24 Jun
2013
24 Jun
'13
2:56 p.m.
On 6/24/2013 4:38 PM, John Wilson wrote:
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
--
Jim Brain
brain at jbrain.com
www.jbrain.com