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Texas Instruments Speak & Math freezing

Discussion in 'Power Electronics' started by bflo, Dec 27, 2020.

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  1. bflo

    bflo

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    Dec 27, 2020
    Just found my old TI Speak and Math in parents basement. Gave it to my kids and it works at first but after 3-4 math problems, screen freezes and batteries have to be removed. Seems to do this everytime. Any suggestions? Also found my speak and spell and it works fine to date. tia.
     
  2. Martaine2005

    Martaine2005

    3,104
    851
    May 12, 2015
    Hi bflo
    Does this game have a VFD (vacuum fluorescent display)?.

    You’ll have to open the unit.
    Depending on model, it could have a separate PCB which is the power supply. Visually inspect the board for corrosion, leaky electrolytic capacitor or signs of heat.
    Then check both boards for dry/cracked solder joints. Especially near and under the VFD.
    If you have no luck with initial checks, you can post close up pictures of the boards here.

    Martin
     
  3. bflo

    bflo

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    Dec 27, 2020
    It is a VFD I believe. I will try to open it up and send what I see. Thx
     
  4. bertus

    bertus Moderator

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    Nov 8, 2019
    Martaine2005 likes this.
  5. Martaine2005

    Martaine2005

    3,104
    851
    May 12, 2015
    Nice find @bertus
    I couldn’t find a single picture.
    But then again, I have one in a cupboard somewhere.

    Martin
     
  6. bflo

    bflo

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    Dec 27, 2020
    Thank you @bertus I am very inexperienced in this area.
     
  7. bflo

    bflo

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    Dec 27, 2020
    here's what she looks like on the inside.
     

    Attached Files:

  8. Martaine2005

    Martaine2005

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    851
    May 12, 2015
    And the component side?.

    That will tell us more. Was there screws or clip in plastic?
    I have checked the cupboards here and can only find Action man, sindy and Barbie. But I found a “penny puppy walker”. The batteries had leaked but still worked. Now I have to clean her lol. I love old electronic toys.
     
  9. bflo

    bflo

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    Dec 27, 2020
    Screenshot_20201228-163723_Gallery.jpg Screenshot_20201228-163713_Gallery.jpg Screenshot_20201228-163651_Gallery.jpg Screenshot_20201228-163632_Gallery.jpg here's best I could get of the under belly.
     
  10. 73's de Edd

    73's de Edd

    2,999
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    Aug 21, 2015
    Sir bflo . . . . . .
    What I am seeing there is only two suspect parts, for what trouble you are experiencing.
    These are all being on the side mounted PC board .
    The least likely will be the BLUE tantalum drop E- capacitor and the most likely, the conventional radial leaded black E-capacitor right beside it.
    There is being a third grey cased axial leaded E-capacitor at mid board, but it should be the filter and storage capacitor for the auxiliary step up power supply created by the ferrite toroidal transformer encased within the black 8108 code dated unit from Angeles City. That group supplies an approximate negative 30-40 volts potential for the VFD displays readout electrodes, with the displays spaced apart dim filament strings, being supplied from a level of the conventional 6V power supply.
    There is probably only a 50% chance, from its rotational positioning, that you will be able to read the grey caps printed on capacitance value AND its HIGHER than 6 volt rating.
    I can see 2 of the 6 transistors being related to the just related negative voltage boost supply, and possibly two with regulation down to the 5V logic supply level . And possibly a complementary pair of two audio transistors, if so, they are being associated with a real . . . . . s . . . . .t . . . . .r . . . . .u . . . . .n . . . .g . . . . apart audio system. With its initial conception being within a portion of one of the custom IC's and then a feed into the two complementary audio transistors, with them then feeding into the primary of the yellow taped audio output transformer down near the earphone and aux AC power connectors. Then the audio transformer secondary dumps its audio into the units 8 ohm Z speaker.
    That all said . . . . .now would be the most appropriate time for any TI'ers / readers of the Lou Bock Texas Instrumentations plant,of that 80-90 ish era, to chime in with any solid additional tech info

    DOIN' THE DEED . . . . . .

    Now, how come that my SEVENTH sense is absolutely telling me, that you DO NOT have a nearby whole giant assortment of 1,000 E-caps. . . .with 10 of every cap and voltage value.
    Instead, you will have to be scrounging from any electronic cadavers for possibly even finding a short leaded pull of an ~47- -thru - -100 ufd E-cap of a > > > > > 6vdc working voltage rating.
    Then using some stripped down Cat-5 cable for yielding hook up wire to initially tin and then solder on as E-cap wire lead extensions.

    Now we have two situations . . . . . powering of the unit is being from the TI wall wart adapter . . .or . . . . being from 4 alkaline C cells installed in the unit.

    If being from the wal wart, check the specs molded / printed on the unit and see if it is specified as AC or DC output and if it is DC it will identify the coax connections polarities.

    AND with my suspicion that if it is being a DC power output unit, that the 4 full wave bridge diodes inside are feeding into a 470 or 1,000 or 1,500 or 2,200 ufd E cap that 40 years of dormancy has resulted in capacitive decline as well as . . . more importantly . . . its bypassing /decoupling effectivenes . . . . .as being related to causing your wierd effects.

    So, if you were AC line powering, revert to the use of alkaline C battery powering i an evaluation and see if the wierd quirks then all dissappear.
    If not . . . . . I will continue . . .

    CAVEAT . . . .

    On one particular camera shot you can see the use of a flexicable from the units frontal keyboard to the mid PCB plug in connector.
    To make it "beefier" and less flexible at the connector end, and its handling while plugging in and a grrip while unplugging, it has a MUCH heavier strip of clear plastic contact cemented to the flexicable .
    With your extreme transpositioning of the board it has the two now starting to come unbonded.
    Repair with either an end wrap around, on both ends, with clear 3M boxing tape or some clear E-2000 cement in bonding them together again with clothespin clamps during drying.

    The 13 printed / sprayed "wires" are being of deposited carbon strips and are picky to excessive flexure . . . in their then creating micro breaks.
    Loosing connectivity of even one of them results in dead / unresponsive keypads. . . . .until being bridge repaired.

    Thaaaaassssit . . . . .



    73's de Edd . . . . .



    An 'ole country bumpkin stands in front of a food truck and then s l o w l y reads the menu . . . being
    resplendently complete . . . what, with his accompanying silent mouth movements and all :

    "Cheeseburgers: $5 . . . . . Fries: $3 . . . . . Handjobs: ( out back ) $10."

    He then walks up to the window and asks the sole beautiful blonde that's working behind the counter,
    "Are you the one whut likes that done gives them a thar handjobs?"
    "Why Ye s s s s , I am," she replies seductively.
    "Well then , go over yonder and wash yore hands . . . R- E- E- E- E- L- Y . . . R- E- E- E- E- L- Y . . . guds,
    cause I done wants you to makes me one a them thar cheese-a-burgers."



    .
     
    Last edited: Dec 29, 2020
    Martaine2005 likes this.
  11. bflo

    bflo

    6
    0
    Dec 27, 2020
    @73's de Edd . . . . .
    You are very kind to help with such detailed information. You clearly have taken significant time to try to assist. I apologize that I am but a novice (at best) and most of what you shared is "over my head". But at the risk of offending you- I did want to say THANK YOU and I truly appreciate your time and effort. I will do my best to follow your advice.
     
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