[TenTec] pilot light bulbs

[Dr. Gerald N. Johnson]

On Mon, 2008-08-04 at 11:31 -1000, Ken Brown wrote:
> Hi Jim,
> 
> Since Marinus' first post referred to a Ten-Tec 228 tuner, you are 
> correct about the 12 to 14 volt supply. Marinus also mentioned the bulbs 
> in his Omni 546-C, and asked whether they are 6 volt lamps. I am not 
> familiar enough with the 546 to speak on the pilot lamps it uses. I do 
> have a Omni VI 563, and a manual for it.
> 
> The Omni VI 563 uses pulse width modulation to control a regulator 
> circuit that determines the meter lamp brightness. The manual says that 
> the lamp voltage varies from about 2.7 to 5.7 volts. I have not found a 
> part number in the Ten-Tec manual for the bulbs, though I suspect they 
> are number 47 bulbs, commonly used in tube radios with a 6.3 volt 
> filament supply. With only 5.7 volts maximum supplied to a 6.3 volt (I 
> am guessing) bulb, you should already be getting extended life from the 
> bulb.
> 
> I like to buy bulbs from Mouser. They have a good selection of Chicago 
> Miniature lamps, and you get a price break at ten units. Interesting to 
> compare the 47 bulb with the 755. They have identical voltage and 
> current ratings, yet the 755 produces less light (0.330 M.S.C.P. versus 
> 0.500 M.S.C.P. I'm not sure what M.S.C.P. is. Perhaps mean spectral 
> candle power?) and lasts almost seven times as long. It also costs 
> almost twice as much.

Those are EXACTLY the trade offs I wrote about. Longer life less light
output (and MSCP IS Mean Spherical Candle Power, e.g. in all directions)
for the same electrical power.
> 
> When running incandescent lamps at various voltages, the light they 
> produce does not merely change intensity. The spectral distribution of 
> the light also changes. Running at a reduced voltage lowers the 
> temperature, and shifts the emission towards the longer wavelength, 
> redder end of the visual spectrum. When television studios get more 
> sensitive CCD cameras, requiring less light, they cannot just dim the 
> existing lights. They have to get new lamps to maintain the same color 
> temperature at a lower light level.

The longer lived lamp will have the same color shift as the short life
lamp run at lower voltage.
> 
> Ken N6KB
> >> Unless the stock bulbs are 6.3 volt lamps
> >>     
> >
> > The lights are wired in parallel and run on whatever power supply is 
> > plugged into the RCA connector on the back. For most of us, that's 
> > 12-14 volts. 
> >
> >
> >   
> 
73, Jerry, K0CQ