Thanks to all that replied with info. I had hoped there would be more
definitive data, but the mystery still remains.
Here's what I know for sure:
In 1969 Amperex was owned by North American Phillips. The 3-500Z *MAY*
have been manufactured in Holland. It may have been inspired by the
3-400Z but according to the short form catalog I have, it was NOT just a
3-400 with a bigger anode. There are other differences listed. The Mu at
this time was 200 or more depending on which set of data you are
inclined to believe.
At some point between 1969 and 1980, manufacturing was moved to France.
Amperex was still owned by Phillips in 1980. It is not known if the Mu
spec was changed coincidently with the move or not. My tubes are date
coded 1980.
In 1985 or 1986, Amperex was purchased by Richardson Electronics as part
of their world wide takeover of tube manufacturers. It is not clear if
only the name was purchased or if the production facility was included
in the deal.
Today, The Amperex name is still owned by Richardson. The tube is
manufactured in Brive, France by COVIMAG. It is not clear if COVIMAG is
a subsidiary of Richardson or just under contract for production. If you
go to the Amperex/COVIMAG/Richardson web page (which is not easy to find
by the way) and click on the 3-500Z data sheet, a PDF of the Eimac 1980
3-500Z data sheet pops up!!
What is clear is that at least once during the long production life of
the Amperex branded tube that the Mu spec changed. Possibly more than
once. What is very unclear is when these changes actually took place.
If current production tubes are built to the Eimac spec, then the RF
Parts statement that they take more drive is false. If the tubes were
built to the old Amperex spec, then the statement must also be false.
Some folks claim more drive, some say the same drive, but nobody offers
date codes for the tubes they used. The only way they could require more
drive is if the Mu were to be drastically lower or the user failed to
adjust the bias voltage for the proper idle current.
This matters to me for two reasons. First is that I'd simply like to
know the answer. Secondly I need to know to meet the design goals I have
arbitrarily established for my latest project. Yes, I know, there is no
on-the-air difference to be seen. But I already have a 1200 watt drive
limited amp. The whole object of this particular project was to meet the
1500 watt limit EVEN THOUGH I DON'T NEED IT!
It would be easy to plug them in a test but doing so even for a couple
minutes will drastically reduce the sell price if I do wind up selling
them. RF Parts currently lists Amperex 3-500Z's at $269 bux. Ebay prices
on tubes the are NIB with the seals intact will surely approach that.
Anybody interested at $500 for the pair postpaid USA?
73, Larry
--
Larry - W7IUV
DN07dg
http://w7iuv.com
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