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this is a long story, but might be interesting to someone, especially a cheapskate who might want to get their knock-off opti working again... or just someone interested in electronics
i pulled apart my dead opti recently, which was a reman gm with a knockoff optical sensor in it, which obviously have a pretty high failure rate.
attaching the opti as a unit to a scope, and running it with a drill revealed intermittent signals, especially when tapping gently on the metal part of the opti.
in the future we might be stuck with this thing; as mitsubishi isn't making an opti sensor anymore.
as this seems to be the sensor used in all the recent GM remans, i examined it closely to find out what the deal is. i believe the sensor in the "$100 ebay special" is the same unit, but i haven't taken one of those apart (yet)
the majority of the surface mounted components on the sensor board are of reasonable quality. the soldering of the components on the upward-facing side of the board is all done by machine. the board itself and etching are good.
this doesn't suprise me -- chinese electronics factories are actually pretty good at board layout and etching, and they have tons of good robotic soldering rigs.
the board is marked with numbers that don't mean anything (probably internal production codes..)
there's a pair of LM2903 of unfamiliar brand, which i suspected as a failure point.. but i desoldered and tested them against a texas instruments LM2903 i had laying around, and they appeared to be a good enough clone.
the internal electronics are well sealed with silicone, and are likely to be fairly water resistant, meaning any water intrustion problems even on a cheap opti are probably with the slotted wheel, not the electrical part. all the same, with the design of the casing, water instrusion is possible.
the control board is hand-soldered to the 4-pin opti connector. the work is sloppy but strong. the sealing of the connector pins through the case is perfect.
the big nasty kill-your-opti fault i found was in the stage of assembly where the optical pickup (looks to be a standard photo-diode) are hand-soldered to the board.
of the four connections made between the two sensors, none of the solder wicked to the photodiode at all. gently vibrating the photodiode while monitoring a scope, as it was originally mounted to the board, resulted in lost conductivity. i'm certain this caused the intermittent failure i was experiencing
the photodiodes were attached so poorly, they could be removed from the board by simply pulling them.
interesting part is, the photodiodes were siliconed into the casing, then the board was attached. there is quite a bit of silicone in between the photodiode and the board.. in fact, it's everywhere.
i can only draw the conclusion that the silicone contaminates the contacts, preventing the solder from adhering
i cleaned the contacts and reflowed the solder, and the opti seems to be behaving itself in a simple 'scope test driven by a hand drill
i pulled apart my dead opti recently, which was a reman gm with a knockoff optical sensor in it, which obviously have a pretty high failure rate.
attaching the opti as a unit to a scope, and running it with a drill revealed intermittent signals, especially when tapping gently on the metal part of the opti.
in the future we might be stuck with this thing; as mitsubishi isn't making an opti sensor anymore.
as this seems to be the sensor used in all the recent GM remans, i examined it closely to find out what the deal is. i believe the sensor in the "$100 ebay special" is the same unit, but i haven't taken one of those apart (yet)
the majority of the surface mounted components on the sensor board are of reasonable quality. the soldering of the components on the upward-facing side of the board is all done by machine. the board itself and etching are good.
this doesn't suprise me -- chinese electronics factories are actually pretty good at board layout and etching, and they have tons of good robotic soldering rigs.
the board is marked with numbers that don't mean anything (probably internal production codes..)
there's a pair of LM2903 of unfamiliar brand, which i suspected as a failure point.. but i desoldered and tested them against a texas instruments LM2903 i had laying around, and they appeared to be a good enough clone.
the internal electronics are well sealed with silicone, and are likely to be fairly water resistant, meaning any water intrustion problems even on a cheap opti are probably with the slotted wheel, not the electrical part. all the same, with the design of the casing, water instrusion is possible.
the control board is hand-soldered to the 4-pin opti connector. the work is sloppy but strong. the sealing of the connector pins through the case is perfect.
the big nasty kill-your-opti fault i found was in the stage of assembly where the optical pickup (looks to be a standard photo-diode) are hand-soldered to the board.
of the four connections made between the two sensors, none of the solder wicked to the photodiode at all. gently vibrating the photodiode while monitoring a scope, as it was originally mounted to the board, resulted in lost conductivity. i'm certain this caused the intermittent failure i was experiencing
the photodiodes were attached so poorly, they could be removed from the board by simply pulling them.
interesting part is, the photodiodes were siliconed into the casing, then the board was attached. there is quite a bit of silicone in between the photodiode and the board.. in fact, it's everywhere.
i can only draw the conclusion that the silicone contaminates the contacts, preventing the solder from adhering
i cleaned the contacts and reflowed the solder, and the opti seems to be behaving itself in a simple 'scope test driven by a hand drill
