Connect with us

Activate Casio Scientific 197 Alarm

Discussion in 'Troubleshooting and Repair' started by JohnCR, Jun 27, 2012.

  1. JohnCR

    JohnCR

    8
    0
    Aug 8, 2010
    My Casio Scientific 197 alarm no longer functions. I have tested the signal from the watch module between the tiny coiled spring and the thin flat springy metal that each contact one of both surfaces of the thin flat rectangular piezo buzzer mounted on the interior rear cover of the watch. The coiled spring contacts the piezo surface directly and the springy metal contacts the rear watch cover on which the piezo is mounted. A scope shows a signal present that appears to be similar to the alarm sound when it functioned.

    I made contact between an inset reset point within the watch module and the positive side of the watch battery to activate the LCD display. There is a second inset point next to the thin coiled alarm spring. I do not know if this is a reset point for the alarm to be used as with the display - perhaps controlling the volume of the detected scope signal to the piezo. Any information on the function of this inset point would be appreciated.

    Both the springy metal and coiled spring are sufficiently extended to make good contact when the rear watch cover is replaced. I note that the surface of the piezo where the spring contacts is worn such that an ohm meter shows a high resistance between that point and the other surfaces. Contacts between other surfaces on the same side of the piezo show readings close to a short circuit. I suspect that the point of contact for the spring must be for the whole piezo surface so that this point should read a short circuit as well. I presume the piezo material must be surfaced on both sides with a conductive material for it to function.

    What can I do to resurface the piezo spring contact point to make it electrically conductive with the remainder of the surface and not damage the piezo material, or is the piezo beyond repair and can it be replaced?
     
    Last edited: Jun 28, 2012
  2. JohnCR

    JohnCR

    8
    0
    Aug 8, 2010
    Alarm Activation Solved

    Hoping to solve my problem without a hit or miss with possible negative consequences, I was forced to make a decision when part of the piezo attached to the inside of the rear cover broke away from the remainder still attached. This happened when I opened the cover as I have usually done many times.

    To attempt to recover the piezo, I used MG Chemicals Silver Conductive Epoxy by spreading a thin layer to the entire surface of the piezo while the separated part was reunited with the remainder and held in place. Care was needed to avoid the silver epoxy from contacting the rear cover that would create a short between the two surfaces of the thin piezo. After drying, amazingly the watch alarm now functions. Both the broken piezo and the conductive surface for the tiny spring contact on the piezo solved in one delicate operation.

    One step remains to securly glue the whole piezo to the rear of the watch. I am thinking of ZAP-A-GAP, a type of crazy glue sold in hobby shops. My concern is that the chemicals in this product might seep into the piezo material and affect its performance. A tiny amount of epoxy around the edges might be better. Any suggestions to securly attach the piezo in place would be appreciated.

    I do not know if the loudness of the alarm has been affected either because only the piezo part in contact with the spring is functioning without the attached part, or the piezo has deteriorated with age. I would appreciate information on where I can purchase thin piezo material to replace the existing one.
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-