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CTC187 intermiitent RF

Discussion in 'Electronic Repair' started by [email protected], Sep 21, 2005.

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  1. Guest

    Set came in with the usual complaints: "goes snowy, and sometimes a
    vertical problem". Customer said that the set was never worked on so I
    figured I would do the tuner sheild and that would be it. I found that
    the soldering had in fact been done at some point and it actually
    looked pretty good. I have seen this repair done before on a
    symptomatic set and after re soldering the problem was resolved. I
    understand that there is a "template" for this repair, but I have
    never used it and have not had any problems with returns. I redid all
    the points on this set and reinstalled the chassis. I noted that
    tapping on the top of the tuner causies an intermittent loss of RF. I
    opened it back up and re did the sheilds as well as all the points on
    the board within the tuner area. I must be missing something but I
    can't for the life of me see what it is. I still have intermittent RF.
    Has anyone seen this before? Thanks, Lenny Stein, Barlen Electronics.
     
  2. Guest

    Lenny:
    Either you "missed" a solder point, that is why the template is
    nice.... or there is a solder bridge, cracked trace, or cold solder
    joint.
    electricitym
     
  3. kip

    kip Guest

    Lenny get out the Biggest Mag glass you can get ,what
    I use is an old lens from PTV works wonders.


    kip
     
  4. Jumper wires done also?

    Tom
     
  5. Guest

    Which jumpers are you referring to?
     
  6. kip

    kip Guest

    Ground shield..
     
  7. Jumper wires which are backups for the various solder grounds.
    Reliability through redundancy. I worked in a Thomson warranty shop,
    and it was the manufacturer's standard for the repair. Some maintain
    that they are not necessary if the repair is done correctly, just like
    some don't think the flexible solder is necessary.

    Tom
     
  8. Art

    Art Guest

    Also be advised, Rare but it does happen! Occasional the glue that was used
    to secure the smd devices becomes slightly conductive, esp after a few years
    of operation. This may contribute to your symptoms, however, IMHO: follow
    the leads, get some good flux cleaner and clean the area of the tuner,
    solder side. Diligently inspect all the connections for the coils located
    within the tuner. comparing the top of the board with the bottom will
    indicate where the coils come through and are soldered. Do not ignore other
    devices and the probability of a small solder "dot" or splash that errantly
    is conducting. Good luck, these can be a bugger at times.
     
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