Hi Philco4Me,
With tubes other than power output tubes, not much goes wrong other than low emissions, dead due to open heater (filament) or gas. A "weak" 12BA6 will generally not cause a dead radio. If this radio did not work before you started (I believe you stated that it would trip the breaker), failure to operate is usually caused by only one failure EXCEPT:
- Parts that fail while the radio sits in storage such as electrolytic and other capacitors.
- Connections that fail due to oxidation (rust, tarnish, corrosion, etc.) while the unit is in storage. This includes open transformer and coil windings.
- Wiring mistakes while replacing parts, wires, etc.
- Poor solder joints, solder splashes, "bridged" connections (caused by too much solder connecting 2 joints that are not supposed to be connected).
God bless you, you jumped into the deep end of the pool on your first swim. This is a rather complex radio, as opposed to a simple 5 tube AC-DC AM radio, but you are doing well so far.
Do you hear anything on either AM or FM? And by anything, I mean hissing, static, squeals while turning the tuning dial, etc.?
How is the Bluetooth installed? Was there a "Phono" jack on this radio or did you wire it in. Is there a switch between Bluetooth and radio? If you can send a clear picture of how you wired in the Bluetooth adaptor.
Try the following: ALL previous warnings about protection from electric shock still apply!!!
- With the set on, confirm that all tubes are lit.
- Slowly turn the band switch between AM and FM. Wiggle the bands witch. There should be quite a bit of noise as the band is changed. If no noise, further investigate how the Bluetooth adaptor is installed and check the connections to the band switch from the AM Detector and FM discriminator. If you have DeOxIt D5 Contact Cleaner, use it to clean the band switch. Return the switch to AM.
- Take a meter lead not plugged into the meter. Attach a 10 ft piece of wire to it. Nothing on the other side. It is being used as an antenna of sorts. Put the band switch into AM.
- Touch the probe to pin 1 (grid) of the 12AU6 2nd IF. You should hear static or hum. If not, there is a problem with that stage or the detector stage.
- Touch the probe to pin 1 (grid) of the 12BA6 1st IF. You should hear static or hum. If not, there is a problem with that stage.
- Touch the probe to pin 7 (Mixer grid) of the 12AT7 Osc Mixer tube, and attempt to tune in stations. You should have either tunable noise or actually pick up stations.
To troubleshoot each stage, start out by measuring between the chassis and the plate of each tube / stage of the RF Amp, Osc. / Mixer and IF Amp tubes. Concentrate on any stage where the plate voltage is either very high (open circuit in a transformer, cathode circuit or miswiring) or very low (short circuit, open dropping resistor, miswiring.
Finally, carefully inspect all wiring, solder joints, etc. Pay close attention to the condition of the band switch. With the radio unplugged, check continuity of primary and secondary coils of the IF transformers and oscillator coil.
You have done a lot already on a complex radio. You have cleared the short in the power supply and have gotten the audio circuit to work. Next, concentrate on getting AM. When that is fixed, then try to get FM (this may be the hardest part.)
Again, good luck and congrats on progress so far.