The PHILCO Phorum

I am almost finished recapping a model 16x (5 band) type 121. The tone control has two caps inbedded in the control and two in separate tin box. It is a 4 position control in position 1 a .006 mfd cap connects the plate of the 1st audio tube to ground in the next position it seems as though a .09 cap is in the circuit in the next two positions a .15 cap and a .5 cap are added to the circuit according to my schematic. The tone control had very little variation in positions 2, 3, and 4. There was no change after recapping. Is this typical? Could it be that the cap values on the schematic are not correct? The last two in particular seem a bit large for a tone control but my simple analysis would be that lowering the values would result in even less variation in tone between switch positions.

Thank you,

JT in Albany

I made a mistake in that the radio is a Model 16 type 122. I also found another schematic that had cap values of .003, .025, .025 and .09. I swapped out the .006, .09, .15, and .5 called for in my original schematic and the variation in tone between switch points is much improved. Apparently, in the original setup after the .09 siwtched into the circuit the additional capacitance made little difference in terms of tonal variation. By starting from a lower base and narrowing the range of capacitance the second setup seems to hit the correct range in which the additional capacitance at each step differentiates the tone.

JT in Albany

Good to hear you found the problem.

I was away all day yesterday and could not respond before now, sorry.