23 mod.jpg
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 Post subject: Re: Heathkit HP-23 power supply mod
PostPosted: Oct Wed 23, 2019 11:59 am 
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Joined: Nov Mon 06, 2017 2:35 pm
Posts: 120
Location: Texas, U.S.A.
....
Excellent work. Thank you for posting. What is the resistance of the choke shown in the schematic above?

-----------
WB5HDF


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 Post subject: Re: Heathkit HP-23 power supply mod
PostPosted: Oct Wed 23, 2019 3:28 pm 
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Joined: Apr Thu 12, 2007 3:24 am
Posts: 2198
Location: Milwaukee WI
The Heathkit manual states it is an 8H choke with a rating of 175ma continuous. I measured 103 ohms resistance.


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 Post subject: Re: Heathkit HP-23 power supply mod
PostPosted: Nov Wed 06, 2019 12:24 am 
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Joined: Feb Sun 10, 2013 3:31 am
Posts: 52
I'm looking forward to the rest of your modification. This might work for my Morrow MBR-5 and MB-560 twins.

Ted, KX4OM


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 Post subject: Re: Heathkit HP-23 power supply mod
PostPosted: Nov Wed 06, 2019 1:06 am 
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Joined: Apr Thu 12, 2007 3:24 am
Posts: 2198
Location: Milwaukee WI
After wiring and measuring the voltage and current for different loads I lost the scrap of paper I wrote them on. Hopefully some time this week I'll squeeze it into the line of stuff waiting on the bench now.


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 Post subject: Re: Heathkit HP-23 power supply mod
PostPosted: Nov Thu 07, 2019 1:52 pm 
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Joined: Apr Thu 12, 2007 3:24 am
Posts: 2198
Location: Milwaukee WI
I found the scrap of paper. I didn't load it down quite as heavy as last time but its still an informative list. The lower B+ windings have a tap. Here are the 2 sets of readings.


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low B+ taps2.jpg
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