🚀 go-pugleaf

In article <14058@acorn.co.uk> agodwin@acorn.co.uk (Adrian Godwin) writes:
>In article <1992Apr11.010124.6186@newstand.syr.edu> ldstern@rodan.acs.syr.edu (Larry Stern) writes:
>>To all: a neighbor of mine has a 6-7 year old Sony Trinitron, which works
>>well except for the remote control. The remote had an intermittent problem
>>where it would work fine for a few weeks, not work at all for a few days,
>>start working ok again, etc. It seems it is now, finally, dead. There is
>>one IC, a crystal, a few resistors and caps, and an LED inside. My question
>>is, what usually goes? Is this worth fixing? And finally, can this LED be
>>tested with an ohmeter like a "regular" diode?
>>
>
>It's often the keypad that goes, not the electronics. The conductive rubber
>pads on the buttons wear out, and don't connect any more. Check the buttons 
>that you don't use much, and see if they don't work either. Also, clean the
>PCB  under the keypad - if one of the buttons is permanently shorted, the
>others won't work.
>
>I don't know how reliable the LEDs are, but they tend to have a much higher
>forward voltage drop than an ordinary silicon diode - about 1.6V. This may
>be too high for an ohmeter, so it will indicate open circuit both ways.
>Test it by connecting up a voltage source & series resistor to limit the
>current to about 10mA, and measure the voltage drop over the diode.
>
LEDs are very reliable!  About the only way an LED could die is to give
is too much current (typically more than 25mA) or too high of a reverse
voltage (don't they have a lower PIV than "regular" diodes?).

In a remote, too high of a PIV is probably impossible; too much current is
also very unlikely.  It would require the current limiting resistor to go
bad and at the power level in a remote control that should never happen.

As for testing the LED... The forward voltages on LEDs range from about
1.6 volts to over 2 volts depending the the type (I don't have anything
exact to quote, but I seem to remember some green LEDs being about 2.2v).
The voltage source and resistor method above will work though.

I seem to remember a post saying to look for hairline cracks in the pcb.
You should use a magnifying glass and a good light source for this since
they can be very tiny and hard to spot.  You can also try testing the
continuity of the traces on the pcb, but some small cracks can give you
an intermittant signal (sometime they test ok, sometimes not) so you may
want to try this under SLIGHT stress. (Don't you too much or you may actually
cause problems!)

Good luck!


-- 

Steve Day
N7VHY