Touch Screen MS-DOS PC from 1983

hello everyone welcome back to adrian's digital basement this machine is an hp 150 which is a 1983 desktop computer released by hp to compete with the ibm pc 5150 and xt 5160 while this runs ms-dos and has an intel 8088 processor just like the pcs this is actually not pc compatible hp's first true pc compatible came out with the hp vectra soon after this machine this machine was hp's attempt to get a little bit of the exploding personal computer market that was really taking off after ibm released the 5150 pc in 1981. in exploring the hp 150 i have been intrigued by it because it's so similar in some ways to pc architecture but in other ways so so different i've also found that it has some faults which are going to need to be addressed so let's get right to it [Music] so the hp 150 desktop computer as you see here it's got a nine inch green crt inside and if you can believe it the actual computer itself is just this little section here on the top where the monitor is in fact if i lift it up it comes right off the tilt stand and yeah what i'm holding in my hands is the entire computer this middle section here is simply a tilt stand and has a button on the side that allows me to tilt the monitor or the actual computer backwards and forwards this on the bottom is the hp 9121 double disk drive unit this interfaces to this computer and actually any computer use this with using the hp ib interface hp ib was hp's name for what was also known as gpib on other machines and also is the same interface standard used for the commodore pet to hook up its disk drive and other accessories as well ieee 488 if i recall i'm not sure when this disk drive came out and i think this might have come out actually a little bit earlier than this particular computer the 150 because there were some precursor machines to this that ran the z80 or z80 processor but this machine as you see here is running ms-dos and is running an 8088 processor notice this computer is running ms-dos version 2.01 and even though it is running dos and it's running in 8088 this machine is not pc compatible that didn't happen until the following machine after this which was the hp vector line of computers which continued many many many years and that was hp's pc compatible line that could run regular pc compatible dos in all the applications that went with it the hp 150 came with this mechanical keyboard that has a somewhat unusual layout compared to pc compatible machines at the time but it does feel very nice to type on i've popped off a couple keys so if you recognize what the key switch is let me know but the keys are relatively nice chunky keys although i don't think they're double shot so the printing which is sort of a purplish color is on top of the keys some of the keys have double functions like this user and system key here and the extra shifted function is in a blue writing as is the shift key to tell you that you need to push that to get that second function take a look at this section of the keyboard has the normal kind of up down left right but it has a home key that has an arrow that points to the upper left corner insert character insert line delete line delete character so definitely got some buttons that are different than a typical pc previous and next a select key above the numpad are four blank keys there's a clear line and a clear display button and on both sides of the space bar is an extended character key instead of an alt key up here is a break in our reset key and to reset the computer you would hit shift control and that key and it's the equivalent of control alt delete i haven't given this keyboard a thorough clean yet and unfortunately it was really really dirty when i got it now while it has a pretty nice sound some of the keys don't work super well and some of the keys are very bindy if i push like the t up in the corner here it doesn't really go down it it binds pretty badly in fact all the keys are doing that i'm not sure if that's indicative of this type of key switch or if this keyboard is just so filthy that that's happening on most of the keys this machine also came with an original hp mouse it's an interesting shape quite bulbous here pretty uncomfortable very loud button clicks and it's just a typical ball mouse and unfortunately here you might notice the screws a little bit rusty and that's indicative of this entire machine it was exposed to a ton of moisture wherever it was stored and unfortunately some of the parts are rather corroded on the machine but that doesn't seem to stop it from working i'm not really sure what exactly the mouse is used for obviously doesn't seem to do anything while it's plugged in and you're just in this text mode but i did notice that there's a copy of windows 1.03 for the hp 150 machine but after doing a little bit of reading it seems that you need to have an external hard drive that hooks up through the gpib instead of the double floppy drive to use windows 1.0 on this particular machine you'll see here on check disk that it shows the machine has 256k of ram in it unfortunately there's a fault in this machine because it does have a ram expansion board in it that should bring that up to more potentially up to 640 but clearly it's not working on the keyboard if i push the system key you'll notice here it shows service keys and here's an example of a touch screen i can actually touch those options and they are selected there are some diagnostics to run here and if i push memory test right away it reports memory test failed 3f08 i've looked in the technical manual or was the service manual for this computer and essentially it says that any 3-f code is a memory board problem with a logic chip on it and the entire board needs to be replaced and let's do system test testing i turned off the studio light so you can get a clear look at these incredible monochrome fonts these hp fonts which are also used in a bunch of other hp equipment like terminals and stuff like that look so legible and readable on this monochrome screen and one of the reasons why is they're not just bound by the normal pixel resolution which i think is like 720 by 350 or something like that because these actually use a half pixel shift here's a page from the manual that explains how that works exactly but that makes incredibly legible monochrome type that is so sharp and unbelievably good looking you might notice here it says system test failed 0 0 0 c sometimes work on powerup it'll say one zero zero c i think the one zero zero c and possibly this zero zero zero c is due to the fact that there is no cmos battery installed in this computer right now so it's running the total defaults here's a side view of the machine and you can see that this top part which is the computer itself it's just so small and compact and then here if i do the tilt stand there it goes it's just pretty cool how that works so this is the actual hp 150 computer taking a close-up look at the crt you'll notice these little holes that run up and down the side they're also along the bottom both sides and the top and what that is is infrared beams are shot across and up and down on the picture and when you stick your finger it interrupts two of the beams one of the vertical beams and one horizontal beam and with that the microcontroller or the little controller chip in here is able to tell where exactly your finger is on the crt now of course the alignment of the image on the crt is important because it doesn't know where that is versus these beams so there's a test pattern that comes up with these little cross hair marks and you need to line up the crt image in line with the bottom corners of the little sensor beams all the way along here and once you do that it's actually relatively accurate when you move your finger around it seems to track really well on the back this is where all the i o connections are along with the iec mains input and there's an output as well so you can plug in like a printer or something else so when you turn the power switch on it will turn on that external device there is a cooling fan grill which actually i took out of the computer i need to put it back in there's some controls for the crt and then down here are the main controller boards including two expansion slots so there's one on the left and there's one on the right and this card here is the ram expansion card i had mentioned along with the mouse port this unusual looking port with two dots is actually where the mouse connects to and it looks kind of like an rj45 right above that the machine has two regular rs232 serial ports data com port 1 data com port 2 and then next to that this is uh looks like a regular phone jack connection this is where the keyboard goes this is the hp ib which is also gpib or the one on the pet as well all look like this this is for connecting those disk drives and also other accessories it uses a cable like this which has it's double-sided so you can actually chain devices together so you can plug something like from here into the disk drive and then from the disk drive into something else and that's because each of these connectors has a male and female side on it now i had mentioned corrosion take a look at these connectors now i've cleaned this up quite a bit but these were just a mess originally i found a ton of mouse droppings all around this computer especially inside the keyboard so the corrosive p that really screwed up that franklin ace 1000 i showed on the channel kind of got to this machine as well luckily they did not get inside of this computer so there were no mouse droppings in here the same goes for the disk drive which didn't have an opening that was big enough for a mouse although there is an opening here and if this were open a mouse could have gone in there and made a little nest in here but what this opening actually is for is the cmos battery holder and this takes two 1.5 volt little stubby looking batteries you put them in here and then you slide this in and clip that in and then that's three volts for the cmos now the reason why this is out is because of course they had leaked they weren't in this machine when i found it but they had leaked caused corrosion well i've already cleaned up the corrosion in this but inside there there's the battery contacts on the main motherboard one of them is all green and corroded so i need to sort that out i think i'm just going to probably install a cr2032 or something and and i don't know i haven't figured out what i'm going to do exactly now on the top of the machine there's something that's really quite cool if you push here this actually opens up and then this cover lifts off as well giving you this compartment on top of the computer now there's also a cable that normally sticks in here and i guess um when i put this thing back together i had the cover off i forgot to route it through but it's a little ribbon cable just sticks through and after looking at pictures what it seems like this upper compartment is for is a printer you can get a thermal printer that sits in this space and it comes with a new lid where the paper feeds through and when you print the printout just comes out of the top of your computer i really have to laugh at that at that silliness now i guess on this particular machine you can just store cables up here um let's see put this down like this and you can close it all up so i guess it's like a little storage area for your maybe your gpib cables and things like that but um yeah it's up there there's space and a printer can go there now of course in typical hp fashion this machine is very serviceable it's extremely well engineered like all hp stuff is and um the top cover here around the monitor and power supply comes off by releasing these two screws and then you just lift up on it and the whole top cover comes right off this is that ribbon cable for the printer that i forgot to route inside of the top cover but and this gives you access to the high voltage board so this is what runs the crt of course and on the other side is the power supply for the entire computer right here so they're not easily accessible due to the small packaging of this computer but on the crt board there are some adjustments for the geometry of this picture and you can get to them very easily by just adjusting those controls down there and then to remove these boards first we'll take out the expansion card here this is the ram expansion board with the mouse controller port on it so we just have to loosen these screws and that pulls the board out and there it comes so this is it so all of these chips here are 64 kilobytes and unfortunately everything is soldered nothing is in sockets pretty rude so on this board each of these ram chips are 64k by one bit so one two three four five six seven eight that's 64k and then we have four banks there so that's 256 plus another 64 and another 64. so that's another extra 128. so 256k plus this the 256 built in the motherboard that's 512 and then an extra 128 is 640. so this would be maxing out this machine to its full potential now i have put deoxit on the connector here and sliding it back in and it still gives that memory error and the diagnostics do have the capability to kind of tell you which bank is problematic so if it told me that i had a problem with the bank i could look for a bad ram chip but it is telling me that the whole card is bad which would imply it's one of these logic chips now fortunately this thing isn't just 74 ls logic including this ram it has some pal chips and of course you can't test this without it being inside this machine which has a backplane in there so i don't really know how to diagnose this and there's no i don't think there's schematics that can find maybe there are i just need to look up the part number but like pretty crappy troubleshooting instructions it literally just says oh you get that error replace board it doesn't tell you like look for this chip or whatever just replace board anyhow on the main chassis there are extra screws that i've already taken out i think there were four of them or maybe five and then that lets me take out this entire thing let's just pull this out of here there we go and in here you'll see there's quite a bit of a sandwich now i know that this board here is called the mezzanine board and this has extra ram on it or maybe has all the ram on it and the board on the bottom is the cpu board and that has the 8088 processor and there's a speaker there and obviously some other logic that that runs this machine and then this board right here is the second serial port board so this stuff is all sandwiched on to the main processor card and we can kind of see down in there and then you notice it has this large multi-pin connector here which is what plugs into the back plane back there and then in the machine there's still one more board and this from my understanding is the video board so you have to flip these little levers here and then it slides out come on it's really stuck in there well so this has a crt 9007 controller chip on there um i think these are either these must be rom chips or maybe these are ram chips i'm not sure but yeah so this is the video board and right here this is where the cmos battery was connecting and luckily the corrosion is minimal like the traces are not damaged at all but take a look at that post yeah that's pretty green and crusty the corrosion on there means if i clean it up with vinegar it's probably just going to expose unplated metal which will just oxidize and corrode again so i may just desolder these entirely from here and then install that that cr232 battery holder made with a little bit of wire so that you can pull it out of the machine install a new battery and just sort of place it back in there so i really enjoy how modular this computer is but what i don't like is that it's really difficult to do any kind of troubleshooting because you can't access any of the system while it's running maybe there's a way to disassemble this entirely where i can take that back plane out power it up from the power supply and then have these cards at least outside of this cage but i i'm not quite sure there's probably some crazy test jig that hp had with like these ribbon cables where you could plug it into the back of the backplane and then run the board outside here for troubleshooting but when you read the service manual technical manual it does not explain any of that at all it is fascinating to me that the machine runs fine with this install it just gives that ram error and it does take a really long time to turn on i assume it's doing boot diagnostics but it's able to detect that there's a problem and just disable this board entirely and then the machine is working normally just with reduced memory this is so wild i'm looking at these barge wires and for whatever reason like this blodge wire here it's it's replacing a trace that's was there so it goes from that pin up to here and around here they've cut through the trace there and there and then they installed a shorter barge wire why i think they did the same thing here so this barge wire there there's a cut trace there and it goes down and loops around and it makes its way back to over there and then they've cut that trace there why did they do that was it like too long to go around or there was a timing issue and they just had to do a shorter wire it's this barge wire is the same thing they've cut the trace there they cut the trace there and the original trace just goes like that and it's cut one thing that's a bit disheartening but it shows how expensive this whole thing probably was a it says it was made in the usa but b this is a six layer pcb you see the one there's a two and a three four five six i think this uh pin this fourth layer is obviously a ground plane or something like that but that's how they're able to pack so much onto this thing and there just seems to be hardly any traces visible visual inspection not to mention i did tone out all of the barge wires to make sure they were still connected and everything looks flawless on this board there's no corrosion of any kind no bad side of connections everything looks great now incidentally the date codes on this thing are from 1985 so someone added this later in the life of this machine because on the main motherboard on this thing it's from 1983 and up at the top here it says hp hil slash 384k ram accessory card hp hil i'm pretty sure is the interface for the mouse that's what that's called and in very typical hp fashion every single chip including for instance this regular old 74 ls 21 has an hp part number on it some of them like this part here it's just 1820-2075 i'm not sure what that is i assume that's just a normal 74 ls logic chip kind of like um this one up here this 74 ls244 but here is a pal 16 l8 so that's something that this chip is bad i can't replace that even the ram chips have 18183059 part numbers on every single one of them so i went ahead and removed this very green and corroded post which was the negative terminal and then i went ahead and installed a cr2032 battery holder the yellow black wire here is the negative and that goes back into the holes where i remove this post and this one is soldered onto the other post which is not corroded at all which is the positive and i've added a little extra length because i cut out the inside of this battery holder and now you can just shove this in here like so and then put this into the computer like that so it's um that hole is not there anymore this is the top cover and i just i need to reinstall the fan i forgot and i'm just going to clean out this little bit of dust that's in here all things considered this computer is really clean on the inside it originally had a panasonic panaflow fan um it's 12 volts hopefully it's not too noisy has a rubber kind of a grommet thing on here to keep it from rattling around too much this sort of slides in like so into the holder and then this plastic piece clips in like this and that holds the fan in place like that hopefully it's not too noisy but luckily it's a standard size fan and the way it mounts in here with this clip i could put a lower profile fan and it would be fine okay before i fully clip this in i just want to see if the fan is working because it had a connector that was unpolarized or non-polarized yep fan is running i did run the cable through so let's pop this cover back in okay i've left the bad ram card out for now i want to see if with the new battery installed i've gotten rid of that zero zero zero c or one zero zero c error that i think were was due to the cmos okay so it beeps oh it came up pretty quick default configuration used hey that's a great sign okay so i'm going to push service mode service keys uh-oh oh dear um the touchscreen is not working that's interesting i wonder what's happening there let's go into service keys and i'm going to do a system test i wonder what's up with that oh look system test failed 1000 now oh come on what's what is going on here so i'm doing the memory test here which at least it doesn't immediately give that same error it gave before where i had that 3f08 error so this is now obviously testing the memory i must have four banks of 64k that comes up to 256k that's on that mezzanine card attached to the processor card the fact is getting this far is a good sign i guess that means it worked if it didn't show any kind of error hey the the touch screen is working all of a sudden interesting so i wonder why it wasn't working and then now it seemingly works so we're still getting system test failed 1000 though but if i go touch screen alignment so this is that crosshair i was talking about for aligning the crt to be lined up with the little sensors here all right well i'm still getting these same power on test failures so we're getting 100c sometimes i have 1000 i actually have the that extra 384k of ram reinstalled in this machine and i'm getting that still but uh seems weird because when i look up these codes it says everything that starts with a 1 is memory bank 0 replace mezzanine card but it's funny because once even with those errors i was going into the service mode and i was running the ram test and it seemed to run through the ram test without an error that's when i don't have the extra ram card installed let's see right now if i do memory test right away with that extra card in there it goes and shows that it fails all right adjusted my camera so hopefully you can actually read this right now so i've gone under global configuration and one of the things that's interesting is you see it says power on computer and if i hit next choice there are two choices either terminal or computer if we leave it in terminal when you power on the machine it does not attempt to boot the operating system which keeps complaining about it can't find the disk because i don't have the drive plugged in and it ends up in terminal mode where it basically is just a terminal that hooks up to the serial port we're looking at the port configuration in terminal mode and we can scroll through these different baud rates and we're at up to 19.2 is what this thing supports from 110 to 19.2 and so this can act like just a regular dumb terminal this screen here we're seeing the terminal configuration itself and lets you control the terminal id either 150 or 2623a i guess two hp terminals it does not emulate any deck terminals not without extra software which you can run in dos you can also go to accessory configuration and accessory card one that's the card that has the mouse interface in the ram but a clickiness doesn't actually do anything i don't know if you would normally even be able to get into that if that card weren't bad but yeah it's not doing anything here there's some other stuff device control you can adjust the margins i mean i'm not sure what this stuff even does here margins tabs enhance video uh define field set enhancements i mean i don't even know what this stuff security video inverse video blink underline half bright who knows what this stuff does so i took a break from this machine to have some dinner and i was thinking about how i might troubleshoot the memory problems that this thing is having and what popped to mind was dos debug if you recall my franklin ace 1000 video where i used the machine language monitor on the apple ii to figure out what the memory problem was on that machine debug on dos works exactly the same way now this is the master disk that came with the machine for booting into dos and it has no debug command but i went and checked out the hp museum website and i found a disk image for the programmer tools so i've just stuck that in the a drive and like take a look there's debug right there so if i run this that should allow me to at least poke around and take a look at what's going on with the memory now i do have the ram expansion card with the extra 3 84k installed in the computer right now so boot it up and you know gave me an error and then if i do a memory test i will get that three whatever 083f08 error right so i checked in the service manual and i found the memory map of this computer and starting at the bottom with all zeros you have up to 4000 which is the original built-in 256k of memory which looks like you can use 232 because a little bit at the bottom is firmware blah blah blah and reflectors whatever whatever starting at 4000 and you go up from there you have the 640k well the 384k on the ram expansion it goes up to a zero zero zero zero zero and see here it says used for 640k config which is what's going on there so i need to look to see what's wrong with that memory card i need to check with debug what's going on in memory locations four thousand through well one byte less than a zero zero zero so let's do that so first off we can take a look at what's in like um you know two thousand two thousand dot zero sorry the keyboard is acting up so this is just the onboard memory the stuff that's built in the computer and you notice there's like a bunch of stuff in there with it which is normal if we take a look at 3000 this is still the onboard mezzanine type memory i just reduced the exposure a little bit hopefully that makes the green screen show up really clearly in the video anyhow so this is what's left in the memory probably after the memory test now 3000 this is the built-in or the mezzanine memory of the 256k it's not the expansion card so what i'm going to do is i'm just going to do a test and i'm going to fill this memory the first hundred bytes of it with um zero zero and then let's take a look at what we what we just wrote into memory okay so there's all zero zero and let's do the same thing again um 300 0 0 100 and we're going to put ff and let's look at what we wrote there and look there we go ff so this part of the memory appears to be working correctly now let's take a look at 4 000 so this is on the memory expansion card now this looks a little unusual what's going on in here like but i assume this is probably the beginning of the memory test when it's starting to test the ram it will write some patterns into memory and read them back and make sure they look correct and perhaps if they're erroring out it's sort of aborts part way through and that's why we're not seeing what we see up there let's just quickly take a look at 5000 which is uh bank one sorry 4000 is bank zero the first bank of the expansion card 5000 would be the second bank okay so we're seeing a very similar pattern right both of these look similar but i'm actually noticing that they do not look exactly the same and let's see if you spot it see if you spot the difference okay well i'm going to make the difference obvious because right away i see something that looks different between these two banks which i think can lead me to figuring out what's going on i'm going to fill 4000 i'm going to fill the first 100 bytes of 4000 with zero zero all zeros right every bit is zero and if we take a look at what we just wrote to memory look at that it came back as all zero eights i'm going to fill the same memory space first hundred bytes with ff so all ones and if we take a look at what we see here look at that that is coming back correct but then we were getting o8 instead of zero zero that implies a stuck bit now right off the bat i can't assume that this is bad memory chip in this bank this could easily be say a bad ls245 on the card causing that data bit to always be stuck and come back as a one instead of a zero which is why we were seeing the o eights but that's pretty easy to test all all i have to do is let me just fill what's uh the first hundred bytes of five thousand which is the next bank i'll fill that with zeros and let's take a look at what we see here and there we go we're getting back zero zero let's do the same thing again but we'll write ff and then we will take a look at and then let's look at what's there and now we have all ffs so we got zero zeros and we got ffs that implies that the ls245 bus transceiver that connects this card to the data bus of this computer is not faulty there is only one of those and if it were bad we would be seeing that same 08 up in the 5000 here so to validate that the rest of the banks on this card are okay i just need to go through and do the same process on all of the other banks as well all the way through 9000 and just to make sure that this test is working and yep we're looking at the 64k up around 9000 and look it's still working correctly we've got zeros and we got ffs okay so here's a little chart to explain what i saw so i wrote 0 0 to that first bank and i got back all 0 8 and when i write 0 0 i should be writing while i am writing basically eight zeros into memory and when i read it back what was happening is we were getting o8 which would imply that this bit right here was actually coming back a one when it should be coming back a zero so it implies it's stuck that means that bit number three now don't forget it starts at zero so it's the fourth bit but bit number three on the data bus is stuck in that bank and the bank is 4000 which translates into bank 0 on the memory card so unfortunately i can't find the schematics for the memory card i found another schematic for a memory card that goes in this computer that gives it 384 k but it's not exactly the same as the one i have and i think it's because the one i have has that hp il or mouse port on there and this one doesn't appear to have that and it really sucks that this is not the right schematic because if it were i'd be able to tell exactly which chip is bad based on the chip markings on here so bank zero is these top eight chips and if we look for data bit three so zero one two three it would be this chip right here u54 now here's the expansion card and there are markings there cu4243 there's no 54. it goes 49 and then it goes up to 410 four so it's almost like this is the fourth row of chips third second first and that's the way the u markings are so the fact that the schematic here calls for u 54 clearly means it doesn't match this card now the problem is there's six banks of memory on here and i really have no easy way to know which is which because uh this pal chip here is probably doing the decoding the address decoding that maps to these appropriate banks so i don't really know like what's coming in and what's coming out of this which would be which bank now one thing i can do is i can figure out which data bit is which so over here is an ls245 and that comes from the connector that goes into the back plane right and i can see exactly which is data bit 3 going into the 245 and i can find the pin number there that matches the 245 and then i can trace it through the 245 and to the ram chips to at least figure out on the card i have which would be the possible chips that could be affected how do i figure out which chip on mine is the bad one well i think first i need to figure out which are the possible candidates and then i'm going to try to look at the layout on the board and maybe i can figure out like a rhyme or reason to how the banks are organized on the board the chips themselves and you know figure that it's it's i know it's bank zero so if there are six chips and they're in some pattern well it's going to be the one on the very far left or maybe the very far right that would imply to be bank zero because i'm sure they're not just randomly arranged it's probably zero one two three four five six all right i figured out the candidate chips so the signal comes in here and i it's um that pin right there so from there to there are the data bits that matches the schematics for the other memory card right because the standard this connector is standardized and data bit three specifically the one that i want is that so that signal comes over and it goes to the left side of the tail is 245 and then there's a corresponding right side this is the side that faces the memory chips and whatnot on this board so all i did was figure out from there where on these memory chips it goes and it's this bottom row here every other chip is the data bit three it appears that the chips are organized in banks of eight chips like this so this is 64k 64k and so on and so forth so logic to me would dictate and i didn't lay this board out so of course i have no idea what the designer had in mind but i would think either this here is bank zero or this one is bank 0. and i'm going to probably say that this one is bank 0 because it's closer to all this logic stuff and that bank 6 or sorry bank 5 rather is over here but either way it's going to be that ship or that chip most likely now the designer could have been evil and made like bank zero one of these in the middle somewhere i mean who knows right but either way i'm gonna start by replacing this chip over here and if that doesn't fix it i'm gonna go there next and if that doesn't fix it then i'm gonna have to keep replacing them chips at least i know what's the bad bit so i don't have to go and replace all of these chips okay time to replace this one okay i'm back and i haven't replaced the chip yet what i did is i cut the old chip out i feel that this is the easiest and safest way to desolder from this multi-layer board remember this is a six-layer board so i've just removed this chip and i'm just gonna pull each of these legs out one by one but i thought what i could do to see if this was the right chip if i did the right thing is put this ken board back in the computer so i can test to see if i hit the right chip by just looking in debug at all of the banks and if i got the right chip then it should still be 4000 that has a problem with the bit there it just i won't be able to write to it it'll always be it's probably stuck or floating or garbage or something weird like that but the others should all still work or if i hit one of the wrong ones then i should start to see a problem one of the other banks and then obviously i'll still see a problem in the original bank so let's pop this in and see what happens the reason why i'm doing this now is because if i did the wrong chip then i can just cut the other chip i think is bank zero and test again and keep doing that until i hit the right chip and it's just so i can minimize the amount of time i'm soldering i just basically do assembly length and do with all the chips and sockets that have cut off and put them back on otherwise install a new chip and stock it test it if that's the wrong one i gotta pull it out again and then i gotta go through the soldering and the cutting and all the testing over again and just keep doing that over and over again and this way i'll just keep going until i find out which ship is the right one when i don't see any changes in debug and then i can just solder all the chips at once okay good news i've gone through all the banks and i wrote zero zero and ff into all of them from 4 000 all the way to 9000 and i still only see a problem in 4000 that's the only one that looks weird and it's exactly the same fault i see 08 instead of 0. so that would actually imply to me that that original chip was simply bad what's likely happening is that the ls245 when it sees a floating bus on the side for the ram chips are it just interprets that as a one or maybe it's actually pulled high there might be a pull up resistor and it's failures like this which is why sometimes when you piggyback a chip it works and that's because the original chip's output drivers are bad and then a new chip line on top can just override it if the original chip is like stuck say it's stuck at ground like it shorted the data bus then that probably causes all sorts of other problems with all the other chips but anyways it seems like that original chip was just dead completely and now i'm going to replace it and hopefully that's going to fix this memory board so here's the bad chip that i cut out while i hopefully it was bad and these are the pins that i then subsequently pulled out and then here is the replacement chip installed in a socket on the board now it was pretty hard to pull the ground pin off there's a really chunky ground plane on this entire board and it's obviously a really good quality copper and it just wicks the heat away so so quickly i ended up having to use hot air to heat up the board so i could get that pin out so time to slide this board back into the chassis here and you know it's funny there's plenty of clearance so there's there'd be no reason why hp didn't socket all those chips maybe it was a reliability thing when you do have sockets it is more unreliable probably in the long run all right board is back in power up the disk drive make sure the cable is connected oops the power switches on the back now i'm still expecting this boots error that's gonna be like the 100c or whatever i still have no idea what's causing those i did poke around with debug at all the lower 256k of ram and everything looks totally fine there although maybe there's like a bad bit just somewhere in there and i just need to look at it carefully but i don't know how to find that oh interesting we have a different error power on self does fail 1004 now i've never seen that particular error i got this operating system error because i noticed that the disk drive wasn't plugged in so let's uh reboot the computer and try that again and here it is it's booting dos this shows hp bios at the top there and then this goes into something called pam i think which is a kind of a program manager it shows you what's on your disks oops and then you would you know i pick the start ms-dos executive so i can get to the command prompt i switch the disk to the programmer tools let's go right forward i'm filling four thousand with zero zero oops maybe if i typed it wrong right right i mean there we go here we go look at that we got all zeros so let's write ff into there a hundred and we're going to put ff there we go ff that is looking correct so i'm going to call up the system menu here service keys and we're going to do memory test oh look it's showing all the banks now so without the card in there before it was showing zero one two and three so that's four banks of 64k that built into the computer and now it has four five six seven eight nine which implies the additional six banks but the thing is before i couldn't even get here it was just immediately giving me that error interesting it still says testing but the numbers went away so what's it doing now okay that acts very similar to how it was without the card in there of course operating system failed is because i don't have the right disk in so if we go back to service keys and i do so memory test was good let's do system test there's that failed with the 1000. why is there always just this random 1000 it's either 1004 or one thousand c or now one thousand it's ridiculous okay let's go back into dos and the only way i really know how to see how much ram the computer has of course is check this command should show 640k oh it does look at that so the card is fixed and this bad chip was causing that ram card to fail and pretty lame diagnostics that it couldn't even tell me that there was a stuck bit on just one bank what crap crap diagnostics anyways debug to the rescue once again it shows that looking at memory directly with a debugger or machine language monitor really can help you figure out your ram problems it goes without saying that this bad chip goes into the dead parts bin goodbye so that just leaves me with these weird error messages we're going to be 1000 i saw 1004 i saw 1000 and c and i also saw zero zero zero c so we're getting a whole slew of different error messages if anyone has any ideas what these are pointing to please please let me know but it's weird that the system appears to run normally so i just don't get it if there's really a failure with this machine why does every piece of software that i run on here just work perfectly it just makes no sense all right so this machine is now working if i run the system test there's no more failure codes the ram card is installed everything is looking good if i run the power on test same thing no more errors so i'm sure you're asking what exactly did i do to get this machine working well i was reading through the service manual and i noticed that it has a section on led diagnostic codes and there we go past the test no issues on the back of the machine when you power it up there are a series of leds that light up and they will show codes i recorded it with my phone because they're really tiny and then i wrote down what the codes were so the way it works is there are six leds total the first two are a binary counter so zero zero zero one one zero and one one so that's showing you four nibbles that make up a total of 16 bits which is one of the error codes so the first one i just wrote it down the first nibble is one one 101.001 zero and all zeros and that comes from these extra bits these lights that are on there and if you translate that into hex that gives you 91co and then there was a second error code being flashed if there was this one a pause and another one and the second code came out to 2702 so if we focus on this first one 91co in this back of the service manual it has error codes and 91co falls within this range here touchscreen failure of one or more led photodiode pairs so what i did to test this is i went into the config keys and went to global config so it's just a regular config screen and the way this works is as you touch the screen it moves the cursor around well i use something like this to just move the cursor across the screen and sure enough right over here there was one column that wasn't working it was like somewhere in this area here i identified it down to a single column and it just was not registering the cursor would skip entirely over that well clearly it was detecting that at boot so i took compressed air and i put it down into the hole on the bottom sprayed did the same on the top it didn't seem to fix it but then i power cycled the computer no more errors in fact no more errors of any kind on the very first boot up when i was recording these flashing led codes i got the same you know 1000 or 1004 or whatever area code error code the one i've been getting all the time booting that's computer up but it's weird that was showing me that code because in the service manual it makes it seem like the codes it shows on screen translate into the ones that you see in the back of the book but to all those 1000 codes all point to like ram bank 0 replace mezzanine card that doesn't make sense because any of those any errors in that part of the ram i don't think would create a working computer but anyways once i cleared the air once i blew air in there and i power cycled the machine now that bad row is is fixed it now works fine and no more errors so you may be asking what was this second code 2702 well according to the book here 27xx was user ram bank 7 failed ram refresh test non-socket component failure okay so i thought maybe there was another bad ram chip but what doesn't make sense to me is when i fixed the bad row or the bad column on the touch screen there are no more errors no more at all now if i just power the computer off and i let it sit for a while and we power back on it will get no more errors it just goes straight to trying to boot off the disc i really can't believe that this 91co which pointed to the touchscreen led me to look there see it booted no errors oh it's going to say operating system not found in a second but i can't believe that led me to blowing compressed error and fixing that bad column and now the machine is working i just like those diagnostic messages were such nonsense i can't believe it kept showing me these stupid codes of power up that really meant nothing i really should have ignored those stupid messages and i should have focused on these error leds so just know if you're working on an hp 150 take a look at the error leds and decode what they mean spend the time to do this because that might tell you exactly what's actually wrong with the machine none of these bs codes that don't get you anywhere well i think i'm going to end the video here i didn't honestly think i was going to get this computer fully functional with all the 640k but i guess i did the documentation actually came in pretty handy and then a little thinking a little logic i was able to figure out exactly which chip was bad and replace it and then of course that strange touch screen error that was causing those strange errors i don't know what was going on there if you're familiar with these machines and you recognize the crazy error codes i was getting i'd love to hear about it in the comment section below in part two i'll dig into this hp 9121 dual disk drive and talk about these crazy sony disk drives that are in here which are weird and non-standard and then show you how to get a gotek drive working inside of here and getting the disk images working so you can get software running on this thing without any physical disks so i hope you enjoyed this video if you did i would appreciate a thumbs up but if you didn't you know what you do you can hit that thumbs down button subscribe for more videos and get that bell icon if you want to be maybe notified if youtube decides to do that and put your comments and your suggestions down in the comment section below i'd love to hear what you think about this interesting and odd machine and that's going to be it stay healthy stay safe and i'll see you next time goodbye [Music]

Channel: Adrian's Digital Basement

Views: 139,010

Rating: 4.9453173 out of 5

Keywords: retro computer, vintage computer, hp 150, ms-dos, repair, troubleshooting, crt, touch screen

Id: ExKowj2g8N8

Length: 50min 33sec (3033 seconds)

Published: Sat Sep 12 2020

Reddit Comments

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[u/plainjanie22]

What the ffffff

[u/Nopeeky]

The oldest actual PC I can recall is is the one that used to serve as the server on our sortation system at work. I started there in 2003, it had a sticker on it that said 1996, and it lasted until 2008 or so. It was pretty badass for it's time.

[u/athenanon]

I remember being allowed to play with one very briefly in a university computer lab in the late 80s. I think they only let me near it because I was a little kid. They were around, just really rare.

[u/theevilpackrat]

Ok this is a mixed topic here some say the did not have touch screen technology others do.

My self i believe quite possible because it is not a true touch screen technology. It is Lazers past the screen that reads where your finger is by a grid fashion.

Now having said that I do not believe there's anything but a play thing for the rich and powerful of that time.

There where computers at that time that had stylus as well but the sheer cost meant the only groups that had them where movie studio and not a single individual unless like said rich and powerful.

In my old timeline reality the first computers where used in WW 2 on battle ships for guidance of the big guns. The first use of bug in computers was at that time as well. Having said that about 1% of the population in the states was aware of them. The only reason I was aware of the first use of them was my grandfather who served in WW2 and was willing to talk about after 12 years of me asking about the war.

So I'm I one from this reality, dimension, and or whatever or did I get false memories. I can not say for sure I would love to say it was just my reality and not the download effect.

[u/DerrickJoestar]

The first touchscreen device I ever had was a calculator in the Mid to late 90’s, but I don’t remember PCs having them.

[u/throwawayjustastory]

I remember touchscreens in the early 90's ... so not an M.E for me ... some ATM's use this technology since a long time ago

[u/TheGalaxyEater]

Personally since my family was in the technology area, I was well aware of computer touchscreens back in the 80's. It's not an M.E. for me personally.

[u/incognito_asd]

Man. This all keeps getting more wild (for me). Question is... where is all this going? Will we wake up with some futuristic contraption new to some of us that others will recall as always being here?

Edit: Deleted excess word.