| Posted By
xahmol
on 2024-09-01
04:38:01
 |  1551 not working, please advice
Well, finally got hold of a 1551 without having to pay both kidneys, but unfortunately do not get it working yet.
Was sold as untested, so took a gamble here.
Like some advice.
After typing DIRECTORY on the demo disk the drive appears to do something, nothing is shown and get a red blinking LED. Same with other disks I tried (C64 formatted ones).
Trying to format a disk with HEADER gives BAD DISK after a while.
Would this be a symptom of a dirty drive head? Or something more?
Probably need to have it serviced?
Also, my Plus/4 has a CPU4Plus4 CPU replacement, a PLA replacement (not sure which, bought it this way) and JiffyDOS without a switch.
Does JiffyDOS work with the 1551 (only not accelerated)?
And would those CPU and PLA replacements be an issue for the 1551?
Also do not get that Script/Plus cart working. Manual says F2 to start, but that is taken by JiffyDOS. Also if I switch JiffyDOS off with @F or @Q, F2 does not start the cart.
Any ideas to start that cart?
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Posted By
gerliczer
on 2024-09-01
12:38:19
| Re: 1551 not working, please advice
AFAIK, the drive mechanism is exactly the same as in the 1541 or 1541C. If that's true, replacing one such part and cross-testing it with a 1541 may help to identify the problem, or at least narrow the possible sources.
Neither the CPU I/O port nor the PLA have anything to do with 1551s, so those replacement shouldn't cause these symptoms.
Try getting rid of the JiffyDOS. I'm not sure, because I don't have much experience, but I can imagine that it kills proper Autostart ROM discovery at startup, just to have exclusive control over key F2.
Edit: Some additional things to examine would be checking if the 1551 can read disks formatted in a 1541, as it uses the same disk format, or check the disk formatted in your 1551 with some advanced disk utility in a 1541 to see what is the result of the 1551's operation. Another idea would be checking if the 1551 is modified with WarpDOS 1551, although I think it is much less probable than the drive is actually being faulty.
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Posted By
BSZ
on 2024-09-01
14:57:46
| Re: 1551 not working, please advice
@xahmol: Your description of 1551 faults fits the classic D500 disk mechanism head fault. As mentioned, the easiest way to test this is to connect the mechanics from a well-functioning 1541 drive. But the head can also be measured: 1 of the 4 wires the common, the other 3 must have a resistance of a few ohms in comparison. In the classic head fault, one of these lines is broken. (A simple multimeter that can measure resistance is suitable for this measurement.)
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Posted By
xahmol
on 2024-09-01
15:54:17
| Re: 1551 not working, please advice
Thanks for the advice, got similar advice on Facebook. First will try a good clean of the 1551, but yeah, also others said it might come to sacrifice a 1541 for the head.
On the cart auto start: also heard that elsewhere. Is there a way to manual start a cart?
My JifffyDOS does not have a switch and I expect to use JiffyDOS far ,öre often than this cart. So removing JiffyDOS is not an option.
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Posted By
gerliczer
on 2024-09-02
01:38:09
| Re: 1551 not working, please advice
Analyse, or maybe copy from the original sources, how the built in 3-PLUS-1 starts on key F1 and write a similar routine, of course with changed ROM paging, to start your cartridge.
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Posted By
siz
on 2024-09-02
17:51:41
| Re: 1551 not working, please advice
I've downloaded the script/plus cartridge from here, attached it to YaPE and checked the startup routine. It's really simple:
sei
ldx #$0a
stx $fb
sta $fdd0,x
jmp $8003
so if you enter monitor and type in this short routine and start it you should be able to start script/plus.
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Posted By
SukkoPera
on 2024-09-02
07:39:04
| Re: 1551 not working, please advice
Is STX addr,X really a thing?
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Posted By
xahmol
on 2024-09-02
15:24:02
| Re: 1551 not working, please advice
Super! Will try.
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Posted By
siz
on 2024-09-02
17:52:18
| Re: 1551 not working, please advice
thx, @SukkoPera . of course it was a typo. I fixed it to sta addr,x 
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Posted By
SVS
on 2024-09-03
03:01:23
 | Re: 1551 not working, please advice
If reading a disk you don't notice multiple head resyncs (you should hear a rattle sound) the problem is not due to the head mechanic. More probably by a critic component inside the cartridge.
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Posted By
xahmol
on 2024-09-03
11:39:16
| Re: 1551 not working, please advice
@SYS I do hear drive rattling. So stick with the head cleaning or head failure diagnosis.
Drive ID string is correct after typing JiffyDOS @ command, so communications appears to be OK.
All:
But I am now seriously baffled by trying the Super/Script cart again.
The little asseembly startup routine did not do much apart from garbled screen. But to my big surprise after a reset suddenly the cart was there on F2.
First thought: OK, start routine in assembly works, just needs a reset after. But that was not repeatable.
Did a power cycle, and cart appeared directly without the assembly code.
So tried to reproduce: repeated power cycles while cart remains plugged in: remains working. Power off. Take it out, power on, power off, and back in again, power on: no cart on F2. Try again, it is there.
Can not see any consistent behaviour, but if I try long enough, the cart apparently takes preference on JiffyDOS.
Almost seems that JiffyDOS and the cart have a race condition to see which one takes preference, and that winning is dependent on a factor I did not yet discover.
Or something is iffy about my cartridge port of course.
The word processor itself is by the way (as I already expected) not that exciting: same as SuperScript on C64. And have way better word processors for the C128 I also have (VizaWrite128 and GeoWrite128). So this cart for me is in the category: cool to try it once and see it working, not more.
Oh, and obviously did try if several attempts did anything on the 1551 as well. But there the results are completely consistent: communications appear to work, disk head not.
Any thoughts?
Photos:
First tru after that assembly routine:
Then suddenly the cart is there, but not always:
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Posted By
SukkoPera
on 2024-09-03
11:46:53
| Re: 1551 not working, please advice
@siz: Ahhh, now I see! It was not very obvious to me, as I thought stx could be a typo for sta/sty but since nothing was loaded in those registers it still didn't make sense to me. Now I see that it doesn't really matter what you write to $fddx, so I finally understand  . Thanks!
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Posted By
xahmol
on 2024-09-07
07:50:56
| Re: 1551 not working, please advice
Well, cleaning the head unfortunately did not help...
So probably broken drive head indeed. Communication appears to be working, hear drive rattling.
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