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Old 20th September 2005, 01:05 PM   #1
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Default Capacitor value

I went through the parts list and compared to the schematic, added to the list what was missing except for one item. The 200 mf capacitor in the power supply section is not mentioned in the parts list, anyone have an idea what the value should be.


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Old 20th September 2005, 01:27 PM   #2
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Meh, I'd just use a 220uF SMPS cap rated for 450V. Rob one from an old computer PSU - they're almost always good, even if everything else is smoked

** edit **

You might wanna use uF instead of mF there - 200mF is 200,000uF and will cost you plenty
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Old 20th September 2005, 01:34 PM   #3
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Hi dstockwell,
Your 200 uF cap is a pair of 100 uF's in parallel. It's rated at 500 VDC like the other dual 100 uF. You need the 500 V rating for the period in time before the outputs draw current and drop the supply voltage.

You may be able to get away with 450 VDC. With no tubes in circuit, install a smaller 500V cap and read the voltage. Also note the AC supply voltage and leave some safety headroom.

-Chris
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Old 20th September 2005, 01:40 PM   #4
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Hi dstockwell,
Also, after you have it running, note the level of hum in the output. Then try to bias the heater strings up to 30~40 VDC via a bleeder string from B+ to common, add a cap to common from the bias point.

Sometimes larger caps will generate a buzz due to the higher peak currents due to the higher capacitance.

-Chris
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Old 20th September 2005, 01:56 PM   #5
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OK I am way confused then, is the 100/100 uf @ 500 the same as the can capacitor on Wellbourne 100uf x 100uf/500V

I figured 2 of these according to the schematic if not I am lost guess I got way more to learn before I try doing even the easiest of schematics.
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Old 20th September 2005, 02:00 PM   #6
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Hi dstockwell,
Yes, you have it right. The schematic should have indicated a pair of 100 uF capacitors, not a single 200 uF.

-Chris
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Old 20th September 2005, 02:30 PM   #7
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So I eliminate the 200 shown and place the (2) 100/100 in the (2)100mf spots.
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Old 20th September 2005, 06:50 PM   #8
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Old 20th September 2005, 11:41 PM   #9
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You install a 100 / 100 @ 500 in the 200 uF spot. You then install one section of 100 / 100 @ 500 in the two 100 uF spots. Or you can use four capacitors depending on layout and space.

That should do it. Again, you may be able to use 450V units instead of the 500V specified. Test and measure first.

-Chris
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Old 21st September 2005, 12:17 AM   #10
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Thank you very much I understand now.
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