11-13-2006, 09:25 AM
The hum-bucking coil is part if the speaker filed coil pot, which is missing. It's obviously only needed when the "magnet" for the speaker is the filed coil. If you're subbing a PM speaker, it's not needed.
BTW, it's not a 400 Hz hum-buck coil. The 400 Hz. refers to the test frequency that the VOICE COIL is rated at it's 5.1 ohms impedance. An 8-ohm PM speaker will work fine.
You should check Play Things Of Past at http://www.oldradioparts.com for a NOS or pull speaker. Gary has lotsa stuff.
A large 1,100 ohm, 15 watt power resistor will sub for the field coil. Be sure you have plenty of clearance around it. It will get HOT. I'd suggest an aluminum-clad unit that will heat-sink nicely to the chassis with some thermal grease - just like a power transistor. Mouser sells them. 284-HS15-1.5KF $2.39
Spec Sheet: http://www.arcol.co.uk/uploads/products/hsseries-10.pdf
1.5K will be the closest and that will be ok, as the A/C line voltage is 120 instead of 115 so the B+ in the set should still be a nominal value.
BTW, it's not a 400 Hz hum-buck coil. The 400 Hz. refers to the test frequency that the VOICE COIL is rated at it's 5.1 ohms impedance. An 8-ohm PM speaker will work fine.
You should check Play Things Of Past at http://www.oldradioparts.com for a NOS or pull speaker. Gary has lotsa stuff.
A large 1,100 ohm, 15 watt power resistor will sub for the field coil. Be sure you have plenty of clearance around it. It will get HOT. I'd suggest an aluminum-clad unit that will heat-sink nicely to the chassis with some thermal grease - just like a power transistor. Mouser sells them. 284-HS15-1.5KF $2.39
Spec Sheet: http://www.arcol.co.uk/uploads/products/hsseries-10.pdf
1.5K will be the closest and that will be ok, as the A/C line voltage is 120 instead of 115 so the B+ in the set should still be a nominal value.
Chuck Schwark,
The Philco Repair Bench
[Image: http://www.philcorepairbench.com/images/philog3tiny.gif]
http://www.philcorepairbench.com
