RadioBanter - View Single Post

August 2nd 05, 05:21 PM

wrote:

You haven't posted anything contrary to the +/- 10% rule given by RCA.

Geez, Frank:
I was answering a specific question posted earlier: "If you take a tube
that has reached end-of-life with a reduced heater voltage; I wonder if
it would still have a bunch of time left at the correct heater voltage?"

I noted that the answer was yes - and that it is a common (recommended)
practice with certain tubes in certain types of service (I.E. running at
reduced voltage until the inevitable emission fall-off required
gradually restoring full filament voltage).

I'll further note that many tube testers (B&K 700 series, for instance)
have a "Life Test" where the filament voltage is reduce by some amount.
If the tube is "fresh" emission falls very little. If the tube is
"long in the tooth" - emission falls significantly. This shows that
tubes that are in trouble at reduced voltage can still (for a time)
perform OK at "rated" filament voltage.

This is all I was addressing in my earlier post; and demonstrate even
further in the above.

--- So what's your point? Where did I imply I was going to comment on
RCA's "rule" - contrary or otherwise?

But now that you make an issue of it -- and so as to not disappoint you
- I will post something "contrary" to RCA's "rule":

Mullard's general recommendation was +/- 5%.

Were RCA's tubes that much "better" than Mullard's that they could stand
twice the variation?

Or was Mullard more concerned with quality and how their stuff was
used-- while RCA rated their tubes as being just mass-market junk?

That oughta stir some crap... Happy now Frank? Something to sink your
ever present teeth into?

Sheesh.
--
randy guttery

A Tender Tale - a page dedicated to those Ships and Crews
so vital to the United States Silent Service:
http://tendertale.com