Working on a Sharp Image SI-134/ KTM-F33 Chassis with vertical collapse and am at my limit.
Repair log thus far:
Following the schematic, in order from the point that sync enters -
R524 1 ohm in circuit (10k ohm out of circuit which is what it's listed as, seems ok. No idea what it should read, as I don't have a working chassis to compare)
IC501 no shorts, all pins have continuity to the next pad they lead to
C523 This one stumps me. I have a BSIDE ESR02 ESR meter I use to test caps. This cap comes up as two diodes with a reading of "uF=2.37v 2.09v." Ordered replacement to see what happens
C524 Same thing, except the reading is "uF=3.55v 4.48v." No idea what is going on here. Ordered replacement
Outside of that section I found some other components not reading correctly and replaced them:
R903 reading 1k ohm in and out of circuit, should be 15. Replaced
Filter cap read low, replaced
C205 read low, replaced
IC201 It was recommended this be replaced in a troubleshooting guide I found about this model. This was replaced by someone before me, and they lifted SO MANY PADS. I replaced the IC with a new one and was able to get continuity to each pin. Pin 11 seems to lead nowhere, though, so can't test that one.
So, while waiting on shipping to replace the two other two caps (C523, C524), I put the chassis back in to see if any of my fixes made a difference. Well, it did, sort of. I still have vertical collapse, but it's slightly higher and now there is a faint but noticeably new high pitched squeal. The squeal changes pitch when the screen pot is adjusted on the flyback, and is present when the pot is turned all the way down.
So... given all that: what's next? I'm at the limit of my knowledge and abilities for now. Hope this makes sense to someone else.
Repair log thus far:
Following the schematic, in order from the point that sync enters -
R524 1 ohm in circuit (10k ohm out of circuit which is what it's listed as, seems ok. No idea what it should read, as I don't have a working chassis to compare)
IC501 no shorts, all pins have continuity to the next pad they lead to
C523 This one stumps me. I have a BSIDE ESR02 ESR meter I use to test caps. This cap comes up as two diodes with a reading of "uF=2.37v 2.09v." Ordered replacement to see what happens
C524 Same thing, except the reading is "uF=3.55v 4.48v." No idea what is going on here. Ordered replacement
Outside of that section I found some other components not reading correctly and replaced them:
R903 reading 1k ohm in and out of circuit, should be 15. Replaced
Filter cap read low, replaced
C205 read low, replaced
IC201 It was recommended this be replaced in a troubleshooting guide I found about this model. This was replaced by someone before me, and they lifted SO MANY PADS. I replaced the IC with a new one and was able to get continuity to each pin. Pin 11 seems to lead nowhere, though, so can't test that one.
So, while waiting on shipping to replace the two other two caps (C523, C524), I put the chassis back in to see if any of my fixes made a difference. Well, it did, sort of. I still have vertical collapse, but it's slightly higher and now there is a faint but noticeably new high pitched squeal. The squeal changes pitch when the screen pot is adjusted on the flyback, and is present when the pot is turned all the way down.
So... given all that: what's next? I'm at the limit of my knowledge and abilities for now. Hope this makes sense to someone else.