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Author Topic: A500 external and internal floppy conflict  (Read 1964 times)

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Offline Dr LaserTopic starter

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A500 external and internal floppy conflict
« on: October 07, 2011, 04:18:42 PM »
Hey ALL

I'm having a strange issue with my Amiga 500. When I boot with both floppies attached booting goes to first screen both drives go insynch and start reading together like they are both fd0. Of cuz this cuz a error message appears. I took external floppy part. It's the same fb-354 but with different control board. When I disconnect external floppy drive my 500 boots up no problem. HELP!

Thanks.
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Offline LaserBack

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Re: A500 external and internal floppy conflict
« Reply #1 on: October 07, 2011, 06:36:29 PM »
Quote from: Dr Laser;662831
Hey ALL

I'm having a strange issue with my Amiga 500. When I boot with both floppies attached booting goes to first screen both drives go insynch and start reading together like they are both fd0. Of cuz this cuz a error message appears. I took external floppy part. It's the same fb-354 but with different control board. When I disconnect external floppy drive my 500 boots up no problem. HELP!

Thanks.


it seems that your external floppy is damaged
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Offline Zac67

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Re: A500 external and internal floppy conflict
« Reply #2 on: October 07, 2011, 06:56:17 PM »
Either that (ie. the floppy interface board) or a 8520 (U8). Check pin 22 of the floppy port (_SEL1). While the internal drive is operating it must not be low. You can also try swapping both 8520 to see if that changes anything. (If this is the problem your printer port will get non-functional.)
« Last Edit: October 07, 2011, 07:03:02 PM by Zac67 »
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Offline amyren

Re: A500 external and internal floppy conflict
« Reply #3 on: October 07, 2011, 07:26:55 PM »
Ah, I remember back when I had the A500 in use. Broken CIA chips could do strange things to floppy drives. I had one that was defective, and did not know about this at first. The symphtom was that every time a new disk was inserted, the internal drive started to "chew" on the disk until it was unreadable. We thought there was somethink wrong with the disk and inserted a new one, and then that was gone as well.
Replaced the CIA 8520 chip and it was ok again.
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Offline lost_loven

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Re: A500 external and internal floppy conflict
« Reply #4 on: October 07, 2011, 10:11:22 PM »
A quick test would be swap the cia chips and see if it works. if the drive works then it could be that but on the other hand it could knock out a mouse or something.

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Offline Dr LaserTopic starter

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Re: A500 external and internal floppy conflict
« Reply #5 on: October 08, 2011, 12:07:54 AM »
Thanks a lot guys. I swapped 8520 chips....and it works. I'm formating floppy right now. Will need to get replacement chip. Thanks again!!:)
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Offline Zac67

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Re: A500 external and internal floppy conflict
« Reply #6 on: October 08, 2011, 01:30:06 PM »
Glad you could fix it - no trouble.
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