Re: Modifying W Plugin to use 6DJ8 Tubes


Bill Perkins <sales@...>
 

I know, it's seven years later. But I just acquired a Type W in the usual state, to wit, 8416's stolen.
It looks to me like there's enough empty space to fit a small mains-powered 18V regulated supply.
6DJ8 heater is 360mA vs 180mA 8416.
Normally R290 drops 77-50 = 27V at 180mA. We need to drop 20V more.
1) Add R9290 110 ohm 5W (20V at 180mA) in series with R290
2) Add isolated regulated 18V 6.3VAC-powered supply
across V124-V214-V114. It will put out 180mA, raising
V124-V214-V114 to its nominal 360mA so they will drop their
nominal 18V.
This can be done with a 24V transformer on pins 13-14 with
primary and secondary reversed, rectifier, filter, and LM317.
The transformer needs to have low magnetic field because it's
right next to the tubes.
Unless a miracle drops a few 8416's in my pocket, I might try this sometime.
But I'll try 12AT7s first.
I wouldn't, those parts aren't even remotely alike. The 'DJ has half the mu and three times the gm.

Bull

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