68kMLA Classic Interface

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Recap LC475 mainboard
Posted by: Mustermann on 2024-11-25 13:33:03 First have two capacitors in a row. Lets say 1µF each. So you can measure 0.5µF for both. Next detach C Meter as it will disturb charging. Then charge 1 capacitor to 5V. Second capacitor uncharged. When removing battery, capacitor stay charged. Then charge the other capacitor with reversed polarity. Both capacitors are charged, 5V and -5V. So result is 0V Now remove battery. Both capacitors are still charged. Connect C meter. As Voltage at C meter is 0V it is able to measure without changing the DC Voltage at the capacitors. You are able to measure capacitance of DC charged capacitors. Because of DC degrading resulting capacitance is different (smaller). As leaking current is not so high, DC voltage stay for at least minutes (enough time to measure capacitance and verify that capacitors are still charged. Does this make sense?
Posted by: zigzagjoe on 2024-11-25 14:02:50 First have two capacitors in a row. Lets say 1µF each. So you can measure 0.5µF for both. View attachment 80688 Next detach C Meter as it will disturb charging. Then charge 1 capacitor to 5V. Second capacitor uncharged. View attachment 80689 When removing battery, capacitor stay charged. Then charge the other capacitor with reversed polarity. Both capacitors are charged, 5V and -5V. So result is 0V View attachment 80690 Now remove battery. Both capacitors are still charged. Connect C meter. As Voltage at C meter is 0V it is able to measure without changing the DC Voltage at the capacitors. You are able to measure capacitance of DC charged capacitors. View attachment 80691 Because of DC degrading resulting capacitance is different (smaller). As leaking current is not so high, DC voltage stay for at least minutes (enough time to measure capacitance and verify that capacitors are still charged. Does this make sense? Yeah... that's what I had pictured, I just did not expect that the capacitance meter actually would work in that scenario. I assumed it was the simple charge/discharge type that is commonly built into multimeters. What are you using to measure?
Posted by: Mustermann on 2024-11-25 21:56:34 Vichy DM4070 LCR Meter.
Posted by: Mustermann on 2024-11-30 00:43:19 Board now reacped with all OS-CONs Board is working. 5x 10SVP56M 56µF 10 V for 5V and -5V 4x 25SVPF47M 47µF 25V for 12V and Booster 2x 16SVPC100M 100µF 16V for 5V and -5V in audio section All capacitors were within +-5%
Posted by: joshc on 2024-11-30 03:18:34 Board now reacped with all OS-CONs Board is working. 5x 10SVP56M 56µF 10 V for 5V and -5V 4x 25SVPF47M 47µF 25V for 12V and Booster 2x 16SVPC100M 100µF 16V for 5V and -5V in audio section All capacitors were within +-5% Nice work!
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