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post #14 of Old 04-17-2013
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Re: Wanted- Otto, Dead or Alive

That's why I'm thinking it's a power supply issue. Most of the rest of the unit will be "off" and not getting power when the power is "off" even if the power is still connected. If it was up-stream from the power supply, then merely powering it off and on again would work. Having to remove the power to get it to work suggests to me that it's in the power supply.

The long wait between power off and power on suggests that it's either an energy storage device (capacitor or inductor) or something that's attached to it. For example, if a transistor is attached to the cap, if the transistor is overheating, the capacitor may not be discharging. The charged state of the cap keeps the transistor "warm" until it finally loses the charge from the cap, at which point the transistor begins to cool and you're able to turn it on again. The same thing could also happen with a bad solder joint in the power supply.

Granted, this would be an academic exercise and won't really help you fix your problem, but I'd be curious to know what happens if, once it turns itself off, you just let it sit. Leave it alone for 20-30 minutes. Does it come back on at that point? I know I'm not patient enough for this to have happened in real life if this were my unit, so I'm just curious if you've tried this (even by accident). At some point, if the unit has powered off, the current draw should be minimal and it should cool down sufficiently (again, assuming this is a thermal issue, which is very common with electronics). If it still doesn't work after 20-30 minutes, but it does work after you've pulled the power, then I agree with you, it's probably not a bad solder joint or even external gunk causing a short. Again, though, I'd look to the power supply, and to some of the components near the input end of the power supply.

All that being said, if you can find a replacement that's in your budget, that's the faster way to do it.

- Jim
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1975 Albacore 15

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