[R-390] RE: Help with R-392

[Drew Papanek]

Jim Brannigan wrote:

>Wow, for a constant load, that capacitor is waay too big.  2,000 Mfd. 
>should
>be more than enough....

With a 3 amp load and 2000 uF filter cap you'd have about 8 or 10 volts of 
ripple (Hummmmmmmmmmm).

If I recall correctly, the R-392 has 2 input pins for the 28 volt source; 
one supplies the heaters and t'other supplies B+. (If I recall incorrectly, 
maybe it could be made so with minimumodification).

Some have reported improved performance by upping B+ to 35v or so while 
leaving filaments at 24v.  If one were to go that dual power supply route, a 
low quality 24v supply (maybe even AC?) could heat the filaments and a well 
filtered supply at higher voltage could provide B+.

The better filtered B+ supply would need less filter capacitance because the 
'392's B+ current requirement is miniscule compared to its heater current.

Drew

"Vicariously repairing and modifying R-390x via advice to others"

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