[Kenwood] Kenwood TS-130S

[Bryan Swadener]

David,

They're just "Grain Of Wheat" lamps with a T1 (3mm diameter) bulb & wire leads.  IIRC, Kenwood used 14V/25mA lamps.  Your local hobby supply store should have them.

Their lifetime is determined by the supply voltage/current and the number of times you cycle the power on/off.  Each increase of 5% voltage/current results in a decrease of approximately 50% in lifetime.  Likewise, a decrease of 5% voltage/current results in an increase of 50% in the lifetime.

The number of times you cycle the power on/off has an effect as well.  Incandescent lamps have a low cold resistance.  This results in an inrush current pulse of around 5X or more of the running current. This is a huge mechanical shock to the filament and causes early failure.  Leaving it ON isn't practical but you can limit the inrush current with a simple current source.  The LM317L voltage regulator works well, is easy to implement, and costs pennies.  The LM317L datasheet shows how to use it as a current regulator, using one resistor.  Since the 317 will drop around 1.25V, use it with a 12V lamp on a 14V source.  Mine's been working for many years... so far.

vy 73,
Bryan WA7PRC

From: David KW4DH
Subject: [Kenwood] Kenwood TS-130S
To: kenwood at mailman.qth.net

Before I adventure inside the case of my TS-130S, is there a bulb to 
illuminate the S meter?  I have gone back and forth over the schematic 
but I can't seem to find any indication.

David
KW4DH