Heathkit GC-1000 Power Supply Design Fails and Fixes

Likely a bit too low in voltage, but others have asked me to look at that option.

Fran Blanche

Nice video. Very enjoyable. I’m wondering if, since you have 12 VAC, . you could drop the voltage with a large film cap in series.

nj Phil

Can't you put the primary windings in series on 120V so it halves the output voltage?

Of course... He's Big Clive! Honestly the bench area is too crowded for an overhead cam if I intend to work there too. I'll find a workaround.

Fran Blanche

Regarding the camera position for showing you drawing, look at BigClive's channel. He's got it perfect!

How did you modify yours ? Fran might be able to do a similar mod.....

Sometimes I wonder if my comments are read by anyone, let alone Fran. I will stop making comments on your vids Fran - they just go down a /dev/null type hole :o) Keep up the good work though...

Thanks Fran! 😁

That was my first thought as well.

John Arild Lolland

The power supply is operating at around 13.8V from the rectifier and this allows the substitution of 12V (or 13.8V) from a car or other 12 volt system instead of AC. But, granted this is not an optimum design for the rest of the power supply. I modified my clock right after I built it in 1983.

Have you thought of rewiring the primaries in series? The secondary will produce 6VAC instead of 12VAC (provided you stil run it at 120V). That might just be enough...

Jac Goudsmit

Wow! Another old-school fountain pen user. Was fun just watching you draw.

Rick Lett

Linear regulators are not that inefficient but it would definitely be more current draw for the voltage drop.

Fran Blanche

I checked the schematic after I edited and it was 3.9 ohm 5W. I was close.

Fran Blanche

The resistor should never have been 3.5 ohms. More like 30 ohms, 2W. At 200mA, drops 6V, so input would be 8V. Power dissipated 1.6W.

Did this one have a switch mode power supply replace the linear regulator as a aftermarket fix? If so, then the current into the switch mode will be less than the current drawn from the 5v rail, probably by a factor over 2.

Ed Luke