09-01-2015, 10:19 PM
From the schematic, it looks like the field coil terminals on the speaker/output xformer assembly should have 1140 ohms between them. Find those two terminals with your ohm meter. Call them terminals #1 and #2, just for reference. Call the other terminal #3. Connect #3 to pin 3 of the 6F6G tube.
Between terminals #1 and #3 should read either 400 ohms or 1540 ohms. If it reads 400 ohms, then connect terminal #1 to the + side of capacitor 53 (8 uF) and #2 to the + side of capacitor 56 (12 uF). If it reads 1540 ohms, reverse the 2 capacitor leads (#1 to 56 and #2 to 53.)
If terminal #1 to #3 doesn't read near either 400 or 1540 ohms, then something is wrong in either the field coil or the xformer primary or one of the connections to them. Just for fun, measure between #2 and #3. You should get the opposite reading as #1 to #3.
I've never seen one of these; I'm just going by the schematic and assuming from what you said above that the output xformer is mounted on the speaker, not inside the chassis. If that's wrong and the xformer is inside the chassis, then what I wrote above won't work.
Once you have it wired, check it by measuring resistance between + of cap 53 and + of cap 56. Should be 1140 ohms. Between cap 56 and pin 3 on 6F6G should be 1540 ohms. Between cap 53 and pin 3 of 6F6G should be 400 ohms. Between 53 and 6F6G pin 4 should be a dead short, and between pins 3 and 4 of 6F6G should be 400 ohms.
Between terminals #1 and #3 should read either 400 ohms or 1540 ohms. If it reads 400 ohms, then connect terminal #1 to the + side of capacitor 53 (8 uF) and #2 to the + side of capacitor 56 (12 uF). If it reads 1540 ohms, reverse the 2 capacitor leads (#1 to 56 and #2 to 53.)
If terminal #1 to #3 doesn't read near either 400 or 1540 ohms, then something is wrong in either the field coil or the xformer primary or one of the connections to them. Just for fun, measure between #2 and #3. You should get the opposite reading as #1 to #3.
I've never seen one of these; I'm just going by the schematic and assuming from what you said above that the output xformer is mounted on the speaker, not inside the chassis. If that's wrong and the xformer is inside the chassis, then what I wrote above won't work.
Once you have it wired, check it by measuring resistance between + of cap 53 and + of cap 56. Should be 1140 ohms. Between cap 56 and pin 3 on 6F6G should be 1540 ohms. Between cap 53 and pin 3 of 6F6G should be 400 ohms. Between 53 and 6F6G pin 4 should be a dead short, and between pins 3 and 4 of 6F6G should be 400 ohms.
John Honeycutt
