peter jones wrote:
>> Another thing that could cause HV diodes to heat is if frequency
>> (actually dV/dT) is too high. By that I mean:
>> 1) Oscillator frequency actually too high
>> 2) Resonating capacitor(s) too low in value or open.
>>
>> Either way the diode doesn't get a chance to fully turn off as the
>> reverse voltage rises, it ends up pulling current and gets hot.
>>
>>
>
> has anybody tried different diodes?
> not related to this problem i mean, just in general?
>
> in europe HV diodes are hard to get and expensive, as i just discovered when my scope started showing symptoms.
>
> given the fact that you cant walk down the street here without tripping over vga monitors sitting out by the side of the road, has anybody tried extracting the diodes from a 32Khz lopt?
>
In the old days you had a transformer followed by one external HV
rectifier. Now they wind a partial secondary, insert a much lower
voltage rectifier, wind some more of a secondary, insert another
rectifier, wind the rest of the secondary, add ANOTHER rectifier and
then DC leaves the transformer. OR you make a lower voltage transformer
and build a voltage multiplier. Either way, even if you could extract
the rectifiers I doubt they would be usable.
Mostly why we keep sticking to the same part is because of mechanical
size. Most better parts are different diameters so they don't fit. At
some point either the connection for the rectifier will have to change
to allow using a different part or something unconventional will happen
(like going old-school and using a tube).
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Received on Thu Feb 26 11:44:00 2009
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