SPRAGUE capacitor for Tektronix 4051.

[drlegendre .]

"The mains-side filter caps for switching supplies tend to be large in
capacitance (100-200 and > uF), and typically are not suitable for
replacing the ~ 8-40uF B+ filter caps in vintage tube electronics that have
tube rectifiers."

This is true.

All of the common vacuum diode rectifiers have fairly significant
limitations, for the 1st cap in a cap-input PSU.

Devices like the 5U4 and 5AR4 might tolerate as much as 40-80uF at the
first pole (which is still fairly light), while others such as 5V4 might
only tolerate as little 4uF.

Point of my post - it seems as if the tube audio folks were being blamed
and/or shamed for the cost of high-voltage electrolytics.. and if anything,
they keep both the volume and demand up, and the prices reasonable.



On Wed, Nov 16, 2016 at 11:37 PM, Brent Hilpert <hilpert at cs.ubc.ca> wrote:

> On 2016-Nov-16, at 8:44 PM, Jon Elson wrote:
> > On 11/16/2016 10:10 PM, drlegendre . wrote:
> >> "Note the "tube audio" folks gravitate to that stuff and tend to cause
> >> seriously sick prices, because tubes."
> >>
> >>
> >> FYI - I've installed dozens of the new-production CE / Mallory caps,
> all of
> >> them in the 350-525V range. Zero complaints, zero comebacks, in as long
> as
> >> I've installed them. For those of us in that field, they're like a gift
> >> from the gods.
> >>
> > Vintage tube audio doesn't need to get involved, except for the
> old-style twist-lock Mallory cap design.
> > All the off-line switching supplies use either 250 V (120 supply only)
> or 400+ (120/240 supply) capacitors as the main input filter. So, at least,
> capacitors in that voltage range are STILL being made, and are in all
> computers, TVs and other home appliances.  (Yes, I know the OP needed a 30
> V cap.)
> >
> > So, some other tube gear replacement parts may be scarcer than hen's
> teeth, but the HV caps are easily available.
>
> (tending off-topic . . )
>
> As long as one is being careful about the size (capacitance) of the
> replacements.
> IME, I've found limited benefit in trying to use/source/scavenge
> switching-supply caps for tube gear.
>
> The mains-side filter caps for switching supplies tend to be large in
> capacitance (100-200 and > uF), and typically are not suitable for
> replacing the ~ 8-40uF B+ filter caps in vintage tube electronics that have
> tube rectifiers.
>
> Maybe there are smaller ones in the smaller switching supplies around
> these days, I haven't looked at those recently.