[Boatanchors] Diode replacements for 866 tubes, ratings needed?

[Rick Poole WA1RKT]

From: "Rob Atkinson" <ranchorobbo at gmail.com>
Sent: Tuesday, November 11, 2014 6:23:53 AM
>>
>> You can also put in 3B28s instead of silicon.

Good morning, Rob.

Yes, but the 3B28s are even more expensive than the RF Parts 866 solid-state replacements, and I really need to do this project on the cheap.

>> What may be an issue is regulation with a mode like
>> CW since you are drawing a lot of current with each
>> dit and dah, then zero signal idle current.

That is my big concern.  This amp will be used with CW and SSB, mostly SSB, and I remain concerned about that choke-input back-EMF issue; reports are that this is most prominent with CW and its full-on, full-off mode of operation.  That's why I need to get a handle on how many 1KV PIV diodes I need to use in each leg of a full-wave rectifier.  The RF Parts 866 solid state replacements are rated at 10 KV PIV (and if I recall correctly, isn't the 866 also rated at 10 KV?) so if I want to be really paranoid about it I suppose should use 10 of those diodes in each leg.  So far I've gotten three answers to my question... one person said 5 is plenty, another said 6, and another said 8-10.  Hard to know what to do exactly except to just be ultra-conservative... those diodes are just 23c apiece so using 10 in each leg won't break the bank, exactly.

>> perhaps Heath designed it to regulate with CW.

One would certainly hope so!  Surely Heath didn't intend a four-811A amp to be used on AM as a primary mode.  SSB was just entering its adolescent phase when the Warrior came out, and CW was a LOT (!!!) more popular back then than it is today, so I have to believe they at least tried to design the power supply to be adequate on SSB and CW.  The Warrior power supply uses a 5-25 mHy swinging choke and an 8-uf capacitor, and full-on, full-off modes like CW are what swinging chokes are supposed to help mitigate.

Rick WA1RKT