>
>I have a Johnson porcelain socket that I modified with grid to ground
>tabs for the 3CX1500A7/8877. Unfortunately, in my chaotic New York City
>radio shack, I cannot for the life of me locate my Eimac Data sheet for
>the pinouts. Perhaps someone can help? Looking at the socket underside
>(with the indexing pin at the 6 o'clock position, I think that's pin 4.
>Moving clockwise the numbers are 5, 6, & 7. Moving from the indexing pin
>(#4) counterclockwise, that's 3,2,&1. Would like that confirmed for
>obvious reasons before I complete the final wiring. Any assistance would
>be greatly appreciated. Ron W2CQM/2
>
/\ Ron -- Pin 4 agrees with the Eimac drawing. Also, pin 5 can be
identified because it is connected to the center pin on the base.
- Free, unsolicited advise: I have autopsied a number of 8877s that had
been damaged by a cathode/heater arc which opened the heater. To prevent
such an occurrence:
1. connect pin 4 (cathode) pin 5 (heater).
2. gnd neither side of the heater.
3. use an approx. 10 - 20 uH bifilar heater choke. Check for
undesirable ham-band resonances with a dipmeter. The pin 5 side of the
heater choke can be used for the cathode/B- return.
good luck
- R. L. Measures, 805.386.3734, www.vcnet.com/measures.
end
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