I doubt it's a parasitic, but if you want to explore that, Measures has
his special parasitic kits for sale on his website.

Cheers as they say
Dale, K9VUJ






In article ,
Skipp can be reached through the sonic server
wrote:

The grid to cathode short is a clue... You might want to review the
parasitic issues with this and similar amplifiers. A parasitic "bang"
might be the source of this and or similar problems.

Have a look at Rich Measures (ag6k) web page... used to be at
http://www.vcnet.com/measures but is now moving (or has moved to)
http://www.somis.org

There are protections for grid to cathode shorts in 3-500z amps. I like to
use a proper triple bypassed grid resistor and have never had grid/cath
shorts in any amplifier with said after an upgrade to the parasitic
network(s).

If you have questions, you can contact me through the sonic server Email
icons or review Rich's web page and he will also reply to Emails.

cheers and good luck
skipp
http://sonic.ucdavis.edu

: "Chuck \(Jack\) Hawley" wrote:
: A friend has an AL80B (bought new) and is on his fourth 3-500 in two years
: or so. It just developed a grid-cath short. Supposedly there was a batch of
: tubes that were prone to go bad, but the latest ones from MFJ are supposed
: to be ok. Apparently not or something is wrong with the amp. He's a good
: operator and seems to be tuning and operating within safe limits for the
: AL80B. The latest tube is an Amperex as was the first ones in the reported
: bad batch. He reduced the filament voltage last time from 5.7 (from the
: factory) to about 5 before the present tube was installed.
: Any ideas?
: Chuck, KE9UW



--
Dale J.
Bloomington, Minnesota

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