I am bringing out of storage - not counting the actual computers - probably 5 large boxes of Commodore 128 and 64 hardware accessories, software, books. Collected mostly from the Bay over the past 20 years.

For the 128 and 64 computers, should I power them up with low voltage on a variac for a while before giving them the full 120v? The idea being to perhaps give the old caps a better chance of surviving powerup after long storage?

Or would low voltage give the power supplies and internals problems?

I will have a dim bulb tester in series also in case their are any serious problems with the units.

thanks,
LT

Kenzo <kjambrose@gmail.com> wrote:
>
> For the 128 and 64 computers, should I power them up with low
> voltage on a variac for a while before giving them the full 120v?
> The idea being to perhaps give the old caps a better chance of
> surviving powerup after long storage?
>
> Or would low voltage give the power supplies and internals problems?

It should be OK so long as you don't connect any externally-powered
accessories such as a disk drive when they're under test, in which
case the voltage difference between the different devices could
cause damage in various ways.

Usually that technique is used with equipment with higher internal
voltages though, I'm not sure whether it will prevent much in this
case where the difference is only a handful of volts.

> I will have a dim bulb tester in series also in case their are
> any serious problems with the units.

That should only be needed for the power supplies themselves, as
the voltage regulator inside the PSU should limit the current to
the computer if something inside draws way too much power.
Furthermore I'd suggest you check the PSUs separately from the
computers, and always test the computers with a known good PSU.

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#_ < |\| |< _#

Computer Nerd Kev <not@telling.you.invalid> wrote:
> Kenzo <kjambrose@gmail.com> wrote:
>>
>> For the 128 and 64 computers, should I power them up with low
>> voltage on a variac for a while before giving them the full 120v?
>> The idea being to perhaps give the old caps a better chance of
>> surviving powerup after long storage?
>>
>> Or would low voltage give the power supplies and internals problems?
>
> It should be OK so long as you don't connect any externally-powered
> accessories such as a disk drive when they're under test, in which
> case the voltage difference between the different devices could
> cause damage in various ways.
>
> Usually that technique is used with equipment with higher internal
> voltages though, I'm not sure whether it will prevent much in this
> case where the difference is only a handful of volts.

Actually the extra ripple resulting from the voltage from the
transformer being under the value of the voltage regulator could
possibly be a problem with the electronics in the computers due
to capacitors causing different voltages to exist in different
places.

Probably best not to use the variac when powering the computers,
and if using it at all then just for the PSUs connected to a dummy
load (high-wattage resistors).

--
__ __
#_ < |\| |< _#

not@telling.you.invalid (Computer Nerd Kev) writes:

> Furthermore I'd suggest you check the PSUs separately from the
> computers, and always test the computers with a known good PSU.

I especially seem to remember the old US C64 power supply can produce
quite high voltage ripple and that can damage the computer. So testing
the output with a scope would make sense to me.

On Friday, April 29, 2022 at 12:46:18 AM UTC-7, Anssi Saari wrote:
> n...@telling.you.invalid (Computer Nerd Kev) writes:
>
> > Furthermore I'd suggest you check the PSUs separately from the
> > computers, and always test the computers with a known good PSU.
> I especially seem to remember the old US C64 power supply can produce
> quite high voltage ripple and that can damage the computer. So testing
> the output with a scope would make sense to me.
thanks to all, very helpful!

On 29/04/2022 1:44 am, Kenzo wrote:
> I am bringing out of storage - not counting the actual computers - probably 5 large boxes of Commodore 128 and 64 hardware accessories, software, books. Collected mostly from the Bay over the past 20 years.
>
> For the 128 and 64 computers, should I power them up with low voltage on a variac for a while before giving them the full 120v? The idea being to perhaps give the old caps a better chance of surviving powerup after long storage?
>
> Or would low voltage give the power supplies and internals problems?
>
> I will have a dim bulb tester in series also in case their are any serious problems with the units.
>
> thanks,
> LT
>

Neh, just don't just a genuine C64 brick of death or at least use a
power saver. If you're determined to use an original brick do measure
voltages first, they are notorious for failing and taking out the computer.

On Tuesday, May 3, 2022 at 11:18:58 PM UTC-7, Clocky wrote:
> On 29/04/2022 1:44 am, Kenzo wrote:
> > I am bringing out of storage - not counting the actual computers - probably 5 large boxes of Commodore 128 and 64 hardware accessories, software, books. Collected mostly from the Bay over the past 20 years.
> >
> > For the 128 and 64 computers, should I power them up with low voltage on a variac for a while before giving them the full 120v? The idea being to perhaps give the old caps a better chance of surviving powerup after long storage?
> >
> > Or would low voltage give the power supplies and internals problems?
> >
> > I will have a dim bulb tester in series also in case their are any serious problems with the units.
> >
> > thanks,
> > LT
> >
> Neh, just don't just a genuine C64 brick of death or at least use a
> power saver. If you're determined to use an original brick do measure
> voltages first, they are notorious for failing and taking out the computer.
I did have an aftermarket power supply, with cables attached to either power 128 or a 64. The first 128 I tried powered up no problems and composite video screen looks very sharp. I will try GEOS 128, and the 512k memory cartridge, and GEOS 128 soon. And then I will try installing the 128 Superchip roms I have. Not to mention boxes of other software and cartridges. I knew there was a reason I retired! And a VIC 20 is what started me on my interest in programming, resulting ultimately in a 20 year database programming career. So Commodore has a special place in my heart!

On 6/05/2022 12:07 pm, Kenzo wrote:
> On Tuesday, May 3, 2022 at 11:18:58 PM UTC-7, Clocky wrote:
>> On 29/04/2022 1:44 am, Kenzo wrote:
>>> I am bringing out of storage - not counting the actual computers - probably 5 large boxes of Commodore 128 and 64 hardware accessories, software, books. Collected mostly from the Bay over the past 20 years.
>>>
>>> For the 128 and 64 computers, should I power them up with low voltage on a variac for a while before giving them the full 120v? The idea being to perhaps give the old caps a better chance of surviving powerup after long storage?
>>>
>>> Or would low voltage give the power supplies and internals problems?
>>>
>>> I will have a dim bulb tester in series also in case their are any serious problems with the units.
>>>
>>> thanks,
>>> LT
>>>
>> Neh, just don't just a genuine C64 brick of death or at least use a
>> power saver. If you're determined to use an original brick do measure
>> voltages first, they are notorious for failing and taking out the computer.
> I did have an aftermarket power supply, with cables attached to either power 128 or a 64. The first 128 I tried powered up no problems and composite video screen looks very sharp. I will try GEOS 128, and the 512k memory cartridge, and GEOS 128 soon. And then I will try installing the 128 Superchip roms I have. Not to mention boxes of other software and cartridges. I knew there was a reason I retired! And a VIC 20 is what started me on my interest in programming, resulting ultimately in a 20 year database programming career. So Commodore has a special place in my heart!
>

Cool! There are many facebook groups for retro computers generally and
of course a lot of Commodore specific ones. If you're not on facebook
consider joining up as there is a lot more traffic than there is here.

Happy retirement :-)