[Chas]

462ron...If your signal generator has a 3 prong plug so it is grounded and you connect the ground from the signal out put to either the chassis or B-, you have put a direct short to ground depending on which way the AC plug is in the receptacle...

462ron's comment on the direct short can also occur to the live of the generator test lead. Many service instruments do not protect the signal attenuator thus the resistor/network gets roasted, occasionally destroying any wafer switch as well. For RF generators, loose coupling often works well via just a couple of turns of the RF lead. An alternate is a small coil of ten turns in the vicinity of the antenna coil or mixer output.

There seems to be a trend to ground service grade instruments by adding a grounded 3-wire cord system. The AA5 (typical) live chassis receiver was very popular at the time these instruments were made. Servicemen routinely used isolation transformers, some did not   depends how much they trusted their knowledge of fault circuits and their work environment, UGH!

Replacement of components without a through triage can often be problematic. Resulting in an inoperable receiver, that will now require stage by stage analysis to repair as well as finding the initial fault.

"Triage" is simply verifying that RF/AF coils are viable, tubes good, speaker functional. Then replace only the power filter condensers, any clearly destroyed components as well as any AF coupling condensers. Carefully power the set and there is a good chance it will work. Note any peculiarities. Then, replace capacitors/resistors as required but two at a time and then power the set. At any point the set quits, retrace to the last two components. Be aware on occasion, a defect can occur on an aging component during a test. This is often caused by leaking bypass condensers overloading a voltage dropping resistor.

Components in the RF sections such as mica/ceramic condensers should not be replaced routinely, often they are temperature compensating types that may not be available. A receiver that will not align is often a clue there is a failure with these components. Do NOT rotate a mica condenser on its leads as that breaks the seal in the Bakelite housing allowing the entrance of moisture or mechanically break connections and eventual failure.

Classic vacuum tube electronics on a metal chassis has now reached the point that any soldered or riveted connections to the chassis will be problematic... Despite a continuity measurement the connection can act-up when passing RF creating havoc in RF/IF circuits.

These are YMMV suggestions to help avoid "creating" what professional servicemen referred to as a "Tough Dog"...

If the receiver safely stays powered without overheating, consider safely injecting an audio tone into the AF circuits, this is done at the grids via a .01 blocking capacitor, Actually since the AF generator may also be grounded set up a .02 on the return lead and a .02 on the hot lead of the AF generator. That will protect the AF generator from a AC line short. Trace this tone backward into the circuits until it disappears at the detector. From that point switch to the RF generator, modulated, and set for IF frequency and test continuing backward to the mixer grid. If there is still no clear indication of what is happening the Oscillator may be non-functional generally from either a poor connection, failed coil or poor contacts on any band switch. DO check the phono-radio switch for poor contacts.

Tune the receiver to 1mhz inject a RF un-modulated signal that is 1mhz plus the IF frequency the may come alive at 1mhz. An alternate to oscillator test is to use a pocket portable radio and tune for the oscillator radiation at 1mz plus IF. The should be a carrier un-modulated (so called "dead-air") detected by the portable radio. A bit of twiddling is required to sense the radiated oscillator if it is working.

The phono does not make noise may be from a melted salt crystal. The signal can be detected on a 'scope if it is working. The phono cartridge can be rebuilt.

I hope these are workable service methods for you.

Chas