I fixed the TRS-80 Model II

hello everyone and welcome back to adrian's digital basement today's video we're going to be looking at the trs-80 model 2 again this is part i don't remember actually maybe four previous videos we've looked at the disk drive made sure that worked we've looked at the power supply i looked at the crt module part of this thing and made sure that worked and in the last video i tried to power this thing up as a complete unit and while it did power on and have correct voltage rails there was no life out of the unit so on today's video i'm going to try to revive some life into these digital boards here this is the cpu one we'll see if we can get this thing working so without further ado let's get right to it [Music] so in the last video when i powered this up and it didn't seem to work i mentioned that one of the difficult things is that all of the digital cards go inside this card cage here with this back plane and when you have cards that are stacked next to each other troubleshooting them is that much more difficult because on most of the computers i work on i'm used to just having direct access to both sides of the motherboard while it's powered up so i can probe around and try to figure out what the problem is with some amount of disassembly i can actually remove the card cage from this machine and these metal side plates do come off so it's just the bare pcb with the slot connectors here so in the end i'm probably going to have to do that but right now i don't feel like it because you have to remove a bunch of other components just to get the screws out for this card cage so the very first thing i'd like to do is take a look at these digital cards on the bench without having them in the card cage so here are the three digital cards from the model 2 that you require to get the system to at least power on there's also a disk controller which i took out in the last video just because obviously that's not going to be required for at least the initial boot up or initialization of the computer from right to left we have the cpu card which also includes the serial port which is connected to this edge connector right here we have the video display and keyboard interface so this has the crt controller and the crt plugs in right here or maybe it's that one and the keyboard also connects to this so this is the keyboard interface and then we have the ram board which is filled with 64k of ram obviously for the cpu to utilize once the system boots up all of these communicate with each other through the edge connectors here and there is no difference between all the slots in the card chassis the cards can be installed into any sock it's just a complete backplane inside the case luckily we have the model 2 technical reference manual which has very detailed theory of operation and schematics for each of these cards looking at the schematics here for the cpu card we see most of the edge connector and you'll notice that this has plus 12 minus 12 plus 5 volts and then ground which is down here so i think what i want to do is power up the cpu card and that's going to allow me to check for a valid clock signal a reset signal that's working properly and then any other activity of the cpu obviously since we don't have any ram on here we only have rom this thing will not boot all the way but it should at least execute some code from the rom before it tries to do a ram test and then fails i have a few hunches though right off the bat that might be an issue for the system booting these cards communicate with each other using bus transceiver chips and it's these ics right here these actually carry the data bus between the various cards this fujitsu chip is one of the bus transceivers now it's marked with mb424 but the actual part number is the 8t26 this is a 4-bit bus transceiver and these days these are very rare and they're not really used on anything ever in a way it's kind of funny they use these because you'll see there's 74 ls logic all over this board including the 74 ls 240 and some of them have 244s but on a normal system you would use 74 ls245s in place of these and those are 8-bit bus transceivers you just need one of them but whatever reason they use the at26 now you may notice right off the bat that the pins on here really don't look so good they're in sockets and they're very corroded at least these fujitsu parts and that's actually a very common problem with fujitsu ics when they're exposed to the elements that can cause of course connectivity issues especially these sockets are probably pretty junky so i am thinking that right off the bat these may be problematic now this board that i was just holding is the video board and it's possible that system was actually trying to boot but the video board wasn't getting any signals due to these bad transceivers or the bad sockets therefore this screen never initialized and that's what we were kind of looking for the ram board also has the same two fujitsu chips and the pins are looking mighty black and horrible as well so that could be a problem as well the cpu board is using motorola parts as opposed to fujitsu's and these don't have the same corrosion issues on the legs hopefully you can see that okay they look pretty good there without any issues since this computer was kind of left for dead and obviously was exposed to the elements corrosion is probably a factor in the problems we're having here but first things first let's troubleshoot the cpu board let's refer to the technical documentation for the cpu board just to see exactly what this board is doing so obviously it performs the data processing activities that's the cpu itself and it supports dma operations it does provide the rs232 serial ports as i mentioned before it provides all the timing for the system so either two or four megahertz there's also an eight megahertz clock for the floppy drive controller there's a real-time clock now there's no battery on this board so obviously the real-time clock is something that is kept while the system is powered up and you just have to set the time when you boot up the machine provides the control signals for the other boards it provides the bootstrap firmware which is a 2716 compatible rom chip which when powered up will start initializing all the various components of the system before it hands off to the disk controller and starts loading the operating system and the rest of the code to run the machine it does say here that it includes self-diagnostic software on that 2k rom and then finally this cpu board handles the power on and the manual reset logic the primary large ics here on the board are the cpu the dma controller there's a serial i o chip a ctc which is a counter timer that's going to be doing the real-time clock and then finally the rom chip which is this one right here okay so first things first let's figure out how to power this board up sitting right here on the bench as i mentioned we look at the schematics here there's 5 volts in ground but there is also plus 12 volts and minus 12 volts now i don't need to worry about powering this board with those 12 volt rails because that specifically is for the serial port portion of this board and i don't really care if that's working or not rs-232 signaling uses plus and minus 12 volts typically up to 15 volts actually on those signal lines for proper operation so we can just ignore those rails everything else on here is just five volt logic which means i should be able to clip my bench power supply leads here onto the five volt capacitor whichever one it is here to power up this whole board so taking a look here we can find five volts on 71 and 72 and 9 and 10. all right so the multimeter probes here are connected to virtual bench and set for continuity mode the board is actually marked with pin 80 here so we know that this is 72 74 76 78 and 80. so this pin should connect to one of these capacitors that's the plus side but the plus side of this one's on the negative rail so i know that's a minus rail and then we have these two over here it's not that one and then that one has continuity and just to confirm that this is the 5 volt rail according to the schematics also pin 10 is 5 volts 2 4 6 8 10. there we go okay so this is definitely the 5 volt one of course we can confirm that by going from the positive rail to some of this ttl logic here there we go so it absolutely is the 5 volt rail so that cap right there i'm just going to draw a little mark on it so we know that it's the 5 volt okay bench power supply is off i'm just going to clip this on here i have the bench power supply set to 5 volts at 1 amp i don't really know how much this is going to draw but i don't think it's going to be more than that and it's a constant current supply so of course if it tries to draw more than an amp it'll just drop down the voltage here we go let's turn it on okay 700 milliamps right now on this little board all right the scope probe is ready to go on the virtual bench it's hooked up to the ground lead there and we're ready to start looking at things okay so the very first thing i want to check is the reset circuit now people talked about this this is the reset and power led connector right here on the board and people thought that maybe when it was unplugged the system would be in reset all the time a quick check of the schematics does confirm that is not the case here's the reset button it's a momentary contact switch what it does is it grounds the input to this gate right here which is normally pulled up to 5 volts through this 10k resistor that same 5 volt rail and ground line also powers up the led which was being powered up with the system what this reset circuit does is kind of handle the power on reset and there's also a little bit of complicated reset logic for the z80 processor because if you reset the z80 processor while it's at the wrong clock phase you can actually have data corruption in the ram so you have to do the reset properly based on the clock signal input just to ensure that a reset won't corrupt within memory so you get like a soft reset so to speak looking at the reset circuit here this is the output right here test point 11 this goes to cpu and other things the page is cut off because it's always scanned on two pages but i have a feeling that this little part of the circuit right here actually is that clock phase part of the reset signal because this very last gate here well it's a second last gate most likely has it so let's check this signal right here and yeah i'm pretty sure it's this one right here and that is the clock signal anyway what we need to do is take a look at test point 11 to make sure that the reset is working properly this signal here is the reset circuit so when i power on the board it should stay low for a little while and then go high as the cpu starts to execute here we go we are currently at 5 volts per division so 1 two three four it's between four and five volts which is good enough for ttl here's the cpu and it's pin 26 that is reset one two three four five six let's just make sure when i turn it on that the socket is good and the reset signal is coming through appropriately yep okay it looks exactly the same as that test point next thing that's essential for operation of a machine is a working clock signal so let's take a look at that and there is our clock signal and it looks good although i don't know what's going on with the virtual bench it's not showing what the frequency is all right i just had to zoom in a little bit more as you can see down there it's running about four megahertz now it's actually the capability of this board to run either two or four megahertz but not sure why you would want to run at the slower speed anyhow that clock signal looks really good no issues there okay so let's take a look at some of the address lines this is address line zero so the one that should toggle the most and i'm going to power cycle the board i should really hook up a reset button to it okay so it just immediately goes to this and we don't actually see it doing anything else let's just check out the next one i want to see some activity that's more than just a continual pattern like this because this seems suspect that it's not actually doing anything at all hmm okay something's wrong with this address line that's interesting that's address line three it's sort of in the middle okay yeah something is definitely up okay i think what i'm going to do i'm just going to quickly check all the address lines four looks fine and one more address line right here that looks good as well okay so let's check the data lines all right so we have a data line here which has some activity on it which doesn't look so bad stuff going on there let's turn it off and on and see what that does that one looks okay that looks okay as well stuff going on there that pin is not a data line there we go that looks okay that one looks alright as well as does that one okay so the data lines look okay as do the address lines except for three now there's a bunch of things on the address lines right there's all sorts of stuff on this card including the rom and these other chips here but i'm gonna suspect that the rom might be the problem so we're gonna pull that chip right out of here and we can actually test this in the retro chip tester pro everything looks okay on here it's not like it's uh badly corroded or anything all right let's power this back on nope that's still not good okay so the rom is not the problem could be the cpu as well so i'm just gonna pull out the cpu and we'll substitute in another one why not this computer is definitely not going to boot properly with address line 3 looking like that why don't i just probe this pin with the cpu removed let's look at what that looks like okay it just sort of floats there let's check out the adjacent ones okay they're floating in exactly the same way i think what i want to do to try to figure out if the cpu is the problem is i'm going to try to drive that signal with a 460 ohm pull up resistor to 5 volts with the resistor in here i expect to see 33 pulled high now this thing supports dma and what that means is there is probably a transceiver on here somewhere that can disconnect the address bus from the cpu here and basically allow other things to drive the address bus that means that certain components in the machine can talk directly to memory and to do that they have to take control of both the address bus and the data bus and i don't think the z80 has the capability of disconnecting itself from the address bus or the data bus that is something like the 68 000 can do but the 6502 cannot now i'm not super familiar with the z80 so it might be able to do that and i'm just not sure but let's test this pull-up resistor and let's see what we got here i gotta say this socket is looking very corroded so that could be part of the problem right there so this one should be five volts and it is and on this side okay we're getting five volts so that's pulling up to five without any problem which means i think this cpu might be bad i mean the z80 is a very reliable chip but certainly not out of the realm of possibility so let me grab another one here's another dialogue chip it's a z80b from 1982. so a little bit newer than this machine due to how crusty and corroded this socket looks yep that means deoxit is going in here do it for the rom socket as well okay here's the spare chip i don't actually know if this one works i haven't tested it myself let's pop it in see what we get okay i'm on address line three okay um well it's better but that's kind of low it's just over three volts so i wonder if there's a problem on there oh no this one's the same this is weird this thing has sort of lower address line output yeah it's only a bit over three and the power supply is not current limiting let's just check um the five volt input here all right i'm on the input here yeah it's getting a solid 5 volts and yet why is it putting out such a low voltage here yeah peak to peak is 3.5 volts hmm that is a bit suspect in and of itself although we can see that address line is working now so i have a feeling this cpu is a problem i'm gonna grab another z80 how about this lovely italian made one i assume this is italian made made by sgs here z80b as well from um well could that be 1987 it seems kind of late doesn't it okay here we go let's try this one in here i mean the other one might have worked to be honest but um i just didn't like how low how low those signals looked all right let's see how this one looks uh okay better better better better peak to peak is almost 5 volts there so yeah this one's looking good and that is the problematic address line and it looks good i'm just going to probe the other ones that are nearby yep looking good okay so let me power off and we're going to reinstall this rom actually before we install this rom again let's try to read this out on the retro chip tester pro 2716 what sort of profile we're going to use because it said it was compatible look at that trs model 8 and model 16. so that's interesting this is a model 2 but maybe the rom is exactly the same the bootstrap rom in both but the fact is it read it it did a checksum and it worked i am just going to dump this to the sd card interesting how most of it's blank it's not even taking up that whole 2k but whatever we know this chip is working properly at least in the chip tester that is cool all right so let's get this chip back into the board here now when we power this up i expect to see more activity on the address lines and the data bus than just that permanent repeating pattern so let's just try this line right here okay look at that that is normal activity folks that is how it should look oh this is so cool so i'm going to go out for sure and say that this original cpu this was the one that was in there um and this is a bad chip let me get the marker boom bad i see look at that cpu not what i expected okay so back on the schematics these ls240s are what send the address bus over this edge connector to the other cards let's check those signals and there is also some other regular signals coming through on the ls244 and there's also some other signals that go through an ls125 but honestly the ones i'm most concerned about are the databus signals through these two transceivers here the 8t26s these are bi-directional i'm on pin 13 which is data line 13 here in the schematics and we turn on the power of what are we going to see there we go we see activity good sign that's a good sign so a lot of activity is going to be relegated to on this board right because it's talking to the roms and stuff but then when it goes to do the ram test it's going to try to talk over this external connector to other things so the pins i want to look at are 3 6 10 and 13. all right so there is pin 3 we have pin 6 which is yep that's activity um pin 10 doesn't seem to be doing anything might have given up let's power cycle it again um pin 10 all right well there's a little no okay there's activity okay okay we're good 11 12 and 13 we know 13 add activity yep let's check this one over here 9 10. okay it's just okay there was a little bit there 11 12 13. okay i'm getting a bad contact on the pin okay yeah the pins on here aren't rusty but they are corroded so i gotta scratch them a little bit let's see if we power it on now there we go hmm that is solid signal that's coming through there though it doesn't really look like i was getting on this other one let's scratch that one too yeah weird how that's a little bit different how it kind of goes up and down thing is i don't really know what this is doing right now it's probably trying those ram tests like i said so i'm not really sure how it should look okay yeah well anyways we're getting what looks like output on those two pins on those two chips because um everything is so corroded i'm actually gonna pull stuff out of the sockets and the power's off right now and i'm going to deoxit the sockets these are dual wipe sockets so that's not terrible if they were single wipe i would be more concerned about issues and i think i mentioned this in the last video but without the rom working without the the cpu executing code it's not going to initialize the crt controller the 6845 on the display card and that means we're never going to get any kind of signal out of the display card whatsoever so this is the z80 dma controller chip i have no idea if this is sort of required for operation of the machine but just in case we will definitely hit this with the deoxit there and then this large ic here is almost certainly uh does it say i'm pretty sure this is like the serial controller used for the serial port okay there we go everything that's in sockets has been reinserted let me just double check for bent pins all the chips are in the correct orientation nothing is one socket off okay so i think this is good to go let's inspect the other boards all right next up is this board this is the crt board it's not going to do much without the cpu board connected but what i can do is remove these four sram chips these are the 2114 display chips we could test those in the testers make sure they're good the bus transceivers we can actually test those you know what i should have just done that i forgot to say that this thing can actually test the bus transceiver chips why don't we just do that let's just rule them out as problematic we'll start with these uh sketchy ones here because these have rusty pins on them if these aren't dual wipe sockets i may end up having to swap the sockets oh these are stuck in there i'm gonna hit them with deoxit first very crunchy sounding don't like the sound of that oh and sure enough that one got damaged a little bit oh look at this look how bad the pins are see all that discoloration in that black color that is corrosion on these now it doesn't mean the chip is bad these are hermetically sealed but it's possible that corrosion can get inside the chip in the package and damage the dye now i can always just replace this socket but i'm just going to try to push it back into shape a little bit that might be okay maybe how about these other ones will you come out without damaging the socket don't damage the socket so crunchy sounding that one survived a little better okay that one's okay all right so the four bus transceivers are out all right over here we are going to look up 1826. all right at26 the quad bus transceiver receiver with inverting outputs it's under miscellaneous logic ic102 this is one of the issues on here trying to find the chip you're trying to test here we go 18 26 there we go 4x bus transceivers so let's put this first one in okay that one's good next up let me just quickly test all of these that one's good oh yeah okay so all four test good that's excellent i'm just going to quickly test the two that are on the cpu board here i think these are going to be fine as well this might as well run this test yep that's good and the other one in the cpu board that passes as well sweet all right so back to the video board the sockets took a little bit of a beating taking those chips out but it had to be done because i couldn't leave them in there like that so i'm just using an x-acto blade sort of poking down on the wipes that sort of push them back into position now the deoxide is in there these are going to come out much more easily next time if i need to remove them all right so these other ics so the 6845 i can't test this in the tester but i do have lots of spares of those if that's bad the rom chip here is almost certainly the character generator let's pop this out we should be able to test that in the tester it is most certainly going to be probably a 2716 let's just try that yep there it is trs-80 model 16. so that actually tested good as well this thing it's a survivor well i like to think it is i mean i'm sounding excited the reality is there could be so many more problems with this machine for all i know this machine was put out of service because it was not working like maybe it was stored in a garage or out in the open or wherever it was um because it broke and that's what ended its life and if it's just a bad cpu i mean that's great and all but it could be a lot worse than that okay we got s ramps here just pop these out these are for the video display buffer on the retro chip tester one fours are very easy to test okay that one is excellent working properly next test passed the third one works as well and the last one looks good some of the bits are bad on those chips you end up just having like bad characters displaying on the screen stuff like that i had to replace i think both or one of the 2014s on my commodore pets the 4016 i have and on that one if i recall i put some in that i got from aliexpress and the system worked for a while without any issue and then it started having all this weird like display corruption issues and yeah sure enough those ics had gone bad again excellent let's move to the ram board all right so the ram board has a ton of chips and sockets obviously all of the dram here i can test this in here i'm not going to bother doing that what i can do is just remove the two bus transceivers because these are the rusty fujitsu types good that socket survived looks not good and we'll test these really quick and i'll de-oxen these sockets success success both of these test good that's a relief i did some looking around uh to try to buy some more of these and they're not easy to find i think there's a way to maybe make an adapter uh so you can use basically the 74 ls type chips but it's not super easy and i just wanted to show close up the state of the pins i mean just look at that that is not good these chips hopefully they won't get any worse i'm just not sure how much longer they're gonna work for and back into the board they go all right unfortunately i apologize about the audio my wireless mic battery died i forgot to charge it last night and i'm really eager to test this thing out so we're gonna use the internal microphone when we get back to testing uh any further if this works or doesn't work i will switch back to the better microphone all right so the computer set up here it's not plugged in yet but i have a mirror right here so we can take a look at the crt together just to see if we see any activity on it i have the brightness and the contrast knobs right here so they're just lying there i can fiddle with those to get the screen set up correctly all three boards are in here but the disc controller is not in here because um i actually kind of misplaced it it's somewhere in the basement it's in an anti-static bag and those silver bags all look similar so whatever it is it's i'll find it but for now we don't need it we're just gonna do this testing i'm gonna connect up the power i don't even know if it's on or off so it might just turn on let's see nope okay are we ready everyone crt is connected i think we're good to go here we go what's gonna happen whoa hey everyone look look let me turn down the uh the brightness oh it's working i can't believe it all right so first of all i think i have the yokon upside down because uh looks like the picture's upside down but it does say boot error dc that is telling us it's something and we were getting an image i am i'm so ecstatic it freaking works it was the bad cpu well at least to get to this point oh i'm so happy that is so cool so cool so before i do any further troubleshooting i'm just going to shut the power off here and what i want to do is try to find the disc controller and put that back in because it may not be booting any further because it can't find the disc and i have a boot disc because i made it in that last disc drive video so this thing might be so close to actually booting okay time to find that disc controller card all right well luckily the card has been found and while i did the searching i was breaking into some candy here rutgers sent me these and they are very tasty hairy bows very unlike any of the the type i've ever had before i can't quite remember because it's been a little bit of time but i think these ones come from the netherlands either that or belgium and uh they're delicious and tasty so they have been fueling me while i look for this card all over the basement yeah i pretty much looked everywhere why couldn't i find the card this is a case of putting things away for safe keeping without labeling them this box here which looks like maybe a 36sx motherboard for two dollars i might add it's not actually a 3d6sx motherboard we opened it up yeah it doesn't nothing is marked on there to make it seem like it's not there's the card there's the floppy controller cable i mean i'm really good normally with labeling stuff i put post-it notes on everything because one of the problems down in the basement here is there's a lot of stuff down here and i need to be able to keep track of it otherwise i will totally misplace things left and right well for whatever reason i stuck it in here at some point after filming the previous part to this computer series and i didn't label it so always label your boxes especially when you think it's a motherboard and the worst thing is this was sitting over there on some other stuff with other motherboards in the boxes and they were stacked together so i looked at it and thought no those are just motherboards i even opened the top one i'm like yeah yeah it's just motherboards yet it was in this one anyhow back to testing i think what i want to do is power this up with the computer turned around front ways like this and just make sure that yes i did reverse something on the crt yo cause i think it's gonna be backwards let's do that first all right here we go boot up number two let's see if we get that text like we did the first time there it is yeah okay so just like i thought i have the yolk rotated 180 degrees boot error dc whatever that means that beat by the way was my phone i was eating that candy not just because i needed some fuel but because my blood sugar is very low all right power this off i'm going to flip the yolk around there's not a ton of room in here to do that hopefully this doesn't require some kind of full disassembly to flip this that would be horrible now the card cage is in the way but flipping this is possible excellent okay okay here we go let's try again i do hear the crt starting up you know the high voltage that's obviously a good sign there it is boot error dc now in previous testing it seemed like the crt was pretty good gotta say it's not particularly sharp actually yeah when you get this up to a brightness that looks acceptable it's definitely on the soft side so i may end up having to try to swap this out okay i'm going to make it so i can see the raster like there and i'm going to tweak this to straighten it all out all right well i'll need to do some centering work but i'll do that later no big deal let's turn the brightness back down okay boot error dc let's see if we can figure out what's going on there and i think i'm just going to stick the disc controller in there because that dc disk controller is probably what it stands for now with this disk controller i didn't talk about this before i don't think i haven't gone through and reseeded any of these ics first of all i'm just gonna try it as is but also on the back there's a zener diode that has broken it's no longer connected anymore and it goes from one of the rails i don't know it's probably the positive rail to a pin on the disk controller chip now the strange thing is is in the schematics this isn't even listed that that doesn't exist on the schematics that i found but i sent a picture of this over to isaiah dwf and it turns out that the zener goes to pin one on the floppy controller which is an fd1791 on the data sheet for this pin one not connected pin one on this pcb has no traces going to it either so the zener is all that goes to it and it does go to ground frank's theory is that potentially when tandy radio shack implemented this design they use this floppy controller ship maybe they were having a lot of them that died they reached out to the manufacturer and said like what's going on we've done it according to your data sheet and the manufacturer got back them and said why don't you add a 2.5 volt zener right here that does something this is also obviously a little mod of some kind i can see that there is a dip package on there and it's flipped upside down and sort of stuck on the board soldered on with a few pins there's a capacitor on there this is also not on the schematic so this obviously some modification done after the fact maybe to improve reliability on this board who knows overall this board has seen better days you see it's a little crusty and corroded here on the side of that chip there let's just take a look at this one here it also has sort of green legs to it obviously water was running down the entire board at least on this this section right here so who knows if this is actually going to work but you know i've seen worse like on my field found commodore 64. and it it worked for the pet video where i was trying to fix that spot i ended up buying a bunch of zeners here uh so let's see what i got in here so unfortunately that is it i don't have anything but the 3.3 that's the smallest i have oh wait i'm sorry there's more here 24 volts these are from digikey obviously oh 3.3 from digikey 33 volts 5.6 and 7.5 okay same problem well since we're in uncharted territory here and i don't even know what this is doing exactly i'm just going to put a 3.3 on there and hope it's close enough and there is my replacement barge 3.3 volts what it should have been a 2.5 hopefully that does not cause a problem all right so the newly bodged floppy controller is installed i have the cable going from the drive to the controller this is not the drive that came in this computer because this is the quieter one that wasn't exposed to all that moisture let's put in trs-80 model 2 trs dos 2.0 alpha into here one of the discs we made hooked up to the pc in the previous part okay there we go something's happening to my camera i keep a battery pack connected to it and it runs for a little while and then it stops charging so i may run out of battery soon but we have enough battery left to power up this machine and see if it boots i'm so excited just make sure everything's recording yes it is audio is working here we go everyone okay insert diskette all right wow it's bright let me turn this down a bit well that means it sees the controller but why is it not booting did i leave this set to drive select one for the pc oh i bet you i did i bet you i did but look at that no disc controller error now that bar you see there that is just the camera it just says insert diskette this is what it's supposed to do wow exciting okay turn this off and yes looking back here on the drive i have it set for drive select one and that was from when we hooked up to the pc the pc expects everything to be on drive select one this computer on the other hand expects the internal drive to be drive select zero all right there we go it's on drive select zero from a termination perspective i don't have that external terminator connected to the back of the machine and that's because this drive is not wired up appropriately for the termination to work that way it actually has termination jumpers installed so it is terminated that means i can't plug in an external drive chassis to this thing i'd have to take those jumpers off this drive first and then the last drive on the external chassis would be terminated okay we ready for test number two here we go oh seeking noises all right well it doesn't say insert diskette oh oh it's working it's freaking working it said 64k ram and it's like look i can't believe it it freaking works left for dead and this thing is working that is simply amazing all the ram passed the test i don't i just i can't even believe it i can't even believe it trs 80 model 2 trs-dos 2.0 january 1 1981 copyright 191 tandy corporation enter date the keyboard of course isn't going to work there's a lot more work to do there but this is freaking working wow wow wow wow look at that i wonder if this is right like does it have those little symbols there i mean the text looks fine it's just weird how it has little little marks on the side i expect that to be a more solid i don't know whatever you call it um okay all right um one thing that's interesting i should turn it off and on so we can see that boot up process from the very start so let's do that all right there the disk drive was initializing so watch this cursor's in the center which is funny but hey there you go it will say 64k memory which is correct and then initializing right here that's because the bootstrap rom in here just does very minimal stuff and then the disk is required for the rest of the initialization of the computer and the ram check and all that stuff oh i see a big dead spider right in there that i didn't get rid of you see the little uh little beauty in there the spider balls and guts and things i can't believe it i just i still can't believe that it works this there's so many hours i put into this thing and to think that at least so far nothing was actually wrong from a digital perspective except for the cpu of all things but there it is there's the proof this thing is a survivor left for dead leaves inside bugs everywhere and yet it's working it's freaking working wow all right so i think i'm gonna end this video here the next video i really need to start working on that keyboard so i can try to type something on here i need to finish cleaning up the case that'll probably be a different video i already kind of started because it's painted it's sort of like a car you know you can use some card products on it things like that there were people who had good suggestions on one of the previous videos so i'll have to go back and review those and get to that but cosmetically i think it can be fixed up quite a bit there's some scuffs and stuff but we can make it look nice and the keyboard hopefully can be made to work and then really it's a matter of making more discs using imd on the pc the entire archive is there so i can finally start playing around with this thing and see what the model 2 is all about radio shack's extremely expensive professional business machine from the late 70s how cool is that so if you enjoyed this video thumbs up would be appreciated if you didn't you know what to do um let's see here hit that subscribe button if you haven't already check out the second channel i put all sorts of cool videos on there of course if you haven't seen the previous parts of this series yet there are links in the description to all of those parts i recommend you check those out it's been an interesting journey so to speak with this machine thanks to my patrons their names are scrolling up the side of the screen i appreciate all the support and if you want to become a patron of course you can do so at the link in description below and lastly i'd like to thank the viewer in town here in portland who found this thing in the trash basically and saved it to give to me so i could have this journey and share it with all of you so stay healthy stay safe and i'll see you next time bye-bye [Music] maybe that'll be the thumbnail

Channel: Adrian's Digital Basement

Views: 90,546

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Id: -h1ZGxwbsPg

Length: 42min 26sec (2546 seconds)

Published: Sat Dec 11 2021