[ARC5] Plate modulating a BC-696 or BC-459

[Tom Bridgers]

If you have a stand-alone modulator capable of plate modulatingsay a BC-696 or BC-459, a short note in the June 1953 issue ofRadio-Electronics (page 105-106) might help if you experience alot of distortion.
The article says:o Replace R-78 (51 ohms), that leads to the 1625 screens, with aa 50,000 ohm 20 watt resistor.   o Now disconnect the screen lead from pin 4 of the power inputreceptacle, and connect it to the PA B+ pin, which is pin 7.
o Replace R-76 (20 ohms) that leads to the PA coil with a 2.5 mh300 ma RF choke..
o Replace the plate bypass capacitor, C-66) with a .002 mfd,2000 wvdc capacitor.
o And finally, for AM service, connect pin 7 on the power inputreceptacle to the top of the modulator's output transformer.
The article says the distortion before these changes was likelycaused by not modulating the screens (IOW, pin 4 might nothave been connected to B+ by the correct amount of resistance.)And that a substantial amount of the modulated voltage was bypassed to ground by the .01 mfd value of C-66.
Was wondering what experiences others have had with plate andscreen modulating the SCR-274-N series, and if you made any changes different than those recommended above to get goodresults.
If there is any interest in having a scan of the article (which includeda partial schematic), please let me know.   I'll be glad to make one and send it to you.Best,-Tom  KE4RHH