>"There was a production issue related to Eimac and the two MRI equipment
makers who used the 8877."
Here's a chronological timeline from Dick Ehrhorn. It's an interesting case
study and a horrid time period for ETO. I know that the first 8877 QC
issues predate 1986:
In 1979, I nearly lost my college job as a result of several failed 8877s,
purchased new from Richardson Electronics. I don't know where Eimac's Ken
Atkinson is today, but he alone saved my job and my credibility with the
station owner. Ken sent a tested tube from the SLC plant and the transmitter
finally made licensed power.
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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 -- 09/87
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
Statistical data on average end of tube life in our MRI amps
(corrected from earlier off-hand estimates). Excludes small
"infant mortality" humps for both types @ 2400-2600 hrs.
3CX800A7 18,500 hours (very sharp peak
between 18,000 - 19,000 hours)
3CPX5000A7 In excess of 30,000 hours. (Of
course tube costs $2-3k in qty.)
Dick W0ID
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