Where? Where does the time go to? Seems that I just sent in the last issues material and here it is again time for another issue to be submitted. So here goes!
For the Z88 users: There is help to cheapen the expense of batteries. Use RAY-O-VAC RENEWAL batteries. I understand that the Z88 uses four AA batteries and they are at Wal-Mart in Auburn for the price of four for $4.25 and you will need two sets so that one can charge while you use the other set. And the Charger is $10.00. So for $18.50 plus state tax of $0.93 that comes to $19.43 and two sets of batteries means 50 cycles at 25 cycles per set which yields a cost of $0.39 per cycle of use. And since the charger is already paid for then on the second set of batteries the cost will be $8.93 divided by 50 or $0.18 per cycle of use. I don’t know who is buying them but they sell out of the batteries and charges fast.
And see the article by Les Cottrell on scratch building a LarKen dock board, and the LarKen I/F too. It can be done but not for the faint hearted. If anyone is interested, Paul Holmgren has the WD1770 chip for $9.00 postpaid, address elsewhere in ZQA!
There is a magazine or newsletter devoted to the early computers and one issue had an article on the ZX81. I got a couple of sample issues and it put me more in mind of the early issues of BYTE magazine. It is The Computer Journal and runs to 52 pages plus cover and is published 6 times a year. Sort of pricey at $24.00 a year but if you are into old computers it is worth a look. The address is:
THE COMPUTER JOURNAL
P. O. BOX 535
LINCOLN CA 95648-0535
TEL.: (800) 424-8825 or (916) 645-1670
Anybody out there working with the AERCO FD-68 disk interface for the T/S 2068? There are some still working with it and still doing programming and improving the original system. There is a non EPROM SPECTRUM for the AERCO that is on disk and apparently the software POKEs SPECTRUM into the AERCO memory and it works from there. There were two programs on disk and they worked in the SPECTRUM mode. Of course, the AERCO has RP/M capabilities and that is a mystery to me till I get a copy of a CP/M manual. I also have a possible source of PD software for the AERCO. I am working on that.
I started a project that will make articles for ZQA (if I don’t get submissions) available for future publication. I have my newsletters filed according to name alphabetically and I started with the first one and I have gotten through THE PLOTTER (filed under PLOTTER) working with issue one through December 1984. Some newsletters are not represented and a few have all issues in that group. I have typed in all the articles that I have found that were usable and I could read. Some reproduction made articles unreadable. There were some great articles in that time period. Some day I will continue the project and I will when I finish the newsletters take a look at the magazines and when finished with the first issue to December 1984 will go through again with January 1985 through some new cutoff date. It is quite a project.
I got through the agony of the living room decorating. All the furniture was moved to the center of the room for several days, about a couple of weeks probably but Masako, my wife, felt like it was an eternity. And we finally got it done and it was worth it. That took up most of the month of May, first getting it done and then recuperating afterwards. Whether I want to or not I find that there is other things to do besides playing with my T/S toys.
I have a good question that I have asked before. Is there a way to calculate how big of a heat-sink to use to dissipate one watt of power that is dropped by a 78XX regulator or its equivalent? I have a disk drive power supply project halted with that question. Also, does anyone know if the regulators in the TO-3 configuration have overload and thermal shutdown? These are 5 amp 5V and 12V regulators. I am mounting them in a IBM PC type power supply case and the only things left in the case are the bare circuit board, power switch and fan. Not having more details I guess I will barge ahead after all this delay and plunge ahead and see what I can do with the project. I guess I can test the thermal shutdown by covering the regulator and seeing if it will shut down if too hot. Same for short shut down. Might fry the regulator but it is not that expensive. I have some heatsinks wit fins so will try them.
[Figure: Finned heat-sink]
Use any heat-sink that you have on hand. Any heat-sink is better than none. The flange have to make good and tight flat to flat contact with the heat-sink with paste in between (Wakefield heat sink compound). You didn’t say how much current you are going to draw from this regulator nor what its part number is. As a rule of the thump, the larger the heat-sink the better. If the regulator is a TO-3 then use a TO-3 heat-sink, a TO-220 use a TO-220 heat-sink and so on. They are available from electronic stores. I will mail you information on how to design your own — it gets pretty involved.
Yes, all regulators have thermal and overload shutdown (shorts too). To test for that, you have to draw heavy current from it until it shuts down. Abed
Instead of filling (wasting) space with my comments I will fill it with other stuff. With that I will leave this.