4 Nov
2019
4 Nov
'19
3:57 a.m.
On November 4, 2019 at 5:12 AM Liam Proven via cctalk
<cctalk at classiccmp.org> wrote:
On Mon, 4 Nov 2019 at 06:59, Kevin Parker via cctalk<cctalk at classiccmp.org>
wrote:>>> These voltages appear to neatly align with most PC power supplies so
Ishould be able to tap into an old AT power supply of which I have quite afew.The PSU
apparently outputs AC, not DC, which is unusual... but a PCPSU can do it, and Molex
connectors can be bodged into fitting.
Does this help?
http://oldcomputer.info/8bit/ti99/index.htm
Schematic:http://www.mainbyte.com/ti99/hardware/power_supply.html
A couple of notes. First, I'm not all too familiar with the TI, but I was always
under the impression the PS provided +5 and +12 DC. For a while in the 80s the power
supply module was available separate (even from Radio Shack!) and I bought one.
I did a quick search and found the same site Liam linked above. It shows a schematic of a
transformer providing 8 and 16 VAC, but then also mentions that there are various
schematics floating around and that the author has been told his is non-standard. It does
also mention, however, that the machine uses 4116 RAM which requires -5V as well. The
summary is that I would make real sure what it takes before connecting anything. If it
does indeed need AC, it may use the AC internally to regulate -5V and providing DC could
damage the RAM.
Another note is that many PC power supplies will have a minimum required load that the TI
may not meet. Some will simply not power on if the load isn't met, but I have seen a
few that will provide unregulated voltage. Been a while since I saw one of those, though.
but do be careful.
Will
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