The perfect way to NOT do SMD rework (RGB2HDMI overview and repair)

well hello everyone and welcome back to adrian's digital basement on today's video i have an rgb to hdmi that's not working properly so i'm going to try to repair it so without further ado let's get right to it [Music] so i've talked about it many times how much i love the rgb to hdmi i really feel that this is one of the best things to come along for retro computers in a while at least when it comes to using retro computers with modern displays i'm really lucky down the basement here to have a really good selection of good crts to use with these vintage computers but sometimes i don't feel like getting out a very big heavy crt just to use really quickly when i'm using like my test bench which is sitting right here so that's where the rgb hdmi comes in so handy because you could just use any old monitor you could even use a vga monitor if you have one with a hdmi to vga adapter on this thing to get a really good pixel perfect image from whatever retro computer you're using now this is the rgb to hdmi that i keep on my bench generally and i got this one from aaron over at retrohackshack and he actually sent me the little case that this is in as well just in case is the first time you're hearing about this particular project what this is is a raspberry pi zero down here on the bottom connected to this top board which has a cpld on it which does the digitization of the digital signal in this case at least and then the raspberry pi on the bottom is what does the heavy lifting to convert those signals into an appropriate pixel perfect hdmi output now this is the cpld right here on the top board there's not a lot going on there's just four buttons and there is a connector on the bottom which i have this nine pin on so this is set up for digital ttl input which means cga ega and monochrome along with any other system that might use a digital signal like say the output from a macintosh and i have a video where i took an rgb to hdmi connected to a macintosh classic and got a nice pixel perfect hdmi output from that machine now if you're a regular viewer of my channel you'll see that this thing makes an appearance often on the channel i think the most recent time i used it was for the commodore pet repair series and this plugs into the user port and then it has the standard nine pin connector here which connects to that well i need to use a cable because they are both female there and there is an appropriate profile on here which i created and i shared with the creator or maintainer of the project so that is now included with the release so you can use your pet 4016 or 4032 with the rgb hdmi to get a pixel perfect display i also have another rgb hdmi here and this one looks a little bit different because this has this 25 pin connector on it the reason for this is that this is designed to connect up to an apple 2gs directly to the motherboard i might add to give you pixel perfect output on the apple 2gs as well and this is completely a digital signal it's picking it up before the signals go into the dac so you're getting a pixel perfect representation of the apple 2gs image on hdmi with this very inexpensive device i'll have some more videos for the rgb hdmi showing off how cool it is but what this video is about is doing a repair on the rgb to hdmi itself so this right here is another cpld board and this one i had been using on this pi here for quite a while i can tell them apart because this has a red and a blue button there this has all black buttons i was using this cpld board in combination with this cable here hooked up to a pc to try to display a monochrome display and i was getting no picture it was strange to me because i know i had used this board with cga like just a little while before and it worked fine but it wasn't displaying anything with monochrome i just assumed i had something wrong with my cable or maybe the video card and the pc was bad so i just moved on to a different card but upon further investigation it turned out that this cpld board is bad over here on the github repo for the rgb to hdmi and i'm looking at one of the forks here from ensb this is actually a bit more of an up-to-date repository of all the code that does eventually get merged back into the original hog let 67 one but i recommend using this one i'll have a link in the description if you're going to download any of the most recent software to run on your rgb hdmi it's a little bit confusing when you're looking at the project for rgb hdmi because there are so many different boards that have come up over the over the years this project is not brand new and you'll see over on the side there's a bill of materials for various digital boards 3-bit 6-bit 6 and 8-bit all the way up to the most current 12-bit now if we take a look at these two boards here this is the 12-bit board that i have on here the one with the colored buttons and this one is one i stuck on here because it actually works but the one that has the problem is this one right here which is a six slash eight bit issue three board now you'll notice they look very very similar the real difference is this one actually has some additional pins that have headers here so notice there are more pins right there than there are there that just exposes some additional inputs to the cpld for more than six or eight bits but actually up to 12 digital bits of information the origins of this project were to output eight color graphics from the original bbc micro which had three bit digital output which is just rg and b now if you think about cga with which supports 16 colors it has rgb and an intensity bit or if you think about ega which supports 64 colors that actually has six bits right so it's rg and b and each one of those has an intensity bit for a total of 64 colors but it turned out to support machines like the atari st or the apple 2gs as i showed with that adapter board you need a full 12 bits of digital information to give you the 4096 colors that those machines support for my purposes on the bench though i'm always using this particular setup right here because all i'm using it was is ega and cga and monochrome which really needs up to six bits so this cpld board is perfectly fine for me all right so back to the problem i'm having with this board what is exactly going on with it and why isn't it working well it turns out here when we take a look at the cga pin out rgb comes in on pins three four and five and then h sync and vsync are eight and nine and the intensity bit is six and as i said cga works perfectly with this board so there are no problems with any of those inputs on the cpld problem appears when we take a look at the pin out for mda and hercules which uses the same pin out take a look at this pin 6 is intensity which is the same as on a cga 3 4 and 5 aren't even used at all and pin 7 is ttl video input so the image is actually on pin 7 and not on any of the other pins which i know are working once i realized the pin out was different because i guess i never really thought about that and i realized that there must be a problem on the cpld here on this board now of course because this is an open source project all the schematics are freely available and this is the schematic for this cpld board and this project uses a xilinx xc9572xlcpld and when you look at the pin out here all these gpio pins are what are talking to the raspberry pi and then there are all these r2 g2 these are the input pins on the cpld now i traced out what is connected to pin 7 which is the video input on the mda cable here through the connector right to the cpld and sure enough that signal is visible i did it with an oscilloscope and i saw the monochrome video signal going to the cpld but it wasn't actually registering anything on the input now here's the data sheet for the particular cpld that's being used on this project and i think we can see the problem right here 5 volt tolerant i o pins except 5 volts 3.3 volts and 2.5 volt signals well the problem is whenever you have 5 volt tolerant pins the chip itself probably runs at 3.3 volts or even 2.5 volts and it's using diodes inside to kind of clamp the input voltage to prevent it from overloading those input buffers while this clearly does work and a lot of things like the floppy emu for the apple ii and the macintosh is a similar 3.3 volt part with 5 volt tolerant pins on it it can cause the chip to get damaged a little bit more easily than if this were a true 5 volt part it's just not as robust on those input pins as a real 5 volt part when you're sending potentially higher voltages into those pins now because of that back on the project here there is actually a ttl buffer board that i probably should be using which actually plugs into the underside right here because this is where this thing was connected directly to it plugs into there and then it adds the appropriate buffer chip in line with the cpld just to prevent it from getting extraneous higher voltages that might damage those i o pins so finally to get the point of what this video is actually about i want to try to repair this cpld board so i can take this one off this 12-bit one and put it back on this rgb hdmi in this bag here which is my analog one which has the analog board on it which i use for composite video input when i need it so for repairing this damaged board i'm going to try to actually do a little bit of smd desoldering and remove this chip and install a new one i had reached out to aaron from retrohack shack and asked him about the fact that this board had gotten damaged and i wondered if he had any other extra cplds lying around and it turned out he did so he dropped it in an envelope with a couple stickers here and sent it my way so i'm going to try to do a little repair before we do that though let's test this to see if it's still not working and that way when it's repaired i'll know because we'll get a working image okay so the bench pc is set up here and i have a cga slash monochrome card in here this is a vtec card and i have the bad cpld board reinstalled on the raspberry pi and i have this connected up to the cga card and i have obs configured here to capture the hdmi output from the rgb hdmi and except for cga and you can see it looks absolutely perfect all 16 colors are represented all those bits are working so let's go into the menu here and let's switch this over to monochrome oh it's funny i actually have it set for ega but that seems to work with this card anyways so let's switch over to i think hercules might be the right one all right well you notice it's flashing right now but you see some text and that's actually a giveaway that there is a problem with that input bit the flashing is coming from the rgb hdmi it's not synchronizing properly to the cga video signal so that's why it's flashing but the fact that there's some text visible it implies that that intensity bit which it does work because it's the same pin that cga uses pin six it's working but the thing is when i reboot this thing a normal pc doesn't really show anything with intel intense text while it's booting well it actually is right now but that's because that's the or the xt ide and it has a little bit of bolded text i'm going to turn this off and there's a toggle switch on the video card here which will switch it to monochrome mode the computer might complain but i think okay i'm gonna push f1 here trying to get to the bios oh look at that we're not seeing any of the video except for the text that has the intensity bit set but when i was trying to use the rgb to hdmi on an ibm pc xt which is when i noticed this problem it doesn't show any intense text when you first turn on the computer in fact you'd have to boot into dos and then run a program to potentially see some intense text so definitely there's a problem here on the cpld and like i said i've already tested to make sure that the signal the video signal is getting from this connector and it's making its way all the way through to the appropriate pin on the cpld and it's just not working so next step swap the cpld all right so for this little bit of smd soldering which i am extremely unskilled at i'm going to be using the end and star hdmi microscope specifically because i can capture the video so everyone can see the work that i'm doing really close up so here we have the board with the cpld that's not working i'm going to need to remove this and i need to remember that the dot here goes towards this capacitor here c1 down in the corner and this is the cpld right here that aaron sent and i guess this looks like it's the same part now i do know that it can be really difficult to find these chips like due to the chip shoulders or whatever not to mention of course you can order and get some fakes i think things are getting a little bit easier to find all right so there is the new part right there it looks good of course nothing is wrong with it so now i need to put this aside and get the old cpld off the board now if you take a look at this board just look at how small these little capacitors are now i think these were all hand soldered by the look of this but if you're going to remove chips like this off boards you really need to use hot air and you need to use flux as well i'm going to be using this kind of flux right here it's like a no clean flux and i'm going to be using a syringe to apply some of it around the ic now again like i mentioned i really don't know what i'm doing here so i might completely screw this up all right so here is a syringe whoops i just squirted a whole bunch of flux okay well this is not the perfect syringe for this um this kind of flux is very thin and it just went all over the bottom of the microscope there this is the hot air rework thing that generates the hot air i have it set for 350 degrees celsius i'm not gonna show the particular one i'm using because it's just an inexpensive one i've got got off ebay i can't recommend it being good or bad if you just put hot air rework there's a whole lot of them and they're very inexpensive and here we go so i'm just gonna move the hot air around here i don't know if this was the right flux i might have to switch to uh rosin i'm just gonna hold the chip down and i'm gonna heat this up seems like all the flux has kind of gone away i don't think this particular no clean flux i'm using is the best because uh it's too liquid you need that thicker paste stuff so actually i'm gonna stop this for a sec and i'm going to switch to rosin flux now this is the rosin flux that i use it's rosin comes from a tree i think it's very very sticky i keep it in a little like squeeze bottle here just so i can apply it to an appropriate place thing is it's messy and it's hard to clean up so that's the negative thing about it but uh there we go so lots of it around there look at that it's bubbling that's how hot the chip is right now but i'm just going to uh start heating this again looks like it's starting to get molten a little bit potentially yep it definitely is you just got to keep moving it around because you need to heat it up entirely all the pins sorry i'm so zoomed in i can't zoom out any more than this this is as much as the microscope can do okay look at that so i just grabbed it by one of its legs and off came the cpld just like that now when we look at this board there's a lot of flux on there and there's actually a good amount of solder already but it might be a good idea for me to add some fresh solder on there so i'm just heating up my soldering iron here to 330 or so i'm just gonna add a little fresh solder onto the tip here okay well that's obviously way too much there we go all right so here's the new cpld now one technique of course is you just uh you just solder on one corner of the chip like say that pin right there and then you do one over here and that allows you to kind of position it because look how fiddly this is it's like moving all around all right so it's looking pretty good at least on the top left corner so i'm gonna hold it down on that corner with one set of tweezers here and i'm going to use another set and i'm going to try to turn it just so slightly now the problem is it's kind of riding up on top of those solder blobs that are there but i think this is going to be good enough right here so i'm just going to oh well that sucked i said i was going to hold it down in the middle there and then i was going to grab the hot air but that didn't work this type of soldering is very much a skill and you know the more you practice it the better you're gonna get at it so i have really never done anything like this it's really my first time so that's why i'm sort of not doing such a great job here now i'm sure there are people watching who have done this a million times and are probably like you're doing it wrong you could do this that or the other thing but i'm just going to see what happens here i'm going to i'm going to leave the chip here i'm just going to hold it in the middle i'm going to hit it with hot air and i'm going to see if it kind of pulls it into position incidentally i'm using these titanium tweezers that we're sending on a mail call episode these are awesome because solder does not stick to these so i'm just going to hold this down in the middle to try to minimize the moving and look it just keeps moving around so let's just start heating the board it's already heated up a little bit a lot of times the capillary action of the solder can kind of pull the chip into position but that may not happen with something as big as this so i'm just gonna try to nudge it i'm not even sure the solder has melted yet may not have moved a lot you know it would really help if i had this uh if i had the board actually attached down oh look it's kind of moving there do you see that let's go come on i know you want to oh no i made a mess in a disaster here oh no this is not good everyone it's sort of soldered like this at an angle no problem we can get it off we can fix this situation i just have to uh grab it here okay there we go come on okay this is a disaster an absolute disaster i'm pulling this off right now there it comes all right so first off i need to see if i have bridged any of the solder joints and no it does not look like i have i'm going to try a new tactic i'm going to try to tap down or tack down some of the legs on this thing all right so i think it's pretty well aligned right now it's not soldered down and i'm gonna hold this down with the tweezers i'm gonna try to just solder one pin over here on okay like that and then i'm gonna try to do the same over here on this bottom corner now the fact is i only did one corner on the other side so that means that you can still kind of move around the uh the chip right okay so now it's actually in place with two of the pins which is good because that means that i can use hot air now to do the rest of it now of course there's a method called drag soldering where you just sort of go around the entire chip but i'm just going to see if i can do it this way so i'm going to hold it in the middle here so it doesn't move and i'm going to try to use hot air here to actually get the rest of the pins down i mean this is a this might be a total disaster and i may end up ruining this board right or this chip now i'm holding it because i don't want it to melt the pins that i've already soldered and all of a sudden move right that's why so see there it's melting those pins there and on the bottom row let's see i'm not sure it's actually making good contact there it doesn't really look like it does it all right so i may need to just do some drag soldering on this because this is uh don't think this is really working what you're seeing here ladies and gentlemen is not a tutorial it's kind of like what not to do or if you're a newbie this is what soldering ics is like okay time to resort to the soldering iron first thing is i'm gonna add more flux onto this thing again right you never have too much so to speak wow it's hot yeah that's a hot chip i have some solder on the tip of the soldering iron here and i just bridged a couple of pins together nice we'll clean that up in a second so after using the hot air i'm not 100 sure if all the connections are good so heating them up with a soldering iron after the fact just ensures that each of those connections is actually made after tacking down those first two pins i probably should just have gone ahead and done the soldering exactly like this and skip the whole hot air part entirely all right to clean up those bridge solder joints i'm going to try to use some of this mg chemicals solder braid here i think that might be okay it's funny i'm trying to see if there's a bridge here between those two pins it almost looks like there is first let's try to get some solder on these pins here which looks like i cleaned off that little fillet there is annoying me on this on this uh capacitor there we go okay i have these probes here and the multimeter set to continuity mode let's just see if any of these things look br are bridged together that is not which is good how about these two pins nope how about these two pins they are fine they are not those are good how about that and like see this pin right here like i'm on the trace there let's just double check that actually has continuity on the chip it doesn't appear to yeah so that one is actually not connected at all so the problem is i put so much of that rosin flux which has got you gotta be kidding me [Laughter] oh i'm like a disaster here this is i'm using the wrong tools this is not right oh let's just clean that up there we go [Laughter] i mean oh i'm sorry uh this is the worst this is not a tutorial do not watch this for any kind of tutorial because uh you're only going to learn really bad techniques here with what i'm doing i'm just trying to test continuity here on this uh pin here okay that now is connected i really need to clean this up because all this flux is such a disastrous mess that uh yeah look at that horrible just horrible okay 99 alcohol here i have a little brush let's try to clean this off a little bit here i'm going to use a little piece of paper towel here try to kind of sop up the mess all right there we have it after some cleaning there's the board uh it's ugly it's really really ugly are all those pins connected i think so it's hard to tell i mean i'll know better oh look at that after cleaning these two pins are bridged right here so let's try to clean those up i highly recommend if you're going to do any kind of soldering like this you really should get yourself a microscope and unless you have really good eyesight and good magnification i'm not sure well i certainly with my regular eyes i wouldn't be able to see that bridge maybe with those goggles i wear i would but the microscope makes it really easy to see so let's just try to get rid of that bridge there we go i think i cleaned off a little bit too much solder though so let's try to reapply a little bit okay i think that might be okay now so this board has sufficiently cooled off it's back at room temperature so it's time to see if i ruined it might have made it a lot worse than it was let's let's see what happens all righty let's reconnect this once again it's really the moment of truth here i have no idea what's about to happen okay cpld recovery all right so it's saying that the cpld is blank and it needs to be programmed so it's a 6 or 12 bit rgb cpld version 94. that's what i'm gonna be flashing on here we're gonna push the button it says it's blank we're gonna hit identifying is it gonna work is it gonna work i tortured it by heating it up and you know multiple times so i don't know it says programming come on how long does this take okay it says successful rebooting doesn't mean it's going to work because there might be damaged io pins things like that all right why is it green that's weird let's reset everything okay i hit the reset button on there oh um yeah i might have caused a problem here because it's it's all green well let's turn this on all right well we're getting an image so that's something i guess i don't know what else is wrong with this thing so i'm perplexed at what's going on because i can see that the video input's now working why are the colors all weird i'm going to remove power from the raspberry pi entirely and let's power back up again yeah it's sort of we see a flash of the color and then it goes right to this i'm going to change this to cga 16 color mode let's see if that changes anything and here we are back on the 16 color test pattern and it's it's showing all the colors it's just weirdly tinted and i don't really understand what could possibly be happening here the weird thing is is here in the palette menu if i change it to invert it's all inverted but if i change it to monochrome we're getting the pink and the green hues it's confusing to me because i think the monochrome mode which is what we're looking at here would be the raspberry pi itself just filtering down the colors and displaying them in monochrome and it wouldn't be happening in the cpld itself so if this were a problem with the cpld like the way it was connected like i i missed pins or something or things were shorted that it wouldn't be showing this weird green and pink now i guess one way to test to see if it's the hdmi or not is i'm just gonna switch to this rgb to hdmi i'll just plug this one in and let's see if we're getting this pink and green color okay we are so this is a problem with my capture setup boy you know i think it was in a recent video where i talked about how it's really important to double check that there is no problem with the capture setup so you don't go down chasing the wrong thing on like thinking something else is wrong and honestly i could have easily thought that something was wrong with the cpld here when i think i did this correctly so i'm going to stop the capture i'm going to reset obs and my capture device and i'll be right back and we're back and take a look at that we have a perfect cga 16 color image i did not break it and all those crazy colors were due to my capture setup all right so now the test i'm gonna switch back to monochrome i think we already know this is gonna work i'll flip this toggle switch hit the reset button we know this is gonna work because we kind of saw it working already in fact we're gonna go into the menu and we're gonna pick pc hercules and there it is looking perfect i think i have a copy of windows 2.03 which is set up for hercules right now so let's run that we should get hercules graphics okay well the timing's not perfect with this particular profile and this card but there it is we have an image it would not be working at all with this cpld the bad one because we know it had a bad input pin so that was my video on the rgb to hdmi and how to do some smd soldering yourself or rather how not to do smc soldering yourself clearly i'm very inexperienced to smd soldering i do really struggle with it i get there in the end like i did with this one but i do need to do a lot more practice so that i can get better at it so i think i'm going to end this video here as i mentioned before in the video i'm going to put links in the description to buy the rgb hdmi yourself but i'm going to also link to the github repo so you can just make them yourself by downloading those gerbers and having the pcbs made at your pcb maker of choice i'm not going to say any which one to use because not a sponsored video thanks aaron for sending in the rgb hdmi in the first place and of course for sending me this replacement cpld i'm sure a lot of people got laughs at my terrible technique at soldering but hey in the end it worked for me and that's what i really wanted to have uh this this rgb hdmi working again i'd love to hear comments about my terrible technique in the description or in the comment section below so go put comments down there uh hit that subscribe button if you haven't already and uh thanks to my patrons their names are still on the side of the screen i i really thank them for their support it's just amazing and if you become a patron there's early access to videos um i have also patreon exclusive content that is for the higher tiers as well so uh yeah there is that and uh the second channel's there if you like more crts and mail call type videos it's all over there so i'd appreciate it subscribe on the second channel if you haven't already and i guess that is gonna be that so stay healthy stay safe and i will see you next time bye [Music]

Channel: Adrian's Digital Basement

Views: 49,648

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Id: atb04zJ390Q

Length: 31min 16sec (1876 seconds)

Published: Sat May 14 2022