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
dillon@CORY.BERKELEY.EDU (Matt Dillon) (05/10/88)
: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 Sounds like either you forgot some bypass capacitors on the LS TTL or you were overloading the poor A500 power supply with the combination LS TTL and foreign disk. Have you checked the amount of power the floppy + support LS TTL is pulling? An IBM 150 watt power supply could certainly (appear to) fix both problems. Where are you pulling the 5V for the LS TTL from? How many chips and of what type are they? Are they *all* LS? Apart from simple LS gates (4-8 ma avg), some of the MSI LS parts pull 80+ ma! -Matt
frohne@pur-ee.UUCP (Henry R Frohne) (05/10/88)
In article <8805100305.AA09860@cory.Berkeley.EDU>, dillon@CORY.BERKELEY.EDU (Matt Dillon) writes: > : 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. > : > Sounds like either you forgot some bypass capacitors on the LS TTL > or you were overloading the poor A500 power supply with the combination > LS TTL and foreign disk. I have include bypass capacitors on all the 74LS chips (a 74LS38 and 74LS74) The floppy is a Toshiba FDD4206A0K. It may draw more current than the A1010. >Have you checked the amount of power the The voltage drop across the drive was a couple of tenths of a volt when in use on the 5 volt line and something similar on the 12 volt line. > floppy + support LS TTL is pulling? An IBM 150 watt power supply could > certainly (appear to) fix both problems. Where are you pulling the 5V for > the LS TTL from? I am taking the power from the DB-23 connector on the amiga. >How many chips and of what type are they? Are they *all* > LS? (Answered above.) By the way Matt, thanks for all the nice software you have shared with the Amiga community! Rob Frohne pur-ee!frohne
hal@hpscdc.HP.COM (Hal Work) (05/11/88)
Was there anything tricky about hooking up the IBM power supply? I've been having, I assume, power glitches which show themselves by the monitor 'blipping' off and on very quickly. Not long enough for the screen to blank, but long enough to cause irritation.