you have tested some voltages and did the audio grid test and all is good. audio is working. you have eliminated audio as being a problem. somewhere the RF or IF is missing. as this happened while shoving the chassis into the cabinet the assumption is that something was disturbed either loose or touching. could be something as simple as the antenna came loose. tracing circuits in each section ahead of the audio section may reveal where the problem is. unplug/plug-in each tube may clear the trouble. also you can check the oscillator by having the radio ON while another AM radio is playing at the high end of the dial. turning the dial of the radio in question should cause a squeal in the other radio. this would indicate that the oscillator is working. if the oscillator is not working the radio will not play any stations

The antenna terminal screw is on the back of the chassis. I removed all the tubes and tested them on my tube tester and they were all well into the "good" range. I'll try the oscillator test tubeAmp described as I have another radio right next to the minerva. Can someone explain to me testing the IF and RF sections?
Thanks
Joe

Mornin' Joe-I'll put the schematic on this page so no more jumping back and forth;

http://www.nostalgiaair.org/PagesByMode ... 010877.pdf

Start by checking plate voltages on the other tubes,just like you did on the output tubes and post results.
Phil

The other tubes test as follow:
Plate to ground
6SC7 pin# 5 87V
pin# 2 0
6SQ7 66V
6SK7 111V
6SA7 111V
6SK7 111V
I didnt check the plate to grid readings yet because I have a question. When the schematic shows more then 1 grid then how do you know which one to test off of, or do you test any one of them, or all of them? (like the 6SK7 tube in the schematic if I am reading it correctly shows pins 4, 5, and 6 as grids)
the 6SC7 pin appears to have two plates so I took readings from both and i'm pretty sure I did it correct. Is it normal to have a "0" reading?
Thanks to everyone for all the help, I am really learning alot from this thread.
Joe

Am I right in that pin #2 on the 6SC7 is a plate? if so why does it read 0 when i test for volatge?
Joe

Yeah. #2 is one of the plates, but of course you know there are 2 plates on this tube. You might have a bad tube socket or need to re-sweat your tube. If you have a spare, that'd help. Either way, does not point immediately to output transformer.

Read the schematic. Pins 2 & 3 are grounded.

http://www.kpsec.freeuk.com/symbol.htm

http://www.kpsec.freeuk.com/compon.htm

funny phase inverter. first triode half of 6SC7 tube is grounded same ground as the tone control. other triode half tube grid is connected to signal through voltage divider as an inverter. tricky

So what is the function of this tube, the 6SC7? Could this be where the trouble is with this Minerva? I will check my tube stock and see if I have an extra one here. I think I will break out my 2nd tube tester also and just run the tubes through that quick and see if i get similar readings as with my Jackson daily driver tube tester. Your thoughts on my next step?
Joe

I am not sure what you mean testing plate to grid. I have never done that before. usual voltage tests are made with the NEG lead at B- and the POS lead on the intended electrode like plate for instance. that would be testing B- to plate. you would get a POS reading. or you could test B- to screen grid or ground to cathode. screen test would be positive DC voltage and cathode would be positive voltage. control grid voltage can be tested NEG lead to cathode POS to control grid. should be a NEG voltage. one of the 6SC7 plates is grounded (funny use of ground symbols cabinet AND chassis). should be zero between ground and ground. I am not sure how they are representing B- and ground. the other plate should read DC volts B- to plate. 6SC7 is a duo triode tube. one of the triodes is being used as a phase inverter for the push/pull audio amplifier tubes. can you see which is the phase inverter ? if not you may want to do some reading

Hi Joe-I forget-have you recapped this radio yet??
All resistors checked/replaced as needed?
Phil

yeah I recapped it and checked everything else. Its a shame because this thing was playing beautifully and picking up stations even on SW EVERYWHERE on the dial. Even in the middle of the day. It was really performing well then I went to put it back in the case after I changed the power cord and I guess I unplugged the wrong cord from the power strip and BAM! Sparked off of something now it just powers up but doesnt pick up ANYTHING just a very light static from the speaker.
Joe

So I got SOME good news, not alot but SOM. I rechecked the two output tubes on my other tube tester and one didnt test that good. I have a box full of 25L6's so I pulled out two that tested really good and switched them out. I can now recieve stations on the shortwave band but still nothing on AM (BC
JOE

troubleshooting is thinking in a process of elimination. what have we eliminated so far ? touching the center tap of the volume potetiometer, the wiper that connects to the 6SQ7 grid, getting a noise through the speaker means that everything works from the volume control to the speaker. we have eliminated that whole area. can you find the volume control on the schematic ? trace the circuit from the volume pot through to the speaker for practice. this is a working circuit. something is not working on the other side of the pot anywhere all the way to the antenna. there are switches, wires, tubes, voltages, grounds, possible shorts to check along the way. you have to trace the circuit from the pot to the antenna to find what the problem is. anyone can guess all day but guessing is not troubleshooting. most likely there is an open or something in the signal path shorted to ground

that would still allow one band to come through but not the other? I would think if something is shorted it would stop everything from coming through. I have a brand new on/off/vol pot so you are saying I should trace the circuit that goes from the vol pot to the antenna? Thanks for all your help. I am actually learning something from this post and all the folks helping me.
Joe

switches are in the path from pot to antenna. guess, could be a switch. reason. what is the difference between the two bands ? switches and coils and the connections

I cleaned and lubed the band switch and basically spent the better part of today looking over this radio to see if anything was touching and I cant find anything that looks out of place, bent, touching ect. I looked closely at the band switch and watched it as I switched between BC and SW. Everything appears to move smoothly. Again, nothing looks bent, out of place or broken. The radio works great on SW as soon as I switch it to BC it just turns to a really quiet static that is not affected at all by tuning the radio dial.
Joe

Take an orange stick and start pressing on the switch contact points while in the BC mode. There might be an intermittent. If that don't work, unplug the radio and check the resistance of the coils associated with the BC band for continuity since you saw sparks fly. Since the radio works on SW, the ball is in your court now. Check loop antenna and tuning cap for any broken wires. Check the point-to-point wiring for cracked insulation where a lead might be shorting against a tube socket lug.

I will check the areas you described and post my results here tomorrow.
Thanks
Joe