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Old 21st Sep 2020, 6:27 am   #1
Clay1905
Tetrode
 
Join Date: Sep 2020
Location: Blue Mountains City, New South Wales, Australia.
Posts: 51
Default Power Supply for AC/DC portable

HI folks,
Presently I have a Philips "Town & Country" model 168 on the bench. The mains supply transformers' H.T. secondary has gone open. After some searching, I came across the power supply on the projects pages at this site.

https://www.vintage-radio.com/projec...y-set-psu.html

I'll be darned if I can't get the HT side of the supply circuit to work as per the description. The best I can get is about 45VDC at the output. This isn't quite enough to get the valves functioning.
I've modeled the circuit in LTSpice, and voltages I'm measuring are what the simulation suggests I should find.
Now, my theory isn't very strong, but I would have thought that as the multiplier circuit does full wave rectification, the input, 15VAC, should be multiplied by 1.41, then doubled twice, as that's what the circuit should do. Accordingly, I should expect an ideal 84.6 volts at output, or realistically, about 80 VDC allowing for diode drops etc.
However, the same calculation, omitting the 1.41 bit (i.e. doubling the voltage twice), gets me very close to the actual measured voltages. For why?

There's a very good chance I'm overthinking things, and/or I have messed up the spice simulation too.
Any help or advice would be very welcome, I can tell you.

Files for the spice modeling are here:
https://drive.google.com/drive/folde...Z8?usp=sharing

Clay.
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