Johnson Viking Valiant 866 rectifier

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kc4umo:
Good evening all.

A friend brought his Valiant over to the shop due to no output.

I fired the rig up and and let it warm up for about 5 minutes. Flipped the plate on and started hearing a hiss like there was something arcing.  Shut the rig off and started inspecting things.  Found a terminal strip for the 866 had carbon build up like it was starting to burn.  First thoughts is someone powered the rig up without letting it warm up or had the rig on its side.  He confessed to the latter.

At the moment I do not have any 866 or 3b28 tubes in stock.  And would like to get these mercury vapor tubes out of here.  I have heard of folks switching these to diodes and making it solid state.

I have plenty of 1N4007's, 5404. 5408, and 6A10 diodes in stock.  I would think if you did this there should be a resistor in series with the diodes. I also have some old tubes I could use the base off of.  Is my thinking correct?
I searched a bit today to see if anyone had posted a diagram on doing this but did not find anything.

Thoughts?

WD5JKO:


Buddy,

   Your picture shows solid state replacement modules for the 866 tubes. If that is what you currently have, then just repair the carnage where it is arcing. Also remove the 2.5v filament winding from going to the 866 sockets.

Jim
Wd5JKO

kc4umo:
Quote from: WD5JKO on November 27, 2017, 05:59:08 PM



Buddy,

   Your picture shows solid state replacement modules for the 866 tubes. If that is what you currently have, then just repair the carnage where it is arcing. Also remove the 2.5v filament winding from going to the 866 sockets.

Jim
Wd5JKO


Hi Jim and thanks for the reply. Yes those are replacements that I use for testing. Really did not want to give them up lol.  That's why I wanted to build a replacement in an old tube socket.  This rig belongs to an elderly gentleman  so I told him I would repair it at my cost.

N1BCG:
The good news is that the 866 Mercury vapor tubes have a fairly low voltage drop (about 15 Volts) so changing over to a set of 1N4007 diodes (4) should work. Given the higher supply voltage these days, plate loading should be set lower, such as around 300 mA for AM and 350 mA for CW.

WD4DMZ:
What type of solid state rectifier replacements are those? Any #?

Thanks, Rich

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