24 Jun
2013
24 Jun
'13
3:02 p.m.
On 6/24/13 4:56 PM, Jim Brain wrote:
On 6/24/2013 4:38 PM, John Wilson wrote:
FWIW, the 64 will run without the AC signal. I set up one to run on
DC, and it worked fine, excepting the jiffy clock. (this is from
memory, I can't remember the details, but I recall desoldering a
regulator and injecting 9vdc. ) It booted just fine. I'm sure some
things would be broken, but the 60hz wasn't used for any critical
interrupts or timing AFAIK.
-Ryan
Getting 9VAC out of an SMPS design sounds tricky
though. I looked
into the same kind of thing a bit (wondering whether having an output
for AC spindle motors that takes care of 120/240 V and 50/60 Hz
differences would be worth the trouble, to make any drive work in any
country) and decided it was over my head and probably very expensive.
Maybe you can cheat (and cover 90% of users) if you know what the
9VAC is really used for though? I mean, do peripherals ever really
use it to drive another transformer, or rectify negative voltages out
of it? Maybe just having a switch that makes it put out pulsed +9VDC
(yech) for xfmrs, or straight pos or neg DC, could cover the cases?
Just yammering here... John Wilson D Bit
On the VIC/64/128, the 9VAC is internally
turned into unregulated
9VDC, shunted to 6.3V and fed to the cassette port MOTOR pin under SW
control. The original 9VAC is also fed to the user port.
ON the SX64, I believe, has one leg of the user port grounded where
9VAC would normally be found.
Very few peripherals used it.
On the 64/128, the 60hz (or 50, depending on the country) cycle was
used to drive the clock in the 6526, so it's required for machine
basic operation. Though, only a trickle square wave is needed for
that purpose.
VIC folks can cheat and just put 9VDC there, but 64 folks need the AC.
I am considering a switch like you suggest. BUt, it's somewhat kludgey.
Jim