[Kenwood] Bulbs - Grain of Wheat for LCD Display TS-940S

Mon Sep 26 13:11:15 EDT 2011

Incandescent lamps have a very low resistance when cold - the inrush current is on the order of five to ten times the running current. This causes a high mechanical stress, and early failure. Use of a current regulator will dramatically increase lamp life. A super easy way is to use a LM317L + one resistor (see LM317LZ datasheet). Also, decreasing running current 5% will effectively double the lamp life. The only caveat is that the LM317L will lose (or loose) 1.25V across it. So, you use lamp(s) that are rated to run at 1.25V or less than the supply voltage.
Most GOW lamps run at less than 40mA. If you don't know what yours are rated, apply rated voltage and measure the running current. Select the current-setting resistor to run the LM317L at this current or lower. Since the LM317L is in a TO-92 package, it can easily be added inline. I replaced the GOW lamps in my TS-120 rig and added current limiters ten years ago. No failures yet.
vy 73,
Bryan WA7PRC
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From: Dennis Younker NE6I
To those looking for the 10 volt grain of wheat bulbs for the TS-940S LCD display, this may be the place to get them.
http://www.discounttrainsonline.com/Brawa-Bulbs-Grain-O-Wheat10V-ClearFZ2-Pc/item186-3290.html
Manufacturer's web site for this bulb:
http://www.brawa.de/en/products/h0/electrical-accessories/miscellaneous/3254-pea-bulb.html
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From: Dr. David Kirkby
IIRC, they are not 10 V. It might have been 8 V, but I'm 80% sure it was not 10 V. I ended up using 5V ones with a series R - not an ideal solution, but it was the best I could find easily.
Dave
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From: Donald Burns
I found 12 bulbs at Radio Shack. Not quite as bright but adequate. Replaced them about 10 years ago.
Don KB8F
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From: Donald Burns
I found 12 volt bulbs at Radio Shack. Replaced them about 10 years ago. Not quite as bright but adequate. Will probably last longer operating at reduced ratings.
Don KB8F
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From: Jim Miller KG0KP
I used radioshack.com to find bulbs for my KW mobile radio TM732 several years ago. search for bulb on their site and they have a 2 pack for 1ドル.99 that worked just fine for me in the mobile. I also found out on the website that they were available in the store nearest to me here. I printed the page and took it in with me. Good deal because they only had one in the bag instead of two like the website says and they gave me two bags to account for what the website says (still today).
http://www.radioshack.com/product/index.jsp?productId=2103780
73, de Jim KG0KP