 Well, shrob tries to fix a thing. Remember this, you never know, it could be the socketed chips, ah, there we go. So it turns out that as I press down on this area, specifically this chip, I sort of heard a crack and the machine started to work again. So I'm guessing that these sockets are probably not the best and over the course of months, maybe the temperature differential sort of, you know, shifted the chip up and it lost electrical connectivity. So when I snapped it back in, it worked again. So again, I'm suspecting these sockets are actually not that great. I might replace them with maybe higher quality sockets. Okay. Now the problem, the remaining problem really that I've been having is the fact that some of the items like the tanks don't actually appear while some other items do. Now we know that one of these DACs, or possibly both of them, I can't even remember whether I replaced both before, we know that that was bad. I think it was actually one of them and probably the X DAC. And we know that that was bad so I replaced it and that worked just fine. So the thought was, and I'm having trouble holding this light up because again I don't have any light in this room, sorry about that. So the speculation was that there was a Z DAC which controlled the intensity and maybe that was failing. Now I found these two DACs and then there's another one here called DAC which happens to be connected to the Y output as well. So I only see X out, there's a test point here for X out and Y out, there's a test point there for Y out, but I don't see Z out. So where is the intensity generated? Let's take a look at the schematic. Now what I've got here is the schematic for the vector generator board which includes the analog output. So let's see, I can focus in on this area here I suppose, okay. So this is one of the DACs right over here and the inputs are labeled DVX. So that's the X data input and hopefully you can see that. If we go ahead and look to where it ends up, if I can scroll this, it ends up here where it says X out. So this is the analog output circuitry for X. So let's see if we can find Y and here over here is Y. We can see that the inputs are DVY, so that's the digital data and the output is right over here. So if we just follow that over, we can see over here Y out. So this is the analog output for Y. Now the question is where is Z or intensity and right over there we can see Z out. So there could be something wrong with this circuitry. So let's take a closer look and we can see that actually it's interesting there is something like a DAC except it's basically handmade. So we've got these flip flops over here which actually take some of the DVX and DVY lines this goes to a multiplexer and you can see that there's also Z0, Z1 and Z2 which is kind of interesting because maybe that's Z data, I'm not quite sure. And the outputs for this multiplexer and for this flip flop go to resistors. So these resistors alternately get tied to plus five or ground and there's a resistor ladder basically that goes from plus five down to ground here. So effectively this is a digital to analog converter. So the question is, is there something wrong with this flip flop, this flip flop, these XORs, this multiplexer, this AND gate, probably these resistors are fine and probably these transistors are also fine because I do get some variation in intensity. So I think that what I'm going to do is I'm going to pull those chips from the board and then just stick them in a breadboard and test them just to make sure that they're working. Okay, so I'm looking for F8, C7, D7 and H8 on this board. So let's take a closer look at it. Okay, so the way these old tiny boards are laid out, basically the chips are all on a grid and typically with a four-layer board you've got traces running say horizontally or vertically and the traces underneath go the other way, which indeed they do and that makes routing pretty much a snap in most cases with the inner layers being power and ground. We can see over here on the side it says B and B and I think, oh that's silkscreen. Okay, I was kind of hoping that that was going to be a layer marker, but I believe this is only a two-layer board. So the columns or rows or whatever in one axis is labeled according to the letter and in another axis it's labeled according to the number. So here we have A6, B6, C6 and so on. So because we're looking for F8 that means we have to look along the F and there's F8. So I'm just going to mark that F8 so that I don't forget. We're also looking for C7 which should be here, C7, we're looking for D7 which should be right next to it and we're looking for H8. So let's see H8. So there's H8 right there. So those are the four chips that I'm going to remove and test. Now the other thing that I suppose I could look into are those transistors. And those transistors were labeled Q7 and Q9 which unfortunately doesn't do anything because those aren't numbered according to the matrix, but they're going to be somewhere around here. And in fact here I see Q7, no that's Q2 I think, okay there's another Q that's Q3 so that's not it. The output is labeled Z out, I don't actually see, ah here we go, there's Z out right over there. And we have Q9 over here and Q7 is right over here, Q8 doesn't seem to be in that circuit so there are those two transistors. Maybe there's something wrong with that, with those, but I think it's a little suspicious that some of the levels of intensity work and some of them don't. There was one other chip that I didn't mention that I didn't notice and that's this AND gate right over here so that's J9. So I'm also going to pull that out. So J9, FHJ9 that's right over there so we've got these five chips to look at. So I've got my HACCO FR300 desolder and I've marked out J9 right over here, I've got some extra solder in case I need to refresh this, which I probably will just to be able to get enough solder in there so that it sort of flows to the other side of the board and then when I suck it out it sucks out the entire thing. So let's go ahead. The ground and VCC ones, especially the ground one is most difficult to do because there is a larger, usually there's a larger bit of metal connected to ground so it's harder to heat all that up and get it going. So in any case now that I've got all the pins desoldered I'm going to wiggle them a little bit to make sure that they're all loose, seems like they're loose and then I'm going to attempt to pull it open. So J9 is this one, yes. So it does look like, there we go, I'm just doing it gently because if you're still leaving solder in there it's probably going to pull up a trace or even worse it's going to pull up the coating inside the holes which is really bad so that's pretty good. I just also want to make sure that there's a pin one designator and in this particular board it's a square pin instead of the round pin and there's no dot so that corresponds with the dot on the IC so that's pin one right over there. So now I can take this out and test it. Now instead of putting it into a breadboard what I think I'm going to do is I'm going to get out my TL866 programmer because that also has the ability to test some of these TTL chips so let's go ahead and take a look at what that looks like. So here is the TL866 interface and here's the TL866 itself. So what I should be able to do is pull up, let's see, select IC and now I should be able to search the device. I think I'm going to have to pull out the keyboard for this one. So I'm looking for a logic IC and it's going to be a device 7.4, it's an LS11, great, there it is. So I'm just going to select it and now it shows me how I'm supposed to put the chip in. So pin one, where's pin one right here. So pin one is going to go up here and I'm just going to hold that down like that and then I'm going to hit test and it tests the gates, in this case there were only three gates in here and it says that the test result is normal. So at least in theory, if we are to believe the company's methodology of testing this particular logic chip, it's gone through all the combinations and determined that this chip is okay. So that's one chip down, four to go. Okay, chip H8 is, according to this, a 25 LS399 which is the same as a 74 LS399. So let's see if it exists, 74 LS399 and we're out of luck, there is no such thing. Sure I can look for 25 LS399 but of course it's not going to be in there. So this chip we're going to have to breadboard. And the problem again with something like this that's not open source is that there just is no way of adding anything yourself. You basically have to go to the company and petition to have it added for you. Chip F8 is a 74 LS175, 74 LS175, it's there so we can test it. So let's go ahead and stick it in and run test and it says that the results are normal. So we guess that this chip F8 is okay. Okay, the next chip is a 74 LS85, that's an XOR chip. So 74 LS85 is most likely in here, 74 LS85, what? It's not, seriously? That's like the simplest chip to, wow, 74, 85, okay. If it's not in there, it's not in there. There's a 7486 which is also an XOR but okay, the 85 is not in there so that will need to be tested on a breadboard. And the final chip leading up to the analog section is chip C7 which is a 74174. So let's see if it's there, it is. We'll select it. Make sure we've got pin one in the right place. Let's see, where is pin one on this thing? I believe that's this, that's test. And it's showing that it's good. So three out of five chips are testable and they all show good so we now need to breadboard these other two chips. Now interestingly, on the schematic we see that D7 is an LS86 which is an XOR. The chip that I pulled is an LS85 and a 74 LS85 is a 4-bit magnitude comparator which is interesting because it bears no resemblance to an XOR, to a quad XOR gate. So was the problem simply that somebody put the wrong chip into this board? And the answer to that is perhaps. So I suppose what I could do is just re-solder all of the chips and replace this chip with a 74 LS86. And that presumably will have the correct function. Now before I do that I still want to check this other chip which is the 399. Now again I know it says 25 LS399, what's the date code on this? 1979. So I think at that point the 25 series from AMD was pretty much the same as the 74 series. I'm going to go look that up just to make sure 25 LS399. So the idea behind this particular chip, the 399, is that it's a combination 4-bit multiplexer and 4-bit register. So the 4-bit multiplexer lets you put 4-bits on section 1 and 4-bits on section 2 and then you've got a word select which selects between section 1 and section 2. So if word select is low it selects the first 4-bits and if word select is high it selects the second 4-bits. Then there's a clock which takes the output of that multiplexer and just clocks it into the output. So what I've got set up here is 5 volts. I've got my logic probe right here. So the idea is that what I've done is I've taken the first bit, so I've got section 1 is this blue wire going to ground and section 2 is this yellow wire going to plus. So we've got 0 and 1 and word select is this green wire which I've connected to ground and the clock is this other green wire. So if I strobe the clock it will register whatever bit is being selected. So in this particular case I'm selecting this bit right over here. So the output should be 0 when I clock it. So let's go ahead and measure, this is the input of the first section bit, low, and the input of the second one is high. So currently the output is high and the word select is low. So if I strobe the clock, let's see what happens to the output, it's low. So if I strobe the clock again it should remain low and if I change word select to high it's going to select the other bit. But of course I haven't clocked it so the output is still low and when I clock it it's going to clock the other bit which is high. So that means that this chip is working at least for the first bit. So all I have to do is check the other bit and then I can say that this chip works. Okay so all the bits on that chip were checked and they all work fine. So that's the 399 that works. The LS11 AND gate that works, the 175 flip-flop that works, the 174 flip-flop that works, and the 86 is the one that we were not able to determine works because it was an 85 on the board. So I think all that's really left to do is to replace all the chips, including the 86 with the correct one, and then plug the board in and see what happens. Okay so I scrounged through my parts bin and I found a 74 LS86 that I pulled from some random circuit board. So of course I need to test it to make sure that it works. So let's go ahead and search for 7486 and there it is. It's going to be the first one. So let me make sure that I'm putting this in the right way and it goes in like this. And test. And it's showing that this is a good chip so I can take this and put this into the board. Okay, with that chip replaced I just want to check out this ROM right here and specifically the socket to make sure that there's nothing weird going on with this thing. So oh well that's one of these kinds of sockets. So those are the wipers in there and these are the spacers. They just sit right on top and then you stick the chip in right there. So I'm going to examine the chip for any signs of corrosion. I don't see any and I'm going to examine this for any signs of corrosion. I don't see any. I as a rule really don't like these kinds of sockets because well they're weird and I just don't like them but apparently they're okay. So I am just going to whack the chip back in pretty firmly. I may as well do the same thing for the one right next to it, right? So there's that, there's that, that's done, place it in, give it a good press as well. Press some of these other chips in. They seem pretty, pretty rock solid. So let's go ahead and put this board back in the machine and fire it up and see what happens. Okay so the board is back in and let's just plug the machine in and give it a shot. Okay I'm hearing sounds which is good and let's take a look. Okay we've got some video output now coming. Great that looks pretty good. I actually see the radar, I don't know if you can see it, it's kind of it's kind of hard to see with the with the glare. Let me go to the other side maybe, I don't know if you can see the radar is actually spinning which it didn't do before. So I think and in fact we've got some blinking up here, let's see, it's not blinking anymore but that wasn't doing that before. So let me go ahead and open up the coin slot and get it started. Okay here we go, radar it's straight ahead, I thought the tank was straight ahead, I think there is a tank. Well I guess what I'm going to do is I'm going to play it a little more and see if I can actually see the tank up here and then report back. Okay well I did see the tank, the tank still seemed a little bit dim to me but you know at least I could see it. So I guess I count this as a success. So I guess that's it, so the reason that this thing wasn't working was that there was the wrong chip installed. A7486 is an XOR, not a7485 so I don't know if you know maybe they were looking through their chips and they saw an 85 and they thought it was an 86 because the 5 looked like a 6, I don't know. Anyway, that's about it, I hope you enjoyed and remember that a part of troubleshooting is hitting that like button. See ya.