Posted By
Guest
on 2012-04-23
01:04:31
|  1551 ?Device not present error
I am trying to get my 1551 working. I have swapped the drive out of a 1541 (the R/W head of the 1551 drive gave an open circuit when I checked the resistance), replaced the 7406 and 74LS14 but still get the "?Device not present error".
How do I diagnose the problem?
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Posted By
siz
on 2012-04-23
03:29:32
| Re: 1551 ?Device not present error
Make sure to switch the 1551 on BEFORE the computer because the reset routine in the computer KERNAL does the initialization of the interface chip of the 1551 paddle.
Device not present means that the computer cannot communicate with the drive. It should be working without a functional drive mechanics.
Check if the 1551 paddle is visible in the plus/4 address space. For example in monitor m fec0 feff repated several times should return a stable value in either fec0-fecf (device #9) or fef0-feff (device #8) ranges. (for example clear the screen and enter the statement to the top then press home and return several times)
An example result from yape:
M FEC0 FEFF
>FEC0 00 00 00 00 00 00 FE FE :Ţ®Ţޮ֮Ţ
>FEC8 00 00 16 FE FC FE FE FE :®Ô®®®®®®
>FED0 FE FE 00 00 00 FE 17 70 :®®®Ţ®®®®
>FED8 FE FE FE FE FE 00 00 00 :Ţ®ŢޮޮŢ
>FEE0 00 00 C0 FF 00 40 00 00 :®®€ß®€®®
>FEE8 00 00 C0 FF 00 40 00 00 :®®€ß®€®®
>FEF0 00 00 C0 FF 00 40 00 00 :®®€ß®€®®
>FEF8 00 00 C0 FF 00 40 00 00 :®®€ß®€®®
In this case the drive is #8 so fef0-fef7 range is stable (mirrored 4 times from fee0).
If you can't see something similar it probably means that the TPI chip in the paddle is broken. These chips are hard to find as they were used in the 1551 only.
For the drive mechanics: 1551 has the same mechanics as the 1541C (normal 1541 will not do as it does not has the optical track 0 sensor)
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Posted By
Guest
on 2012-04-23
04:39:14
| Re: 1551 ?Device not present error
Thank you.
1. As it has been almost 30 years since I last used the Plus 4 I do not understand:
Check if the 1551 paddle is visible in the plus/4 address space. For example in monitor m fec0 feff repated several times should return a stable value in either fec0-fecf (device #9) or fef0-feff (device #8) ranges. (for example clear the screen and enter the statement to the top then press home and return several times)
An example result from yape:
M FEC0 FEFF
2. I found this article but do not know if the replacement chip is available:
http://www.zimmers.net/anonftp/pub/cbm/documents/projects/drives/1551-tia.gif
3. I was not aware that a normal 1541 mechanism would not do. I have seen no mention until I read your post.
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Posted By
siz
on 2012-04-23
08:22:23
| Re: 1551 ?Device not present error
1) When you switched on your computer (I have to repeat: AFTER the drive because the wrong switch-on order will result in a device not present error) you'll get the basic prompt. Type in the command 'monitor' or 'mO' (m and shift+o) to enter the built-in ML monitor. Clear the screen with the clr button (shift+Clear/Home). Then enter the command I wrote earlier: m fec0 feff. You should get a similar output that I wrote earlier. If you don't see lines like the last one I inserted then it's probably a TPI fault (I don't remember if it's a 6523 or 6525 - both of them are very rare). To make sure you can press home and then return several times to see if the output changes. If there are stable rows then there is an expansion there - as it should be for a functional 1551.
2) One of the chips is more common but they are rare; hard to find either of them.
3) I don't know where but I've read this several places.
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Posted By
SVS
on 2012-04-23
14:47:21
 | Re: 1551 ?Device not present error
I guess your problem is on IC on the paddle. If you have another available 1551, try this:
- detach the 1541 from serial if any, before to test.
- Connect the other1551 inserting its paddle on rear of that one to test (WHEN POWER OFF of course). Steps to test are:
a) ALL turned off (Plus/4, 1551s)
b) Power on the sure-working 1551
c) Set it as device #9
d) Power on the 1551 to test (it will be device #8)
e) DIRECTORY U9 to test the sure-working 1551
f) DIRECTORY (to test 1551)
Remember that unit #9 works only if unit #8 is connected and powered on.
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Posted By
Guest
on 2012-04-23
21:04:07
| Re: 1551 ?Device not present error
siz - When I press home and return the output does change so that means that the chip is faulty?
SVS - I do not have a spare 1551. The one I have is arguably the only unit in Australia. I brought it back with me when I returned after working overseas. It has been packed away for about 15 years!
Thank you both.
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Posted By
siz
on 2012-04-24
03:21:57
| Re: 1551 ?Device not present error
Yes, most probably it's faulty.
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Posted By
Guest
on 2012-04-24
04:04:26
| Re: 1551 ?Device not present error
Thank you. I will have to keep my eye out for a replacement chip.
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