SPRAGUE capacitor for Tektronix 4051.

Brent Hilpert hilpert at cs.ubc.ca
Wed Nov 16 23:37:16 CST 2016

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.

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