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

On 11/4/19 7:39 AM, Allison Parent via cctalk wrote: It seems to depend on the variant. I've got a /4 and a /4A which have 4-pin plugs on the back, and these use an external PSU outputting 18VAC and 8.5VAC. 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). cheers Jules

On 11/11/19 2:12 AM, Eric Smith via cctalk wrote: 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 windings. 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! Allison

On 11/14/19 3:02 PM, Jules Richardson via cctalk wrote: OK, the cord "fits", but having looked at it now I'm not at all convinced, either. The two-pin socket is actually the same as the four-pin socket on the other two machines, but with the upper two pins (intentionally) missing. The PSU board inside appears to be a switcher, but I'd be inclined to agree with Allison that it's intended to run from low-voltage AC (I've put the machine back together now, but just realized that I should have checked the voltage rating on the rectifier stage's caps). cheers Jules

On Fri, 15 Nov 2019, Jules Richardson via cctalk wrote: If somebody found a mains cord that "fits" and plugged it in with the low voltage AC input connected to the wall, then it might not be happy now. You might want to avail yourself of some of Allison's expertise. Might I suggest a box of 8" floppies for XMAS?

On Fri, 15 Nov 2019, allison via cctalk wrote: And, the machine and cord get thrown into a box in the back of a closet. Eventually, somebody else gets it, and sees that it has a cord, . . . Price these days is probably similar to what it was 45 years, ago. And availability is heading towards what it was 50 years ago.