1541 Alignment disk

From: ard at p850ug1.demon.co.uk Subject: Re: 1541 Alignment disk To: cctalk at classiccmp.org Date: Tue, 28 Jan 2014 21:04:47 +0000 In general when an electrolytic capacitor (the type that fails the most) fails on such a board, it does notdo any ther damage. The unit stops working, but will be fine if you replace the capcitor. And givne that such capacitors are easy to obtain, it's not a big prblem to do this. Well, unless you're one of the people who beleive that soldering is impossible :-) No, I don'tthink it is It's been a logn time since I've been insdie a 1541, and tghere are at least 2 main verisons of the main PCB. THe older one used anumber of small chips and a ROM for the data encodign/decoding, the later one (qhich ahs at least 2 sub-versions) used a 40 pin custom IC. Needless to sya that custom IC is not goign to be available. I don't think the 6502 is still beiugn made as a 40 pin DIL chip, is it? There are plenty of them around, thouhg. Some of the TTL parts fro the first verison fo the board may bbe no logner maide, but again, gettign them as NOS is not hard. So I think, if tyou wanted to, you could ake the controlelr board using at orst NOS parts, and close equivalents, like EPROMs raehr htan ROMs I also think, withoug trying it, you could fit the entier controlelr board into an FPGA. Whehter you call that a 'clone' I don't know, It does the smae things, it's the same design. But to me it's nto the same circuit. The problkem, I think, is the mechcnail side. The 1541 is not a normal drive + a controlelr board. It's a bare drive chassis + controller board. What I mean by that is that all the elctroncis -- things like the head amplifier, the stepper mtoor driver, etc are on the controller board. The drive chasiss is just the motors, heads, etc. So if ytou want ti to be 'origianl' you can't jsut use a standard drive. You have ot use one with the sutiable motors, etc. And given that 5.25" drives are n logner made, you are not foinf to find a current one. My guess, again without trying it, is that given any 48tpi 5.25" drive you could make a controller board using easily avialable parts (not necessarily ones in currnet procduction, but you could probably do that too if you don't maind it all going in one FPGA), that would act jsut likea 1541. Whether that's a clone of a 1541 is open to debate, though. -tony