Replacement of the
TS-930S meter backlight with new bright LEDs. 3 July 2018
The
incandescent meter backlight(s) had failed and required replacement
and while a simple like for like replacement was possible there was a
much superior solution available with bright LED (Light Emitting
Diodes) lamps.LEDs while having many superior characteristic when compared
with traditional incandescent lamps, particularly when it comes to
reliability are not always an ideal solution. A key performance
difference that can make LED not ideal for display backlighting is
that they radiate the light forward in a narrow beam of between 10 and
20 degrees as compared to the more omnidirectional pattern of most
incandescent globes, therefore if the backlight as is often the case
relies on a more omnidirectional light the replacement is not as
straight forward as simply replacing the existing incandescent globes
with the newer LED light. Fortunately the TS-930 radio is well suited
to LED back lights for the meter and in fact the 5mm LED is almost a
perfect physical fit; that said the two LEDs required for this job
produced two intense spots in the dial. This problem was solved by
scuffing the LED lens with fine sandpaper to create more light
diffusion and the value of the LED current limiting resistor was
significantly increased to reduce the LED brightness. See below photo.
Photo:
TS-930S with new bright blue LED meter back lights installed.
The
TS-930 radio’s dial light is powered by a 28V DC supply and it was
found that two 1.8k (3.6k) ohm 0.5 Watt resistors in series with each
of the 5mm Blue, 23500mcd LED gave a good results, however a bit more
resistance may prove to give a slightly better result and is of cause
subject to personal tastes.
LED
details
Size
(mm): 5
Colour:
Blue
Lens:
Waterclear
Viewing
Angle (Degrees): 15
Wavelength
(nm): 470
IF
Max Continuous (mA): 30
VF
Typical (V): 3.2
IV
Typical (mcd): 23500
Current
limiting resistor calculation.
The
below current limiting resistor calculation is to achieve the LED’s
maximum performance which is based on an average life span for the LED
however it is prudent to sacrifice brightness for extended reliability
and the resistance value should be at least doubled or more.
As
in the fitting of this LED with the TS-930 radio it was determined
that a 3.6k resistor for this particular LED was more than sufficient.
Video
of the replacement of the
TS-930S meter backlight with new bright LEDs
