Keeping in mind the Sam's Photofact for the Admiral 19A1 chassis has a paragraph in the "production Changes" stating that early versions used a transformer designed for a 5U4.
They say “if you use a 5Y3 with a 5U4 transformer the B+ will be too low”.
I discovered this after I had the set together on a shelf for morning news testing.
My transformer's secondary HV resistance is closer to the 5U4 measurement than the 5Y3. 150 ohms for a 5U4, 175 ohms for a 5Y3, mine measures 137 ohms). They also say there is a red dot somewhere on the 5U4 transformer (I haven’t looked yet)
When I first started tinkering with this set I was using my Heathkit PS-3 bench supply for B+ because I wasn't getting sufficient High Voltage. When I had the B+ cranked up to about 250 volts things worked better. Resistors and capacitors are OK in the B+ string.
It was quick and easy to stick a meter in pins 4 and 6 of the rectifier socket and check the resistance of the transformer.
I plugged in a 5U4 and have been running the set in the cabinet with the back in place and monitoring the transformer temperature being aware of the higher 5U4 filament current.
The set performs considerably better with the 5U4 probably due to B+ being about 20-30 volts higher making the High Voltage probably 500 volts higher.
The tube layout on the bottom of the Bakelite cabinet is destroyed although I can make out 5Y3 and the set had a 5Y3 in the socket when I bought it.
This little TV set has become the restoration from Hell
and I still need a Fine Tunning Knob.