Fixing a couple arcade CRT boards for David Murray

well hello everyone and welcome back to adrian's digital basement 2. what you see on the bench here are two crt driver boards you know i always wonder what they're actually called but like this is the board that would be inside your monitor that actually runs your monitor like it generates the high voltage for the crt it does all the deflection video signal amplification cathode drive all that kind of stuff anyways the reason why we have two almost identical ones here along with the deflection yoke is that these belong to david murray yes the 8-bit guy he is working on a cocktail arcade cabinet that uses a little black and white crt in it i forgot which game it is either like space invaders or or something like that and he was having trouble with one of these boards and from my recollection he has two of these arcade cabinets and that's why we have two boards here and one has a working monitor inside the cabinet where you have a good picture and the other one doesn't now this is the one he's been having a whole lot of problems with i've gone ahead and marked it as a number two right there just to differentiate it from the number one which is the the working one now over the last few months i've given david a couple tips and pointers on troubleshooting uh the non-working board which is this one right here and he's even gone as far as to remove this board from the arcade cabinet and take it to an arcade or a monitor repair person in the dallas fort worth area just looking at this board i can tell that it has been recapped so if we compare it to this one here the caps are original on this board on the right but on the left here they're recapped and otherwise everything seems to be intact now david reported that this thing had a picture like it generated a picture but it was really not looking good it was like very bowed in and the picture was rolling and no matter how you adjusted these controls on here you could never get it to actually lock on now my advice to anyone who's working on a board like this trying to repair it especially if you don't have schematics is to go over the board and check all the semiconductors using your multimeter to see if they are shorted so diodes is a good example and also check your passive components like your resistors to make sure none are open because that's not an unusual failure mode of a resistor to just go open entirely and you can imagine this the video signal and this uses composite video by the way it comes into the board and there will be a circuit that removes the sync signals from the video the composite video and sends it to the appropriate sections of the board so because it's had a rolling vertical sync issue it could be as something as simple as an open resistor between the video section where it's stripping that sync signal out and the vertical deflection circuit in this monitor now david had gone over every component on this board like i had mentioned and everything seemed to check out and obviously it's been recapped as well which i kind of recall him saying that that fixed some of the issues like the boeing picture was now corrected but the picture continued to roll so when he brought this to the repairman the guy who is a experienced guy he didn't actually test anything but what he did tell david was that this one ic down here that's mounted on this heatsink which is like a combo ic that sort of does a bunch of things that's a my crappy explanation the repairman said that that was the problem so this is the circuit in question and is the tv vertical deflection system so it's kind of a single circuit that does it all vertical synchronization oscillator sawtooth shaper vertical output circuit clamping circuit for the blanking pulse and temperature compensation as well just to make sure that you have a really good vertical lock so david on the phone told me that he desoldered this chip from here and he actually went online and found a source of some new ones and here is one of the new ones right here and it's actually a samsung part like the one we were just looking at and the original one is this one right here which you can see is an nec part and you can tell that i mean i don't know what's going on here with the heatsink or like the part that goes on the heatsink is very blackened now i don't think that's necessarily burned i think this is some kind of corrosion and the problem is as you can see this metal tab actually goes inside the package and the corrosion can creep along the metal and actually break the hermetic seal of the package which can cause it to fail over time now we can tell from david's description of this part that it was partially working and that's because this generates the vertical deflection itself but it also handles the synchronization of the vertical sync to the video signal and while it wasn't locking on to the vertical sync from the video signal it was generating the deflection because you had a full picture you did not just have a line across the screen so what happened is after david replaced this part in here he said he powered it up and it did not work at all and he said immediately he could smell a burning smell i don't remember if he said there was any smoke coming from it but he unplugged it turned it off so he gave me a call he asked me if i could take a look at it for him because he was just at the end of his rope he had spent so many hours trying to get this board working it was just not having any success then i said sure no problem so i asked them to send the working board along with the non-working board so i could compare them if some other component on here is bad and i also asked him to send the deflection yoke off of one of these boards because you cannot run these without this this is an integral component of the entire circuit the horizontal deflection circuit on a crt with in conjunction with the flyback and the deflection yoke is a tuned circuit and you need to have a deflection yoke that's basically the right one for the monitor or things may not work properly there's probably certain amount of leeway you can get with the deflection yoke and like i might have had the right one in the basement here but it was a lot easier if you just pop this off the monitor sent it to me so i could test a lot easier now for powering this up this thing has an integrated power supply which is this part of the circuit right here you can kind of tell there's a giant heatsink here large power resistor we can see four diodes right there which is a bridge rectifier plus there's a lot of discoloration on the board from heat from running for a long time so because there's a bridge rectifier that implies that this takes probably natively an ac input signal just for simplicity the original power supply inside the arcade cabinet would have been a big transformer with some different taps on it it's just like the commodore pet to be honest it uses a very similar setup so it just needs a dc input but of course it has a facility to take the ac signal and regulate it down to the b plus voltage and i can see there's a potentiometer right there for adjusting the b plus so let's get to some troubleshooting i'm just going to move the working one out of the way here let's just take a quick quick look at this board see if anything has gone catastrophically wrong that is obvious okay so let's compare these two parts here so the original one here is the nec pc1031h1 and uh there's the samsung part that he got as a replacement now i haven't looked up the data sheet for this original nec chip here let me just quickly do that just to double check that it is actually a drop-in replacement all right some data sheet checking there and yes absolutely they do appear to be the same pin out looks the same everything looks compatible between these two parts now from a troubleshooting perspective david said that before you replace that part this board was working except for the vertical sync issue that i already described so the most logical thing to assume is that something is wrong inside this section like maybe the part he installed is the the wrong part maybe there's a short circuit back here when i did the de-soldering and re-soldering so let me just do a quick inspection here yeah i'm not seeing anything wrong here i don't see any immediate shorts everything looks completely fine here i can definitely see where the caps have been reinstalled but um nothing looks out of the ordinary here incidentally you see that black wire that's on there the other board has it as well and oh yes by the way there's a corner missing on the original board apparently that was broken already in the cabinet so this green wire here was installed to replace the broken ground plane that goes around the corner here but it doesn't look like any other trace no other trace was affected it's just this ground that runs around the edge of the board so that's a perfectly acceptable fix all right now let's see looking at the top side here let's try to move this stuff does anything look out of the ordinary okay i am seeing an issue so this is the original part does any c part there you can see is pin one it has a little dot it has a stripe painted on the package as well now the samsung one here which looks like it might be rebadged because that looks like pretty nice shiny laser etched writing on there as opposed to the printing that would probably have been on there so who knows this thing came from i think ebay or aliexpress so it's probably been rebadged but the original stripe that might have been on there is gone not to mention there's no particular dot so what is pin one exactly well in absence of a stripe or a dot i'm going to say that the beveled edge which you can see it's far more beveled on the left side than on the right side i'm going to say that that is pin one so that means the way that these are sitting right here is basically you know the same orientation when you're looking at the label the pin one is going to be on the left now it's probably going to be very difficult to see but there's actually a pin one silk screen marking on the pcb there and it is to my right i think i'm going to struggle to get the focus right but you can see there's the samsung part you can see the writing is facing us and that notch is towards the left on the picture but look at the silk screen marking there you see it says 10 and on the other side there is a notch and a 1 printed on the silk screen marking which would indicate that that part is in backwards now i can't say for sure if having that in backwards was going to damage that part or not but the problem is is looking at the pin outs on the datasheet for that part it connects directly to the flyback which is connected to this connector right there on the board and hopefully that didn't send a ton of current into the flyback which might have potentially caused some damage to the flyback hopefully not hopefully that's a robust part and all that got damaged was that so let me remove that part from this board and let's see if this thing can work with this this new replacement part okay there it is i just take it out with the heatsink because these caps right here are in the way of unscrewing this part from the heatsink so let's uh let's get that off there it looks like david installed a little bit of thermal compound on that one let's put the other one on but we're going to flip it around let's put this back in oh getting compound everywhere gross all right there it is with the part reversed in its positioning you can see right there on the pcb there is the very clear pin one marking and that fits back in the board perfectly so i'll just quickly re-solder all of the points back here now the reason why i'm using my desoldering iron to actually solder this back together because it has a very high thermal mass so for these heatsink connections here it's really easy to use this as opposed to my um my little pine sill soldering iron that thing is not well suited for things with a lot of thermal mass all right there we go it's pretty warm because uh like i said i put a lot of heat into it and now we can see that the notch is over here on this side facing towards the one on the pcb now i'm curious with these two let me grab the multimeter you know i should have done this before i put the new one back in but let's just see if we see short circuits here on this uh the one that goes in backwards i'm going to put the multimeter here on diode check and let's just see what we see here doesn't appear to be dead shorted at least none of the pins that i've been touching here and i do see diode drops and stuff like that across the various pins all right well anyways that looks okay let's just see how this one looks here i think pin two is the voltage input pin yeah it's very similar i see diode drops like between pin 2 pin 4 i see 0.75 and on the samsung one pin 2 and 4 0.76 yeah so very similar so quite possibly this one that was in backwards is probably fine but um you know better safe than sorry because we have another one let's see if that works all right for testing i have this phillips magnavox whatever amber 12-inch monitor it's gonna have a crt that's a little dim but it should work perfectly for testing out uh with this board i didn't ask david to send the original because that would have been heavy and potential breakage and stuff like that so better off just uh you know sending the boards and the deflection yoke like i asked and then we'll just connect this thing all up it's a pretty long high voltage cable here and that's because most likely the crt is mounted in the cabinet in a certain way where this board is like off to the side like mounted on the wood or whatever so that's why you have plenty of length look at all these cables here are quite long we're not quite ready for powering up because there is a ground lug on the crt connector it is right here and that would have had a black wire or a cable that ran from this over to the band here or the dag ground or whatever was on the original crt so i do need to get a clip lead or something i'm going to clip right here which is actually where the original monitor electronics connected to there's a little terminal right there i'm going to connect from there to there now i will add that sometimes these boards actually have a connection on them and you'll see like a similar metal post that would go from here also to the ground but i'm not i'm not actually seeing that oh wait i know right here crt earth so there's a second connection i have to make from there also to this point now please if you're ever working on a crt and please only do it actually if you know what you're doing around these high voltages this is probably like 10 to 12 000 volts right here while operating do not ever operate it without these ground leads connected these absolutely have to be connected for safety from my understanding if you don't have these ground leads connected and you power the monitor up the crt outside this mat surface here which is the dag can end up at a very high voltage potential which can cause arcing between that and the electronics itself which can cause components to be blown out or whatever so really do not ever operate it without those hooked up for powering up this monitor i'm going to use my dc power supply here the reason why dc works on ac is because the monitors doesn't need any negative voltages it just quickly converts or rectifies the ac into dc and then it uses a voltage regulator to create its b plus so all you need to do is give it dc voltage and of course the polarity it does not matter because it has a rectifier so whatever whichever direction you hook it up it's going to send the correct polarity into the voltage regulator and i'll be able to monitor the current draw as well on here and the only thing i do not know is what voltage the monitor is expecting so what i'm probably going to do is start at a sensible voltage like around 12 or 14 volts and then if it's not running then i'll go up little by little keeping a close eye on the current draw and as i had mentioned there's a terminal right here all this discoloration is that's the ac input so i just need to hook my two test leads up to those connections right there and unfortunately these clip leads these are crap and they're not working i'm gonna have to use something else okay much nicer i found some to plug into power supply that are alligator clips or crocodile clips as they're called in some places and to initially see if this monitor is working i'm going to use this app here called spectroid which is just a free app in the android app store which is super useful for testing monitors the reason why is at least on my pixel 6 here it is able to let me zoom in over here it's able to go up to about 25 000 hertz with the built-in microphones on the on the phone and you can basically tell if the monitor is running because it has an internal oscillator that this is an ntsc monitor should run about 15.7 kilohertz well same with the power one as well which will create a big peak which will be very visible to us to know if this monitor is actually running now that 15 kilohertz sound is what you can hear if you have really good ears but i'm in my late 40s and even though i protect my hearing with plugs at concerts and things like that i can't really hear it very well anymore it used to be very loud as a kid so i always rely on this app to see if a monitor is working and it's really useful because like a commodore pet it runs at 22 kilohertz which i don't think many people could hear even if you have really good hearing but yet it shows up clear as day on here so we'll keep that running right here in fact i'll just zoom up to the upper ranges so there we go it's ten thousand and twenty thousand so we should see a peak in there when this thing turns on and i guess i'll position the camera like this so if any smoke is let out which i hope it's not please no then uh we'll see it alright so i'm turning the power supply on i'm starting at 14 volts and i'm gonna start uh let's see why don't we start at 500 and well 60 milliamps that's that's enough and i know you probably can't even see these numbers because the multiplexing and the camera is just it looks bad it's 14 volts 560 milliamps and i'll reposition the camera before i turn this on and let's see what happens um well okay i think it's running so what happened just there is the power supply um it went to current limiting mode for a second because the capacitors are charging but then it actually settled back at 14 volts at about 400 and something milliamps and i saw a peak on the phone so let's try that again now i paused it it seems to be running at about 14 kilohertz right now so that's too low but there's going to be a horizontal hold which is this control right here and i'm going to hit play again and watch this i'm going to adjust this and it's going to move that see let's zoom in a little bit so see the purple line there when i turn this control it moves back and forth now the thing is this monitor is currently running in free mode or free oscillator mode so there's no video signal going into this for it to even lock onto it's generating its own oscillations so what i need to do is get a video signal into this thing and then let's see if it locks in because 14 kilohertz or whatever that's not good enough for an ntsc signal well anyways let me get a let me get a test signal but there was no smoke no weird noises i could hear the sound that the monitor was making i'm assuming we had high voltage um why don't i test that before i even bother with the video signal okay we have way insufficient voltage here we're getting 2000 volts that is not enough okay that is interesting um that may well be because there is just not enough voltage here so i'm going to turn this up okay i've turned it up to 16 volts no we're still at two kilovolts so that is not really enough for a working monitor now i have to wonder why is the high voltage so low right now and the monitor still is running it's around 14 kilohertz that's just not fast enough now the part we changed was strictly a vertical oscillator part had nothing to do with the horizontal oscillator whatsoever and the horizontal oscillator is what generates the high voltage on a monitor like this all right i've repositioned it here so we can see the front of the crt i have the power everything is connected video signal from my pattern generator is connected in here and it's on let's turn the monitor on okay we're getting what we expect 450 milliamps at 14 volts now when i raised the voltage it didn't seem to change anything i could see the oscillator running on my phone it wasn't changing the frequency or anything like that all right so there is a little bit of an image visible it's like that big right here in this little section and if we turn this off there we go we do get a dot there and we turn it on and it takes a while and it's the reason why it's all turned is because of course the deflection yoke is incorrect here let's turn this if i turn the controls it does have an effect it looks like there's some deflection actually happening this big here all these controls do anything nothing really when you see that on the camera let's see yes you do see you just see that let's try to create a little shade over the crt now let me just try to adjust the voltage a little bit on here i'm going to raise it up all right it's having a little bit of an effect isn't it well certainly seems to be running better so looking at these caps on the good board they're 35 volt caps and i'm giving this thing 14 volts when it goes through the diodes that's only going to turn into about 12 volts you know because there's voltage drop is going through two diodes before it gets to the regulator not to mention then there's regular circuit so there's even more voltage drop so it's quite possible the 14 volts dc that's going here is just not enough and definitely that seemed to be the case as i turned it up we ended up getting a much brighter picture and i started to actually see the crosshatch pattern that i am sending into this thing so i'm going to set this for one amp and i'm going to send i'm going to raise this up let's see it's at 19 volts certainly looking better but i don't really know let's uh let me show you what's on the screen right now look we have something that is much more akin to an image all right vertical size vertical linearity but the horizontal holes absolutely not locking on and the phone confirms it's running at about 14.6 kilohertz at what we see here and the range is just not enough with the control turned all the way to one side the phone indicates it's running at 15 kilohertz so it's getting close and the image is certainly getting better but unfortunately when i turn the deflection yoke to the correct orientation so the picture is correctly aligned here it's still very bowed in on the sides which would kind of indicate that whatever problem with the bowing existed on this board is still happening unfortunately all right i'm going to kill the power on this bloop there goes let me hook up the other one and let's just see if they act any different all right the working board is connected i've changed the power supply back down to 15 volts we'll start there let's power this up okay this is only going at 300 um milliamp all right it's running at 15.3 kilohertz now although there's no image let me turn the brightness into contrast all the way up yeah nothing all right it's now running at 16.1 kilohertz so there's a lot more adjustability in the in the range here there now i'd have it at 15.7 but why is there no image let's power this off we don't get anything on here let me double check what i have going on here earth connections connected the video signal is definitely connected neck boards on grounds connected yeah everything looks to be correct let's do the old high voltage probe here let's see if we're getting a more appropriate high voltage all right and this thing is running at even lower voltage it's at 500 volts that would really explain why we don't have a picture at all i mean 2000 volts that's kind of on the fringe of working but 500 volts i think i saw between 1000 and 500 volts not enough all right so the question is this thing is off right now why is this thing running at the right frequency so at 15.7 kilohertz you know with the horizontal control but it's generating almost no high voltage the only thing i can think is that the deflection yoke is part of the problem now i mentioned this earlier the deflection yoke is a tuned part of the circuit that definitely is necessary for high voltage to be generated if i unplug the deflection yoke and i turn on the monitor you're going to get a little bit of high voltage but barely any because like i say said it's a big inductor and it's necessary for proper operation the other thing i noticed is that even at 20 volts this particular monitor board was only pulling about 500 milliamps and the other one was close to 1 amp not having the original cabinet with the original transformer hooked up to these boards means i don't really know what should be running now 20 volts at 1 amp if that's what was really going into the other board is about 20 watts which seems a little bit high i don't think i think that's a little bit more than it should be although when you have this type of voltage regulator that's basically bleeding off a bunch of the voltage into this heat sink in that case that doesn't seem that bad i'm gonna have to do a little bit of thinking a little bit of reading and i'll be right back we'll see if i can figure something out with these boards well it's the next day and uh let me turn on the power supply up here let's see what happens on the screen would you look at that we have if i switch this a good looking pattern it's actually totally working and yes indeed this one that's right here is the one that had the ic that was backwards this is the one here that was the working one so let me grab a pointing stick let's take a look at what i did to make this thing work i'm going to use the other board here to point to things because it'll be a little bit easier so as i mentioned previously this here is the power supply for the board and the ac voltage comes in on these two pins and it gets rectified then it goes through this resistor here and then there's a little bit of a voltage regulator happening here so one thing i actually did on this board is i connected the dc power supply which is still these two wires taped to the top of the monitor here and i put them directly into the board bypassing the bridge rectifier now why did i do that you might ask well because obviously when you have an ac waveform going into the the power input here these four rectifiers are sharing the load as the ac waveform goes through its i don't know up and down so let's just call it well obviously when i'm putting dc into it it's putting more load on i think two of the diodes or is it just one of the diodes actually looking at the bottom of the board allow me to figure out the way it all works at least from a power supply perspective the bridge rectifier gives you a ground and a positive voltage right and the positive voltage then goes through that fuse which we saw right here and then it goes through these capacitors right here which are 35 volt capacitors so that's sort of like the uh the bulk capacitance for that rectified ac waveform and then it goes through this resistor there's a transistor and some other components there and that is actually creating the b plus so just clipping onto the fuse right here still keeps the fuse in play and also onto the heatsink here just allows me to just bypass that so that's what i've gone ahead and done right here and you can see the ground lead is connected right there and the positive lead is like i said connected to the fuse bypassing the bridge rectifier as i did here really didn't have much to do with actually getting this board working the biggest problem was the horizontal oscillator which we saw on my phone was running too slowly consequently because the oscillator was running too slowly the high voltage that was being generated by the flyback was far too low but in addition the flyback on a monitor like this actually generates several other voltage rails that are used by different parts of this circuit and with the oscillator running too slowly all of those voltage rails were really really too low which explains exactly why the picture on here looks so screwed up with the bowing and all those other issues back on this board again the horizontal hold control which adjusts the oscillator is this one here and i looked on the bottom of the board and i found that it goes over to this section of the board which makes sense because this little circuit here is the video amplification circuit has nothing to do with horizontal hold so the traces went over here well looking at the way this was set up it looked like this inductor here this variable inductor was in play now i wasn't sure if anyone had adjusted that so i took a tool which is actually the one i'm holding right here and i started adjusting that and while looking at my phone i could see that this absolutely had an effect on the frequency of the oscillator and just turning that several turns actually got it running at the right frequency and as i was getting closer to 15.7 kilohertz the picture was getting brighter and brighter as the high voltage came up in addition those geometry issues that we were seeing were going away as well and now it just looks like this it's basically completely working perfectly incidentally from a power supply perspective i'm giving it 18 volts at about 1.5 amps i have the current limit set to that it's drawing about 1.2 to 1.1 amps so it's running at about 18 or 19 watts now i know the 18 volts is the correct dc voltage that this thing needs to run in before it goes through the regulator so remember the regulator needs to drop the voltage down to that regulated b plus voltage the reason why i know it's 18 volts because that is the perfect voltage where the geometry is looking good any lower it starts to have issues and i'll demonstrate here so actually 17 volts looks okay okay actually 16 volts still looks okay but 15 volts it starts to freak out and as i drop it down notice it starts to get dimmer and have all sorts of issues here so if we go back up to 16 volts okay so actually 16 volts 16 17 volts all works but if i go up any higher than that notice nothing really changes anymore and that's because that voltage regulator is doing its job and it's keeping that b plus at the correct voltage for all the electronics in this board now keep in mind i am bypassing this bridge rectifier on here so there will be some voltage drop in there so if i had the dc connected to the two pins here i would probably need a couple extra volts on the power supply for it to work and if you have ac hooked up to this i would imagine 15 16 volts is probably the right voltage under load that is for this thing to do its job i called david murray and i asked him about that adjustable coil there to ask him if he had twiddled with that to uh that would have resulted in that frequency being off and actually he did confirm that on the non-working board which was this one he did adjust that if you are troubleshooting a crt and like we're seeing those weird symptoms there then using your phone with that spectrum analyzer app is an amazing way to tell if you're on frequency or not i mean that that was extremely useful i didn't even have to hook up the oscilloscope or anything to do any testing okay so the broken board is completely working now had two problems the ic was in backwards and also the oscillator was quite far off frequency oh there's something else that's kind of funny when david swapped out that chip he was doing it in front of his brother who runs the geek pub youtube channel apparently his brother said hey david you have that chip in wrong or backwards david's like nah that's not possible this is definitely the right way it goes and uh well turned out that it was wrong well david said when he was swapping it out he was so sure about the orientation of the ic because he said he compared the side that the writing was on to this board right here well currently the samsung part that's in there the writing is facing me so pin one is over to the left and unfortunately with this board right here it's actually the same i can't read the brand of the ic that's in here it just says japan but i can see the stripe for pin one and the dot towards the left so i think david just might have been a little bit confused and i don't know why but he put that one in backwards luckily no harm was done the board is now working properly now let's take a look at this one because earlier when i tried it it didn't seem to work there doesn't appear to be any kind of bleed resistor on these so they do maintain some amount of high voltage when you turn them off incidentally now that this one is working properly it seems to generate about 11 000 volts okay we're ready to go with the uh the working board i have the spectroid up here and zoomed in right on the part of the spectrum that we are going to need to look at and i have the power supply up there set to 17 volts 1.5 amps i hooked up bypassing the rectifier as i did on the other one let me just double check i got the ground lead on the board ground lead on there high voltage connected the deflection yoke is connected everything looks ready to go here we go okay oh wait it's working as you can see it came right up so i am not totally sure what was going wrong now you can see it 15.750 kilohertz what a very useful tool any oh what was that did you see that i think we got a bad connection somewhere when i banged on the table it was kind of screwing up i'm going to use this plastic tool here and kind of poke things see if anything acts up here okay something's going on there when i hit the board yeah we're getting deflection changes well now it's really i wonder what's going on i wonder if there's like a cold solder joint on the bottom here just going to check my connections are all solid here yeah i'm not really sure everything looks totally fine let's power this back up again yeah okay i think i'm going to power this off the deflection is looking weird i'm going to check the solder joints on the bottom of this thing it does look like some dodgy solder joints on some of these pots here and when i poked on this one here the picture kind of changed quite a bit so let's just reflow all the stuff that looks a little dodgy all right i think i see the problem there's a crack in the pcb right here goes from that pin on the flyback to that screw terminal so kind of like how this corner was broken off i think the same thing is happening here and it might be breaking this ground plane right here there's also this pin right here which this trace here looks like it's breaking so what i'm gonna do it's funny i just recently fixed that monitor the commodore 1084. i'm going to grab the pen here i'm going to scrape away some of that solder mask across this and i'm just going to try to maybe solder some metal wires across it solid core wires just to reconnect that stuff i'm going to wear a glove here because i haven't been doing that and i know that this fiberglass stuff can be kind of irritating to your skin yeah that's broken right there you know i got to say i'm not really having any luck with this ideally a dremel or something to to really clean that up i think what i'm going to do is i'm just going to solder a thick wire between here and there for that one and this is just the ground plane so between there and any of this other stuff here on the ground plane sort of similar to what happened in this corner here all right there we go i installed a few more barge wires i installed this wire right here there's a little jumper link right there that one and that one the main crack seems to go just here and stop at that pin but it might be moving over here too i'm not sure it might be like a scratch on the board or not or a crack i couldn't quite tell so what i did is i just um added this solid core wire there as well so in case that is a dodgy connection then it should stay solidly connected i don't see any other issues when i talk to david i'm going to tell him that he really needs to reinforce this board at least maybe 3d print something that goes around the entire bottom that way it's not just held up by these screws anymore but is supported on the entire weight in fact something that probably supports the board here too that's made out of plastic of course um just where the flyback is would probably be good because knowing arcade cabinets they're probably pushed around like on their wheels casters and there a lot of shock is gonna happen so maybe rubber mounting the board something like that but yeah this type of pcb material is just very fragile fragile clearly this one has experienced some shock so i'm going to go on a limb and say that that problem we saw earlier where there was no picture and no high voltage was very specifically caused by the cracks in the pcb over by the flyback there so let's reconnect to the cables here let's give this thing one more test should be good to go at this point all right uh let's see current has settled ah there we go this is just turned this doesn't look so great i'd say that this potentiometer here for what is this a vertical linearity oh it's probably bad let me just drop a little deoxide on there here's my deoxit dropper these are the old oh you know what i shouldn't use deoxit right this is the carbon type of pots or deoxy can actually damage them so i'm gonna use the qd cleaner here this stuff is uh move my phone out of the way i don't want that to be hit by this stuff let's just get these pots with this stuff okay let's try now there we go oh yeah that's working way better now let's just turn the alignment of the yoke geometry on this one not the best so this is vertical hold here which is obviously working properly we have vertical size and we have linearity i'm not sure where this deflection you came from which board but you see we can adjust the picture up and down and yeah it's looking pretty good it's a little curved at the top this one hasn't been recapped so it's possible that these caps are slightly problematic oh that's a scratchy pot too that's the horizontal oscillator control let me just spritz that yep much better no more scratchiness that's looking pretty good let's hit this board a little bit there's a little bit of something going on here on this edge let's see what's happening here is this a bad loose connection i think it's like a uh i don't know yeah that's let's see if it's still doing it no no stop now i think that might have been a slightly dodgy connection on the yield connector here probably is a little dirty okay cool well um that is fixed as well so broken traces that is surely why we had no picture earlier uh when i first tried this up and it was just giving us like 500 volts clearly the flyback wasn't i think one of those traces that was broken was probably going to the deflection yoke because without the deflection yoke you're going to see like 500 to 1000 volts maximum out of this so i bet you that wasn't connected anymore to the flyback so it wasn't able to get create that resonance and all that tuning that's needed for the high voltage to work and there we go two repaired arcade boards for david's arcade machines he will have a video on his channel soon talking about this stuff well i don't know when it's going to come out but he told me he's been working on it forever and the fact that these weren't working well at least that one wasn't working was really throwing him for a loop so as soon as he gets these back from me he'll be able to finally finish his video so if you enjoyed this video thumbs up if you didn't you know what to do the second channel subscribe all that you know usual stuff thanks my patrons and yeah that's gonna be that stay healthy stay safe i will see you next time bye

Channel: Adrian's Digital Basement ][

Views: 64,348

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Id: 9QiSXeCf9tw

Length: 41min 42sec (2502 seconds)

Published: Tue Aug 16 2022