> On November 4, 2019 at 5:12 AM Liam Proven via cctalk <cctalk@classiccmp.org> > wrote: > > On Mon, 4 Nov 2019 at 06:59, Kevin Parker via cctalk<cctalk@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 "A designer knows he has achieved perfection not when there is nothing left to add, but when there is nothing left to take away." -- Antoine de Saint-Exupery "The names of global variables should start with // " -- https://isocpp.org
