>
>Rich Measures wrote:
>>>I don't use equalizers in any new power supply, but I do take care to
>>>use more and better matched diodes - so we agree on that much, Rich.
>>
>>Indeed, Ian. And do you measure the avalance potential of each unit?
>>
>No, because I don't have the capability to measure it at the actual
>junction temperature it will reach when operating at full load.
Hair dryers are not costly.
>
>Instead I buy quality parts and rely on uniformity from mass-production
>- and if in doubt, use more diodes. That goes along with using mains
>filters and VDRs to minimize the risks from incoming line-side spikes.
>
>
>>>On the other hand, I won't tear the equalizers out of existing power
>>>supplies that have proved reliable.
>>>
>>If you have 4x as much piv as needed, it should play ok..
>
>Let's not overstate the risks. Hundreds of thousands of equalized diode
>strings in older equipment (designed back when PIV was expensive) are
>running successfully and reliably at lower PIV margins than 4x.
>
Good point. The unequalized, ancient, non-avalanche type diodes in the
SB-220's anode supply have a safety factor of c. 35%, yet they do pretty
ok.
>I would never build a new rectifier stack that way, but still think the
>best strategy is to let existing ones run till they drop... if they ever
>do...
>
The ''equalizer'' resistors used in my TL-922's hv supply are rated at
250v max. Does it sound like good engineering practice that they are in
parallel with 1000piv diodes?. If one of these resistors fails, the
string of diodes is virtually certain to domino-short.
cheers
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