Can you tell us more about the "supercap"? What is the part called and does anyone know where these can be purchased? How long does the memory last as compared with a more traditional battery?
Thanks! rcs On Sun, Mar 17, 2024 at 2:52 AM Brian White <[email protected]> wrote: > It should definitely at least be opened and looked at, and really > especially in the case of a 100 vs the other models, it should just be > preemptively recapped and new battery regardless, even if it looks perfect > today. > > Because there is no getting around the passage of time. The batt and caps > WILL leak eventually, and in both cases the fluid corrodes all the traces > all around them, and by now the bulk of that theoretical maximum > "eventually" time has already passed. If your machine is somehow still > clean, then you are lucky and now is the time, not after corrosion starts. > > It's not a "if it aint broke" situation. > > I know it's not convenient and not appealing if the machine is working > fine. > > In particular, the 100 (vs 102 or 200) are known to have caps that all go > bad by now. 102 and 200 seem to be holding up better on average, as > reported by people that do a lot of repairs. All my own machines had some > level of corrosion started already, but that's only a few machines. > > They can be leaking and corroding while still looking fine from a cursory > glance too. No bulging tops or anything. But they leak and it makes an > invisible thin film that spreads far and wide on the surfaces of > everything, and travels under the solder mask sometimes, and the pcb can > sometimes look fine until you look real close and see sort of dark areas, > and when you touch the soldermask there, it flakes up and you see the dark > area is all corroded copper sometimes eaten all the way through. The > machine runs perfectly with no hint of a problem right up until some trace > finally gets the last connecting copper atom oxidized, unless one of the > caps also goes out of spec enough to make the machine unstable. And then > you discover it's not just one trace but a bunch all over the place. > > The good news is it's actually all fixable even in really bad cases. Big > old through-hole stuff, even densely packed, is big and easy by todays > standards. > > bkw > > On Sat, Mar 16, 2024, 11:52 PM Will Senn <[email protected]> wrote: > >> This sounds important. So far as I know, mine's original equipment. Do I >> need to be worried? >> >> Will >> >> On 3/16/24 8:21 PM, Doug Jackson wrote: >> >> Every time I see one of those evil NiCad batteries, I replace it with a >> 0.5F supercap. >> >> I have never had an issue with my M100, or with the Olivetti equivalent >> (number escapes me at the moment) >> >> Having said that, the oldest would have been 8 years ago, so I don't have >> the same 30years of experience regarding leaking characters. >> >> Doug >> >> On Sun, 17 Mar 2024, 11:44 am Brian K. White, <[email protected]> >> wrote: >> >>> You can run plugged in to the wall for all normal random on/off >>> operating times without worrying about it too much, IE, all day long for >>> 8 to 12 hours or whatever, and for multiple days in a row, if unplugged >>> when turned off. >>> >>> And you can leave it plugged in turned on or off overnight for one night >>> to a few days. >>> >>> And you can even get away with exceeding those pretty badly once in a >>> while. >>> >>> What you want to avoid is plugging it in and leaving it plugged in 24/7 >>> for weeks or months or years, whether it's on or off. >>> >>> The harm is the charging circuit that charges the internal nicd battery >>> soldered on the motherboard. The battery is not a lead/acid or gel cell >>> that has a float value where it can just stay floating at a certain >>> value forever, and the charging circuit is not a smart modern battery >>> manager that knows how to stop charging when the battery is full, it >>> just keeps on supplying a bit higher voltage than the the cells own >>> voltage, and current just keeps on flowing backwards through the cell, >>> and sooner or later this kills the battery by a couple different >>> possible mechanisms from plain heat & pressure making it leak and cook >>> off all the electrolyte, to things like the electrolysis process like >>> electroplating, eating away all of one plate and building gunk up on the >>> other. >>> >>> It's pretty forgiving so you don't have to be super careful. You can >>> *mostly* never even think about it, and a normal random usage pattern >>> will just naturally be fine. Just don't plug it in and forget about it >>> for a year. >>> >>> It doesn't touch the AA's and it doesn't matter if the machine is turned >>> on or turned off. >>> >>> Now that you make me run through it all like that, I realise this might >>> finally be be an actual valid useful reason to install a supercap >>> instead of a new nimh cell. >>> >>> Mostly there is no point, because both a cap and a battery will only >>> last about the same number of years, and both will start to leak >>> corrosive juice after about the same number of years. A cap is not >>> harmed by being allowed to go all the way dead (which a battery is), nor >>> by being allowed to stay dead for a long time (extra especially bad for >>> a battery), but even a battery that has been so badly treated still >>> supplies more standby time than a brand new perfect cap. All in all, no >>> point. >>> >>> But one difference that matters, a cap should not be harmed by the >>> crudeness of the charging circuit. A cap will just charge up and stop >>> conducting and won't care about the charging supply at all. No current >>> will keep flowing through the cap, no cooking or electrolysis etc. >>> >>> I have always been very much not in the supercap camp, but this is one >>> real thing. >>> >>> -- >>> bkw >>> >>> On 3/16/24 16:33, Will Senn wrote: >>> > Wow, Brian! Super clear. Now, I want a REX# :). >>> > >>> > When you say that leaving it plugged in will kill the battery, do you >>> > mean that I should run it off AA batteries most of the time and not my >>> > 6v 200ma adapter? And the battery you're talking about killing is the >>> > nicad on the board, right? >>> > >>> > Thanks, >>> > >>> > Will >>> > >>> > >>> > On 3/16/24 3:21 PM, Brian K. White wrote: >>> >> I summarize REX as: "An on-board software-controlled option rom >>> >> library and ram image library." >>> >> >>> >> That's the shortest way I've found to say what it does, but that's >>> not >>> >> the same as saying what it's good for or why you want one. >>> >> >>> >> Because of the particular features and limitations of a M100, >>> probably >>> >> the single most life-improving thing you can do to one is to have >>> >> TS-DOS in ROM. >>> >> >>> >> That one thing addresses a few different pain points. >>> >> >>> >> The biggest pain points of a M100 are: >>> >> >>> >> - Battery-backed ram only storage. Very little storage, and easily >>> >> erased or corrupted, either by dead batteries or a software crash. >>> >> >>> >> - The way in manages machine-language software. How they all want to >>> >> run in the same place in ram, yet the OS does not provide very much >>> in >>> >> the way of automatically moving programs into and out of that spot, >>> so >>> >> software is always clobbering other software, or you limit yourself >>> to >>> >> just having a single machine language app installed, or you have to >>> >> figure out the arcane way to hack the binaries to relocate them to >>> run >>> >> at different addresses side by side, or you have to keep double >>> copies >>> >> of binaries so that the running copy can get clobbered and later >>> >> replaced from the ram file copy... >>> >> >>> >> - The main rom provides no binary file transfer other than the >>> >> cassette. And no *convenient* file transfer even for text. >>> >> >>> >> These things combine to make life kind of difficult. For instance you >>> >> want some better file transfer app, but since you have no binary file >>> >> transfer to begin with getting the file transfer app itself installed >>> >> is a pain. Then once it's installed, it consumes precious ram, and is >>> >> easily broken because of the way machine language apps are are run, >>> >> and the simplest way to address that is to have a 2nd physical copy >>> in >>> >> ram, which uses up yet more of that precious 32k. etc. >>> >> >>> >> Having any tpdd client at all installed in any form makes >>> transferring >>> >> files a breeze, including binary files. This somewhat alleviates the >>> >> small ram problem because you can easily put files away and get them >>> >> back, as long as your tpdd software stays working. >>> >> >>> >> Even better is having a full featured tpdd client like ts-dos instead >>> >> of teeny, and having it in rom instead of ram. >>> >> >>> >> That alleviates all kinds of annoyances. >>> >> - It consumes almost no ram. >>> >> - It doesn't require a pain in the neck bootstrap/loader process to >>> >> get installed. >>> >> - It isn't subject to being clobbered and needing to be reinstalled >>> >> because of some other software writing over it or crashing. >>> >> - It isn't lost after a hard reset or dead batteries. >>> >> >>> >> With TS-DOS in rom, you can pick up a totally dead machine, or >>> totally >>> >> kill your machine with a hard reset on purpose, or suffer a total ram >>> >> corruption from buggy software, and with just "CALL 63012" you are up >>> >> and running again, connect to a computer and pull down files. >>> >> >>> >> But even though this makes a lot of things a lot better, this still >>> >> needs a computer and serial cable. The tpdd client just makes it so >>> >> that you can effortlessly connect to a pc and move files back & >>> forth, >>> >> and having it in rom just means you can effortlessly always have the >>> >> tpdd client regardless of crashes or dead batteries. >>> >> >>> >> That still leaves a couple things that could be better: >>> >> - If you had a plain ts-dos option rom, it means you can't use any >>> >> other option rom because the single socket is occupied already by >>> ts-dos. >>> >> - You still need a serial cable and pc (or a real tpdd drive or a >>> >> Backpack or PDDuino) to actually get the files from somewhere / put >>> >> them somewhere. >>> >> >>> >> REX gives you ts-dos in rom just for starters. It gives you ts-dos in >>> >> rom which just that right there alleviates several things above, but >>> >> also: >>> >> >>> >> - all other options roms besides ts-dos >>> >> - full ram image backups >>> >> - all on-device self-contained with no computer or serial cable >>> needed >>> >> (after initial loading) >>> >> - impervious to dead batteries or resets or crashes >>> >> >>> >> And although you do need a computer to install option rom images onto >>> >> the rex one time, ts-dos in particular is pre-installed, so that >>> >> single most-needed one never needs even the initial one-time install >>> >> from a computer. Only all the other roms need to be loaded from a pc >>> >> once. And the loading process is easy, because REXMGR uses tpdd >>> >> protocol internally to pull the rom images from a pc. No >>> >> bootstrapper/loader procedure. >>> >> >>> >> The other option roms give you mostly a few different office software >>> >> kits, ie spreadsheets and word processors, and a few other things >>> like >>> >> there is a FORTH rom and an assembler/debugger/renumberer. >>> >> >>> >> The ram image backups give you essentially more copies of 32k ram. It >>> >> helps a few different ways: >>> >> - you can physically hold more than 32k of apps or data. >>> >> - you can recover from a dead battery or reset or corrupted ram from >>> >> crashed software by restoring a ram image. >>> >> >>> >> There are something like 30 or so available slots, and each slot can >>> >> be either an option rom or a ram image. That's a lot. >>> >> >>> >> All without a computer. In the coffee shop, on the train etc, just >>> >> recover from dead zero in a few seconds. Just "Call 63012" and away >>> >> you go, all interactive app and menu driven after that. >>> >> >>> >> So that is why you want a REX of any stripe, REX Classic, REX#, or >>> >> REXCPM. >>> >> >>> >> Now for REXCPM in particular.... >>> >> >>> >> Those particular advantages are something the REXCPM is less good for. >>> >> >>> >> REXCPM does give you all of that, but only as long as the M100 >>> >> internal battery is not dead and the REXCPM and bus adapter board >>> >> remain installed in both sockets. >>> >> >>> >> You can recover from software crashes that scramble the ram, and from >>> >> intentional hard resets that wipe all ram (ctrl-break-reset), but not >>> >> from dead batteries or switching off the memory power switch on the >>> >> bottom for more than a few minutes, or removing the device from the >>> >> m100 for more than a few minutes. >>> >> >>> >> If the M100 internal battery runs out, or you uninstall it for more >>> >> than a few minutes (you do get a pretty good grace period of several >>> >> minutes, maybe even over 10 minutes) then you have to reload the >>> >> REXCPM from scratch as you just experienced. If you had a REX Classic >>> >> or REX# instead of REXCPM, all you would have done is type "call >>> >> 63012" and you'd be all back up & running. No pc, no "37 easy steps". >>> >> Done. And to remember "call 63012" just write it on a sticker or >>> >> label-maker on the bottom. Put it on the underside of the option rom >>> >> or battery cover if you want to hide it but then you have to at least >>> >> remember that it's there. >>> >> >>> >> I did make a "UPS" for REXCPM that should keep it alive for a few >>> >> years, but it's pretty involved to build and ultimately hard to >>> justify. >>> >> I don't pretend it's practical for most people, but it does work and >>> >> exists. >>> >> https://github.com/bkw777/REXCPM_UPS >>> >> >>> >> You have to buy the parts from digikey or mouser etc, order pcbs from >>> >> elecrow or oshpark etc, and then it's a pretty fiddly soldering job, >>> >> and it ends up costing as much or more than the rexcpm itself just to >>> >> give it a battery. And for all that, I think I only estimated 6 >>> months >>> >> per cell x 4 cells = 2 years, but that's after the M100's own >>> >> batteries run out, and if you have fresh alkaline AA's and a charged >>> >> internal battery, the M100 itself can last anywhere from a few months >>> >> to a year. So maybe up to 3 years? >>> >> >>> >> A better long-term solution would be a keeper. You remove the rexcpm >>> >> and plug it in to something with socket and a big battery. But that >>> >> doesn't help with one that's installed in a machine. You'd need to >>> >> remove it from the machine to put it in the keeper. Plus the molex >>> >> sockets are no longer made. There are a few around available still >>> but >>> >> this would be a wasteful way to use one up instead of keeping them to >>> >> repair machines. Really, for the long term like over 5 years, it's >>> >> probably more practical to just let it die and reload it. With a >>> >> convenient bootstrapper and tpdd server on a pc, it only takes a few >>> >> minutes to reload a rexcpm from scratch. It's several steps that >>> >> requires a cheat sheet to follow, but none are very difficult or >>> long. >>> >> The hard part is just deciphering the original directions to figure >>> >> out what actually are the steps you need to do. >>> >> >>> >> So all in all, I'm not sure how necessary the ups is. It's probably >>> >> more practical to just do 2 things to live a happy life with a REXCPM: >>> >> >>> >> 1 - Keep it installed in a machine. And keep that machine charged. >>> >> (Unfortunately, you can't just lave the machine plugged in to the >>> wall >>> >> 24/7 for months, that will cook the internal battery.) >>> >> >>> >> 2 - Get good at reinstalling it. It's several steps, but it's >>> possible >>> >> to write a little cheat sheet that is easier to follow than the full >>> >> original documentation. And none of the steps are very difficult or >>> >> long. You don't even need the cheat sheet after a few runs through. >>> >> >>> >> If you aren't specifically wanting to run CP/M then I always say a >>> >> REX# is far more practical. REX# is an nvram device that acts like a >>> rom. >>> >> >>> >> Instead of ever needing to recover the REX, the REX is what recovers >>> >> your M100. >>> >> >>> > >>> >>> -- >>> bkw >>> >>> >> -- *Níl aon tinteán mar do thinteán féin. *[Irish Gaelic] (There is no fireside like your own fireside.)
