where do I find a person to fix this?

Discussion in 'General Electronics Chat' started by russian, Mar 19, 2014.

  1. russian

    Thread Starter Member

    Sep 1, 2012

    On the picture we have failing car scales main control panel.

    These are ~20(?) years old, you can see 8 AA batteries are power supply. The screen barely shows four zeros - so the device is kind of alive but not really :)

    I was able to find a datasheet for the BT21608 screen. Between pins #1 & #2, I got a steady 5 volts - that's the main screen power.

    Between pins #13 & #14 - LED backlight - I got a variable voltage, I saw as little as 2.10 to as high as 2.75 volts. I believe this is wrong.

    That's the limit of my troubleshooting abilities. I wonder what is the chance of finding anyone to repair this piece of hardware, and what would be the best place to look? My local craiglist repairs either iPhones or appliances, and this random device is kind of in between. Chicago South suburbs.
    Last edited: Mar 19, 2014
  2. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    where there supposed to be pictures?
    googling for bt21608 seems like just a fairly common character LCD screen..

    Could just be the contrast or could be a failing screen.. They do have a lifespan..

    cheap attempt could just be to purchase a new screen and desolder/solder in a new one..
    russian likes this.
  3. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
    According to the datasheet, the back-led volts should be 3 to 4.2V.
  4. russian

    Thread Starter Member

    Sep 1, 2012
    Ops, now with a picture.
  5. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    The display is a 16x2 text LCD, and has what appears to be a standard 14 pin connector.

    LCDs with 14 pin connector don't have a backlight! Also the backlight LED terminals on the ends of the PCB are not used, also the short physical height of the display frame shows it has no backlight.

    Does the display normally show those 4 zeros?

    If that is a normal thing to display then your only problem is the LCD contrast, or LC material degradation. One can be fixed by adjusting the contrast voltage, the other requires a new LCD.



    Above shows the pinout, forget the last 2 pins they are for backlight which you do not have. (They are only on the 16pin pinout.)

    Contrast control voltage is pin 3. It is usually close to 0v, maybe 0 to 0.5v. If you trace that pin back on the PCB you may find a contrast pot, or the contrast voltage might be controlled from the micro as PWM through an RC filter to give a DC voltage under micro control.