[wa2ise]

Originally Posted by maxhifi

To answer my own question, I looked at things like this http://www.smpspowersupply.com/ATX_p..._schematic.pdf
If the junk atx supply I have has such an input filter there's a Crosley which will be receiving some surgery tonight.

That should work, I'd use everything from the powerline input to the bridge rectifier. I'd also leave the ground not connected. We want to keep RFI from riding in via any ground or power wire.

The power resistor is 300 ohms, but this set runs the output transistor with a B+ of about 90V. So it's not the same as a battery portable.