Tubelab SE heaters

[famousmockingbird]

http://www.tubelab.com/images/AssemblyManualTubelabSE/TSE_board.jpg


Say you only have a 6.3v winding without a center tap what is the preferred method to hookup?

A) Place a jumper from pad 1 to 4 and run one tap of the 6.3v winding to T1-6 and the other tap to T1-8. Is this a half wave rectifier? It should give me ~2.8v for the regulator and ~5.6v for the 5842 heaters? Would I then have to remove the 2.2R serial resistor doing it this way? The transformer I have is wired for 115 so I actually have a hair more voltage to play with for headroom as far as dropout is concerned and I should get closer to 6v for the 5842 heaters. Well this is if my theory is correct.

B) Place a jumper from pad 1 to pad 3 giving me 8.8v to regulator input. Looks like a standard bridge rectifier and the 2.2R serial resistor drops the voltage down for the 5842 heaters. The regulator will pass more power to heat this way and I do have a large heatsink on there, 15w lost in regulator.

C) A totally better way that I can't think of.......


Thanks

-bird

 

[thewwwall]

Hey - What power tube are you going to run on this board? if you need 5v like for a 300b, then you don't really need to worry about a CT hookup to T1-6 and do nothing with pad #1, just go with the jumpers 3 to 4 and 5 to 6 - hook up the T1-7 & T1-8 to your 6.3VAC taps... unless I am missing something? If you need 2.5v, you could try an artificial CT, see Valve Wizard, etc., but that may not be an option with this circuit. If you need 2.5, you can try asking on George's forum if a moderator doesn't move this there anyway ;^)

Best regards and luck - W

 

[famousmockingbird]

Hi I am using 45 tubes so I need 2.5v.

I don't believe an artificial center tap will work for this but I could be wrong.

 

[thewwwall]

Ok, I'd be tempted to shoehorn in a separate 6.3VCT filament transformer, say 5A or 6A minimum if you have real estate - Good luck! ;^)

Edit - now that I think of the current draw for the 45s/5842s you'd probably be ok with 4A, which should be 15 bucks max...

 

[famousmockingbird]

Thanks for the advice. I will take some measurements to see if I can fit a separate filament transformer but I think I can work with what I got at the expense of dumping energy into heat, the regulator is good for 45 watts max dissipation.

Or the half wave idea might work but half wave will yield a harder to smooth 60Hz ripple so there could be a him issue.

 

[famousmockingbird]

Bump

 

[famousmockingbird]

Option "B" is what I chose, the heatsink gets warm but not hot and I have 2.4v on the 45's and 6v on the 5842's.

All is good!

Thank you thewwwall

 

[thewwwall]

Nah man, good experiment - thank you for trying the option, expands the use cases ;^)

BTW what type (and digikey/mouser # etc if applicable) heatsink are you using, i just stacked/bolted a bunch of the standard types together, ugly but working so far, but i doubt i'm dissipating as much heat either... this is my 'fear' with this circuit if anything, meaning having a DC regulator and thus a heater leg go out but not the B+/HV - anyway,

Best regards again - w