How much capacitance

[Fred Wittman]

-----Original Message-----
>From: Paul Kraemer <elespe at LISCO.COM>
>Sent: Aug 22, 2009 7:55 PM
>To: HEATH at LISTS.TEMPE.GOV
>Subject: [HEATH-TEMPE] How much capacitance
>
>Those following recent discussion on the SB-200 and SB-220 (or any) 
>amplifiers and considering replacement of the (6) electrolytic capacitors 
>with newer, better, higher capacitance value units might do well to consider 
>for a moment the slippery slope down which they may be headed.
>Pick out any book on power supply design and observe what happens to inrush 
>line current and diode (same as transformer secondary) current as the 
>capacitance value of the filter capacitor is increased by orders of 
>magnitude. THEY INCREASE!
>If you are in the design phase of a new product, fine, put in as much 
>capacitor as your pocketbook can afford, then pick out the remaining 
>components to stand up to the stress.
>If you are working with vintage products with un-obtainium components that 
>you care to prolong the life of you might be well advised to follow the 
>advice of one author "use the minimum capacitance which results in 
>acceptable ripple"
>An argument might be made that Heath would have used larger capacitors if 
>they had been readily available 50 years ago. Or, was it a decision which 
>involved all the factors in play? Switches, diodes, transformers, 
>performance goals, and marketing.
>We seem to have grown to a point in this society which presumes that more is 
>better than a lot more is even better still.
>Sometimes more is not better, it is just more.
>To me, the promise of a few more watts resulting from a slightly increased 
>high voltage and possible slightly improved IMD (I'm guessing on that one) 
>just aren't worth the potential damage to other components I can't replace 
>and paying twice as much for filter capacitors as I would need to.
>Just some ramblings for your consideration.
>Paul K0UYA
>
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Paul -

Here,here.  I never understood why someone would want to re-engineer vintage equipment.  If you want a modern station, get modern gear, it's so far ahead of the game anyway.  If you want to keep your beloved Heathkits running, great, but you're dealing with 30-year-old+ technology that probably should just be enjoyed it for its own sake.

Fred - KG6NYK

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