866A Power Supply ?

L

lugnut1

Member
I'm using 2x866A in a full wave DC power supply. Power transformer is 1300vct @.5A with a shield wire. Filament transformer is 2.5vct@10A. Choke input filter is 10H@05A 65ohm. Can I use a CL-80 in series with the mains primary to slow things down while the filaments heat up? Would adding an additional thermistor in series with the mains secondary also be necessary? I've thought about using a relay to delay the B+, but this is simpler and hopefully has enough delay to work ok. I have all the trannys & tubes on hand.
Any thoughts greatly appreciated!
 
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The 886 data sheet says filament needs 30 second heating before plate voltage is applied. You’ll still get plate voltage instantly even with the thermistor in the circuit, and since there is no conduction until the filament of the 866 warms up, you’ll get full secondary voltage instantly on the 886 plates.

So I don’t think a thermistor will get you what you need.
 
Use an amperite time delay relay. Looks like a 6SN7, pick one with appropriate delay. Can find them surplus pretty cheap.
 
maxhifi said:
Use an amperite time delay relay. Looks like a 6SN7, pick one with appropriate delay. Can find them surplus pretty cheap.
Click to expand...
They also come in 9-pin mini packages. I do believe the contact voltage rating is the same.

In any case, you do need to light up the 866's for half a minute before giving them *ANY* HV to their plates.
cheers,
Douglas
 
Thanks for the info! My plan is to use this power supply as a basis for an amp built around a pair of 100w Chicago BO-14 output transformers.
 
While the 866A is a very good and rugged rectifier,it is also,like all mercury vapor types,extremely noisy. In many applications,the need for shielding is a must,and filtering can also be rather demanding.And pre-heating is an absolute requirement,not just a casual suggestion.And if you ever move them from a vertical position,preconditioning is a must in order to redistribute the mercury before HV is applied.A unique tube these days,but it wouldn't be my choice. But they sure do have a pretty glow!
 
Since I have almost everything on hand I thought I'd go for the glow on this one. Any thoughts on how to use the BO-14's would also be welcome. Perhaps another thread when the PS is done.
 
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