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goodmans 32" crt tv 11ak37 pic too large

 
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perkinsprima



Joined: 08 Feb 2009
Posts: 1
Location: westwales

PostPosted: Sun Feb 08, 2009 8:21 pm    Post subject: goodmans 32" crt tv 11ak37 pic too large Reply with quote

hi
got given a goodmans gtv76w4 . 11ak37 but seems that pic is too large as writing is off tre edge of screen & any straight vertical lines ie door frames etc, nearer edge of screen, curve inwards at middle like an hour glass. HELP! Have tried various settings in service & geometry menu but they only seem to work vertically but not horizontal size or shape, tried all settings as per manual so any ideas welcome. Happy to change components if required if someone can tell me which parts & how to discharge set, have restored a few jukeboxes in last few years so dont mind soldering etc. probably not worth sending for repair. many thanks for any replies
regards
Glyn
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torbjorn



Joined: 07 Jun 2007
Posts: 370
Location: Sweden

PostPosted: Mon Feb 09, 2009 8:46 am    Post subject: Reply with quote

If the picture width is too large and it has E/W pincushion distorsion as you describe, then the fault is most likely one of the diodes in the E/W modulator (usually, two diodes that are connected in series between the collector of the line output transistor and ground). You should also check the capacitors that are in parallel to the diodes, and the drive circuit that is connected to the mid point between them. If one of the diodes or capacitors fail, this will usually cause some more components to burn out (fusible resistors and/or a transistor/IC in the drive circuit).
When replacing the diodes, make sure to use the original types or a replacement that not only withstands the same voltage and current as the original type, but also is at least as fast as the original one. Look for the parameter "reverse recovery time", trr in the data sheet.
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