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Old 23rd October 2006, 11:03 PM   #1
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Question Stupid electrolytic cap question.......

I am putting together an SDS Labs power supply capacitor board for my ongoing W-5M rebuild. My question concerns the main caps on the board - 9 47uF 450V electrolytics. The original spec'ed caps are no longer available. Finding the the required value in existing caps is not the problem - the caps are too tall to fit without some modifications to the bottom plate. How much can I increase the uF value before I run into problems? I found the thread concerning blocking so I am aware of that potential problem. So......... how much is too much?

thanks,
Kevin
ps - Feel free to flame if question is too stupid. I am wearing my Russian made two piece asbestos suit with welded fly (with extra pair of pants).
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Old 24th October 2006, 12:22 AM   #2
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I'm not familiar with that amp, what are you using for a rectifier?
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Old 24th October 2006, 02:19 AM   #3
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Old 24th October 2006, 11:45 AM   #4
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Sorry, wasn't specific. It's a Heathkit model W-5M. It's tube retified using a 5R4GY tube.

Kevin
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Old 24th October 2006, 12:26 PM   #5
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Download duncan amps PSU designer and modulate your power supply if you want to be fancy. It is free and easy to use.

Don't blow money on excess uF that you don't need...

Go for 105 degree low esr type caps if possible. Don't feel bad about buying cheaper electrolytics though. Some motor run caps work really well in some power supplies i am told.

Be careful if you are new at this... Those caps can hold alot of volts - please read the safety thread that is at the top of the forum.

I use a big 11 Watt 250 to 400 Ohm resister to ground out every power supply Cap before starting work. Don't use a screwdriver!

Its good practice to leave that resistor B+ (high voltage) to ground during work (some caps build up charge on their own!).

DON'T forget to take it off before you turn thing on again.
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