The Secret Society of Lathe Trolls

EpicenterBryan wrote: ↑

Mon Sep 20, 2021 9:24 pm

I have a manual for the D7 including schematics. Alan Graves bestowed upon me his collection before he passed away.
I can provide a copy for a fee (USA only). Sent me a PM.

Bryan

PM sent.

It's a type D7. Like this one (but not this exact one):

https://lathetrolls.com/viewtopic.php?t=7960

I assume that a manual and/or schematics aren't to be found, but figured I'd ask anyway. Thanks.

Hi Mark, I removed it completely but no markings. I then "dissected" it. Cap 1.jpg Coiled lead windings at either end with a core of black material. Infinite resistance measured when probing across a millimeter of the black core, so it looks like it is a cap. It would seem I can swap in anything aro...

Hi, The cap of the 6C6 is the signal grid, not the plate as is the case with higher power tubes like you might find in the horizontal output on a TV. So, there are no high voltages or currents present. Just low level, high impedance. Mic grade shielded cable should be fine here. Mark Hi Mark (or an...

Never mind. Apparently, I was measuring the wires for the hum bucking coil. The field coil wires are tucked further back. There I measure about 1,000 ohms.

I measured it again, this time with the tan lead wire disconnected from where it was soldered to the terminal strip, i.e. free floating. The black wire is still connected to the lug that also ties into the lead that goes to the main speaker coil. I'd think that would be sufficient to get a true read...

Hi, That speaker has a field coil rather than a permanent magnet. The field coil was usually used in dual duty as a choke in the B+ supply and as an electro-magnet for the speaker. I'm guessing that the speaker is fine, but the B+ supply is dead (bad rectifier tube or shorted filter cap, etc.). Not...

Hi Mark,

Thanks for clearing that up for me.

Matt

Side issue question involving the female three pin Cannon connection in on the top of this lathe. The original wire is broken and needs to be replaced. The center conductor ties in with that of the wire connecting to the anode cap for a 6C6. The shielding of the Cannon wire is tied to ground via wha...

Hi Mark, Thanks for the detailed reply and advice. Very helpful. I had forgotten about field coils. The last (and only!) time I dealt with one was during the repair of a Zenith 5S237. All the tube filaments are lighting up and all caps were supposedly replaced, but I'll pull the amp to check that th...

New here, but not new to working on electronics. BUT I am new to lathes, and could use some help troubleshooting this one. The owner says that there's no sound from the speaker. Before I pull out the amp, I want to check what I can to confirm that either the speaker, the output transformer, or the c...