SR-52A rebuild project (SR-52A 942058 LTA4176)
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03-13-2021, 10:00 PM
Post: #19
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RE: SR-52A rebuild project (SR-52A 942058 LTA4176)
Card reader works, reads and writes
Hello Everyone, the card reader is now working ![]() First we disconnected the card reader and checked the resistance for every channel Yellow with Black : 681 Ohm Green with Black : 675 Ohm Orange with Black : 700 Ohm White with Black : 718 Ohm we do not have (yet) an Impedance Meter so we couldn't check those values as well but never mind, the head looked ok, we polished the face of the magnetic head with a Dremel and a cotton tool, is less aggressive than using the cleaning card which is abrasive and has the same effect as for removing the dirty patina one thing we learned todays is that rather then putting oil in order to lubricate the card reader motor (we were using WD-40) is way better to use a contact cleaner (we uses Deoxit D5) we think this is because probably the reason for a noisy and slow motor is that the electric brushes that can be seen from the bottom removing the small black cover are oxidized and the contact cleaner makes miracles, now the motor is fast and way more silent than before Then we removed the TMC0595 (our is a version D, it was printed on the bottom) We cleaned underneath and we also removed and checked all the capacitors C12,C2, C3, C4, C5 checked the nominal value and in the end we used those from the other spare unit as they were .004 microF which was closer than the original ones to the nominal value of .005 microF Meanwhile we discovered and fixed (again) the keyboard that had a loose joint for the fifth column which made Impossible to do any calculation being that the column with the operation keys and the equal key Re mounted everything and ... voila It reads all of the BA Libray and we have also been successfully copying the card BA-1 Diagnostic cards also produce the expected result Next step : check the faceplate and close everything .... We may as well try the same operation on the other spare unit, but first we need to find a good SN27882 because we took one from that unit to repair this ... It's available new on line or it can be found on all of the SR-50 models Picture and video updated here : SR-52A rebuild project (SR-52A 942058 LTA4176) Edoardo & Alberto |
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