Adjusting Forplay III heater supply resistor for different tubes

[Doc B.]

Here's some info from PJ regarding changing the resistor in the heater supply of a Foreplay III to handle different types of tubes. Add up the total heater current draw of the tubes you plan to use and adjust the resistor to the appropriate value listed below. The resistor comes before the filter cap, so its value is not linearly related to the current. Here are some values as calculated:

0.3 amps 1.37 ohms
0.6 amps 0.62 ohms (as used in stock Foreplay III)
0.9 amps 0.35 ohms (close to the upgraded Foreplay III)
1.2 amps 0.22 ohms
1.5 amps 0.15 ohms
1.8 amps 0.10 ohms (as used in the S.E.X. amp)

Two 6SN7s in a stock FP-III want 1.2 amps; three in an upgraded FP-III will want 1.8 amps.

[baddog1946]

Hey Doc:
I was working on my "Foreplay III line stage this afternoon and while wiring up the selector switch I found a horrendous error in the build manual.
the copy of the manual I have shows two connections for the red wires to terminal (20) and.
This is definitely incorrect but the photo shows it correctly. If one was to follow the written instructions first you would be making a mistake.
I think you should check the manual text and advise everyone who bought the kit recently to check this.
I don't know how old the edition of the manual I am using is but I ordered my kit on Feb 17, 2010 and received this manual with it.
this is FYI and anyone who has the edition I have. Be careful! Hope no one else has already run into this.
Regards
baddog1946