Archive for September, 2010

What O’scope Should You Buy?

Thursday, September 23rd, 2010

I recently received this question from a fellow retro-computer hobbyist.  Since it was such a good question, I figured I’d post my reply here on this blog.  Though I can’t make a specific recommendation that is right for everyone,  here is how I responded to this inquiry.

I use an old 100MHZ Tek 465 that I picked up off of ebay for about $80 (shipped). I was  lucky, and it was almost completely functional, when it arrived. I spent another 50 bucks on probes and some minor repairs (replacing broken knobs). Total cost was less than $130.

Prior to landing this unit, I would occasionally borrow a more modern HP 20MHZ 4 channel digital storage scope from work. The user interface was nice and storage was great to have, but the bandwidth was a bit limited, considering early Apple computers have a base  14MHZ clock.

At times, it wouldn’t hurt to have more than 2 channels and occasionally a little more bandwidth would help. So I guess I think that 100 MHZ, 2 channels is minimum for my  purposes. 100MHZ sounds fast, but remember that you want to see glitches and signal  slope, not just digital highs and lows. The real neat thing about using this old scope is that this same tool was in use in the 70’s and 80’s by developers of the first personal computers. The price was right, too. At the time I bought it, I don’t think that you could touch the bandwidth at that price any other way.

A modern digital storage scope would be easier to use, especially on transient signals, as the scope stores the capture and you can view it at your leisure. On a traditional analog scope, a transient just flashes on the screen and is only present as long as the screen phosphor glows (one shot).

There are also digital storage scopes that plug into PC’s USB port and use the PC as the  brains and display. Some of them have logic analyzer functions, which would be nice to have. Many of these units have limited bandwidth, compared to my old 100MHZ Tek.

I guess the bottom line is you need to decide much you want to spend and what kind of features are  important to you.

ACI presale ends in less than 2 weeks

Friday, September 17th, 2010

My presale of apple cassette interface cards is due to end on 9/30/2010.  The presale price is $75.  After 9/30 the price will go up to $100, unless you buy an ACI at the same time as an Apple 1.  The bundle price will be $75.

I expect the ACIs will be shipping by early November.

I currently have a preliminary manual online at:

http://www.willegal.net/appleii/aci-v0.12.pdf

and some information about the  ACI at

http://www.willegal.net/appleii/aci.htm

Full Scale City Point Map

Wednesday, September 15th, 2010

I had zazzle.com print a full scale (45.3″x32″) copy of Merrick’s City Point map on matt UV paper.  The regular $52 price was cut in half by a 50% off sale and shipping was only $6.99.   The result is awesome and i can’t wait to frame it and find a place to display it.  This is going to motivate me to move forward on a railroad.

City Point Map, 1865

Apple II rev 0 inventory cleanout

Sunday, September 5th, 2010

Apple II rev 0 kits sales have been extremely slow.   I have quite a bit of money tied up in parts and boards for the rev 0 and I have some other projects in the pipe that I would like to spend some of that money on.  In order to facilitate this, I’ll be liquidating my rev 0 stock of kits on ebay.  I have 5 kits  on hand and will be posting them for auction one at a time.

After this liquidation, I don’t expect that I will be offering A2 rev 0 kits  for the foreseeable future.  There is some possibility that I might get a batch of motherboard PCBs made at some point down the road, but only if I notice some demand building up.  Unless something significant changes in terms of this market, I don’t think that I will offer kits, again – only bare motherboards and possibly built up computers.

I really wanted to keep this product alive and available for as long as I could find parts.  However  the demand just isn’t there and I’ve have some ideas for some other projects that could use the money that I have tied up in these kits.

ACI build and operations manual online

Friday, September 3rd, 2010

I’ve put a preliminary copy of my ACI build and operations manual online at: http://www.willegal.net/appleii/aci-v0.12.pdf This contains an OCR’d copy (not just a scan) of the original Apple ACI manual, plus a complete assembled listing of the ACI PROM. Take a look and let me know if you see any problems.

Also – remember that this is the last month for discounted ACI presales – get the presale price of $75 through September ’10. Shipments begin late October or early November. Contact me via email at mike@willegal.net if you are interested in the ACI card.