DIYbanter - View Single Post - LCD display on exercize bike troubleshooting.

D Yuniskis

On 12/30/2010 9:48 AM, wrote:
Sorry if this type of problem has been discussed before, I didn't find
any useful usenet search of this newsgroup history. Boy, do I miss
DejaNews! If someone knows of a usable search of
sci.electronics.repair please post it. The google one was pretty
terrible IMHO.

I have a "computer" on a Schwinn exercise bike that the monochrome LCD
is nearly blank. I can see that it is working, but the display is
very light. When I turn it on I can hear the friction control motor
in the bottom of the bike working. That system does seem to work, I
can increase the friction with the buttons on the computer. So
buttons work, display works a little, other functions work.

A single failure in the display circuitry. The problem is just the
display.

This runs on 4 C cell batteries, I did check the voltage on the
batteries and when I press the soft "start" button on the panel the
battery voltage diminishes from over 6V to less than 1V. Something is
dragging it down!

Are you looking at the batteries themselves? Or, someplace
else in the circuit? 4 cells won't drop to 1/4V each (on average)
unless they are *shorted* (otherwise, several would have
to be "completely flat" -- in which case, they wouldn't
read as 6V open circuited).

Are the battery terminals corroded?

I unplugged the harness from the computer to the rest of the bike,
that didn't change anything. So the short is likely in the computer
related to the LCD display.

Do the driver chips for such a display fail shorted? That seems to be
what I have here.

It seems unlikely to me that this is actually repairable since the
large LCD display probably has integrated drivers in it's module. But
I haven't disassembled it yet.

Is there going to be a whole bunch of driver chips along the edge of
the LCD and something that runs those that has failed shorted?

What should I be looking into?