LA 7612N - RCA jungle IC

Discussion in 'Electronic Repair' started by Arnold stewart, Jun 28, 2004.

  1. Re: RCA Chassis CTC197CE2, Model F32683SB
    The jungle IC is an LA7612N. TV has sound but no video & no OSD.
    Orignially TV would click three times and do nothing. I changed the
    flyback. Now I have a raster & sound, but no video. Does anybody know if
    the LA7612N has the same pinouts as the LA7610? If not, could you tell
    me what pins have the RGB outputs? (I may also have a corrupted eeprom,
    however TV turns on, changes channels, & volume functions normally.)
     
    Arnold stewart, Jun 28, 2004
    #1
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  2. Arnold stewart

    JURB6006 Guest

    Go to bdent.com and get a user and pass, it's free. You can also get datasheets
    at datasheetarchive.com, but they are slow. Might not matter if you're on wire,
    but if you got highspeed internet, is't, well, like the old days. Very slow.

    You're probably headed in the right direction though, wouldn't be the first
    time a bad fly fried the ABL network and blew out the video circuit.

    JURB
     
    JURB6006, Jun 30, 2004
    #2
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  3. I've tried bdent.com They don't have anything on the LA7812. I'll try
    datasheetarchive.com
    Thanks.

    JURB6006 wrote:
    > Go to bdent.com and get a user and pass, it's free. You can also get datasheets
    > at datasheetarchive.com, but they are slow. Might not matter if you're on wire,
    > but if you got highspeed internet, is't, well, like the old days. Very slow.
    >
    > You're probably headed in the right direction though, wouldn't be the first
    > time a bad fly fried the ABL network and blew out the video circuit.
    >
    > JURB
     
    Arnold stewart, Jun 30, 2004
    #3
  4. Arnold stewart

    David Guest

    I think what you will find (in the far reaches of my memory) will be
    either a shorted zener or open resistor on the ABL line, or a missing
    h-sync return pulse to the system control for that symptom on that
    chassis.

    David

    Arnold stewart <> wrote in message news:<e30Ec.7948$>...
    > Re: RCA Chassis CTC197CE2, Model F32683SB
    > The jungle IC is an LA7612N. TV has sound but no video & no OSD.
    > Orignially TV would click three times and do nothing. I changed the
    > flyback. Now I have a raster & sound, but no video. Does anybody know if
    > the LA7612N has the same pinouts as the LA7610? If not, could you tell
    > me what pins have the RGB outputs? (I may also have a corrupted eeprom,
    > however TV turns on, changes channels, & volume functions normally.)
     
    David, Jun 30, 2004
    #4
  5. Arnold stewart

    Boris Guest

    RCA197

    Hey Arnold,
    Have you read "RCA/GE TV (CTC175-187+) Solder Connection and EEPROM Problems" - it basically says that RCA EEPROM problems are very
    common and can extend to much more than trivial outcomes. However, I do tend to agree with you that it is very unlikely that only
    the video is completely out due to bad EEPROM.
    http://www.repairfaq.org/sam/rcatune.htm

    It may also be useful to take a look at the RCA197 service manual
    http://schforfree.seedhost.com/archive/?path=Video/products

    I would like to use this post to also ask a few enlightenment questions:
    1. What is the function (and acronym) of the ABL circuit? Perhaps I know about it, but confuse the English name, or might have never
    heard of its function...
    2. How do you "change the flyback"? Do you mean the cable or the whole transformer? I've heard people referring to the fat red
    high-voltage cable as "flyback" and it (typically) cannot be changed. In this case, is there a special term for the big transformer,
    tied to the HOT collector?
    3. Regarding David's message: "missing h-sync return pulse to the system control" - where is this pulse taken from? What's the
    purpose - feedback that the HOT is working fine?
    4. I've heard there is a way to cut off the HOT circuit, connect a regular bulb and test the power supply alone. I never dared to do
    that, however, being afraid of corrupting a feedback from the HOT to the power supply and blowing off the whole TV/monitor. Can
    onyone comment how does this bulb trick work (may be a detailed link)?

    Best regards,
    Boris


    "Arnold stewart" <>
    > Re: RCA Chassis CTC197CE2, Model F32683SB
    > The jungle IC is an LA7612N. TV has sound but no video & no OSD.
    > Orignially TV would click three times and do nothing. I changed the
    > flyback. Now I have a raster & sound, but no video. Does anybody know if
    > the LA7612N has the same pinouts as the LA7610? If not, could you tell
    > me what pins have the RGB outputs? (I may also have a corrupted eeprom,
    > however TV turns on, changes channels, & volume functions normally.)
     
    Boris, Jul 1, 2004
    #5
  6. Re: RCA197

    Boris wrote:
    > Hey Arnold,
    > Have you read "RCA/GE TV (CTC175-187+) Solder Connection and EEPROM
    > Problems" - it basically says that RCA EEPROM problems are very common
    > and can extend to much more than trivial outcomes. However, I do tend to
    > agree with you that it is very unlikely that only the video is
    > completely out due to bad EEPROM.
    > http://www.repairfaq.org/sam/rcatune.htm
    >
    > It may also be useful to take a look at the RCA197 service manual
    > http://schforfree.seedhost.com/archive/?path=Video/products
    >
    > I would like to use this post to also ask a few enlightenment questions:
    > 1. What is the function (and acronym) of the ABL circuit? Perhaps I know
    > about it, but confuse the English name, or might have never heard of its
    > function...
    > 2. How do you "change the flyback"? Do you mean the cable or the whole
    > transformer? I've heard people referring to the fat red high-voltage
    > cable as "flyback" and it (typically) cannot be changed. In this case,
    > is there a special term for the big transformer, tied to the HOT collector?
    > 3. Regarding David's message: "missing h-sync return pulse to the system
    > control" - where is this pulse taken from? What's the purpose - feedback
    > that the HOT is working fine?
    > 4. I've heard there is a way to cut off the HOT circuit, connect a
    > regular bulb and test the power supply alone. I never dared to do that,
    > however, being afraid of corrupting a feedback from the HOT to the power
    > supply and blowing off the whole TV/monitor. Can onyone comment how does
    > this bulb trick work (may be a detailed link)?
    >
    > Best regards,
    > Boris
    >

    Thanks for the website. In reply to your questions:
    1. ABL stands for automatic brightness limiter.
    2. In changing the flyback the whole transformer is replaced.
    3. The pulse is taken from the flyback transformer and used by the
    system control.
    4. By removing the horizontal output transistor you will no longer get
    high voltage, but the power supply will not have enough load on it to
    tell you if it's working properly. Connecting a 100 watt light bulb
    between ground (or emitter of the HOT) and collector, sufficient load is
    placed on the power supply.
     
    Arnold stewart, Jul 3, 2004
    #6
  7. Arnold stewart

    ArnoldStw Guest

    Arnold stewart <> wrote in message news:<e30Ec.7948$>...
    > Re: RCA Chassis CTC197CE2, Model F32683SB
    > The jungle IC is an LA7612N. TV has sound but no video & no OSD.
    > Orignially TV would click three times and do nothing. I changed the
    > flyback. Now I have a raster & sound, but no video. Does anybody know if
    > the LA7612N has the same pinouts as the LA7610? If not, could you tell
    > me what pins have the RGB outputs? (I may also have a corrupted eeprom,
    > however TV turns on, changes channels, & volume functions normally.)


    I have obtained much more information since this post. The LA7610 and
    LA7612 do not have the same pinouts.
    In my original post I said that I had a raster but no video. What I
    should have added is that I had a raster with retrace lines visible on
    the screen no matter where I set the screen control on the flyback,
    that is until the screen was extinguished. The screen control can
    adjust the voltage from 0 to approx. 550V
    I have checked all voltages to the CRT and they check out normal. I
    suspect I have a shorted tube.
    As far as the set clicking three times and then doing nothing, RCA
    explains it this way:
    Dead Set - Degauss Relay clicks
    If the television tries to start three times and then stops (you can
    hear the clicking sound of the Degauss relay energizing), this means
    the EEPROM (U13102) and T4 Chip (U16201 - LA7612) are working
    (hardware is OK). Therefore the problem is most likely power supply
    and/or deflection related.
     
    ArnoldStw, Jul 7, 2004
    #7
  8. Arnold stewart

    john Guest

    Make sure that when you installed that flyback that none
    of the small parts near the flyback got sucked in your solder sucker.
    Those around the base pads...
    Also make sure that filter cap to the left does not have a broken trace.

    kip

    --
    "Watch the return E-Mail addy its false"
    "ArnoldStw" <> wrote in message
    news:...
    > Arnold stewart <> wrote in message

    news:<e30Ec.7948$>...
    > > Re: RCA Chassis CTC197CE2, Model F32683SB
    > > The jungle IC is an LA7612N. TV has sound but no video & no OSD.
    > > Orignially TV would click three times and do nothing. I changed the
    > > flyback. Now I have a raster & sound, but no video. Does anybody know if
    > > the LA7612N has the same pinouts as the LA7610? If not, could you tell
    > > me what pins have the RGB outputs? (I may also have a corrupted eeprom,
    > > however TV turns on, changes channels, & volume functions normally.)

    >
    > I have obtained much more information since this post. The LA7610 and
    > LA7612 do not have the same pinouts.
    > In my original post I said that I had a raster but no video. What I
    > should have added is that I had a raster with retrace lines visible on
    > the screen no matter where I set the screen control on the flyback,
    > that is until the screen was extinguished. The screen control can
    > adjust the voltage from 0 to approx. 550V
    > I have checked all voltages to the CRT and they check out normal. I
    > suspect I have a shorted tube.
    > As far as the set clicking three times and then doing nothing, RCA
    > explains it this way:
    > Dead Set - Degauss Relay clicks
    > If the television tries to start three times and then stops (you can
    > hear the clicking sound of the Degauss relay energizing), this means
    > the EEPROM (U13102) and T4 Chip (U16201 - LA7612) are working
    > (hardware is OK). Therefore the problem is most likely power supply
    > and/or deflection related.
     
    john, Jul 7, 2004
    #8
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