Kip, Assuming the initial visual inspection goes well, the PSU is +always+ the first thing to check.. and that goes for everything from digital computers to vacuum-tube radios.
Do you have a general background in electrical / electronic troubleshooting? Do you have a Variac on-hand, or at least a current-limited AC supply - such as the old light bulb socket in-series, as was popular in the days before Variacs became affordable to the common man? On Sun, Feb 7, 2016 at 6:15 PM, Robo58 <[email protected]> wrote: > Hi Brent, Drlegendre and Eric > > Brent: I took your advice and did a little program to output "A"'s and > monitoring Transmitter empty before looping again. That works fine and it > will run for hours. > > Drlegendre: Thanks for the excellent document link. My buddy has the MITS > 1K static ram and the MITS 4K dynamic ram cards. I've been doing my > testing > with the 1K static ram to limit potential problems. > > Eric: This Altair has the smaller PS with the smaller Electrolytic caps. > They were all replaced and the PS brought up without cards with a Variac. > My buddy bought Kemet Capacitors on the basis of very good ripple current > rating and low ESR. > > > Thanks Ron > > > > -----Original Message----- > From: cctalk [mailto:[email protected]] On Behalf Of Brent > Hilpert > Sent: Sunday, February 7, 2016 4:14 PM > To: General Discussion: On-Topic and Off-Topic Posts < > [email protected]> > Subject: Re: Help with getting an original Altai running: 8080A clock > circuitry and MITS88 2-SIO board > > On 2016-Feb-07, at 6:17 AM, Robo58 wrote: > > > c). I hand assembled some code to exercise the 6850. I know it has a > > software reset and then you set attributes. I tried my buddies echo > > program. It looks for a received character and then echo's it. I'm > > using a laptop and PuTTy along with an RS-232 breakout box. I can see > > characters going in but nothing coming out. The 6850 appears to drive > > the bus for a finite amount of time and then turn off its drivers. I > > don't have any experience with the part and I don't know if that's the > > way it's supposed to work or that the Altair has a bus timing issue. > > How about doing a program that simply repeatedly outputs a character first, > getting that going before trying to deal with input - cuts the problem > space > in half. > The repeat loop should give you some consistent bus activity and observable > waveforms on a scope if you have one, rather than trying to catch events > initiated from external input activity. > > > > >
