At 5:49 PM -0700 5/27/07, Chris M wrote: Not to mention that Apple ///'s are rare enough these days that I'd hate to see one sacrificed that another might live. Though this makes me wonder if this is what is wrong with the /// I have. It was smoked before I got it, I rescued it from the trash. I knew it was smoked when I got it so have never bothered to even look at it. Zane -- | Zane H. Healy | UNIX Systems Administrator | | healyzh at aracnet.com (primary) | OpenVMS Enthusiast | | MONK::HEALYZH (DECnet) | Classic Computer Collector | +----------------------------------+----------------------------+ | Empire of the Petal Throne and Traveller Role Playing, | | PDP-10 Emulation and Zane's Computer Museum. | | http://www.aracnet.com/~healyzh/ |

On Mon, 28 May 2007, Jules Richardson wrote: . . . just like the Lisa and the Edsel used to be

I thought I was the person who always propsed component-level rapair and generally got flamed for it... But perhaps you can explain why soldering in a new capacitor, which is presumable a standard part available from just about any decent electronics suppier, is mroe work than tracking down a somwwhat rare PSU. -tony

_If_ that PSU was easily available, I could agree with this. But it isn't. It's likely to take considerable time and effort to track one down, I think. Time that could equally be spent on repairing the old one. Get a decent soldering iron :-) More seriously, do what just about anyone else does. Flip the soldering iron on, and then start dismantling the machine to remove the PSU module. By the time you've got the PCB exposed, the iron should be up to temperature. As does tracking down a replacement supply, going to collect it (or going down to the Post Office because they tried to deliver it when you were out). fitting it, etc. And then finding the new one also has bad capacitor trouble (Remember these capacitors generally fail from old age, any Apple /// supply is likely to be as old now). -tony

Chris M wrote: Get off this list now !!!! Give me clean air ... The other factor for repair vs replacement is your test equipment and things like a schematic. Repairing a switching power supply is one the last things I would want to do.

--- woodelf <bfranchuk at jetnet.ab.ca> wrote: I guess this is some sort of joke. But again the triviality of such a repair can't be underestimated. In fact, you should be GLAD when a capacitor poofs in yer p/s. It's VERY easy to diagnose what went wrong (ye can smell it, and oh don't it smell nice. I ain't kidding. I LIKE the smell of toasty caps. And machine oil too). And there's only 2 leads. A very easy job. You DO NOT need any test equipment. A schematic is necessary, yes, but I know the value of that cap could be found out by someone on this list, or some other place on the net. Apple 3 parts may not be so common, but docs for it shouldn't be hard to find at all. I'll bet someone (though not me) could guess the value of that capacitor, and would be pretty close too. I'll wager that this is probably THE least arduous of all faults/repairs having to do with an older computer. So easy it's a joke. ____________________________________________________________________________________Be a better Heartthrob. Get better relationship answers from someone who knows. Yahoo! Answers - Check it out. http://answers.yahoo.com/dir/?link=list&sid=396545433

--- woodelf <bfranchuk at jetnet.ab.ca> wrote: Sometimes they just seem to go. This was a common occurrence w/the Tandy 2000's p/s. It could be a faulty design. Regardless of why it happened, if you fix the problem, your p/s will work again. For a time anyway. It might not be worth worrying about. ____________________________________________________________________________________Sick sense of humor? Visit Yahoo! TV's Comedy with an Edge to see what's on, when. http://tv.yahoo.com/collections/222

Geoff Reed wrote: It's neither electrolytic or 22uF (seemingly, the European comma decimal point is confusing the writer), and it didn't fail by 'drying out' as the writer writes. It's 0.22 uF and (probably) mylar or polystyrene, and a replacement should be 'line-rated' as it's somewhat obviously part of the line filter. The writer seems to have gotten the replacement about right regardless (?). I expect many will differ in opinion, but I don't worry much about 'modern' (60's and later) electrolytic caps. Very roughly speaking, my assessment for 'lytics tends along the lines: - industrial quality equipment pre late-50s: worry - " " " post late-50s: don't worry - consumer-quality equipment pre late-60s: worry - " " " post late-60s: don't worry with some gray areas in between, etc. Maybe it's the climate around here (mild) but other than early tube equipment and the occassional leaking one (and the well-known manufacturing problems in the mid/late-90's), I don't often have problems from electrolytics; or to put it another way, I'm of the feeling the concern over electrolytics is overstated. To put it more concisely perhaps, I think the well-justified concern/experience with early 'lytics has carried too far over to more modern equipment/components.

--- Brent Hilpert <hilpert at cs.ubc.ca> wrote: I saw a rather large set of *electrolytics* in a PDP-8e gushing all over the places (I assume they were electrolytics, looked like 1:2 scale coke cans). I've been told a good number of those machines were used in NC environments (actually was told CNC - NOT. There is a difference), so perhaps that had something to do with their demise. The machine was still working though. ____________________________________________________________________________________ Moody friends. Drama queens. Your life? Nope! - their life, your story. Play Sims Stories at Yahoo! Games. http://sims.yahoo.com/

On 29 May 2007 at 14:50, Chris M wrote: Hmmm, then burning selenium rectifier must set your mouth a- watering... :) Cheers, Chuck

On 29 May 2007 at 16:37, woodelf wrote: If you replace the selenium stink-o-matic with a silicon rectifier (you may want to add a series resistor), you'd be doing what many repair techs did in the 1960's. IR touted clip-mounted rectifiers as direct substitutes for seleniums. Not to mention substitutes for OZ4, 5Y3, 6Z4, etc. Cheers, Chuck

Tony Duell wrote: I thought you were the sort of person who didn't buy modern cheap consumer electronics in the first place? :-) Warm dust is quite nice, too... If it was the mains suppression cap then I believe it's a standard X2 class 250V part* in the UK (but then presumably a different part gets used here in the US version) * I think they only sell X2's rated for 275V these days. Farnell and RS do them I belive, but I'm not sure that Maplin do any more. I might haul mine back home tomorrow (it's at Bletchley, but as we now have an A/// there it doesn't need to stay) in which case I can take a look - I need to replace that cap in mine anyway. cheers Jules

Did I ever say I did? I don't have to own something to be asked to repair it :-) -tony

--- Tony Duell <ard at p850ug1.demon.co.uk> wrote: But unless you're good, that doesn't tell you the values of certain components. Bypass caps are usually a typical value I guess, but inside a p/s...your guess would be much better then mine... You still haven't told us how you work up a schematic either. I'm losing my patience. ____________________________________________________________________________________Building a website is a piece of cake. Yahoo! Small Business gives you all the tools to get online. http://smallbusiness.yahoo.com/webhosting

--- Gordon JC Pearce <gordon at gjcp.net> wrote: Not if the cap is extra toasty. uhh, I dunno. You stare at it and gleen what you can Then use an ohm meter to ferret out the rest? I think I've heard something to the effect that *some* chips could be damaged that way though. But I suppose if you're well acquainted with electonic stuff, you'd know when and where to apply that. Like I said, I dunno. ____________________________________________________________________________________ Building a website is a piece of cake. Yahoo! Small Business gives you all the tools to get online. http://smallbusiness.yahoo.com/webhosting

The time to prodcue the shcmatic is when the equipment is still working, that is before components fail. Then if you have a capacitor with undecipheralbe markings, you can measure it. (and if there are readable markings, they'll not have bene obliterated by the component exploding ;-) Actually, for decoupling caps the value is rarely, if ever, critical. 0.1uF seems to work I'll tell you the basic procedure, but to be honest, to produce an easily-read scheamtic takes experience. What you do is start by maing a list of all the main components on the board, or at least he ICs. And separate secions within each IC. You might end up with something like U1 Z80A CPU U2 74LS138 U3 a b c d 74LS00 U4 27128 U5 a b c 74LS10 and so on Then start drawing. Start with the most obvious part, something that will tie down a lot of signals. If there's a 'big chip' that's known -- like a micrororcessor, start with that. The reason is that a microprocessor cna be used in essentially one way -- the addres and data lines have known functions, and so on. If you trace the data pins of a microprocessor to one side of a 74LS245 buffer, and the other side of that buffer to a backplane connecotr, it's a good first guess that those pins on the backplance connector are a buffered system data bus. As you draw each section of an IC, cross it off the list. That way you don't have problems with doing the same section twice. The difficult bits are (a) making sure you draw the circuit in the clearest possible way (for example if you have 2 NAND gates cross-coupled as an SR flip-flop, you want to show them in the conventional way, you certainly don't want them on separate pages) amd (b) assigning senible signal names to signals that go between pages, and indeed between parts of th emachine. This is when experience helps a lot. I thrace connectiuns usising the continuity test range of my multimeter. It's not foold by diode junctions (inclduing protection diodes in ICs). It is 'fooled' by components with low DE resistance like transformer windings. I desolder those from the PCB before I start, Working out the internal connections of a potted transforer (say a flyback) is 'fun'. Often you have to guess based on the external circuit topology. Boards iwth known large chips (micros, memory, LSI I/O devices) are the easiest to do. Boards with just TTL (or 4000-series CMOS) are harder. Boards with all discretes are harder still. Do not tackle an HP9100 as your first project :-) -tony

Actually, if you'll let me use a BGA rework oven so I can remove said chips and get to the connections, and provided I have data on the chips, yes. It'd be a lot easier to work out a board with such chips on than a board with, say , 1000 discrete transistors on it. -tony

www.datasheetarchive.com is your friend, as are the sites of the manufacturers of the chips ;o) Of course, you hardly would find any datasheet about a proprietary ASIC. I see no troubles finding any datasheets. If you need some help, drop a mail! Greetz Alexandre

Chuck Guzis wrote: Surely it's as much effort whether circuits repeat or not? Don't you still have to check all possible interconnects to make sure that you've got everything traced right, even if a quick visual inspection might make it appear that there's a lot of repetition?

Chuck Guzis wrote: No - I'm saying that surely a 1000 transistor board with circuits that repeat is no more or less difficult than a 1000 transistor board where nothing repeats; the level of effort required is largely the same as it's tracing the interconnects which takes the bulk of the time, and that's got to be done fully for both boards to guarantee an accurate schematic. (All of which probably means that the number of PCB layers is irrelevant too - the critical thing is the number of solder points) I'm not disputing that doing a 1000 transistor board is easier than something with BGAs on it... :-)

Jules Richardson wrote: I'd have to say (based on experience) the repetition helps very much in reducing the work effort. Once you have figured out the repeating patterns (i.e. the standard gate construction, flip-flop construction, etc.), you can in large measure stop drawing at the discrete level and draw at the gate level. You still want to check all the internal connections within that gate/repeating pattern for something oddball, so yes, you are right that you do have to go through all the connections, but you don't have to draw it all out. You do a visual confirmation that the gate/whatever conforms to the repeating pattern and then spend your time tracing and drawing the gate/whatever input and output circuits. .. One can also think of it in terms of information content: the info content of 1000 elements arrayed with a repeating pattern is less than that of a purely random array of 1000 elements, and once you can do the compression processing (recognising the patterns) in your head, communicating it over the low speed link (drawing it on paper) takes less time. :) I actually like RE'ing discrete-component digital logic precisely to find out what the repeating patterns are (i.e. how the designers chose to implement gates and flop-flops (in the discrete days there were other flip-flop variations besides JK,SR and D)). Even with analog circuits a lot of design characteristics standard to the system cn become recognisable and make things easier.

Tony Duell wrote: Well if you can cram on *one* more transistor you can clone a PDP 8/S. Why not just get a X-ray machine instead.

So do I. And when I've powered it up, if it seems to be working, I record important voltages (like PSU outputs, CRT pin voltages, etc). -tony

Chris M wrote: Well I suppose it exists already in the form of photo-stitch software (assuming hand-drawn schematics, otherwise copy/paste in your favourite art package [1] will do the job nicely). Beyond a certain level of complexity though it makes sense to separate schematics onto multiple pages according to circuit function anyway, otherwise printing the thing would require either such an enormous sheet of paper as to be unmanageable, or such a tiny level of detail as to be unreadable. Same goes for viewing on screen. (I was looking at schematics for Acorn's Risc PC the other day for someone; if put onto one sheet of paper it'd be around 5ft x 7ft in size - and as a lot of the functionality is provided by custom chips, schematic-wise it's not even *that* complex compared to a lot of systems) [1] I believe some of the Imagemagick utilities will let you do this programatically from a shell script, but I've never needed to try.

Is this avaiable somewhere? ;o)

On Thu, 31 May 2007, Chris M wrote: That is what Dave Thompson made it from, the multiple pages of motherboard schematics in the XT Technical Reference Manual. It was definitely XT, not 5150. You could see the differences of slot #8.

On Thu, 31 May 2007, Alexandre Souza wrote: On Thu, 31 May 2007, Dave McGuire wrote: It WAS commercially available in dead tree form. (~15 years ago) If you can find him (he was the editor of MicroCornucopia), he would probably still have the file. My copy is somewhere in one of too many boxes. -- Grumpy Ol' Fred cisin at xenosoft.com

Fred Cisin wrote: Interesting. I take it that didn't include schematics for the FDC board, MDA / CGA board etc. though, and was just for the system board? I can't imagine it'd be very readable at that sort of size if it included all the 'extras' which turn a bare-bones system into a useful machine (joking aside about how useful the XT ever was :-)

On Thursday 31 May 2007 17:57, Jules Richardson wrote: Still having some quantity of XT-class hardware around, I've been wondering fot some time now what it might be useful for... :-) -- Member of the toughest, meanest, deadliest, most unrelenting -- and ablest -- form of life in this section of space, ?a critter that can be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters" - Information is more dangerous than cannon to a society ruled by lies. --James M Dakin

On Thu, 31 May 2007, Chris M wrote: some of the "hand scanners" had software to "stitch" multiple passes together

Why would you want to? I find a many-page schematic, logically set out with saprate circuit blocks on each sheet, to be a lot easier to follow than a single large page. A few times I've traced out schematics, then later obtained the official manaul with a schematic on one sheet, and find my shcemaitcs easier to follow. I've never found computers (or CAD programs) to be much help in this sort of thing. I just use a pen and paper. Yes, my schematics would be a lot neater if re0drawn witha ruler or on a CAD system, but to be honest, I can follow my hand-drawn squiggles and would rather spend the time investigating or repairing something else. I use A4 paepr (mainly becasue it's what I can easily copy, easily get scannedm etc), and average 5 ICs to a page. So a board with 100 chips on it is going to end up as a 20 page schmatic. (For the pedants here, obviously that average doesn't apply to boards with a lot of discrete components on them, The HP9100B gating board has no ICs or even transsitors on it, just diodes and resistors, but it was still 30 or so pages of schematics). -tony

It was thus said that the Great Tony Duell once stated: Maybe for you it's easy. Possibly not for me. And possibly for the person requesting a new Apple /// power supply (I've lost track of who that was). To put it into perspective you might understand, can you implement a Forth (or Forth-like) system in two hours? I did that the other night because I was rather bored and it was more interesting than I what I was supposed to be doing [1]. If you can't, why not? It's not that complicated. -spc (then again, I'm a software guy) [1] Hanging out online with some friends. Well, I was doing that as I was implementing the Forth-like system [2]. [2] A rather minimal system, and different enough [3] that it probably couldn't be classified as Forth. Forth-like, yes, but not Forth. [3] Managed to get execellent code density (it's a TIL [4]), and I managed to do away with !, @ and most of the stack noise words (NIP, TUCK, OVER, etc). [4] Threaded Interpreted Langauge

It was thus said that the Great woodelf once stated: One version is in C (reference implementation) and I coded up most of it in (severely untested) 6809 Assembly. The "tokens" are 16 bit values, and are broken up as: $0000 - $00FF - push literal values between -128 .. 127 onto the data stack $0100 - $01FF - ALU primitives. Bits 4..7 define the operation: 0 + 1 - 2 * 3 / 4 mod 5 and 6 or 7 xor 8 < 9 <= A = B <> C >= D > E - (operands reversed) F / (operands reversed) Bits 2..3 define the index into the data stack for the second operand 00 - ustack[1] 01 - ustack[2] 10 - ustack[3] 11 - ustack[4] Bits 0..1 define the index into the data statck for the first operand and destination 00 - ustack[0] 01 - ustack[1] 10 - ustack[2] 11 - ustack[3] If the dest index is 0, and the src index is 0 (top two elements on the data stack) then the top of the stack is popped and the result goes into the new top of stack, otherwise, nothing is popped from the stack. So, $0100 would act as "+" does normally in Forth, but something like $0101 is ustack[0] = ustack[0] + ustack[2] or in Forth ROT OVER OVER + >R -ROT DROP R> (I might have gotten ROT and -ROT confused) This doesn't get rid of all the stack noise words, but I suspect it would get rid of a lot of them. $0200 - $02FF - rest of the primitives in the system, typical Forth type words. $0300 - $7FFF - secondary definitions. Value shifted left one bit is the address of the "word" to interpret. $8000 - $BFFF - Mask off two high bits, shift left, address of the value to push onto the data stack. This means that all VARIABLES have to live within the first 32K of memory (I was writing this with an 8-bit CPU in mind). This is the same as: X @ $C000 - $FFFF - Mask off two high bits, shift left, address to store top of stack. This is: X ! I also took a different approach to storing the code. Instead of the traditional headers mixed with code, I split the headers off into their own separate part of memory. So something like: VARIABLE x : foo 3 * 5 + ; : bar x foo -> x ; Would end up in memory like (addresses made up for example purposes only): 2000 variable X 3000 0003 ; 3 3002 0120 ; * 3004 0005 ; 5 3006 0100 ; + 3007 0200 ; ; 3008 9000 ; x 300A 1800 ; foo (address 3000) 300C D000 ; -> x 300E 0200 ; ; 5000 [1][x][_][_] 5004 [previous word] 5006 [1000] 5008 [3][f][o][o] 500C [5000] 500E [1800] 5010 [3][b][a][r] 5014 [500C] 5016 [1804] Over the long term, not only would this format save space, but it would be trivial to chop off the headers to "freeze" the application from futher change, and leave more data space for processing. -spc (I was struck with the idea while reading an old Byte book on implementing TILs)

--- Tony Duell <ard at p850ug1.demon.co.uk> wrote: Very good point. But if you'll remember I, even I was the one who first said there was no point in seeking a replacement when the repair is so simple. It was mainly sarcasm. And I meant real turtles. I have loads of cats too, minus 1 though as of yesterday :( , so I'm off the hook also. Don't even got no Apple 3 anyhow. ____________________________________________________________________________________ Park yourself in front of a world of choices in alternative vehicles. Visit the Yahoo! Auto Green Center. http://autos.yahoo.com/green_center/

At 1:51 PM -0500 5/28/07, Jim Battle wrote: Time to get a better soldering iron. Typically I'd look for a replacement part, but for something as rare as an Apple /// power supply I'll break out the soldering iron, tools, instruments, and figure out what parts I need to order up in order to repair it myself. I'm sorry, this is a case where suggesting you fix it yourself, rather than cannibalizing another system (working or not) is a valid suggestion. This sounds like a pretty easy fix, and there are people here on the list that are more than willing to help talk the less electronically inclined members through something such as this. This isn't something like trying to do surface mount chips, it is very basic soldering. Zane -- | Zane H. Healy | UNIX Systems Administrator | | healyzh at aracnet.com (primary) | OpenVMS Enthusiast | | MONK::HEALYZH (DECnet) | Classic Computer Collector | +----------------------------------+----------------------------+ | Empire of the Petal Throne and Traveller Role Playing, | | PDP-10 Emulation and Zane's Computer Museum. | | http://www.aracnet.com/~healyzh/ |

On 5/28/07, Alexandre Souza <alexandre-listas at e-secure.com.br> wrote: As it turns out, you (and just about everyone else who chimed in) were right - the repair was easy and nothing else in the PS was damaged. I found a power supply at my local junque place with the right cap and used it to replace my blown one. The /// is back up and running fine. It'll be off to its new owner shortly. Thanks to everyone who replied, both on and off topic. ;) -- Erik Klein www.vintage-computer.com www.vintage-computer.com/vcforum The Vintage Computer Forums

Woooo! Now you aren't afraid of trying that anymore, huh? ;o) Congratulations!