I had a bucket full of the Motorola conduction cooled tetrodes (
similar to 4cs250) tubes pulled from repeater and pager amplifiers. Got a
deal on them, I thought, at a hamfest. Just about all of them were bad. It
seems that commercial operators usually did not do anything until there is
a failure.
73
Bill wa4lav
At 03:28 PM 11/1/2007 -0400, Joe Staples wrote:
>We have an Alpha 78 (3 holer) which has a bad (shorted) tube and need a
>replacement. We have found several 8874 tubes of questionable origin and
>unknown conditon. What is the best way to if one or more of them is
>usable as a replacement ?
>
>We have access to another Alpha 78 which appears to have three good tubes
>(usually 1400+ watts into a Bird on 40 M). Would swappng one of its tubes
>with an unknown and checking the effect on the power output be OK
>? (We're concerned that if an "unknown" tube is shorted it will crater
>the Alpha.) Another alternative would be to remove all but one of the
>"good" tubes, check the power out (with low drive) and then replace it
>with an "unknown" ?
>
>Any suggestions would be appreciated. Unfortunately the "sick" Alpha
>lives in another country ... we need to known good replacement before leaving.
>
>Thanks.
>
>Joe, W5ASP
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