When I rebuilt my ST-70, I replaced the power transformer. I found the old one recently cleaning up the garage, and tested it. I used a variac set at 60 VAC, so I doubled the readings (the readings below have been doubled already). All the voltage readings are in spec per Bob's list EXCEPT:
Green/Yellow to Red/Yellow read between 6.3-6.4 VAC (instead of 3 to 4)
Brown/Yellow to Red/Yellow read between 8.8-9.2 VAC (instead of 3 to 4)
So it looks like the transformer is bad to me. Only the white wires had naked wire inside the bell, so I heat shrunk them prior to testing.
I have no problem tossing it if it's really bad, I'll save the two bells and bolts/nuts if someone wants them for a restoration.
You guys concur this thing is toast? I'm thinking so.
Jason
Green/Yellow to Red/Yellow read between 6.3-6.4 VAC (instead of 3 to 4)
Brown/Yellow to Red/Yellow read between 8.8-9.2 VAC (instead of 3 to 4)
So it looks like the transformer is bad to me. Only the white wires had naked wire inside the bell, so I heat shrunk them prior to testing.
I have no problem tossing it if it's really bad, I'll save the two bells and bolts/nuts if someone wants them for a restoration.
You guys concur this thing is toast? I'm thinking so.
Jason
Last edited by j4570 on Sat Dec 07, 2013 11:28 am; edited 1 time in total (Reason for editing : Clarification)