| Electronics > Repair |
| Voltage Increase, failed component? |
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| shakalnokturn:
Well it can't have been a dead short surely? If it was is there more than one linear regulator for the 5V supplies? I doubt 5μF is enough to make the difference but then again if the 5V regulator has been running hot for ages it may not be giving the optimal output any more. Ideally you'd measure DC voltage and ripple or scope at the capacitor pins (CPU decoupling I assume) . If in doubt you can always stack a second 5μ on top of the one you fitted. As for other steppers... Re-check wiring, I'm the first to neglect obvious things when rushing to test after replacing components. Are the other steppers controlled by the same CPU? |
| ajp8868:
Actually you're right, it measured a very slight resistance so not fully dead short. But when measured out of circuit it had no capacitance (DMM) and my little ESR tester thought it was a resistor. What would I be looking for when measuring ripple at the caps? Sorry for noob question but I don't have a scope yet, bidding on one so finger crossed. Fairly certain it's not wiring as it broke as soon as I removed the stepper controller, while live, for the second time. This unit was fully working, I've swapped the board into it to rule out things like wiring, motors etc. |
| ajp8868:
Just to update, light is now fully working! So I think the original issue was simply that capacitor, and I've just blown chips by unplugging steppers while powered up. Replaced one 74HC04 which fixed colour/gobo and then replaced the other which was causing issues with prism and gobo rotate. Thank you for all your help and suggestions. Another light saved from landfill! |
| shakalnokturn:
As for the ripple question it's a bit of a tough one... When scoping a power rail you wouldn't want the min / max values too close to the absolute min / max supply values stated for correct operation of any device powered by that rail. For 5V or 12V rails on a linear regulator I'm usually satisfied with 10-15mV RMS or 100mV p-p but then again it depends where you measure. Such values won't be acceptable for a 1.8V rail though. It really depends on system requirements... You wouldn't tolerate the same amount on an instrumentation amplifier as on your stepper motor supply. |
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