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Thanks Steve. I do not any of the power supply, just the RF deck, but did work it and it pulls in at just under 22vdc -- 73 Nick KC0YKO

Thanks Chuck. I was clearly over complicating this just because I did not recognize the "plate circuit relay" terminology. You were correct, I rolled the variable power supply up and it pulled in at

Hal, Thanks for the reply. I do not have the power supply, just the RF deck. -- 73 Nick KC0YKO

Perhaps that relay was used in that application in an effort to reduce the voltage/current to operate it to low values, such as from a later-model (but older) transceiver with limited T/R relay

Dear Nick, My GUESS is the P&B magnet is 24 to 28 Vdc. However, if you trace the wiring to the coil, back to the power supply, you may there deduce the coil voltage by energizing the xfmr primaries.

Years ago the coil of a plate circuit relay was in series with the plate of a vacuum tube set up to conduct at the pull in current when the tube was biased on. Using ohms law, 0.009 A X 2500 ohms =

All, I have an old homebrew RF deck that the T/R rely is a Potter & Brumfield LM11-2500. I can't find what the coil voltage is. In the 1954 P&B catalog the LM series is titled?Sensitive Plate Circuit

Albany County Fasteners: https://www.albanycountyfasteners.com/Phillips-Pan-Head-Machine-Screw-M4-x-7-p/1066-1010.htm K9ER Lowes have them for delivery!! Home Depot seems to be down here in UK this

I have recently acquired a Ten-Tec Centurion model 422 that is in very nice condition, but has a blown up bandswitch and the plate tuning capacitor was arced.? I might be able to salvage the

Lowes have them for delivery!! Home Depot seems to be down here in UK this morning Im sure some specialists would have them cheaper for mail order When I am in the US on business I try and visit Home

As in any quality-designed-and-built power amplifier, yes, there is a good-sized, large inductor from the output of the pi-network to ground to guard against exactly this kind of failure mode. What

Actually, they read "222M"; so it was clear they were 2200 pF. A 5 kV-rated cap is not likely to withstand 3 kV plate voltage under highly-mismatched circumstances at the legal power limit (such as

Did the caps short and put high voltage on the antenna causing the amp meter to peg? Is there a rf choke at the output connector?

Those oem 220M? caps are each 2200 pf.? ( 6600 pf in total for all 3 of em in parallel). The problem with discs is..... current handling capability.? ?Upper HF will result in the highest RF

Actually, Adrian, I'm glad I didn't buy one of those, because finding short M5 metric screws here in the back-country of the USA would have been a real challenge? 8-D 73, Steve K0XP

I asked to join the 9500 group a week or two ago, but never heard back. I did search the 87A group's archives and have seen Glenn post there. But I've never seen any discussion of any other amp other

There is an Alpha 9500 group HERE: /g/Alpha9500 Glenn, AE0Q posts/replies there often. 73, Alan W5ARM

True, for that one cover page; however, the links don't go through the Wayback machine, so they don't come up with pages. One has to copy the indicated url for a link into wayback machine in order to

W4ZT.COM <http://w4zt.com/> IS GOOD. 73, Mike Mysliwiec KF8OD

Yes, indeed; but my point is that all of this fantastic old amplifier reference material is now on it's way gone... so anybody wishing to personally archive any of it had better get busy saving