[dconant]

Hello, Working on a Westinghouse H104. Been recapped and all the usual stuff. Plays very nice. My question is does this radio really need a 5U4 rectifier tube? Sounds like overkill. Wondering if I could sub in a lighter rectifier? If so what would I use? This radio makes a lot of heat. 

Tube lineup;
2 6Y6 push pull
2 6SK7
1 6SA7
1 6SF7
1 5U4

Schematic here. http://www.nostalgiaair.org/PagesByModel...024229.pdf

[morzh]

Q: Why not use 5U4? Problem with procurement? If not, I usually do not question the existing arrangement.
Also this would likely involve a different socket / rewiring, and you need the same filament voltage and similar current.

[dconant]

While on the subject of tubes the radio came to me with 6V6s (2) installed which should have been 6Y6s. Both work so I wonder which set would be better. My spare 6Y6s are a little tired so I leave them as test tubes in case I run across a dead one.

[TV MAN]

6V6's are beefier than 6Y6's are. They can use higher voltages & currents, but are also more pricey to buy. The Russian versions work well and can be had reasonable. A 5AR4 can sub for a 5U4, (it will raise your B+ so be careful) are smaller and use less heater current, but are more expensive to buy. A 5U4 is filament hungry and might be stressing your power trans. A 5Y3 will plug in but IS lighter. It might red plate (fuse). You can check your current draw across the resistor between your main filter caps by measuring your voltage and using ohms law. Then you can look up the specs online and see if it's within tollerance. Also, has this been recapped? If the coupler caps to the 6V6's is leaky, they will be drawing more current than what they should, causing things to run hot. This might be why you are finding heavier tubes in place of the originals - to "fix" an over current situation instead of fixing the problem. You should have either a negative voltage or 0 on the control grid of your output tubes. A + voltage means you have leaky coupling cap. I'd check this 1st. It might be the root of your problem.

Edit: Also a leaky or shorted cathode bypass cap (electrolytic) can mess up your bias on your 6V6s.

[dconant]

The set has been recapped and most resistors replaced as being out of spec. I shoot for 10%. I have 47s in place of 40 E caps. The grid voltage on 6V6 is +.6 volts. Plates are at 200 volts. Screens are 150 volts. Cathodes are at 8 volts vs 14 volts per the schematic. If I use good (stole from another radio) 6Y6s the grid voltages are 0 volts. Readings are with a VTVM. There is no resistor between the two main caps unless you count the field coil. The field coil is 167 ohms and the drop is 20 volts. So that would be 120ma for 6V6s? With the good 6Y6s the current is 162ma Seems like the 5Y3 is cutting it close. Guess I'll stay with the 5U4.

So why is there +.6 volts on the grids of the 6V6s? The schematic says the grids should be 0 volts. The 6V6s test good.

The 6Y6s are drawing more current so maybe I'd be better off with the 6V6s? AC current is up too. I guess it would be if DC current is higher.

[Arran]

From what I recall A 6Y6 gas a lower maximum plate voltage, 200 VDC, but draws more heater/filament current then a 6V6, 1.25 amps verses .45 amps for the latter, so the net result may be that the heater voltage might be slightly higher for the whole set. I think I would just procure some more 6Y6s, they are not a particularly expensive tube. From what I read the 6Y6G was developed for use in TV sets, one of the first specifically designed for it prior to the war, but I have only found them used in a handful of radios, one being a Canadian Westinghouse 754, another being a U.S General Electric H-116, I have a feeling that your Westinghouse might be similar to the H-116 other then the choice of a 5U4G rather then twin 5Y3s like the G.E has.
Regards
Arran

[dconant]

I think I will stay with the 6Y6s but I would like to know why the 6V6 grid measures +.6 volts and the 6Y6s are zero volts.