Apple ][ plus: 8304 replacement from AliExpress, more keyboard fixes, and a huge surprise!

hello everyone and welcome back to adrian's digital basement this is part five in the apple ii plus repair series and as you can see the machine is still working so this is not really a repair video per se it's more a video about following up on some loose ends that i missed on the first four parts and a couple other new developments so anyways without further ado let's get right to it [Music] i want to kick off this video by doing an update on the two plus it's been a little bit of time since i finished up the repairs on the motherboard as you saw in the previous parts and since then this computer has been working perfectly no other faults have come up i have been using it to do all sorts of things play games and stuff like that there have been no issues with the repair work on the motherboard it doesn't mean this machine is perfect though and the first issue i want to talk about is the keyboard when i last talked about the keyboard i think in part three and four of the video series i had ended up replacing several of the key switches because they just completely weren't working or super unreliable but due to the fact that i didn't have enough working good quality alps skcc switches i ended up having to take the key caps off and dump some deoxit down the key stem into the switch itself hoping that that would kind of make things work better i have notes here from the previous part on the keys on what i did and unfortunately i clearly didn't do a very good job writing down notes about what i did because i just have this list of heat letters here and not really any indication of what i did like which ones of these have had deoxide in them and which had the key switch replaced entirely so i'm not totally sure on that but i can tell you that there's still a couple switches that aren't working very well nothing is totally dead which is good means this thing is usable i have found that the six key is pretty problematic in fact okay so there we go i just got two sixes when i should have had one let me just make sure i type the sequence properly obviously alternating between two keys okay there we go notice there the six i missed the missed key pushes sometimes you get multiple it's actually worse when you first turn the computer on after not using in a while it gets better the more you use the key and it's it's not working super great but i am pleased to report that other than the six all the other keys are working completely fine on this keyboard at this point i haven't noticed any issues with any of them it really is just the six key so let me remove the cover of this machine so i can take the keyboard out because i have a few things to try to see if i can fix that six key [Music] cool the keyboard is out and i have to say the 303 protectant i put on the keys it did a pretty good job they still look pretty good these keys i removed the encoder board so this is what converts the keyboard matrix here into this 8-bit parallel signal that goes into the motherboard now i had mentioned in the previous video pushing reset versus having to push control reset and i'm pretty sure that it's this switch right here on the encoder that's what controls whether you have to push control reset or just reset on the silk screen it does just say s1 underneath there it doesn't really say if that's what that does but i'm pretty sure that's what that is if i'm wrong please i'll put a comment in the comment section below i do also find it interesting that there's a nine pin d sub connector space on this board right here does anyone know what exactly that would be used for would it be for turning this keyboard into an external keyboard with a cable that went to the apple 2 plus and then here there are holes for what looks like another toggle switch so i'm just curious what these two things are used for looking at the pcb here i can see where i marked where i switched out keys i think i put little dashes and dots and stuff around so it looks like i switched out the 8 key and i switched out the 2 key on the top row but definitely the 6 key which is this one right here it doesn't have any kind of marking at all when i last worked on this keyboard i had mentioned that i ran out of key switches that were good in fact i have a bag here that says bad parts and these are all skcc switch parts including a lot of the long stems that are used on the macintosh keyboards which also use the same switches just the stem length is different now here are the two stem types on the left is the taller one from the macintosh keyboards and on the right the shorter stems that are from this keyboard but also other keyboards that use this trcd model 80 ti-99 they all seem to use this shorter one but really the only difference is the length of the slider part the bottom part which is what pushes on the spring and on the little metal pad inside the little metal contact all that stuff is the same so these are completely interchangeable so if you end up buying replacement switches off ebay that are for the long stem like from a mac keyboard and you have a short one that has a problem with dead keys and the stem is not broken you can just take them apart and swap the parts around to get working switches for your short stem keyboard now when talking to someone i can't remember if it was on twitter it might have been on twitter i can't really remember it might have been a friend of mine anyway someone suggested to me that i should take some fully assembled switches and put them in an ultrasonic cleaner and that maybe that would make them work because i had tried everything to get them to work i flushed them out with alcohol 99 you know opening them up to do that really exercise them blowing air through it all sorts of stuff like that and just nothing i could do would seem to get them working especially when they were totally dead so i ended up doing that i took my little small chinese ultrasonic cleaner and i put i think alcohol in there i don't quite remember it might have been soapy water and i left it in there for 10 minutes at something like 40 degrees 45 degrees celsius and you know what i think i put in six or seven switches that i had into the ultrasonic cleaner and these four came out and they seem to work now i took these out i let them dry put them in the warm windowsill in the house for several days make sure they were completely dried out and they did seem to be working with my multimeter at least i could test continuity and they seemed good now it's been several weeks since i've done that cleaning i don't know if they still work so let's uh get the multimeter output on continuity and give it a try for testing these it's really fiddly to try to hold the multimeter probes on both of the pins so what i've done i've taken two of these uh clip leads that i have these hooks attached to the ends and i've clipped this onto the multimeter that way there is no ambiguity that i have good contact with the pins on the bottom of these so we'll just clip this on and when i push it so it's reading down around 1.8 ohms which should be perfectly good for a working switch so this one still appears to work excellent 1.28 ohms on the next switch that one works well as well 1.2 on the next one that's looking good and 1.1 on the last one so it appears that even though it's been a couple weeks all four of these that went through the ultrasonic cleaner work now now remember i mentioned that there were others in there with it too i think i had six or seven the other ones after cleaning and letting them dry out they weren't working properly they were either very intermittent uh or the resistance was too high or there was no continuity at all and i want to mention that before when i put these into the ultrasonic cleaner before doing that and i'm sorry i didn't film it they were all completely dead you would connect the multimeter up just like i did here push the button there would be nothing so the ultrasonic cleaner did wonders for these i wish i had known that before i had done all this disassembly or i would have just taken out the flaky switches and put them in the cleaner in fact i'm going to swap out the six key now with one of these but i'm not going to throw that switch away i'm going to put it in the ultrasonic cleaner as well and hopefully it becomes good as well and i can just put it in the bag for later use it really does help to mark the pcb with a marker for which switch you're going to be removing there have been plenty of times where i'll put the desoldering iron onto the wrong two pins and then i'll have to fix that so you just put a little mark if you don't like those marks you could take it off with ipa that sharpie comes right off but i completely recommend that just to help you not make mistakes for removing the solder i think i'm going to try using something i just bought and it's this thing here which is a sautopult this is a solder sucker and apparently this is the best ones available actually saw this on dave jones's eev blog channel he had a mail call where this was shown the guy who invented this started a company in los angeles at van nuys which is a city within los angeles he started a company selling these things and that same company which is family owned still makes and sells this thing you can find it on amazon that's where i bought this but you can buy it directly from them as well they make an esd safe version which is i guess coated in metal and apparently all of these other cheap solder suckers that you see floating around like this one here i have is a copy of this design and i have never had one of these cheapy ones that was any good in fact the anodized blue aluminum ones those are garbage you use them a handful of times and they're dead apparently this one is the bomb yeah this thing works really well i think it was 22 dollars so it's pretty inexpensive there's a little bit of technique so practice on something took me a few tries to get that working but these are both completely free and it did the trick i love it to make sure they're fully de-soldered just wiggle the pins and they should move freely inside the hole you can do it with your finger or you can do with a screwdriver both of those are free for removing these switches from these keyboards there's clearly a technique which i'm just not good at i think the fact that there was so much gunk on this keyboard though i got that one out without too much trouble i used two flat blade screwdrivers but sometimes there can be really stuck and i think i mentioned in my previous video sometimes taking these out they were so stuck in there and it wasn't the pins on the board it was just the body being stuck in the hole that pulling them out cracked the cases or took chunks out but luckily this six key switch came right out without too much trouble so i just have to remove this little cap here there we go i'm gonna keep this switch separate so i know that's one that needs to be cleaned and i take one of these that i have cleaned the pins on the switch itself are set to one side and they're offset from each other so there's really only one way this can actually go in to the base plate here and clip in so there it is clicked right in and the pins stick through the board in the correct orientation let me just reinstall this little riser cappy thingy here like that and then we just apply fresh solder onto the switch and the pcb let's give the six key a test control reset turn on the monitor of course cool okay let's see is the six key working reliably certainly seems so this is good so i'd say that this problem is fixed so while i was working on repairing the apple 2 plus and this keyboard i was in contact with stuart the gentleman who donated this incredible machine to me back in that first video and while i was mentioning the keyboard wasn't working what turns up in the mail another keyboard now stuart had sent this to me and he found this i think online and mentioned to me that this keyboard was sold as not fully working so this keyboard has issues too now with stuart's intent that i take parts from this keyboard which was sold as not fully working and mix and match parts from both keyboards to make one really good keyboard unfortunately unbeknownst to stuart and also unbeknownst to me i didn't realize that apple had multiple keyboards on the apple 2 plus the alps skcc keyboard is not the only one that was commonly found and this is one of the other types now flipping it over really gives away that it's different it's got a blue pcb has these plastic strengthening bars here there are no solder pads or any kind of pins showing through on this which means this is more like a membrane keyboard or some kind of plate switch that's laying on top of the pcb something along those lines in addition the keycaps aren't even fully compatible with each other these have a more cylindrical profile to them and these are more like a bowl an upside down bowl or a cup and they're also shiny on the top of the keys while these are textured now this keyboard is filthy dirty but i can tell right away that the keys themselves are textured and these are shiny and sure enough when you combine the two keys right next to each other they're clearly not compatible with each other this is the six key off the other keyboard and let's see if it's even compatible with the mount on here it is not it might be able to force it on there but it definitely doesn't just go on easily to these little adapter things which are on top of the skcc both has a plus so you would think it might be compatible but because the key height isn't even the same there's just no way that these are going to work anyways now one thing about this keyboard is it says power yes on this little thing let's pop this off okay there's a little light bulb underneath could it be possible that this is compatible with this one that doesn't say power anymore can i switch them and if i can that would be epic first things first is this thing is filthy so let me clean it just clean it up a little bit i mean i should really test to see if it even goes on the keyboard first shouldn't i but i hope it does because that would be amazing and here's the moment of truth what happens if i push this down onto here well it seems to stay on it's on there oh that's awesome that is exciting let's see if i can put this one back onto the other keyboard yep that goes right on as well so i guess those are interchangeable so that is fantastic let's give it a quick test yes look at that that looks so much better okay so what i want to do now is i'm going to test this replacement keyboard which incidentally is really light feeling it's doesn't have the heft that this one has let me move the alps one out of the way i do appreciate that whoever sold this keyboard did take effort to prevent the pins on the socket here the little socket cable thing from getting bent they put a little piece of foam on here let's pop it off and see how good it looks oh yeah it looks good not bent all right let me just connect this up to the motherboard here make sure it goes in correctly like so and here we go alright so let's see what works and what doesn't work on this keyboard so here's some funny irony guess which key is the one that doesn't work on this keyboard everything works except for one key yes the six key six key is totally dead all the other keys appear to work properly at least on first impression now when i flip this over it looks like the pcb is held on by little screws very similar to the way a commodore keyboard's put together so it's possible that taking those out you can lift the pcb away and underneath are going to be all the little contacts little metal things or whatever is going on underneath this keyboard if it's rubber or metal to allow you to clean it potentially fix this keyboard up also not completely unexpected the feel of this keyboard is not so great it's it's it's fine i've felt far worse keyboards on vintage 8-bit micro computers but this one it doesn't hold a candle to the alps skcc so if you have apple 2 pluses and you have a chance to get the alps keyboard over this keyboard i definitely recommend the alps keyboard i'm definitely glad i have this keyboard though because of course i have a replacement proper power light on the other one now but also if the other one starts to really fail like more switches start to die i just don't have any more replacement switches so having a spare keyboard is certainly a good thing on something like an apple two plus because it seems like these keyboards are now becoming very rare and rather expensive to find now when i first showed this keyboard which was part three of this repair series i had a viewer comment to say that he has had problems with the parallel data signal over this ribbon cable and that from his integrity standpoint putting a ferrite ring on it really did help him with reliability and then he said that some of that double bouncing key stuff that i was having can be solved by the ferrite ring now i know in my case it clearly is bad switches that were causing all my problems because now i just replace six everything is working and uh he hadn't seen part four yet where i do fix this keyboard by replacing key switches so it's understandable he was just offering a suggestion but i thought it might be interesting to try one of these rings now i have one of the ferret rings right here this is from a commodore 64. it's on the keyboard cable on that thing but i thought it might be interesting to try to install this onto here and see if it helps at all or maybe it doesn't but whatever it'll be on there it's not going to hurt right so to make this thing work you don't just put it on and sort of have it floating around on here you really have to loop it around this ring now to facilitate that it's not going to be super easy because of course there is this pin connector on the end here and i have to get this through there which it will fit has to go sideways obviously but i need to do it in a way that doesn't bend the pins and then i have to loop it around it's also going to reduce the length of this cable which makes it a little harder to plug into the motherboard but i think it's doable and the way i'm going to do it is i'm just going to split this cable so this cable is a ribbon right now if i use my fingernails i'm just going to split it apart and that way this cable will be a little bit more flexible to accommodate the looping around of the ring and don't worry this doesn't have an ill effect on the ribbon cable in fact i used to do this all the time back in the pc days where you had 50 pin ribbon cables or 40 pin ribbon cables or 34 pin for floppy disks i used to split them apart like this and when you do that you can then stack them up use a zip tie on them and it just makes it more flexible you don't have this wide cable blocking airflow and whatnot so this was a common tactic the other thing you could do is i could i'm doing like three or four wires at a time here you could go even more and do like one at a time really split this up but because i've done this this makes this cable a little more flexible to go side to side okay let's give this a try try to feed this through i need to be careful not to bend the pins it's not super easy there we go got it through once and i didn't bend anything so perfect so like i mentioned it shortens the cable a little bit but i think it's still going to be completely fine and from my understanding it's best to put the ring closer to the motherboard the connector than the side that would go into the encoder board here and as you notice it was essential that i did split the cable otherwise this really wouldn't have been possible also just for my e's it's not like this is necessary i'm just going to put a black dot right here to indicate pin one and it does say one right on there there's the red stripe on the cable but the dot will just help me with the installation i gave this plastic keyboard a quick clean and interesting is uh check out the damage to the shift key there i wonder what caused that ouch the rest of the board is in really nice shape still a little dirty because i i really just gave it a cosmetic cleaning on the top with the windex and a cloth but you can really see the texture of the keys that i was talking about as opposed to the shininess on the alps case skcc and notice the cylindrical profile of the keycaps as well versus the cup one on the other keyboard next up is to try to address my fix for this machine which is this little stack here right this was a dp3904 if i recall and i ended up doing this little hack job to get this thing running with a 74 ls 245 bus transceiver now in part three when i did that little stack to make that computer boot i didn't have any replacement 8304s but i do now but of course guess where these come from yeah you guessed it aliexpress directly from china i paid just a mere three dollars and seven cents shipped for these five chips all the way from china which is pretty amazing i think these are out of production they may not be to be honest i actually didn't really look on digikey to see if they still sell these these appear to have a date code of 1990. is that real who knows let's do some testing to see if these things are obviously fake so first off let's take a visual inspection these are national semiconductor parts like i mentioned the date code is 1990 and usually i find that when they're fake rebadged chips the date codes don't make sense like they're really new like these would be 2006 chips or something but no these appear to be old the cases look they look old like these are pulls potentially from old equipment but all of the markings on all of these chips are exactly the same something honestly that bodes well for these being pulls is that the ic legs actually have oxidation on them they don't look completely brand new i mean the whole chips don't look completely brand new the legs are a little askew they was shipped on a piece of foam but you know these are probably who knows how they were stored but yeah oxidation i don't know to me that's actually a good sign more good signs on the bottom it actually has an ns logo right in the case so that matches what's silk screen on here so that is good and then there's an a b which is nice my initial sagery in black pretty cool these are made for me obviously so yeah these look they look on visual appearance like these are legit first i'm going to try a little ipa here so i'll get some on this cotton swab and let's let's see about rubbing off any paint or anything that's really a telltale sign no negative effect sometimes a little bit of dirt comes off but nothing's really coming off next i'm going to try a little nail polish remover which is 100 acetone we will see about rubbing these chips with this i'll try clean side of the cotton swab this will probably melt this foam pad if i let it touch it and nothing should happen on the real chips when you have paint and they're fake chinese chips yeah it rubs off yep nothing no effect whatsoever good signs lastly i'm going to use the pin out of the ic which is right here and i'm going to try to ohm out some of these like the vcc to ground make sure there's not just a dead short on this chip so multimeter in resistance mode it's not in continuity mode just resistance mode vcc is pin 20 so i'm going to hook the positive from the multimeter to that and ground is pin 10 and that looks quite good we're getting 21 mega ohms that's something i'd like to see you don't want to see say 10 ohms or something ridiculous like that i'm also going to test from a0 address line 0 over to b0 so these are the two pins that get connected while this chip is powered up and we're also getting 30 mega ohm 32 mega ohm so those are great signs so buy or beware when you get stuff from aliexpress but you can get good deals and three dollars for five chips when i looked at ebay for u.s sellers selling these tips i thought that this was a good deal if the chips are genuine so next thing to do let's try this chip in the apple 2 plus okay let me pop out the stack the big old stack whoop there comes and look remember i was talking about how this tape is not sticky look at this it's just barely holding on such crap and let's get this 8304 into here a little hard with a camera in the way okay moment of truth here we go it works it freaking works so at this point to go back and test the other 8304s in this machine because i want to make sure i can put a little tick mark on them to say that they are good and then i can retire this 74 ls 255 put it back into my spare parts and this little stack adapter well served me well but i don't need it anymore so i have to say with aliexpress you win sometimes and you lose sometimes and in this case i seem to have one because these three dollar chips for five work perfectly gotta give them the thumbs up so that's gonna be it for the loose ends i'm going to cover in this video but there'll be more in next week's video so don't worry we'll take a look at those cards inside the machine but there's actually one more thing that i want to take a look at and it's this right here this is a package from stuart the man who donated the machine to me in the first place alright let's take a look inside here i'll check it out happy halloween here are some goodies for you to enjoy that's right you should be watching this video on halloween so happy halloween to those of you who do take partake in it and have fun with it and if you're watching this on november 1st happy day of the dead for those of you that celebrate that all right well i see some candy and they're pez dispensers check this out cool okay we'll take a look at those in a sec we got a t-shirt oh awesome there's some stickers there's another packet of pez we do have some technical goodies in here looks like something for the amiga and here's a little something maybe some ics and something here that's wrapped up we'll take a look at that in a second what's this oh that's kind of interesting a little old style sony video camera this probably goes with this thing here for the amiga so we'll look at that in a second something looks like a little stand for something i'm not quite sure for what it wouldn't be for this video camera it's not big enough it's almost like for a microphone or something oh look at this okay that's what this is for it's one of those usb microphones on microphones no usb microscopes oh no the stand just broke oh that's terrible i take it this is the stand for it but um i think that maybe didn't quite survive shipping i just barely touched it and it snapped and one more thing in here and that's it just bubble wrap um if this is what i think it is i am uh i'm kind of at a loss for words um okay let's take a look at this stuff on the bench i have to move the apple 2 plus to make space for this all right let's start with these goodies right here so yes pez dispensers and they're really cute oh look it's a cute little pumpkin and two packs of pez in there but it's something about pez that just maybe that brings back memories or something i i don't know but uh there's a little bat i guess he looks like almost like a little bunny but he's got wings so he's a little bat there was one extra pack of pez that was just loose in the box and we have what's this a little mummy head a little pez mummy and this one here is a little witch cute all very halloween themed and there's one more pack and that's another pumpkin it's a little scarier pumpkin this one has a smiley face and this one is a mad manic face right so let's load one of these up gosh i haven't done this in a very long time okay so i think i have to open the pez up unwrap it i wonder what flavor this is okay i think that was not the right way to do it i'm just going to have to eat one of these i think it's maybe candy corn oh yeah it is it says candy corn he actually was able to tell that because a lot of times you eat these you just can't tell what it is okay so to load a pez we just slide it up i am sure there are people who have techniques that are way more efficient than this i think i'm supposed to unwrap it in a stack and just sort of slide the whole stack in there so anyways you load that in like there put it back down and if you're not familiar with pez when you lift the head it kind of spits out a piece you grab it put the head back down and we want another piece you just do that it dispenses another piece all right let's check this out oh neat okay so this is funny looks like the atari logo doesn't it well actually st john's is a place in portland and this shirt which i think has the same logo on it it does st john's saint john's is a part of portland and st john's has the st john's bridge and it's a stunning looking old bridge kind of like a mini golden gate bridge it's beautiful it's green and underneath it is a park called cathedral park and you see the towers and the buttresses that hold up the bridge and they look kind of like this and obviously it's modeled after the atari logo but it is uh st john's that is awesome now um just as a side note in case anyone else wants to send me a t-shirt for whatever reason um this is a medium i'm like in between a medium and a large and some shirts that are mediums unfortunately are too small for me or if i wear it it looks like i'm trying to be a muscle builder or something kind of ridiculous other medium shirts are completely fine but i generally actually tend to buy large these days probably gain a little weight because of the human malware being stuck at home less exercise and all that but also in portland it's cold in the winter and i layer so i might wear a t-shirt like this on top of a thermal or something and it's hard to see if this is a if this is a big medium or a small medium but to be safe large american men's large is a good size for me and there's a business card here and a sticker from final form which i guess is maybe where this shirt came from i think he bought this back east in new hampshire but it was obviously made here in portland from final form and it's in north portland so i actually don't know this store anyways i need to go check it out because it says uh retro games and records so that's pretty cool shop love it all right so let's see what else he sent i couldn't tell what this was it was wrapped up oh wow it looks like a wafer a silicone wafer that they make chips out of wait maybe these are are these is that what these actually are so these aren't coasters cause i can't quite tell what these are whoa that's quite cool they have like a i mean i don't know these must be reproduction right these can't be real they look really cool though really really cool so i'm gonna have to ask stuart uh what's the deal with these if these are real or these are supposed to be coasters or or what exactly and let's take a look at this little bag here looks like there's a couple ics in here a little couple chips so these e prompts say 68764c these actually be 2364 compatible which would mean they would work if programmed directly in a commodore 64 with no adapter yeah i'm checking the data sheet here and it says that the it is pin compatible with a 68364 mask programmable rom and that really does lead me to believe that these are pin compatible with the 2364s used in the commodore 64. i don't even know if i have a programmer that can program he's definitely my mini pro cannot program these but maybe my old dos programmer can next up we have this here this camera and what is in this bag and you can kind of see what this is this looks like a new tech digiview new tech digiview is a parallel port or maybe serial port capture device for the commodore amiga okay this is like the worst rca cable ever it's like a speaker cable from one of those stereos from the 60s anyhow composite video input i think this can capture in color stewart sent this camera along with it although it says a black and white video camera so that's not going to work so great for color not unless you have filters to put in front red green and blue and you would do like a three pass capture with this thing in here oh look it is look at this oh boy oh this is so hilarious yep so you got to do multiple passes of a capture so whatever your capture needs to be dead still you can't capture video or moving objects because you have to run it through the filter okay and we have this which has the little stand with the broken plastic piece and then this here is the usb microscope it's got a micro usb input there led lights button here this probably does some kind of focus or something and yeah it's just uh you could look up close at things in fact it might be good for looking at these wafers so i hooked the camera up to my windows 10 machine and just plugged it in it sees it as a webcam there's a light on there i'm capturing the screen let's take one of these wafer discs and see what we see oh wow that's really cool i mean again i don't know if these are real wafers or what look at that it says 1983 rockwell international so maybe these are real ics uh here's a different one and it says rockwell right there let me try focusing a little better oh it's so sensitive all right i'll switch it to something else so this is my desk this is the wood grain fake wood grain clearly printed on i mean of course this is a fake desk it's plastic or whatever it's not it's not real wood let's check out one of these eproms okay so there's writing like the part number motorola there's the motorola logo it's huge there it is you can see the bond wire going to the actual die there it is mcm68764 so this is amazing i can use this little microscope to look at my chinese eeproms i get from aliexpress to see what brand they actually are and maybe even the part number i have another random eprom it's an amd part just sitting on the side here let's look at this and see if it has writing on it all right there it is amd copyright 1981 and it looks like it says 9716. that's interesting it says 9716 because the actual part number on this is a 2716c but nonetheless that helps me identify what this actually is so stuart thank you very much this is going to be so cool for identifying counterfeit e-prompts i'm probably gonna make a whole video about counterfeit e-prompts now now that i have this i know these aren't that expensive and i don't know why i just never bought one but um i'm i'm really excited to have this this this thing has got me giddy with excitement all right now i think i have saved the best for last i got a glimpse of this when i was opening the box and i purposely put it to the end of the video here because i kind of can't believe it if this is what i think it is my mind will be completely completely blown first i'm going to cut the plastic off of this and let me flip this over oh my goodness oh my i can't even believe it yeah i thought this is what i saw when i opened the package and i just i just saw a little glance of this and my mind had a hard time processing it so i just put it aside oh my goodness oh my goodness oh okay so that's just the packaging so i haven't even said it but what this is is an hp 547a current tracer this is this is probably the ultimate in diagnostic aids for fixing old computers i just i can't even believe this i i am so blown away just oh man once again i find myself at a complete loss for words this is pretty much unbelievable i'm i'm i'm just shocked okay let me try to talk about what this thing is um an hp 547a current tracer what this lets you do is imagine i'm diagnosing a motherboard where a chip is causing a bus conflict and it's probably what was happening on the apple ii plus to be honest with that bus transceiver the one i replaced what happens is if two chips are fighting with each other like say one is putting five volts onto the bus and the other one is grounding it that condition essentially creates a short circuit between those two chips and with this thing which hp hasn't made in a long time it allows you to probe around the motherboard around the traces and look for traces that are carrying more current than they should when you have two things that are shorting out against each other two chips the trace or the traces that connect the two chips together the two chip legs that are fighting with each other they will be carrying more current than they should and that's because of course one is on fi is outputting five volts and the other one is outputting ground which you know what happens if you just directly connect five volts to ground you get a short circuit so this tip on here is red because it lights up and as you probe around the board it's able to sense in the trace itself the current in there and there's an adjustment here so you can turn up and down the sensitivity or you fine-tune it because it's obviously going to be current running through the motherboard all the time while it's running so you want to adjust it so you're not picking up that you're only going to be picking up where there's a lot of current and it can help you zero in on the chip that's creating the bus conflict now of course since this is a very rare item i personally have never used one of these in fact i've never really seen one of these used much at all i think i watched a couple videos where a guy was doing some arcade board repairs and he was using one of these but they're just so uncommon that there just aren't a lot of people using these so i'm definitely gonna have to learn how to use this thing another great example where this can come in handy is imagine you have a data bus and you have five chips on that data bus and one of them is pulling data bus low holding it to ground which is creating a bus conflict how do you know which five of those chips it is unless you pull each one out until that bolt goes away this could potentially help you just trace the traces get near the chips and when you get one that is lighting up the tip i think that's indicating that that chip is the one that's causing that short and all of that current is feeding into that chip there's a lot i have to learn about this thing so i'm not gonna be able to demonstrate it right now but i am so excited so so excited i mean this thing it's like gold ah i can't even believe it i've been wanting to get one of these for the longest time and stuart stewart i you blew my mind with the apple 2 plus i was taken off guard by that and i was really i i am so taken off guard by this my mind is having a hard time processing i think i've mentioned that probably five times already sorry everyone i'm gushing i'm going a little overboard here but really this this is this is incredible this is a piece of test equipment that just will hopefully up my game for problem solving these old machines to just bring me to the next level i hope i hope it will i hope i learned how to use this and i can be worthy of having such an amazing piece of test equipment as the hp what's the model number 547a current tracer and that is gonna be it for part five in the next video i'm going to be taking a look at those expansion cards and also those floppy drives i know several people have been asking to see me work on those drives if you enjoyed this video i'd appreciate a thumbs up but if you didn't you know what to do hit that thumbs down button hit that subscribe button to subscribe to my channel with the little bell icon for notifications and of course put your comments and your suggestions in the comment section below and that's going to be it thanks very much for watching stay safe stay healthy and i'll see you next time [Music] [Applause] [Music] goodbye

Channel: Adrian's Digital Basement

Views: 52,368

Rating: 4.9646387 out of 5

Keywords: Apple, Apple II+, HP 547A Current Tracer, mail call, alps skcc, 8304, retro computer, vintage computer

Id: 984mZex2pKY

Length: 42min 27sec (2547 seconds)

Published: Sat Oct 31 2020