[Amps] What were the problem date codes for Eimac 8877s?

[Peter Chadwick]

Here's a copy of what I was sent on the subject: It includes some infor from Dick at ETO


>Here is the 8877 info. Looks like you want to avoid 8877's with a date
>code anytime frm 1986-1988.
>For those who expressed interest and/or skepticism about the issue,
>here's a reasonably accurate time line of events from our QA records.
>Eimac puts 8877 heat dam design change into production -- ~08/86
> (Completely unknown to us at the time)
>First identified tube failure at MRI end-customer field site -- 12/86
>First suspect tube routed back to Eimac via ETO -- 01/87
>Meeting with Eimac -- 05/87
>FIrst fix devised by Eimac; second meeting w/Eimac -- 07/87
>Third & fourth meeting with Eimac -- 08/87
>Initial Eimac delivery of "fixed" 8877's -- 09/97
>Delivery of "fixed" 8877's to customers -- 10/87
>Problem re-surfaces @ field customer(s) -- 03/88
>FIfth meeting with Eimac --
05/88
>Second fix devised by Eimac -- 06/88
>Initial Eimac delivery of 8877's with second "fix" -- 08/88
>Delivery of "2nd fix" 8877's to MRI customers -- 09/88
>Completion of field upgrade with replacement tubes -- 05/89
>** NOTE: Because tube date codes approximate
> shipping rather than manufacture dates,
> they may vary ~1-3 months from the
> event dates given above.
>Largest MRI RF amplifier manufacturer's record
>of 8877 usage by year:
> In new amps As replacements
> almost 100% due to
> heat dam/g-k shorts
>1987 500 575
>1988 650 1600
>1989 500 550


73

Peter G3RZP