I'm working on my Westinghouse 1946 radio (https://www.tubesandmore.com/schematics/westinghouse-electric-corp/h-110). I recapped it, replaced a blown resistor, and fired it up tonight. However, I'm not getting any audio. I notice that all tubes get warm and/or glow except for the 5U4G rectifier tube. It stays cold and I don't see any glow.

Being new to the world of vacuum tubes (other than my arcade monitor CRT experience), my first question is if that tube can be considered bad based on these symptoms? If so, should I just go ahead and order a replacement or would it be better to find a local who can test it first?

Otherwise, what would be the next steps in troubleshooting? Should I jump straight to having all my tubes tested? Or are there some things I can reasonably do first with a multimeter and/or scope? Given my inexperience in this world, any guidance regarding where/what to focus on in the circuit would be a big help (e.g. x volts should be on pin y of tube z).

The 5u4 sounds bad... ive never seen one not glow... Should see 2 filaments glowing when its on, and they Do get warm... Swap this tube and try again... :)

SR

Tube is most likely.
If not there should be apx 5 VAC on 2 of the pins,
usually yellow wires from power transformer.
The other filaments run off another winding.

73 Zeno:smoke:

Pull the 5u4G. Look at the pins, with the index on the centering pin pointing down at 6 o'clock. The pins are numbered from 1 to 8 going clockwise starting with the first pin to the left of the index. Some pins may be missing on some tubes but you count those positions anyway. Forgive me if you already know how to figure tube pins!

Pins 2 and 8 are the filament pins of the tube. Set your DVM to continuity or low ohms and the DVM leads on those two pins. Should read continuity or low ohms. If no reading, tube is burned out.

Thanks for the feedback, everyone. Indeed, no continuity on filament pins 2 and 8. Looks like I need a new tube! I've never ordered a new tube before so if there are any particular suggestions on vendors or manufacturers, advice is appreciated!

I realized tonight that my TV has a 5u4GB so I popped it in and voila! It did run really hot though. I gather that's normal since it's part of the power supply circuit (whereas other tubes don't tend to run so hot)? It also runs hot in my TV.

As I've read, it should be a reasonable substitute for the 5u4G and in fact the blown one that was in the radio was also a 5u4GB. But if it's an inferior substitute and is likely to have a short lifespan, maybe I should bite the bullet and pay the higher price that 5u4G's seem to command. Any thoughts on that?

The 5U4GB is an electrically and mechanically superior tube.

The only reason the 5U4G commands higher prices is that they are generally older/rarer (except for the Chinese audiophool stuff), and they have the "vintage look" with the old ST style envelope.