TI994/A Power Supply

allison allisonportable at gmail.com
Mon Nov 11 12:24:35 CST 2019

On 11/11/19 2:12 AM, Eric Smith via cctalk wrote:
> On Sat, Nov 9, 2019 at 1:46 PM Jules Richardson via cctalk <
> cctalk at classiccmp.org> wrote:
>> I've got another /4A however which has a 2-pin plug on the back, and that
>> one appears to just take plain ol' 110VAC line voltage and the PSU is
>> completely internal (at least, there's a power cord with it which fits,
>> but
>> that one has a few broken keys and so I've never actually done anything
>> with it).
> I'm about 95% certain that it does NOT take line voltage in. It just has a
> different internal power supply assembly that only uses one of the
> low-voltage AC inputs from the external power supply instead of both. As
> far as I've ever heard, there was no 99/4 or 99/4A that did not use an
> external power supply.
> If it were mine, I wouldn't even consider pluging it into line voltage
> until doing a lot more research on exactly what's inside.

I have at least a few 99/4, 99/4a(black), 99/4a (beige cost reduced).

NONE of the 99/4 or 99/4a take line in.  They differ in the power supply
used internally and the brick externally.  The two pin uses a single AC
voltage brick (dc can be used of correct votlage) and the other uses two

How do the two supplies differ is one is linear and old school for
the three votlages (+12,+5, -5) and the other is a low voltage
switcher based on the 424 IC.

NEVER connect the two pin console to 100 or 230V without the
transformer.  Or you will have a fire hazard!


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