The need of equalizing resistors and spike caps due to diode manufacturing
variations pasted almost two decades ago. Old habits are slow to die.
There is various types of the diode stacks, and in industry many SEMICON or
ITT brands have been in service for years. The smaller stacks/blocks made
for consumer markets(ie:microwave ovens) aren't made to the same tolerences
nor do they have near the surge and peak ratings. General conversation often
finds people mixing facts between these different products since they are
doing same basic task, but with much different 'headroom'. The industrial
grade also leave your wallet much lighter....
Patrick
WB9IQI
At 10:05 PM 5/27/97 +0100, you wrote:
>> Why bother replacing a very heavy duty diode string with a string of
>> much smaller diodes in a case that lowers heat transfer?
>>
>> The potted diodes look pretty and are easy to mount, but that's the
>> only advantage. Everything else is a negative.
>>
>
> Well if you add in the cost of buying the equalizing the resistors,
>the capacitors to go across them, taking the time to build all that
>stuff up on a board, I still think the blocks are the best value. I can
>tell you from experience the ratings are well under rated from praticle
>use. I think the blocks use a better matched set of diodes in
>construction, that helps equalize the surge voltage across them. I have
>never found anything negative about using them! The guy selling them is
>great to deal with. He sent me my first set with out asking for the
>money up front. Said if I was not satisfied just send them back.
> I have still never had a failure in the blocks. Even when the Millen
>HV connector blew up and directly shorted the B+, it blew the 40 amp
>primary fuses and never took out the rectifer blocks. Or the time my
>plate current meter caught on fire, it looked like an arc welder going.
>I have built many strings over the last 20 years but for serious
>applications the blocks have my vote.
> I was also scared to use the blocks before I had tried them and
>questioned the ratings. I have no dought its worth the extra money and
>they can easly handle twice the current rating continously. I thought
>there was some heat so I mounted them on something to sink them. After
>several hours use there is no noticable heat to the touch.
>
>Ron W4WA
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>
>
>
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>
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