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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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Posted to sci.electronics.basics,sci.electronics.components,sci.electronics.repair
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help diagnose old circuit board, fault
hello,
i am trying to repair a fault with an user interface circuit (UIC) board and control board out of an old 1987's computerized programmable Pfaff sewing machine (made in Western Germany). a for fun project for me , a challenge programming consists of storing values in memory locations using keys ( +/- buttons) on UIC board PROBLEM : a group of 3 (+/-) *momentary switch* buttons on UIC board used to change memory values do not make any changes when pressed. the UIC board has a VFD output display (16 chars) and 12 input buttons and 5 indicator LEDs. All but 3 of the buttons register presses correctly. the 3 broken buttons seem to be individually ok as i get continuity changes when i test with multimeter and push buttons. this UIC board is connected to the control board via 12 conductor ribbon ??? I am not sure what kind of things to do to isolate trouble ........ i have dome visual inspection of solder joints and components with no obvious issues. How would the VFD display values , LED indicatiors and inputing buttons be managed through a 12 conductor ribbon ??? in 1980's style ?? how to trace ot monitor value changes. Any troubleshooting or tracing ideas advice would br greatly appreciated. thanks, rob |
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