phtsl
Windows User
Posts: 3
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Post by phtsl on Jul 15, 2020 23:39:29 GMT
I have a 128DCR (Motherboard number 250477). Internal drive motor runs non stop, drive light stays on. Computer never finishes booting to ready prompt. I switched out my jiffy dos roms back to stock, and same thing. Anyone seen anything like this?
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Post by robertb on Jul 16, 2020 17:11:44 GMT
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phtsl
Windows User
Posts: 3
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Post by phtsl on Jul 19, 2020 21:58:39 GMT
Not sure it is. I have busted out the scope to look at the data lines. You can see the drives 6502 data lines with a little data, but then it resets and tries again.
I also have been going over the schematics looking for broken traces. Nothing so far.
Does anyone know how to disable this internal drive per chance? 128DCR
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Post by robertb on Jul 20, 2020 18:05:59 GMT
Does anyone know how to disable this internal drive per chance? 128DCR I can't remember right now. I have a switch mounted to the front of my DCR so that I can disable the internal drive. Perhaps a quick e-mail to Ray Carlsen would be faster than my getting out the DCR and opening it.
Truly, Robert Bernardo |
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Post by feedingdragon on Jul 20, 2020 22:31:58 GMT
Disconnect pin-1 of U113. This is the ATN line to the drive. A switch with a safety resistor is usually used to do this.
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Post by robertb on Jul 21, 2020 17:02:06 GMT
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Post by robertb on Jul 21, 2020 17:05:23 GMT
Hmm, I tried to add text to the above but no go.  So, I will do it here. These are forwarded from Ray Carlsen. The Hard Tips article is from the famous C= hardware hacker, Al Anger. Truly, Robert Bernardo Fresno Commodore User Group - www.dickestel.com/fcug.htmSouthern California Commodore & Amiga Network - www.portcommodore.com/sccan |
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Post by nonefornow on Jul 21, 2020 21:40:43 GMT
And just for reference the "Hard Tip" article was published on Commodore World - Issue 10 - Volume 2 - Number 5 - October 1995.
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phtsl
Windows User
Posts: 3
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Post by phtsl on Jul 22, 2020 1:04:51 GMT
Thank you all super kindly! So last night, I mide it somewhere fixing the issue. Looking at the schematics here: www.zimmers.net/anonftp/pub/cbm/schematics/computers/c128/c128dcr-5-left.gifI went from pin 25 on U101 to pin 9 on U113 (74ls14, center on the schematic) and pin 8 on U113 to pin 22 on U102. Both were about 1.2K and 1.5K ohms. Running a temporary jumper between these made the drive work, temporally. Removing one or the other made it stop working again. I was able to read data from a disk, and even an external drive #9. After a few power cycles we are back to the drive running non stop and not working. Any ideas? Thanks again! |
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So, I will do it here. These are forwarded from Ray Carlsen. The Hard Tips article is from the famous C= hardware hacker, Al Anger.