Jaycar 5300 LED display

[Peter Gargano]

Crescent Kao wrote:
> 
> The big 10ohm resistor on the lower board is burned!!! And now when i power
> up the unit, some of the LED bars on each digit don't light up (including
> some of the bars the vertical LED on the right)!!

I think there's a problem with the power supply design in Silicon Chip's
FMD design where shunt regulator ZD1 can overheat if the (vehicles) power
supply goes much over 16 volts for anything other than short periods. 

If the display circuitry draws little current (no or few LEDS lit), then
at a power supply voltage of 17 Volts, ZD1 will rapidly exceed its power
rating and will overheat, possibly going short circuit and also causing
the 10 ohm resistor to rapidly exceed its power rating. For a vehicle,
17 Volts is probably not an uncommon figure to see for short periods.
There are a couple of ways to "fix" this, and I'll need to look into each
possibility.

In light of some feedback I've recently received, there is another problem
area I'm looking into, that can be easily rectified, and has to do with
calibrating the FMD (at 1.4 and 3.0 Volts). More info soon when I've had a
chance to play with one of the few units exhibiting this behaviour.

If you have any specific info you'd like me to know about then email me
direct at <peter at techedge.com.au> ie. mailto:peter at techedge.com.au 

Peter.

----- End of forwarded message from owner-diy_efi at diy-efi.org -----
----------------------------------------------------------------------------
To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes)
in the body of a message (not the subject) to majordomo at lists.diy-efi.org