frohne@pur-ee.UUCP (Henry R Frohne) (05/10/88)
I have been experiencing a lot of bad floppies lately. (Or so I thought!) I always order the cheapest floppies I can get (usually the bulk types). About 1/3 of them seemed to be bad on my last two orders. I sent most of the bad ones back and the company replaced them with some new ones of better quality which generally worked better than the generic ones. Because I was having the trouble with bad disks I took to writing to the whole disk to check if it was good or not. If I got the dreaded read/write error it was always bad. This means that that particular disk would always give me read/write errors in either drive. If the disk could be written to, in its entirity, with no errors, then I would experience no more problems with that disk even with many writes. These symptoms seemed to indicate that there was a problem with many of my bulk floppies. HOWEVER, THIS CONCLUSION WAS WRONG!! My problem turned out to be the A500 power supply. My configuration is: A500 with .5M extra memory (A501 look alike), one extra 3.5" floppy (not the A1010) which is an IBM floppy made to run on the Amiga using a couple of 74LS chips as has been discussed on the net, and a standard A500 power supply. I substituted an IBM 150 watt power supply for my A500 power supply and haven't had a bad disk yet. (I noticed that I had to reformat some of the previously bad disks before they became good, but I attribute that to a bad format under the previously flakey system.) It is interesting to note that I didn't notice any problems with my A500 power supply while monitoring the voltages on a DVM. I do suspect that if I had used the scope instead I would have seen a quick dip in the voltage or something like that. Summary: If you are using an A500 with two 3.5" drives and 1M total memory and if you are having trouble with "bad" disks you may want to try a heftier power supply. Rob Frohne pur-ee!frohne