RCA BA-6A Heating

Hi

has someone ever measured the heater voltage for the two input tubes? In the schematic one can find 6.3V. But when I measured I had about 5.5V(with no possibility to adjust to higher voltage with the pot) . Reduced voltage for longer tube life or just something out of order?

Thanks
Andre

Hey, welcome to the Lab!

What kind of tube is it?
If it's a 5Y3 recifer for instance, it needs 5 volts. If it's a 6 or 12 something, it needs 6.3 volts.

I believe the 2 input valves are 6SK7, & therefore need 6.3v

the first number in the tube is an approximate filament voltage...

you will most likely find that you have 2 heater supplies

the tube in your power supply might have this 5.x volt heater requirement and if you trace "suspected" heater wires wire back to this tube they probably share this same heater and...in that case...your votalges are probably right

hope this helps
later
ts

Hello


there are two 6sk7, heating for these two is parallel. The rectifier is an old selen rectifier. Yes, the heater supply is rectified...for lower hum.
So coming from datasheet these tubes should need 6.3v. In the shematic there is 6.3v noted.
But the question is still the same: Has someone ever measured this voltage before? And if so, what voltage measured?
From some other designs I know that reduced heater voltage is sometimes used....

By the way has someone a complete manual? As pdf?

Andre

Selenium rectifier transformers many times have 'aging' taps that stepped up the AC into the rectifier as they aged and sagged. The BA-6A schematic instead shows a variable resistor for adjusting this voltage. Replacing the rectifier may be the solution if there's an actual problem with slightly low voltage. 6.3 VAC is a center target for a specified 6-6.6 VAC range. I probably wouldn't worry about it if you hear no problem. Many old sources refer to acceptable lower voltages in certain pieces witth longer heating cycles being the only noted difference.