> > The original adapter was unregulated, so it probably outputs in the 7V > range unloaded relying on the M100 power supply to pull it down to 6V or so.
I'm using the TRS-80 Model 100 AC Adapter (CAT. NO. 26-3804), nominally -6V DC, 400mA. The measured voltage when unloaded is -8.1V. (I made a habit of marking it as "negative" to remind myself to not plug in the typical positive-tip adapters.) —b9 On Tue, Oct 28, 2025 at 3:48 PM Scott McDonnell <[email protected]> wrote: > As far as max safe voltage, the MOV is either a 10V or a 14V trip part (I > believe based on the part number - I could not find an exact datasheet) and > most caps in the power input path appear to be 16V. > > It is a switching supply, so the higher voltage is likely to never reach > the truly sensitive components. The computer is on the other side of a > transformer. The failure would be the MOV clamping and caps on the input > side bursting. > > 9V is probably as far as I would suggest pushing it. The NiCd, I am not > sure about. It is charged with just a diode and a resistor directly tied to > the power input. The diode is not a zener, so the battery is seeing nearly > the full voltage at the power input. But even at 9V, assuming a .7V diode > drop, it is getting about 4.5mA of charge current. I don't want to promise > it will be ok at 9V, but for short duration, it would probably be fine. > > The original adapter was unregulated, so it probably outputs in the 7V > range unloaded relying on the M100 power supply to pull it down to 6V or so. > > Speaking of which, I wonder if some switching power adapters could muck > things up. If the ripple gets mixed in with the oscillation frequency of > the M100 supply, it could cause problems. A higher quality adapter will > probably be in the MHz and be too fast for the components which would > essentially filter it out. But down in the khz range, it could potentially > interfere, especially if the ripple is significant in a cheap crap supply. > Probably best to stick to an unregulated supply like the original. The ones > I had bought previously were from Jameco. > > > https://www.jameco.com/z/DDU060120RG2401-Jameco-ReliaPro-AC-to-DC-Wall-Adapter-Transformer-Single-Output-6-Volt-1-2-Amp-7-2-Watt-2-1mm-Plug-Center-Negative_220943.html > > > > On 10/28/2025 4:08 PM, B9 wrote: > > I tried my 5W, 5V solar panel with a Tandy 200 and it didn't work. It > would show activity on the LCD but never made it to the menu before > freezing up. > > Could be because it was a cloudy day and through a glass window. Could be > because it doesn't output anywhere close to "5W". > > It's too bad, since the panel is only a little larger than the Tandy 200 > and could easily have been mounted on the lid. > > --b9 > > > On October 23, 2025 6:45:27 PM PDT, B9 <[email protected]> > <[email protected]> wrote: > >> Very cool! I remember hearing about that guy but didn't know he had a >> Model T. The article mentions he had "a 12V battery, and a five-watt solar >> panel." >> >> I'm presuming he used the solar panel to charge the battery and then used >> the battery to run the Model T. >> >> "Direct solar" as AbortRetryFail mentioned might be possible, but I'm not >> sure what the advantage of that would be. I think I've got a 5W panel, so >> maybe I'll give it a shot just to see. >> >> --B9 >> >> >> >> >> >> On October 23, 2025 3:48:40 PM PDT, Mike Stein <[email protected]> >> <[email protected]> wrote: >> >>> A solar powered M100... >>> >>> https://bikepacking.com/plog/steve-roberts-computing-across-america/ >>> >>> On Wed, Oct 22, 2025 at 2:53 PM [email protected] < >>> [email protected]> wrote: >>> >>>> What are the limits/parameters of the 100's power supply circuit >>>> anyway. Has anyone dug into it? >>>> >>>> Direct solar power for example would be cool, but I'd be reluctant to >>>> experiment on the 40 year old hardware... >>>> >>>> >>>> On October 21, 2025 4:20:27 PM EDT, Scott McDonnell < >>>> [email protected]> wrote: >>>> >>>>> This shouldn't be a problem. >>>>> On 10/21/2025 10:24 AM, VANDEN BOSSCHE JAN wrote: >>>>> >>>>> I found some stabilized power supplies, discarded but new. >>>>> >>>>> They are not compatible with the models T, but I suppose I can always >>>>> adapt the pin. I’ve done it with USB-cables too. >>>>> >>>>> But these are 7,5 V, 650 mA. Isn’t that too much ? AFAIK, a standard >>>>> Tandy wall-wart is 6V, but not stabilized. >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> *Jan-80 @ work* >>>>> >>>>> Rejoignez-nous sur Facebook - Volg ons op Facebook >>>>> >>>>> -- Sent from /e/OS Mail. >>>> >>>
