[JCB]

The pilot lamps burnt out again on my brothers Kenwood TR-751 for the
LCD screen. I replaced them a couple years ago for him. Has anyone
ever changed over to a LED in place of these grain of wheat bulbs?
What kind/color LED used and what value dropping resistor?

Tks JCB, N9JB

[Bryan]

JCB wrote:
The pilot lamps burnt out again on my brothers Kenwood TR-751 for the
LCD screen. I replaced them a couple years ago for him. Has anyone
ever changed over to a LED in place of these grain of wheat bulbs?
What kind/color LED used and what value dropping resistor?

Tks JCB, N9JB

The biggest issue with LEDs is the dispersion angle -- even the wide-angle
types are pretty narrow for backlighting a display. A friend who runs the
service department for a commercial sound company says to grind/file off the
lens of the LED(s) you intend to use.

What kills the lifetime of incandescent lamps is inrush current. If you
stay with that type, you could use a constant-current regulator (an LM317
configured as a current regulator comes to mind). You may need to use
lower-voltage lamps, to offset the regulator's 1.2V drop.

73,
Bryan WA7PRC