Welcome Guest! Be sure you know and follow the Phorum Rules before posting. Thank you and Enjoy! (January 12) x

Thread Closed
Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5

voltage on tube heater 46-350
#16

You have to remember that with a three way portable the filaments are operating off of the B+ voltage coming off the cathode of the rectifier tube, with a wire wound dropping resistor inbetween. The rectifier tube is usually something like a 117Z6 or 117Z3 because the filament voltage of those tubes has a working voltage of 117 vac. For starters the voltage drop from the line across the tube is anywhere between 10 and 20 volts, depending on current load, then you have the filter network of capacitors and resistors, then the dropping resistor which drops the voltage down to 7.5 volts for 4 tubes, or 9 volts for five tubes.
An extra 6 volts at the line may translate into .5 volts on the filament string. To be sure I would try measuring the voltage across the filament string, if it's a little too high then add an extra dropping resistor calculated according to Ohm's law, or if you don't mind some "sand" in your set add a silicon diode in series with the tube filament string which will knock about .7 volts off.
Regards
Arran




Users browsing this thread:
[-]
Recent Posts
Philco model #20
Hello again fellows , well I powered up the set this evening after I had changed every cap and resistor in this set and ...onlyrick — 09:34 PM
Zenith H725
Yes - better it happened on the repair bench than returning to the owner. The other question is - do I also dissect a...EdHolland — 09:08 PM
Zenith H725
That's a bummer but get them now. Paul BPaul Philco322 — 08:27 PM
Zenith H725
I completed the insulation on the cabinet interior (Al foil and hi temp silicone rubber), and reglued the speaker gasket...EdHolland — 06:18 PM
HiFi (Chifi) tube amp build - but my own design.
Tim - Photos of 8 octal tube sockets. (Top and bottom) Send me a PM if you're interested.RodB — 04:11 PM
VTVM meter moves when my hand is next to it & not on
Haha! I hope so. It seemed rather lost and forgotten languishing in the frozen Northeast of England.EdHolland — 02:36 PM
VTVM meter moves when my hand is next to it & not on
Ed - it's in the Cayman's enjoying the good life.RodB — 02:14 PM
VTVM meter moves when my hand is next to it & not on
Static electricity - but the other chaps beat me to it again. I've seen this before with analogue meters. I've also ...EdHolland — 01:56 PM
Need to purchase some accessories for restoration of my Old Philco Radio
Hi Paulo, Welcome to the Philco Phorum. I can see why you want to find good reproduction parts. That is a bea...MrFixr55 — 11:10 PM
HiFi (Chifi) tube amp build - but my own design.
Tim, I have some bakelite sockets in my work shop that I can dig up. I believe quite a few are NOS. I will take photo...RodB — 10:03 PM

[-]
Who's Online
There are currently 1206 online users. [Complete List]
» 5 Member(s) | 1201 Guest(s)
AvatarAvatarAvatarAvatar
Avatar

>