Re: Plate blocking cap in Alpha 76PA
¿ªÔÆÌåÓýThank you Peter and Chuck. ?I have discarded the Cera-Mite capacitor and ordered a .005 door-knob cap, with similar dimensions to the Cera-Mite, from Surplus sales. While waiting, I am finishing up the current work on the Alpha 76PA and will close it up for testing.? When the new cap arrives next week, I¡¯ll open the Alpha and retro-fit the new cap into the Amp. ? 73, Dave, w6de ? From: [email protected]
<[email protected]> On Behalf Of Peter Voelpel via groups.io
Sent: 7 May, 2025 22:14 To: [email protected] Subject: Re: [ham-amplifiers] Plate blocking cap in Alpha 76PA ? Same here, used exactly the same type to get more capacitance on 160m as a HT bypass capacitor It exploded after a few minutes. I assume those capacitors are not suitable for RF. ? 73 Peter, DJ7WW ? ? From: [email protected] [mailto:[email protected]]
On Behalf Of Chuck Neal via groups.io ? Regarding replacing the plate blocking caps¡.if it ain¡¯t broke, don¡¯t fix it.? ? I blew up one of those red plate blockers by Ceramite.? It turns out that they are not rated for significant RF current, so¡ ? Keep the original caps would be my suggestion¡ ? -Chuck K1KW ? From: [email protected] [mailto:[email protected]]
On Behalf Of Dave w6de ? I am doing some updating to my Alpha 76PA 3-tube amplifier.? I have switched the T/R relay to a pair of vacuum relays and changed the "relay" (AKA Send or PTT) request to send from 24 Volts to be a compatible 12 Volts for modern transceivers.? I am about to replace the original Alpha Plate Choke with a re-wound Ameritron style taller choke. While I'm at it I have a, new-but old, Cera-Mite 5000 PF, 15 KV door-knob capacitor.? I'm planning to replace the original plate blocking capacitors with this door knob cap.? The original plate blocking cap uses dual original 2000 PF, 6 KV ceramic disk capacitors. ? ? I've has this door knob cap a long time and I'm no longer planning on building a tube amplifier from scratch.? As you can see I've fabricated two copper straps to place the cap in the 76pa amp.? I fabricated these straps to put to door knob cap into a previous Alpha 76PA I had.? And when fastened in place it is quite sturdy and has adequate clearance from its surroundings. ? This amplifier will be kept in my station as a back-up for my Solid State PA.? I've found SSPAs to be less tolerant of operator errors than tube amps.? But I still like the instant on and 6 meter capability in my current SSPA (403A/Flex PGXL). What are your thoughts on this replacement other than it is overkill in this situation? ? 73, Dave, w6de ?
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