I've checked the downloaded manual. The lamps appear to be in series and
are run off the 28 volt control supply through a 20 ohm 1/2 watt
resistor. The maximum current (dissipating 1/2 watt) through that
resistor is 158 milliamps which would give a voltage drop of 3.16 volts.
Its a surge limiting resistor and probably the lamp current is more like
80 or 100 ma. And 14 volt rating. But without knowing the size and base
of the lamp I'd be speculating too much to guess at a number like a 756
or 1813 if the size of a 47 or 44. There are some other 14 volt lamps
with more light output but they draw more current than the 20 ohm
resistor can survive but would likely be found at most truck stops being
used in marker lamps. If the package is right for these lamps I'd go for
the 756 because its rated at 15,000 hours while the 1813 is rated for
1000 hours. That package is T3-1/4 with a single connection bayonet
base. That's just over 3/8" diameter for the bulb, actually 3.25
eighths, really close to 10mm.
With the lamps in series, if one opens both go dark.
Seems to me we've thrashed these lamps on this forum before.
73, Jerry, K0CQ
On 10/2/2010 4:42 PM, Ken Brown wrote:
> You could look in the manual at the schematics and see if they are
> powered by the same transformer secondary as the 3CX800A7 filaments. I
> think that is 6.3 V which would make them plain old #47 lamps. Don't
> take my word for it though, confirm before you buy, and when you buy,
> order enough to get the quantity discount from Mouser, Digikey or other.
> You could look at the number on the burnt out lamp. Some just have a two
> digit number, some have a prefix such as CMI (Chicago Miniature). Once
> upon a time this pilot lamp bulbs used a color code. The glass bead the
> holds the wires in position to suspend the filament coulb be various
> colors, which represented the bulb type. Old Amateur Radio Handbooks had
> that data in the back along with the tube and transistor data.
>
> DE N6KB
>
> John Oglesby wrote:
>> Can someone tell me what the lamps are that are used to illuminate the
>> meters in a Titan 425? I can't find them in the manual and both of mine
>> have failed. I wanted to make sure I had the right lamp before I
>> dismantled the station to replace them.
>>
>> Thanks& 73
>>
>> John
>> N9RE
>>
>>
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