Blunderof the Week

[dieseljeep]

Originally Posted by Winky Dink

I read a number of articles and forum posts on resistance line cords.
I had already replaced the two 1200 ohm/3W resistors 1200 ohm/7W ceramics. So I only have to deal with the 566 ohm line cord resistance.



Options that have been recommended include (1) Reproduce a resistance line cord (2) Replace the 35V rectifier with a 117V rectifier (3) Replace line cord resistance with in-chassis resistance (3) Replace line cord resistance with capacitance.

Option 1 is ill-advised (for me) for a number of reasons, and I'll have to pass on option 2 because I want to preserve the original tube line-up.

Option 3 is viable because the heat can be dissipated by cutting a hole in the wooden chassis base to vent the heat into the battery compartment space. I can cobble together 3 or 4 resistors to get 560 ohms at 24 or 25 Watts.



Option 4 is the clear favorite. Informed sources recommend experimenting with estimated capacitance to achieve the desired voltage drop, but I can't do the math to even make an estimate.

Can someone give me an estimate of the capacitance needed to drop 120VAC to 35VAC?

Finally, other than a few motor-start caps, I've been unable to find nonpolar AC capacitors in Mouser, DigiKey, Allied, or the usual vintage suppliers. I'm sure they're there, but I'm probably not using the right search terms.

I've approached that problem a different way.
Install a standard line cord and use a one amp silicon diode and about a 150 ohm 5 watt resistor. Leave the tube in there, for appearance.
BTW, if you look at the newer Warwick models, they switched to a 117Z4, in the later runs.
I've also used 117Z6's, as well, but the socket has the be rewired.