More Bringing up a CPM

"Richard Erlacher" <edick(a)idcomm.com> wrote: ---snip--- Hi I have an SD Sales board but didn't try it. I'd modified it so that I could run RAM all the way up to the video board in my Poly88 and still do a full 48K. This was in the older days when 16K DRAM chips were costly. I've since populated it with 64K and don't need the additional address decoding so maybe I should try it. I'll have to remove the IC I dead-bugged in place of the address switch. Since I got the Static RAM working, this is a less pressing issue. On the subject of LA/scope/logic probe/voltmeter. I personally consider a LA as the shot gun approach. It will often find problems when one has no idea where to look. The only problem is that someone with an oscilloscope can often have the machine repaired by the time one gets the leads connected and the LA setup right. Still I have used LA's in the past when nothing else would worked. I rarely use a logic probe because I don't have one. I can use an oscilloscope just as well with the additional features that an oscilloscope can provide when needed. It is like a logic probe with more added. Still the best overall trouble shooting tool I have is an analog voltmeter. I can move quicker with one of these than many can with other tools. As far as I'm concerned, DVM's are only good for setting power supply voltages. I have one ( an accurate 5 digit unit ) but the analog meter is still the first thing I reach for. I find that most don't know how to trouble shoot. The sequence is simple but many still don't get it: 1. Observe symptoms 2. Make predictions 3. validate predictions 4. If predictions do not pan out add this to the observed symptoms and go back to step 2 or 1. 5. Repair bad part. I find that most don't understand the importance of steps 2 and 3. They try to go from 1 to 5 and usually it doesn't work. Step 2 does require that you understand what to expect from each kind of failure. Dwight