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Heathkit GC-1000 Power Supply Design Fails and Fixes
🕑 Added 2019-11-11 01:01:22 +0000 UTCAnother look at the Heathkit GC-1000 Most Accurate Clock, analyzing why the voltage regulator is prone to failure in this design and the options you might have to make a better linear supply for one of these clocks. Added Bonus - bad technical drawing! Enjoy!
Comments
Fran Blanche
Likely a bit too low in voltage, but others have asked me to look at that option.
nj Phil
Nice video. Very enjoyable. Iโm wondering if, since you have 12 VAC, . you could drop the voltage with a large film cap in series.
Can't you put the primary windings in series on 120V so it halves the output voltage?
Fran Blanche
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.
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! ๐
John Arild Lolland
That was my first thought as well.
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.
Jac Goudsmit
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...
Rick Lett
Wow! Another old-school fountain pen user. Was fun just watching you draw.
Fran Blanche
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.
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.
Ed Luke
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.
