[TenTec] Dial lamps

[Bill Harris]

I understand it's possible to relamp using LED's.  If so, I would think that would be a better option if the price is acceptable.

BillHarris-w7kxb/7 AZ

 
> Date: Thu, 11 Mar 2010 20:39:32 -0600
> From: geraldj at weather.net
> To: tentec at contesting.com
> Subject: Re: [TenTec] Titan III screen current question.....
> 
> The TT manual that I downloaded only identifies the lamps on the 
> schematic and shows them separate from the meter and the meter wiring. 
> The lamps are hard wired to the 12 volt supply but the meters plug into 
> the meter switch board A12.
> 
> Tiny 12 volt lamps can be had in hobby shops for train lighting or for 
> scale doll house lighting as well as sometimes at Radio Shack. Many 
> different 12 volt lamps in tiny packages can be bought from Mouser and 
> Digi-Key.
> 
> Its worth selecting a lamp with a long rated lifetime, though that will 
> reduce its illumination efficiency.
> 
> It can also be worth dropping the supply voltage about 10% with a series 
> resistor which will also lengthen the life by lowering the operating 
> temperature and limiting the lamp surge current. A typical incandescent 
> lamp's cold resistance is in the range of 15 to 16 times lower than its 
> operating resistance. So a lamp rated to draw 100 milliamps will draw at 
> least 1.5 amps the instant its connected, unless the external circuit 
> limits that current, and nearly all incandescent lamp failures seem to 
> be at power on.
> 
> So if that 100 mil rated lamp at 12 volts had a 12 ohm series resistor 
> the peak surge current would be limited to about 0.6 amp. And the 10% 
> drop in operating voltage would quadruple the lamp life. Rule of thumb 
> from a GE lamp book years ago is that a 5% change in lamp voltage causes 
> a 10% change in light output and if going down in voltage a doubling of 
> life or if going up, halfing the life.
> 
> 73, Jerry, K0CQ
> 
> On 3/11/2010 2:33 PM, Jim Brown K9YC wrote:
> > On Thu, 11 Mar 2010 12:09:08 -0600, John wrote:
> >
> >> TT does not stock the original incandescent meter lamps.
> >
> > What's the mfr/part number of the lamp? Is it a standard industry type?
> > Older Ten Tec gear (Titan 425, Herc I, Herc II, 229 and 238 tuners) all use
> > standard bayonet lamps that are easy to source from industrial vendors. I
> > simply buy boxes (a dozen or so lamps per box) of 14V long life bulbs. I
> > replaced all the bulbs in one 229B with LEDs and series resistors, but am not
> > satisfied with the result, so I've stuck with incandcescents in the other
> > four. YMMV.
> >
> > 73,
> >
> > Jim K9YC
> >
> >
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