Dragon32 Trash to Treasure | Repairing the Dragon (pt2)

our MC is supported by monster joysticks calm level up your retro gaming with their joysticks feature in genuine San where arcade parts and one click print calm for your photos on canvas acrylic gifts and more local craftsman and global delivery [Music] hello cave-dwellers welcome to the cave to the dragon's den in fact as we continue our journey of discovery with the dragon 32 the only computer ever to come out of the country of Wales we've got our own machine here which is broken and in part one we discovered we've got power problems with it so as we continue to tell the story about the dragon 32 we're going to try and fix this up and see if we can get it in a working state to demonstrate to you just what it can do we've got a lot to cover so we'll dive straight in and we'll also ask the question as we discovered in part one this is a very similar computer in design to the Tandy color computer and I want to find out is that more than just a passing resemblance is the dragon 32 in fact a clone well let's take it to the lab let's find out and let's continue learning all about the dragon 32 here we are then where we left off on episode 1 with our power board and what we found the problem was is that we have our 12 and 5 volts present but on negative 5 volts is missing that just shows up as a big fat 0 12 5 and negative 5 volts or what the main system Board expects and I'm not prepared to plug it in until we've got that following the nice thick traces on the back of the board it's easy to find the components responsible for our negative 5 volt output and some standout as being a common point of failure for example this 70 905 voltage regulator and a single electrolytic capacitor so these are my first target to swap out and we'll see if that solves our problem and also like to replace all of the electrolytic capacitors on both the power and the system board as a preventative maintenance measure as well as the other voltage regulator in the hope of giving our dragon a little more longevity through which we can enjoy it let's start with that voltage regulator then we'll get that removed which isn't too trickier task and we'll solder a new one in I'm using leaded solder which is in keeping with the system of this age and nice chunky solder joints as per the existing joints both my desoldering gun and my iron are set to 350 degrees Celsius and that seems to work just fine [Music] [Music] that's the old regulator out and our new one is now fitted so let's go back and check the voltages and see if we've got the correct negative five volts now is showing up well this is different not only do we not have our negative five volts but we've also lost our twelve volts that's now given us a zero reading and that makes very little sense to me as it's got no dependence on the regulator we've just replaced so something quite aught is going on here let's just ignore that for a minute and we'll continue with our negative 5 volts problem checking the new regulator with the multimeter we can see that it's receiving no input and of course we've established that there's no output from it so we continued our journey tracing the track from the regulator and it now travels to this resistor R 5 and then onto capacitor C 5 which is next on my hit list so let's get that capacitor swapped out and we'll see if we're in a better position [Music] [Music] okay that's our new capacitor in place and where do we stand now well there's some good news we now have a negative voltage reading now this is an ideal it's way past the negative six volts so that isn't quite right and the confusion continues on testing this time we've got five volts where our 12 volts should be 5 volts present where it should be and negative 6 volts is present and incorrect the regulator responsible for this is not receiving enough voltage to enable it to give us 12 volt but we've changed nothing that would affect that so while I decide how to tackle this I decided to press on with recap in the board and replacing the second regulator as part of that preventative maintenance and who knows perhaps we'll find one of those parts brings our 12 volts back to life it's a little haphazard but if it doesn't work at least it eliminates those parts from the equation [Music] [Music] [Music] the thing we have something of a breakthrough the power enters our board via a right angled nine pin connector and if I give it a twist our 12 volts actually springs to life this is quite a common place to find bad joints because of the stress placed on them from plugging and unplugging the power cable on closer inspection though it's not just the case of reflow in the drinks to fix this I gave that a try and we had no joy notice how the after two legs are shorter than the others this is by design on this particular connector and if we ensure enough solder flows down into the hole then yes contact is indeed made and it works but it feels cheap compare it with this connector on which all the legs are long enough to actually go through the hole which is far preferable so let's solder this connector in instead and as I fit it you can see all the legs are now proud and fully through the holes and that should give us a much better connection [Music] and I'm testing now we actually have a good result our 12 volts is back our 5 volts is present and our negative 5 volts is now bang on a solid negative 5 the belly of the Dragon has fire in it once again and even if we give that new connector a good wiggle the output is still solid and we don't lose our 12 volts like before so throughout all of that we've fixed and refurbished our power board and now I'm happy to plug that into our system board with my fingers crossed to see if any damage was caused to the system board itself as a result of these power problems before we got hold of the machined let's put it all back together and see what happens [Music] this is the moment of truth then we're using the composite out to give us the best possible picture if indeed we have a picture the power cable goes into that new power socket fingers crushed let's press the on button and it works we've got that lovely green screen with 1982 by Microsoft there I hadn't quite realized just how green that green text is it really is green on green but that's incredibly satisfying I'm really surprised actually that this works because I was convinced that the power problems would have created further problems deeper in the machine especially with the RAM and it's an important lesson to learn really always always always test your power supplies and as much power testing as you can before it reaches the system board my guess would be that this has been in storage I need to confirm this with the previous owner I guess it's been in storage for a long time if it's been in storage in somewhere like a loft where there's a lot of temperature changes that creates a lot of expansion and contraction especially on things like the port where we found a problem with the power connector so it may well be that the problems happened while I was in storage may have gone into storage in a perfectly working state and then the capacitors degraded the expansion and contraction has caused problems with the port and I'll confirm this but it may well be that the previous owner hasn't actually tested it before sending it here because I think if they did test it something would have got zapped and we've been extremely fortunate today and our keyboards are working to those keys are incredibly satisfying to press there's an interesting thing with the Dragon actually if you press two keys on the same line too quickly so for example three and four are working fine there but because of the way it scans the keyboard if I press them too quickly we're only getting a three and that's incredibly frustrating if you're a touch typist well I'm incredibly pleased that's working pleased and surprised but it's working and that's great there's more work to be done we need to recap the system board we need to clean it up and we need to give it some longer-term testing but before we come on to that there's a question that's always hung over the dragon 32 and is this is this machine simply a Tandy color computer clone or does it stand out as a computer in its own right I think we should discover more and find out if we can answer that question now [Music] it's a question that's always hung over the dragon the dragon 32 is built to the same Motorola reference design as the Tandy color computer that's the 6809 CPU the MC 68 8-3 synchronous address multiplexer EMC six eight four seven video display generator and the MC six eight to one peripheral interface adapter between these four chips with the addition of some RAM you essentially have a complete computer it's comparable in its code execution speed to that of a Zed 80 a cpu running at four megahertz and its rival does that expect room was running such as ed 80 at three and a half megahertz for comparison the dragon is about 95% the same as the Tandy color computer which was released two years earlier in 1980 and that was built around the same Motorola reference design so naturally a computer based around exactly the same core chips he's going to operate in a very similar fashion there are some key differences though for example the Tandy was built for the 525 line display of NTSC TV sets and the signal output from the video display generator needed no alteration to support this on the dragon extra circuitry was required to convert it to the powell signal used in his home markets and as a result pseudo color generation effects used by American programmers didn't work on the dragon this gave the color computer or KOCO as it was nicknamed an advantage when it came to reproduce in arcade games but compared to the likes of the Commodore 64 video capabilities for both the Dragon and the Coco were seriously like in the dragon did come with 32k is standard though that's greater than the stock 4 or 16 K of the Coco in 1982 although later revisions would rectify this finally there are some differences in the way the internal routines are stored in the ROM for example the keyboard scan routine is different and the full 16 K Microsoft extended color basic interpreter was included on the dragon but that was an option on the Tandy's original release George st. rating in Dragon user magazine no I'm not making this up George st. points out these differences as evidence that cooling the dragon a clone is a myth and it's a case of same chips but different cup of cocoa pointing out that is the 5% that makes all the difference so armed with that information did we think the dragon 32 was a clone well the Tandy was released two years earlier in 1980 it was built on a low-cost platform and it was proving to be very popular given that it should come as no surprise that dragon data wanted to emulate how success in their defense they were using a reference design supplied by and supported by Motorola this reference was to encourage microcomputer creators to use their chips and it allowed dragon data to rapidly create a micro when they didn't already have a design and the UK computer market was perhaps starting to get away from them before they could even get onboard this reference design however was born out of a project good project green thumb this was a joint venture between Motorola and Tandy and it goes back to 1977 and resulted in the Radio Shack trs-80 color computer which would go on to be renamed the Tandy color computer so given the way that that reference design was birthed the joint project between Tandy and Motorola I think it's fair to conclude that yes the dragon 52 is in fact a clone and if any more proof were needed I'm told that you can swap out the ROM on a Tandy color computer and just rewire the keyboard slightly and you have a complete dragon 32 conversion that's my opinion yours may differ if it does leave a comment below and let me know why now let's get back to finishing off recapping the system board on our dragon 32 so we can finally get down to injury in the computer recapping the Dragons mainboard was a fairly quick task relative to some of the more recent recapping we've done in the cave there were just six electrolytic caps to change and the vacuum desoldering done make sure work of that but I think even with a manual solder sucker that wouldn't take you too long if you're undertaking this task yourself the rink would underside of the PCB that's perfectly normal this is tin layered across the copper at the time of production and the solder mask is on top and you'll see that on other micros too like the spectrum unsurprisingly this was the cheap option when it came to manufacturing at the time and he stood the test of time just fine despite looking a little funky [Music] my tools are still set at 350 degrees Celsius and I'm using a little flux paste to get the old solder flowing on the hole it's an easy board to work with and the caps put up little to no fight in being removed [Music] [Music] finally I gave the board to clean down with some isopropyl alcohol and an anti-static brush returned it to the case and we're ready for one last test before wrapping up work for today does it still work with the new capacitors of course it does carefully working away there with a full complement of new capacitors on both the system board and the power board and that's what we're going to do on the inside of this dragon 32 we're just going to leave it there and we're gonna concentrate on cleaning up to make it look like new on the outside including a new sticker but I don't think there's too much work required there and that gives us plenty of time in part three to discuss what happened next for the dragon 32 what upgrades were available what peripherals and ultimately how was the Dragon slain what became of it there's lots to cover I hope you'll join me in part 3 and between now and then I will be live-streaming with this to build up my knowledge of what the machine can do and to capture some footage of it in action for that part 3 I hope you'll join me either on the livestream or in part 3 until then thank you for watching and take care [Music] if you enjoy my content and would like to toss a coin into the hat to support the cave then check out patreon.com/crashcourse you can see on the screen now thank you for your support [Music] [Music] [Music]

Channel: RMC - The Cave

Views: 50,571

Keywords: dragon32, dragon64, repair, refusb, fix, trash to treasure, retro man cave, nostalgia, 8bit, 6809

Id: 7NUhKTe12v0

Length: 18min 20sec (1100 seconds)

Published: Thu Apr 18 2019