This TRS-80 Model 4P is misbehaving

well hello everyone welcome back to Adrian's digital basement on today's video we're continuing with the septandi theme yes it's still September and inside this box is a Tandy or trs80 machine donated by a viewer Seth and I think it needs a little bit of a repair hopefully it will not be a super long drawn out repair and this can be a somewhat quick video but you know I call my super mini mail call videos a mini and yet they're still like 40 minutes long half the time the last couple videos I made which are on the trcd model one they were about 50 minutes each and I tried my darndest to edit those down for length so they weren't super long anyhow hopefully this one won't be as long but you never know so if you like long videos put that down below but if you don't put that down below as well I'm always curious to know if I should really be cutting these videos to much shorter length or keeping them long format anyhow without further Ado let's get right to it and open up this box [Music] I always gotta hand it to Seth I really like the boxes he puts together and uh just here for the king cake he always puts this on here there will be a video upcoming maybe it's already out by the time you see this where he sent me a whole bunch of king cake related stuff but in the past Seth has actually sent in a king cake all the way from New Orleans for me he overnighted it to me here in Portland so I could enjoy some absolutely delicious king cake I'll put a link in the description below if you're unfamiliar with what that's all about but of course it relates to Mardi Gras anyways there's king cakes on all three sides and lots of subtandies let's see what's inside of this I haven't done any unboxing videos on the main channel in quite a while because of course super mini male calls are normally on the second Channel now I made that switch a good number of years ago but since it's a Tandy I'm making an exception here knowing Seth he has probably packed this box with packing material that is not just foam or whatever's probably got who knows what candy and stuff like that and they are like right off the bat I have an unlimited Supply of Haribo Ginger lemons that's awesome all right looks like we got smaller packages inside the bigger packages so let's undo all of this here this here says I O panel you gotta say I'm thankful for uh the labels because you never know with packing material I might just accidentally throw something away that needs to be saved all right there it is this is the computer and it says 4p on it so what this is is a TRS-80 4p while this is an example of how to pack something so it can survive shipping you bought this from a regular seller on eBay they probably would have just thrown the computer with like a sheet of bubble wrap in a box and hope for the best and it would of course been smashed along the way this thing on the other hand has so much bubble wrap I am going to say there's a really good chance that this thing has survived the journey unscathed so let me extricate it from all this bubble wrap so what we have here is a TRS-80 model 4p this is compatible with the model 1 and the model 3 and the model 4 and this is Radio Shack's attempt to make a very small and compact portable and I'm going to put portable in quotes machine that's just a lot easier to move around than the model 4 is the model 4 and the model 3 of the same form factor and I've had videos on my Channel about both those machines they have a 12 inch integrated monitor the keyboard is fixed a couple full height disk drives the whole computer is relatively Big and of course because the keyboard's attached and all that it's just you need a big desk this on the other hand I have to admit it's pretty cool how small it is we have a nine inch CRT two half height disk drives built-in power switch and some controls for the monitor of course the keyboard like I showed is integrated in there is a front cover which he has sent separately it's over here on the side and it's got this creamy beige color which uh well this thing has seen a lot of sunlight I guess because it's pretty yellowed condition wise I gotta say this thing is in really nice shape we have a couple discs in there that were in backwards as sort of like a protector inside this bubble wrap is the front cover let me extricate this so we can take a look at how that looks and that is the front cover look it's got little dimples here so obviously if this is installed on the front it's designed to have the computer sat down on this which will obviously protect everything in the front there so it has some metal clasps on each side that are riveted on and there are some metal hooks on the sides of the computer for that can connect to there's actually a little bit of space in here it says manual right there and diskette right there so I guess you could store your your boot disks and we got something here which uh not sure what this is we'll take a look at that in a second nice attention to detail there's a little Groove around the outside here where you can store your power cord judging by the yellowing on the one side of this this obviously goes on like this let's hook on the clasps there we go this here must be a little expansion slot cover for the back of the computer because it says certified to comply with class B limits product of the USA I'm assuming there's there's an expansion cutter on the back or something that this would go on but this is my first time looking at this I think that's kind of cool this appears to be a carry handle with a little robotic spring-loaded metal arm there that is pretty cool also it says trc80 model 4p personal computer awesome looking at the back of the computer here we have the rs-232 port we have a parallel printer connector and we have an i o bus connection there this obviously covers that up if you are not normally using the i o bus you want to have this cover on there and it's interesting because the FCC labels there are actually written right here on there as well I always see right here they printed very nicely push here to release the handle that is a very nice design you can push on either side which is a lot easier than what I was doing when I was trying to get it out you just get it out like that nice Seth sent this separately wrapped as well it says I O port cover which is a little plastic piece that we'll go on there somehow oh like that okay and I can see here that it has a metal rod so this is obviously hinged ah look at that on the inside so this is model number 26-1080 and serial number is only 6561 pretty low there on the grand scheme of things some would say this was Radio Shack's last-ditch effort to keep the trs80 model line alive and I don't know how well this thing sold but I don't think it really sold that well because I think by the time this thing came out PCS were firmly established as like the business type of computers and CPM machines which this can run were basically Falling by the wayside at that point I'm not going to actually try to attach this right now it might be brittle plastic but it looks like it kind of hooks on like this and then you would flip it down and it's got two clips right here that would clip in there and there just to keep all the ports nice and hidden but probably if you're going to use any of these things regularly it's probably best just to take this off let's take a look at the letter here Seth writes welcome to box two the septandi box and uh yeah there are other boxes from Seth right now that I haven't opened so I'm kind of doing it out of order just uh well you know it's September and all that this box contains the item I'm most excited to submit this round so you'll see that I have done my best to repack it in a much more secure way than it was sent to me originally well yes definitely that is the case there's something like 50 feet of foam and 200 feet of bubble so I hope you can reuse the packing materials for other shipments there are two substanding items in this box but I want to provide some notes comments on the big item the model 4p it took a little troubleshooting to get a power on and I wanted to share those steps with you I had a great time having this on my own desk for a few days and I'm excited to send something in that mostly works I did notice a CRT tube needs some tuning adjustment but the light phosphor is just beautiful please note the discs are inserted backwards for shipping they must be removed that's right right Seth says he didn't know the model 4p reads the ROM at power on I guess I didn't know that either I've never used a model 4p so I didn't know that now here's a weird one Seth says when I first tried to power on the unit it was literally dead the previous owner told me this would happen if the discs were not properly inserted with both levers locked on both drives once I follow these instructions the unit powered right up and it freaking worked with a pH and I had a couple very fun days in model 4p land hoping that providing these steps to will save you spending the same two days I did trying to figure out what was wrong with the unit well I gotta say I've never heard of anything like that let me open this up again I have never heard of needing to have the disk drives latched to get something to turn on that makes absolutely no sense whatsoever I'm thinking that there's a fault of the power supply on this thing and it couldn't possibly be related to the floppy drives here on the next page Seth says he is separately wrapped the i o port cover in the front cover they're both very fragile and didn't want to risk them breaking thanks very much they both survived perfectly and then he goes on to say that the Tandy microcomputer enclosed definitely does not work thank you Seth um what's this here that you sent along um a little pin there let's let's open this up it's like there's a staple of holding this all together uh looks like a message for you this looks like a business card of sorts for probably what's in the little bag here it looks like this comes from micro micro Muse which I guess is who made this stuff here let's take a look looks like we have an HP pin this is the kind you would uh stick to your shirt or your lapel or something like that oh and it looks like we have a little tiny Apple too how freaking cool is this and a little monitor it's a little Sanyo monitor that can sit on there and then we have two disk drives as well I gotta say this is really quite cool oh look at this oh monitor sideways there we go I know it's uh maybe not in Focus but there it is in Focus there looks like it's running load runner on the screen too absolutely freaking adorable very cool all right let's take a look at what's in these package I'm assuming one of these is the uh little Tandy micro computer this is it the Tandy micro Computer Micro color computer I think it's called The mc10 Well I don't immediately see mc10 on here it just says micro color computer 26-3011 and the serial number is 218 000. so relatively high up there and it takes AC 8 volts hmm I don't know if I have that kind of an input now from my understanding this thing is basically a trs80 color computer in here except it has just 4K of memory and then it has this um well you know not so great keyboard but yeah this is an interesting little computer I think it's really designed to compete with like the ZX Spectrum in the UK and the Timex Sinclair they're really inexpensive side of computers but of course this does have the same color capabilities as the Coco so it's like you know 16 colors sort of text mode hybrid weirdness so anyhow we're going to show this for now we'll focus on the 4p all right so the first thing I want to check out is this strange power on condition Nation where you supposedly have to have the disk drives closed that doesn't make any sense whatsoever I just plug the mains into the back and I have both disk drives unlatched let's see what happens here okay so that actually did come on now the computer is probably not going to actually do anything like yeah it's we don't see anything on screen which is very normal for these computers because I think we have to hold down the break key on the keyboard here turn it on or or do the reset and that's probably what is needed or Maybe ah I don't know that's the way it works on the other models like the trt model 3 you don't actually get anything on the screen at all unless you hold down break let's reset here it's trying to boot let's try putting in this TRS dos disk here stick that in there and reset the fact that this came on there it goes it is actually loading up without any issue let's see if we actually get anything on here now this might be what Seth was talking about with the ROM that there is no way to break out into a into basic for instance they might have just done away with basic entirely and you entirely rely on that although it looks like it booted up and yet um we don't have anything on the screen so that's a little disheartening hmm now in this disc box I actually have some floppy disks for the model 4 and the model 4p is completely compatible with the four at least as far as I understand so let me find my model 4 CBM disk which should be in here here it is model 4 CPM Let's uh let's see what happens with this a CPM Plus hit the reset button I'm wondering if the CRT got damaged in shipping here which is why this is a no longer working and you know what it didn't even boot at all off that CPM disk which is a bit strange I'm gonna shut this off and I'm gonna go find some other model 3 discs that I know work we'll see if that does anything on here all right here are the discs I had upstairs they were with my model three I don't have any more model four discs now I'm thinking that the reason why it didn't turn on for Seth actually had nothing to do with the floppy drives I mean although maybe why don't I close this one just for fun uh it doesn't appear to actually be booting either yeah this is interesting maybe I'm just um well certainly sounds like it's trying to boot I'm thinking that the power supply in this probably has a little bit of a dodgy cap situation it's pretty typical on the TRS 80s and uh that means that it won't always turn on right away or it might take like a few minutes to turn on because the little Reservoir cap that runs the switch mode power supply controller has issues now it is kind of weird because I don't seem to be really getting much out of this machine at all and of course the one that seemed to work the best was this original disc that was in here this trs-dos disc let's just try that one again but even with this disc weren't even getting anything on screen at all so like I said I wonder if there's no high voltage yeah it's it's seeking so this is doing the most and yet nothing I'm going to try one of the easiest fixes in the book let's see if we can use a cleaning floppy on this drive it doesn't sound like it's making any horrible noises like uh clunking or you know head banging although this is a PC type disk drives and they don't do the head bang let's just see if that helps it boot a little bit more all right let's get that out of there all right let's put in a disc which I think is a boot disk maybe it's one of my discs from upstairs doesn't seem to be doing anything at this point Hmm this computer's definitely behaving a little oddly so this here is the Spectrum analyzer app that I have used in the past to see if things are working and I'm gonna say right now that the CRT in this is not running at all I'd be seeing a peak right around 15 kilohertz if the CRT if the CRT was working and you know what I just bumped the screen and the computer sort of reset and now we have something on the screen and sure enough we have the peak there so that started up so that's interesting and uh yeah the CRT seems a little on the tired side obviously I have a dodgy Connection in there and interesting is that didn't boot so why don't we try the old brake key again here I could now it's beeping at me this thing is acting very strange I can see oh wait look we have a clock there so that's something a clock boy this machine is mysterious to me uh starts loading off the disk and then it just sits there and then now it's displaying 30 minutes and two seconds so that's like there's some kind of real-time clock all right enough of my fiddling around I think it's time to open this thing up I did a little brief inspection it looks like there are four screws two on each side here and I have a feeling the whole computer slides out of the shell so let me remove these screws here which is going to expose the the white creamy color of the plastic underneath there and let's figure out exactly how hard it is to service a 4p now of course this is a Radio Shack machine so it's going to have a good service manual they were really good with all of their service manuals at least uh in the 80s they were in the 70s so I fully expect that there will be no difference with this machine okay so I'm just going to move the keyboard out of the way it looks like it's permanently attached I wonder if there's any screws on the bottom here not that I can necessarily tell there's a piece of foam in there I think that's supposed to be there I don't see any extra screws I do see what looks like the computer that should be able to slide out of there there are the little button latch things here that maybe this has to come off I find the appropriate screwdriver for this job I took that off in a nut fell inside so I really don't think that that was supposed to come out no I'm going to have to fix that after the fact with the machine on his front here there's like a kickstand screw here I don't think this is necessarily part of getting the back cover off either boy it certainly goes pretty high this is actually unscrew yes it does but as you can see it really really holding on there's probably a trick to this that I don't realize what it is and I'm just going to keep taking screws out this the handle here has two big screws holding it in which seem about the same as the ones that were on the side so I'm going to take those out as well all right there we go the handle is removed how about now oh look at that all right so you had to take the handle out I am sure that probably had to do with nothing so let's slide this off of here there is the inside of the case and there's a date code there it says 12 1983 1983 and this is where the kickstand went into right here so clearly that did not need to be removed so I'm just gonna thread that back in there wow we're looking at the bottom of the machine there's that foam I was talking about and it looks like I'm gonna have to unplug the keyboard here probably before I can do too much more so let's get that out next there's a screw on the side right here it's a little ground lug the keyboard connection itself is plugged into a pin header sideways so it looks like if I just cut the zip tie here then I'll be able to slide that off ah it's like this big zip tie has been there since the 80s and I'm breaking it off horrible right there we got vintage Radio Shack zip tie sorry about that Radio Shack well it looks like I misspoke I was able to unplug that connector it doesn't appear that I can get that off very easily I need to remember that I have to find the little metal washer thing that was on this front panel that I accidentally fell off when I took that side um button off I guess you could call it whatever the front panel clasps onto I gotta say the whole machine is pretty Compact and is very sturdily built even though the outside is all plastic so I guess I'm just going to start taking screws off and hoping that it exposes some of its Secrets some of its inner secrets there are a couple screws that are missing on this top cover I don't know if that means it's because someone has already been in here at some point in the past or maybe they just were never installed by Radio Shack all right I think the covers are all off on there aha check it out we have the power supply here and there it is the switch mode power supply inside of here obviously we have the CRT there is a fan you can't see it right now but the CRT controller board is right there on that side and obviously the main PCB for the entire computer is underneath all of this so I'm just going to unplug this stuff here to get this power supply out of the way there it is there's the trs80 model 4p power supply and if you look right here there's a service sticker I'm pretty sure that's what this is says right there a line and Supply mod so some kind of modification on here don't really see anything off the top of my head that's a modification I see a lot of dirt on actually just looking at this I wonder if these are the mod these things look like mobs just attached on the side wow but what we do have is what looks like some reefa caps right here and here so those are going to need to be replaced in case uh we have any kind of noxious fumes that come out of this thing next up I'm going to try to remove this back metal plate here I think that will hold in the PCB and all that other stuff there's a big chunky metal plate right here that's what the handle screws into so that just adds the extra rigidity to this thing and it looks like there are a couple screws over here right there that I got to get out as well hope those are going to be not too difficult to get back in there when I'm done here all right that did free up this whole back panel here which is good I can clean it up and there's that extra plate there for strength and rigidity all right and at this point there is the PCB for the motherboard let's get the floppy drives disconnected here there's the floppy cable all right rotating this around and I just noticed I put a scratch right in my LCD screen from this metal here it's scratched it I really hope I can remember how to reassemble all of this all right so there you go that is free on that side let's turn this around try not to scratch my monitor worse it's bound to happen little battle scars from being in close proximity to so many computers getting taken apart all the time one thing I noticed about this computer is it does not have any facility for external floppy drives so all the trs-80s before this supported up to four floppy drives zero one two and three and this one just has no external connection at all right I just freed the motherboard but unfortunately there's a bunch of cables on the bottom I think the strategy I need here is try to take this front bezel off the plastic bezel now when I had that motherboard tilted back you couldn't see it on the camera but I saw a lot of barge wires there's some serious bodge activity going on and it doesn't look like this is Radio Shack bodging I don't think because they they seem to be kind of coming off the motherboard they're not neatly glued down like they would be if I this was Radio Shack's doing all right take a look at this there's the motherboard and check out some of this bodge activity going on there's like a a ROM chip there with a couple barge wires and then these these ones here now it's the keyboard I'm trying to get unplugged and it's freaking wedged itself there how annoying I'm just gonna have to loosen the motherboard I guess off this tray all right come on there's a bunch of screws around the ports here which is good it's for strength that makes sense but this keyboard connector situation here is extremely annoying there we go you have to like loosen the board just to get this off I'm not completely understanding why the keyboard connector is not even aligned with this metal plate here so that this sort of makes it impossible to get that on and off without moving the whole motherboard like this all right I just found a nut here this is obviously for that thing I took off so I'll just stick that there I'm trying to get these cables off down here I have one off it is not easy and it's because this front panel is in the way the keyboard is free so I can move this to safety now what I probably have to do is put this thing back down and get those knobs off the front that's probably these here are going to be holding the panel on yep that came off that came off let's throw that in there maybe this will come free now well not quite there's a screw right there there's a screw down there this thing is a pain a pain in the butt to work on unfortunately these connectors are so stuck on there they are non-latching connectors and I have one of them off and the others just refuse to come off okay I got the video connector off there we go okay it is free there is the motherboard there it is there's the last little piece to this button that I took off on the side here and getting that back on is gonna be a pain because I'm gonna have to take the whole face plate off which means trying to get those screws off that are down there okay so if you're taking one of these apart do not I repeat do not take those buttons off the side in case you're wondering most of the structure here like this part here this is all riveted together so there really is no way to actually get to these parts here without I assume a super long screwdriver it looks like there's a little cut here so maybe with a very long Phillips you can easily get to this Screw As for that screw down there well I don't even see a way that's possible to get to that I'll have to figure that out in a moment to get the fan off it looks like I need to take these disk drives off and I can tell here that some modding activity has gone on with the floppy drives and obviously you saw in the front the two drives aren't the same all right and with that fan possibly out of the way a little bit maybe I can get down to that screw down there okay the screw is out there it is another one of those long ones and now when I lift this so there it is there's the front panel so now I can reattach the little button on the side here which I took off and there is the 4p obviously without the disk drives or the motherboard and whatnot these are those cables that were so difficult to unplug and uh I guess there is a little extra length here than I could have tried to access all right I think at this point so much for this being a relatively short video just taking that thing apart has got me sweating here so I don't know why this thing wasn't booting up properly it could be the disk drives it could be the motherboard it might be the power supply is acting up I'm gonna have to do a little bit of Diagnostics even with Seth's handy note uh the machine didn't seem to want to boot at all it just tried and then failed and then we saw those weird characters and then we got a clock and none of that do I really understand what's going on exactly so at this point I think my next step is to consult the technical manual probably something I should have done from the very beginning so I'll do some reading and I'll be right back alrighty I'm back and I've done some reading I kind of wish I had done that before I dug into the machine as Seth mentioned in his letter this machine does in fact only have a very simple boot ROM which is right here as opposed to the older trs-80s this machine doesn't have basic in ROM at all and in fact it really just has a very simplistic boot ROM but yet more complicated than the other machines because it has the capability of running some Diagnostics I think basic Diagnostics it can move from the floppy it can boot from a hard drive and I think it can even move from the serial Port if you're going to run some trcd model 3 software you have to stick in a disc that contains the model 3 ROM set which it then loads off the diskette and then I sort of reboots again and then it's in model 3 mode that ROM set is loaded into the dram which is right here on this board it has 128k which sits at the very beginning of the address space on the computer now normally on the trcd model 1 and 3 if you remember my diagnostic ROM videos the beginning of the address space is ROM and it can't be switched out that's one of the reasons why that the three and the one can't run CPM because it needs to have the full 64k and switch out the ROM so what this thing does is before it executes the ROM that's in the dram it Bank switches out the boot ROM and then basically as far as the model 3 ROM knows it's running out of ROM but the reality is it's actually running out of RAM now I think if I read it properly in the manual the model 4 itself like the regular 4 has the model 3 ROMs on the motherboard but it can switch those out but basically if you're running model 4 specific software it doesn't even use those ROMs on the motherboard and it just switches them out entirely and loads the entire operating system in probably like a simple bios into the ram as far as I can tell functionally the model 4p and the original 4 are the same now in fact this particular machine is not the Gatorade version of the 4p and the model 4S as well comes in a Gatorade and a non-gatory version from what I understand reading the manual the Gatorade version basically takes a bunch of these logic chips and these ICS right here are gal or Pal chips and it combines those all into like one 40 pin dip so there's a little bit of Simplicity on the motherboard there and there might be some other changes as well now I mentioned before that the ROM here has these couple bodge wires going on I think what's going on here is the normal ROM on this motherboard is supposed to be a 25-32 and what's in here is actually a 2732 which is a 4K eeprom the pin out of the 2732 and the 2532 don't match exactly so whoever installed this in here and I mean maybe this was done at the factory I don't really know I'm assuming that part number that's written on here is the actual part number of The Regular Boot ROM well you have to lift a couple pins and then it's picking up probably an address line over here and I think it's picking up a voltage from over there so it's a pretty simple mod and it does work but yeah this will be a normal eprom in here in place of the typical mask ROM I haven't quite figured out what's going on with this barge section but I'm going to leave that be for now I don't think that's actually a problem so I think part of my problem before is that I didn't really know how to boot this system and I was using this boot disk here to try to boot it it wasn't working this may not have the ROM set on it at all there were two discs that were in the disk drives and perhaps it was the other disc that actually had the ROM set on it and I had to boot that one first to load the ROM set and then switch over to this normal trcd model 3 trs-dos disk here what I want to do first is try to power up this board on the bench and looking at the power connector here it's basically the same as what is used on the trcd model 3. now I definitely have to validate that the pin out is correct before I just go plugging this in because this power supply here generates a negative voltage which I don't know for sure if this needs probably does though because it's got the built-in serial Port here and typically serial and these older things is plus 12 and minus 12. so I wouldn't be surprised if that is absolutely used on this board of course the dram in here is just normal 64k dram like on a Commodore 64. so that definitely doesn't use the minus rails like it does on the other TRS-80 models the video outper connector right here looks basically identical to the one that's on the model 3 so I'm going to break out the RGB to HDMI and that's how we're going to get a video signal so that's going to eliminate all the potential problems that were in that case like the CRT board or the power supply board as issues and in fact I'm going to use this disk drive right here which is a five and a quarter inch disk drive in a CD-ROM case and see it has a ribbon cable there I'll just plug that into the motherboard and I know this drive works so we're just going to not even use other drives at this time and that way I can kind of eliminate as many potential problems as possible it is my hope that I was just screwing up the boot sequence there with those discs and that this computer actually just works perfectly and maybe the connectors need a little bit of a clean and I need to fix that cap on the power supply so this may well be an easy fix but let's figure that out okay so this is the power connector right here it does match the actual physical shape of the power supply on the model 3 power supply that's right here but what I don't know is if the actual voltages are the same so I create a little chart here there are four pins with the little slot which is that part of the motherboard there I've already marked out two which I was able to easily test with the multimeter against one of the 74 LS logic chips here we have 5 volts we have ground but we have two other pins which I need to figure out now looking at this power supply here the 5 volts in the ground do so that's a good sign we just need to double check the other two pans which are going to be minus 12 volts and positive 12 volts so I have the service manual up here and we need to find one of the ICS that actually uses the plus 12 volts and the minus 12 volts probably going to be something on the serial port and then I can just test against those other two pins to figure out if the power supply is set up correctly all right here we go right here these are the serial Port outputs u15 there's a plus 12 volts and a minus 12 volt on these buffers and not on the incoming ones only on the outgoing one so I need to find u15 on this PCB alright so that's u15 right there according to the schematics pin one that has minus 12 volts so I'll touch pin one let's see which pin it is it is the PIN furthest to the left on my left right now where's the pen I have misplaced it minus 12 volts and according to the schematics pin 14 is plus 12 volts right there which should be that pin right next door plus 12 volts all right so looking at this wire here this uh like that is how it would plug in the motherboard so it would match so -12 should be this wire right here which goes to the orange wire and I would have made the orange wire the minus 12 volts and I would have made the yellow wire plus 12 volts which does coincide with the one next door but before I plug this in and turn it on I'm definitely going to double check that's the case just just in case I don't want to reverse polarity anything accidentally so I'm just going to plug in the mains here okay the LED came on this power supply seems to work fine well while there's no load so with this connector it would go onto the motherboard just like that so these two pins here we should have plus five volts okay it's 5.1 that's fine next one over to the ground we should have plus 12 and we do 12.3 and then we should have minus 12 and it's minus 11 but that's good enough considering there's no load on this that's sort of typical okay so that pretty much confirms that the pin out on here matches uh what the model 3 motherboard has so I'm just gonna plug that in right there and we're going to grab my favorite thing the RGB to HDMI here and for the RGB HDMI I have this little adapter thing which breaks out to a pin header it's exactly what I used on the model 3 and right here on the schematics is j9 which is this connector right here we have pin two as the video output ground is one three five six is horizontal and four is vertical all right and I switched OBS over you know this camera I use for the bench shot it's like right in front of my vision for looking at the screen okay and looking at the profiles on here at least uh the copy of the software I have on here we have trs80 model 3 and we have Tierra Stadium model 3. I think I made the this one and I think uh model three here is one that I was using in the last video it was one that comes with a distribution okay so system is on but no smoke has come out good sign power supply is running I heard a little tick from the speaker so let me hook up this floppy drive and let's see if we can make a boot unfortunately I don't have enough cameras to also shoot from behind me so you can see the activity on this floppy drive this camera won't pick it up and I can't pick it up on the bench cam but this little floppy Drive in the CD-ROM case has an internal power supply it's just a 360k double-sided floppy Drive set to drive select zero it's what I typically use on stuff like this for testing so I'm just going to turn that on first drive is on and I'm going to plug in the power here let's see what happens here oh there we go the drive seeked and the lights on so it's attempting to boot now this was the disc that was in the disk drive I think it was in the second disk drive when I unpacked this thing but it says Drive zero right here I don't think I tried this and actually it's interesting the um disk drive gave up it kind of was on for a second and then the light went off so uh I don't have a reset button hooked up so we're gonna have to unplug the power and plug it back in it's kind of primitive but say la vie let's see what happens here it's doing something like they're seeking activity on the disk drive and now it's just sort of doing nothing oh wait no it's still going oh I'm expecting to maybe see something on the screen I don't know K is still a black screen it's kind of frustrating um oh I can plug the keyboard in can I no wait the keyboard doesn't have a reset button on it what exactly resets this thing they must be maybe this little three pin header right there maybe that does the reset okay there it is three pin header reset so pin three not connected short pin one and two for reset I'm gonna grab a jumper let's try that reset all right we have a jumper here try to reset this thing all right here we go would that do anything at all did that do anything at all yes the drive is seeking again now it's pretty obvious I'm very unfamiliar with how this works and I didn't read the user manual I just read the service manual for it and I gotta say this entire thing about putting in a disc to load the ROMs it's not super intuitive and especially because it doesn't print anything on the screen unless of course we don't have video output and I don't realize that all right so I'm on what is the video pin and very clearly on the scope we have a video signal so the problems with the rgbt HDMI uh this last pin here this should be the horizontal sync and if we zoom in here there is the pulse and there's the frequency right there 15.8 kilohertz so that's definitely the horizontal pulse and then this one right here two over should be vertical which I have to zoom out to C there we go frequency is of course block because I have this window too small 59.8 so that's definitely it okay so we're getting a video signal and the rgbt hdmi's not decoding it to let me figure out what's wrong now well there it is with the sync signals disconnected and clearly we're getting a video signal um as soon as we plugged in vertical sync we lost the signal obviously whatever's going on something wrong with the profile here with the RGB HDMI so I'm gonna fiddle around till I get a working signal out of this thing because it clearly it's actually booted alrighty well I fiddled around with the settings on there a little bit I honestly have no idea why the profile that was on there for the model 3 just showed a black screen that's pretty frustrating uh but there it is and it's looking pretty good right now so I'm going to hit that reset with this jumper here and let's see what happens the disc in the disk drive here uh no the disc is not on the disk drive it's just it's right here all right so I'm going to power cycle the computer here um that's weird why is there garbage on the screen let's turn it off again plug it back in okay um I'm wondering if that's because the disk drive is on let's try that again sometimes the disk drive has five volts coming through it and the disk drive itself is going to be trying to power up the motherboard so let me turn the drive on let's plug this in now okay there we go just a black screen and the drive is accessing so I'm going to put in this disc again that is the boot disk I guess oh look floppy drive is not ready I never I never saw that happening when the system was connected to the internal monitor it never did this so let's reset again so it's going to the disk loading raw maybe okay you know what if I saw this stuff on the screen I would have been like going oh this is working fine and I would have been able to figure it out but we all saw what it was doing like had weird symbols and then it had that clock and it just was acting weird Okay so is it done I want to see if it it says after it's finished loading here insert boot disk oh wait it literally just loaded the disk itself this is all very confusing um I'm going to take this out let's put in this uh this disc which is the one I was trying to load so strange I mean I'm assuming if I unplug the power and plug it back in okay yeah obviously the system is still running from the disk drive here so let's turn the disk drive off we'll turn these back on at the same time okay so I have the TRS dip loading ROM image again I never saw this I just it's so confusing so are both of these actual functional boot disks uh I'm assuming the power supply um yeah okay it's it's seeking I'm assuming the power supply that's actually in the machine because I never tested the voltages um oh yeah look it worked as well okay so I'm assuming that the power supply that's in the model 4 the one that was there is not working properly Uh something's wrong with the way the rails maybe the five volts low or something that was causing those unpredictable results maybe the 12 volts was low or it came up much later which is why the monitor came to life all of a sudden even though I I tapped on the machine and it started working that might have been completely a red herring not actually the problem I think a good final test is I think this right here is a model 4 boot disk let's do the old full power cycle on this thing and let's see if this actually boots up here we go what's happening loading oh no ROM image alrighty so let's go back to this model 4 CPM disk see if this thing does anything I mean I'm assuming that the model 4 discs don't need to have a ROM or something like that I'll plug this back in this is a really ridiculous thing I have to turn both on and off at the same time but let's see what happens here so with the model 4 disc in there it doesn't really seem to do anything or just getting the old black screen again let me hit the reset jumper on and off the drive is spinning it's not doing anything and I think the light's going to go off okay the light goes off well it's really cool to see that model 3 software at least is working on this motherboard that means that the problem lies elsewhere like I had just said I'm not totally sure why it's not running model 4 software though like the whole thing about the model 4p is it's fully compatible with the model 4 which means that CPM and all that other AD column software that exists for it should work and yet doesn't seem to be working although actually I just had a thought what if the problem is the rgbt HDMI again malfunctioning and when it switches to 80 columns mode which it would putting that CPM disk perhaps it just blanks the screen I don't think that's actually the case because it didn't seem to be actually accessing the disk drive at all and I'm sure loading CPM or that other disk I have would have at least done something on here I think I'm going to end this video here and in the meantime between this one and the next I'm definitely going to take a look at the user manual for the 4p just to see what it specifically says about loading for software maybe there's an extra disk that I don't have that has some kind of four ROMs on it that I need to load or maybe there's something I'm missing I'm not totally sure there so if you have ideas about that definitely put that down below in the comment section I'd love to read up what I'm doing wrong on this thing in the next video I'll dig into the power supply and the analog board on that machine and I'm pointing over there because it's sitting on the floor and uh we'll see what's going on there because clearly this machine was misbehaving with that power supply when with this one well as we can see here it just loaded right up and that's with both of these discs so I know the disc I had in there should have worked oh and of course I'll do testing on those floppy drives as well which are standard sugar drive so I can test them on PC using IMD like I test all my normal disk drives now onto a little other business here I recorded the beginning of this video last week and I'm recording the second video now after I attended VCF Midwest number 17 that was in Chicago and I met a ton of fans and patrons there it was absolutely a fantastic experience really my first VCF show with the channels being as big as they are I attended VCF in the Seattle I don't know it was a few years ago but my channels were a lot smaller than and that particular VCF is also a lot smaller so this time it was just amazing to meet tons of people and of course I met other YouTubers and all sorts of people from the Retro Community it was an absolute blast so if you came up and talked to me thank you very much for saying all those kind words that everyone did and if you did go and you couldn't talk to me because there were lines or I was busy or I wasn't there I do apologize and I'll be going to more vcfs in the future but yeah what an amazing experience thank you to all the people who put that show on you all put in so much hard work to make an amazing amazing show so I think I'm going to end this video here I want to get this one out for some Tandy I will try to get to the next part of this video and put the machine back together in part two which maybe will be next week but I have some other videos I want to make as well so I can't promise that um there'll be another trnt video coming up right away I know people have been saying that they love trs80 videos but at VCF I had people come up to me saying that they love Commodore 64 videos as well and apple II videos and what am I going to do atario videos and all sorts of stuff you know you can't please everyone all the time but I like to kind of mix it up on this channel a little bit and I have some other videos in the pipeline so anyhow that is going to be that if you like this video comment down below thumbs up you know all that usual stuff you know what to do if you don't like it too hit that subscribe if you haven't already check out the second Channel if you haven't already a huge thanks to all my patrons for all the support that you're giving me on the channel really appreciative their names they're scrolling up the side of the screen and I guess that is going to be that stay healthy stay safe and I will see you next time bye foreign

Channel: Adrian's Digital Basement

Views: 26,989

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Id: -EhhU-mCyp0

Length: 48min 34sec (2914 seconds)

Published: Sat Sep 24 2022