68kMLA Classic Interface
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| Macintosh Classic II Analog Board repair Help! | |
| Posted by: macalle69 on 2015-07-06 14:42:30 Hello everybody I have a problem with my Macintosh Classic II. the computer would not start more '. I made the first tests with hot air to the analog board and give satisfactory results booting. The image was moved and the hard disk intermittently started and stopped. At this point, I replaced all capacitors (thanks to Uni for capacitors references )(many were gone) 1 - 1000μf - 10v - radial 1 - 1000μf - 16v - radial 1 - 1000μf - 35v - radial 2 - 2200μf - 10v - radial 1 - 2200μf - 35v - radial 2 - 470μf 25v Now the computer starts, but still has the problem that the hard disk spin intermittently. I tested the gates of the floppy: pin 6 measuring 4.8 v pin 7 measuring 12.3 although it is not recommended I tried to modify the voltage from the analog board, but did not give any improvement. The problem is in the 2 diodes in pictures displayed in red? Unfortunately i can not read 'code and model cause are discolored , someone can tell me the specs model and possibly replacement part?. They may be the cause of my failure? Or the problem is to be found from something else? Thanks for your help  | |
| Posted by: 360alaska on 2015-07-06 15:05:40 Have you considered that the hard drive spinning intermittently could be a hard drive problem? I seem to have nothing but back luck with quantum drives... | |
| Posted by: macalle69 on 2015-07-06 15:27:49 Hi there HD is perfect i have tried also with another hard drive , external SCSI HD and tested it on another Macintosh , when i wrote hard drive spin intermittently mean that it seems that low voltage is powering hard drive, and computer intermittently boots and hard drive spin, then stop than spin again | |
Posted by: macalle69 on 2015-07-06 15:39:17Have you considered that the hard drive spinning intermittently could be a hard drive problem? I seem to have nothing but back luck with quantum drives...Hi there HD is perfect i have tried also with another hard drive , external SCSI HD and tested it on another Macintosh , when i wrote hard drive spin intermittently mean that it seems that low voltage is powering hard drive, and computer intermittently boots and hard drive spin, then stop than spin again | |
| Posted by: techknight on 2015-07-06 16:29:26 Replace QP1 | |
| Posted by: 360alaska on 2015-07-06 17:01:33 Another Possibility is the potentiometer itself, it is a 220 ohm 6mm potentiometer... It's a pattern failure... but try reflowing it first... | |
Posted by: macalle69 on 2015-07-07 03:25:15Replace QP1original is CNY75GB 245 A TK4 0884 , i found on eBay CNY75B 023 A TFK4 0883 can replace original? | |
Posted by: macalle69 on 2015-07-07 03:25:59Another Possibility is the potentiometer itself, it is a 220 ohm 6mm potentiometer... It's a pattern failure... but try reflowing it first...thanks at first i'll try replacing optoisolator | |
| Posted by: uniserver on 2015-07-07 03:47:22 https://68kmla.org/forums/index.php?/topic/21414-classic-analog-board-voltage-problem/ here is a similar thread, and he had some good success! | |
| Posted by: Paralel on 2015-07-07 11:51:13 Send it to Uni, he'll get it straightened out (that's my stock answer for complex issues like this that aren't getting sorted out). I wouldn't let anyone else touch my Macs. But I guess I'm kinda spoiled, I can just drive them over to him. | |
Posted by: macalle69 on 2015-07-09 14:30:09Send it to Uni, he'll get it straightened out (that's my stock answer for complex issues like this that aren't getting sorted out). I wouldn't let anyone else touch my Macs. But I guess I'm kinda spoiled, I can just drive them over to him.i think i'll do it! Thank you | |
Posted by: macalle69 on 2015-07-10 10:12:45i think i'll do it! Thank youProblem Solved : thank you Guys , replaced QP1 with CNY75B 023 A TFK4 0883 now Classic II is back to life ! | |
| Posted by: uniserver on 2015-07-10 12:57:32 thank techkinght, Techknight also was the one that solved this one too! https://68kmla.org/forums/index.php?/topic/21414-classic-analog-board-voltage-problem/ techknight | |
Posted by: macalle69 on 2015-07-10 13:16:30thank techkinght, Techknight also was the one that solved this one too!Yes Yes Yes many thanks Techknight!!! | |
| Posted by: techknight on 2015-07-10 16:51:58 Glad it all worked out. | |
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