3-500Z vs 3-500ZG

[Sandy W5TVW]

At 01:50 AM 9/11/97 +0000, you wrote:
>Not sure about the 3-500ZG designation but I am referring to the
>graphite plate 3-500s.
>
>My friend, WA4VWR, needs to replace a 3-500Z in his SB-220.  He doesn't
>believe he should just replace one single 3-500Z with a 3-500ZG but
>he wants to know, if he replaces both of his Eimac 3-500Zs with the
>3-500ZGs, will he get less than, the same as, or more rf output with
>the exact same driving power?  It's a good question that I certainly
>didn't have the background to answer.

I would not...REPEAT would not...replace just one tube this way!
Where tubes are in parallel or push-pull, it is NOT GOOD practice to
install a set of tubes from different manufacturers OR different
'permutations' of the same type!  You are asking for possible problems!

The same applies to putting say: a 6146 and 6146A, or 6146W and 6146B,
in a rig that uses two of them!  You also run a risk of unbalance by replacing
just one tube with a like manufacturer and type if the remaining tube has
a lot of time on it.  This is especially critical in some of the ceramic
tubes like
the 4CX250B and the 8122.  Manufacturers sometimes design provisions for
 adjusting bias on each tube seperately to equalize idling current.

73,
E. V. Sandy Blaize, W5TVW
"Boat Anchors collected, restored, repaired, traded and used!"
417 Ridgewood Drive,
Metairie, LA., 70001
ebjr at worldnet.att.net
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