Follow up on my recent problem. D8 and D9 changed (one was about 0.7 volts at 1A forward current, the other about 1.2 volts.) It has had heavy use in a couple of contests since with no problems.
Brian D via Elecraft <[email protected]> wrote: > D10 S/c gave me the same problem. several years later it has recurred but > is intermittent this time. I'm about to investigate suspect heat has > affected a dry joint this time. > > If yours is an early amp then there are modifications to bring it up to > current spec. I seem to have lost teh details of that. > > > > "Earl via groups.io" <[email protected]> wrote: > > > Oliver it looks like D10 is cooked not D8? > > > > On Sat, Jun 6, 2026, 06:32 Oliver Bross via groups.io <oliver= > > [email protected]> wrote: > > > > > Hi all, > > > > > > I’m troubleshooting an Elecraft KPA500 that has the following symptom: > > > > > > - TX output is normal (500+ W) > > > - In STBY, receive is normal > > > - In OPER, receive is attenuated significantly on all bands > > > - Elecraft support suggested an internal T/R switching issue > > > > > > While inspecting the T/R Switch Board, I found D8 appears damaged and > > > may need replacement. > > > > > > From the KPA500 schematic I have, D8 on the T/R Switch Board is > > > labelled *S1M*. D7 and D9 in the same area are also shown as S1M. > > > > > > Before I replace it, can anyone confirm: > > > > > > 1. Is D8 indeed an *S1M (1A, 1000 V SMA rectifier)*? > > > 2. Were there any board revisions that used a different diode? > > > 3. Has anyone seen a failed D8 cause receive attenuation in OPER mode > > > while TX remains normal? > > > 4. Are there other components on the T/R Switch Board I should check > > > at the same time (relay contacts, PIN diodes, switching network, > etc.)? > > > > > > I’ve attached a close-up photo of D8 and can provide the relevant > > > schematic section if needed. > > > > > > Thanks and 73, > > > > > > OliverOM0RX > > > > > > > > > > > > -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent > > to this group. View/Reply Online (#3570): > > https://groups.io/g/elecraft/message/3570 Mute This Topic: > > https://groups.io/mt/119676095/324488 Group Owner: > > [email protected] Unsubscribe: > > https://groups.io/g/elecraft/leave/1119757/324488/822510839/xyzzy > > [[email protected]] -=-=-=-=-=-=-=-=-=-=-=- > > > > > > > > > > -- Brian D G3VGZ G8AOE G3T IO94im ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
