Fender lamps

[stingray_65]

What is the apropriate wattage for a fender style lamp?

Radio shack sells 2 different bayonet based 6.3v bulbs 150mA and 250mA

They say they are for flashlights and Krypton filled

or are these completly unacceptable for this use?

I've got about 3 hrs total use out of the light that came in a cheap lamp assembly from Webers

my heater voltage is a little high (7.0 VAC)

thanks

Ray

[Robert M. Martinelli]

Hi Ray,
I would not worry that much about the lamp's wattage, after all a 150 mA lamp makes for some 1 W and a 250 mA one makes for some 1,5 W, and I'd bet that doesn't make much of a difference, either cosmetically or visually.

I would rather worry about your heaters' voltage, 7.0 V makes for a 11,1 % percent difference on the high side, and when it comes to power this results in a 23,5 % increase, this means the tubes' heaters and the pilot lamp are constantly operating well beyond their designed point, and this can surely result in shortening their operating life.

Hope this helps

Best regards

Bob

[stingray_65]

Thanks for the confirmaton of my fears.

Tubeswell pointed out in a different post I can use 2 diodes back to back to lower the supply voltage by 1/2 a volt and put me where I want to be.

[Robert M. Martinelli]

Hi again Ray,
yep, tw is right, you'll only need to calculate the total current that will be flowing through the diodes, based on the tubes type/number, and size the diodes accordingly.

You were talking about a Fender-style amp, so you'll mot likely have 12AX7s and 6L6s inside; if memory serves me well ( don't have any databooks at hand right now ) each 12AX7/ECC83/7025 needs 0,3 Amp @ 6,3VAC ( parallel heaters arrangement ) and each 6L6/5881 needs 0,9 Amp.

Hope this helps

Best regards

Bob

[Enzo]

The standard bulb for a 6v pilot as in Fender amps for decades is either a #44 or a #47. One is a little brighter than the other, causing the somewhat larger current draw. The lamps Radio Shack sells should also say on them #44 or #47. if it is a bulb numbered "PR" something, it is not appropriate. I'd be surprised if the Shack doesn;t have a 44 or 47 on the wall. Certainly a hardware store would.

[stingray_65]

thanks Enzo

I found an old lamp bulb in my junk box, I'd never guessed it would have worked, its got to be over 50 yrs old. its a pull from a junk premier 10 amp out of a movie projector

I put it in before I strated the diode mod to my heater supply and it was noticibly dimmer than the part that came with that cheapo unit I bought

After I get the cab finished and everything eles sorted out I'll change the whole unit out with a genuine fender lamp assembly.

Ray

[Enzo]

Is there a number on the base of your dim bulb? It may be a 7v or 10v or 12v lamp out of place in your amp.

Is there something wrong with the existing socket fixture that it needs changing?

Did you measure this 7VAC with the tubes in it and running? If you measured with tubes removed it would naturally be high.

[tubeswell]

FWIW I use .3A 6.3V bayonet bulbs. They glow really bright and look cool underneath those jewel beizels. Take the current rating into account on your heater winding (i.e. 1 x lamp @ .3A, each 12A_7 pre-amp tube @ .3A, each 6L6 @ .9A, da de da de da...)

[stingray_65]

Enzo

I took the measurements under load

The socket itself just doesn't seem to fit together nicely.

it doesn't accept standard jewels, the tabs seem so loose don't make good contact with the base ( I had to solder one in place just to insure good contact)

I'm not complaining, but if Webers is selling these for less than $2 and making a profit on them how good can they be?
the replacement bulb I can't find a # on.
the old one as far as I can see isn't marked at all

I have to say that it was BRIGHT, enormously BRIGHT, MAGLITE in the face after 2 am BRIGHT.

when i say the replacement was dim I mean it seems about right
even at 7VAC it seemed right


Tubeswell

I'll check into that a bit further today and actually measure the current draw on the heater supply. I don't have the specs on the MM transformer, but they should be available.

Ray