Microsoft multiuser Basic for the Altair 8800

First of all, safety first when working around these power supplies. You have mains voltage exposed all over the place, including the front panel switch. What I typically do is take it all the boards out and disconnect the power supply, and pull it out. I then re-form the capacitors by taking them off completely or, more often, unsoldering one lead. In one case recently the power supply was regulated (an Altos computer), and the power transistors were inserted through the power supply case and into the board from the backside, making removal both a pain and a little risky, so I just clipped one lead of each larger in place to do the re-forming (it turned out that in that particular case, they really didn't need it). I'd be pretty surprised if you actually had to replace your capacitors. For reforming I have had pretty good luck with a 4.7K ohm resistor in serial with the capacitor, and in more than half the cases, the capacitors really didn't need it. The transformer is either good or not - and it is probably just fine. Just measure its output voltages. Do make sure that the transformer is wired for your voltage depending upon where you live. One could disconnect it first, but the odds of it putting out too high a voltage are very very slim, so long as it is wired for the mains voltage wherever you happen to live. Bad ones either put out nothing for one of the voltages (open winding) or get hot (shorted winding). Neither is dangerous to the rest of the power supply. Then, check all the voltages to make sure they are not way too high, and throw and oscilloscope on it to make sure that there isn't a whole lot of ripple (typically caused by a bad rectifier). Remember that on the original Altair and most S100 machines each board had its own regulator, so this isn't an exact thing. (On my machine, I actually had to add a second 8V supply in order to provide power for a backplane completely full of boards.) For bootstraps, perhaps look for a ROM board on eBay (a Bytesaver or the like), and burn yourself a ROM. For a serial card, you can find T-UART or IMSAI MIO and the like show up on eBay pretty frequently. Be patient so you don't overpay. ;) Real MITS Altair cards come up far less frequently. Make sure you research (say, on bitsavers.org/pdf) which ones support current loop if you really want to hook up a real teletype. Not sure where you'd find your multi-user basic, but there is quite a lot of Altair/S100 software available as part of the SimH environment, and a separate web site at http://schorn.ch/altair_6.php JRJ On 7/15/2015 1:56 PM, Kip Koon wrote: