Anyone here know about electronics?

[admin]

Specifically capacitors?

[LordEoin]

I know that:
a: they hurt if you touch them
b: max sheck's power station was just a giant capacitor.
Otherwise, clueless.

[JD]

What do you need to know about capacitors?

[Damofto]

My brother is an electronic engineer, he builds power supplies.  I can ask him any questions you have if that's any help?

[JD]

Hi Tube,
The voltage rating on a capacitor is a breakdown voltage. As long as they operate below that voltage level, they won't breakdown. As far as your case is concerned using higher voltage caps is perfectly fine.

If your original caps failed because they had a lower voltage rating than required, the chances are that the rest of the power supply suffered some collateral damage. The capacitor failure will often manifest as either a short or an open circuit. In a power supply, either condition can mean that the switching circuit before the cap is overloaded and you can get a cascade failure.
Hopefully this is not the case.

If your power supply is cycling, it suggest that a feedback loop is not working. Since the device worked originally, then something has broken in the existing feedback circuit. So, try the following:

• Check your solder joints are all good
• Electrolytic capacitors have a polarity. Check your capacitors were all replaced with the same polarity as those removed
• Check that you've not inadvertently shorted two tracks together when removing or replacing the caps
• Check that you've not accidentally severed a PCB track
• Check any coils for any overheat damage. If any are found, you'll likely need to replace the whole power supply.
• Check all active devices (transistors, ICs, etc.) for heat. If they are too hot to bear when touched, they are suspect. If you find a device that is way too hot, then replacing it might be feasible but typically a new power supply is the easiest and most likely to produce a success

Also, be careful if you are checking the power supply with its load disconnected. Operating a switched-mode power supply without a load is likely to cause damage or at least push the circuit outside of its design limits. Many switched-mode power supplies need a connected load to work correctly. Some have protection mechanisms against it, but not all.

/J

[delzep]

you mean you don't have one of those tellys with the wooden sides just like your ye olde tyme amstrads etc.? 

[JD]

Tube,

Cards on the table: my career took me away from hardware back in the late 80s and I've been writing code ever since. It's been many years since I wielded a soldering iron in anger.

As regards your issue, there is no real 'next most likely' thing to go. Capacitors can be fragile if they are below rating but most other components are fairly robust at the voltage levels concerned. The failure of the capacitors can push the whole circuit over the edge and it'll be the weakest link that fails. That could be any other device. If fate has anything to say about it, it will be the most awkward or most expensive component.

The burnt finger test is the best bet for where to go next.
/J

[delzep]

Tubes gaff will be one of those hoarders shows on discovery in a few years