Page 2 of 2
Re: Recommended fuse rating for 9VAC PSU
Posted: Tue Jun 20, 2017 12:20 am
by R'zo
Bobbi wrote:In the case of the 2 pin VIC, the external brick is just a transformer (with approx 12VAC secondary). The rest of the linear DC power supply (rectifier, smoothing caps) is inside the VIC-20.
Generally with power supplies, it is capacitors that go bad. For the two prong VIC, these components are within the VIC-20 itself. The transformer is a pretty reliable component in general and is unlikely to fail in any way that gives overvoltage at the output.
Any life-extension for the two prong VIC is going to involve replacing the power supply capacitors (and maybe the rectifier) inside the VIC. (Or just bypass the whole lot and use an off-the-shelf external DC supply connected to the output of the built-in power supply circuit?)
Good to know. Thank you.
Re: Recommended fuse rating for 9VAC PSU
Posted: Wed Jun 21, 2017 2:05 am
by Kakemoms
groepaz wrote:NOS should be better - what makes the caps go bad is heat (usually produced by something else in the PSU - which is why its bad design to place them near the components that produce lots of heat)
For non-solid capacitors this happends as the electrolyte slowly evaporates. As a hand of rule, the lifetime degrades about twice as fast per 10C temperature increase. So storing a capacitor for a very long time may degrade it even without actually using it, while operating one at about 40C above the same storage temperature would degrade it 2^4=16 times as fast.
Most capacitors can usually be found with a guaranteed lifetime, for example 2000hours/85C. In such a case, the same capacitor would be guaranteed for 128000 hours at 25C.
Re: Recommended fuse rating for 9VAC PSU
Posted: Wed Jun 21, 2017 5:48 am
by groepaz
2000h are just 83 days.... are you sure you didnt drop a zero in the process? =)