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CrossBow

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  1. CrossBow

    A new 7800 project... nothing major...

    By CrossBow,


    Service Work Stories
    PCBs are designed, created, and already shipped headed my way as are a few components for me to populate the boards. I will go into more details once I have my PCBs and have been able to test and check out if my idea works the way I've planned or not. In the meantime, here is a pic of the PCB. If you are familiar with the UAV layout and install process needed for the 7800, then this should be obvious on what it is.

    While what you see here is rather large, in reality it is only about the size of the UAV board so roughly 24mm tall and about 33mm wide. Pretty small.
     
  2. CrossBow
    A 7800 I worked on over a week ago was sent to me for a 'No Power On' condition. There are many reasons for this and I have found over the years two main issues. First is simply a faulty power supply adapter. Given these things are nearly 40 years old it isn't unreasonable to think that the PSUs are nearing their end of life. In fact I've had another client send back their 7800 when it started to develop power on/off issues and found nothing wrong when they were sent back. Sure enough, it was due to a fault power supply. So when speaking to this new client about their 7800, I suggested making sure the PSU was good and if they wanted to try something quick for not too much money, to get a replacement from Best Electronics. So they did...
    However, it didn't resolve the issue 😞 . At that point it was decided to send the 7800 to me so that I could look into the issue in more detail. I honestly figured at that point it was either a faulty power switch (Because those original OEM switches are kinda crappy and get corroded internally). Or perhaps a bad 4013 flip flop IC that controls the logic for power on/off status to the system. It is basically the same circuit the 5200 uses with a few less passive components in the mix.
    So the 7800 arrived and I first tested it with my PSUs. Sure enough... no power and no amount of massaging the power button would change it either. Took the cover apart and started to look at stuff. First thing I do is short the power switch to absolutely rule it out of the mix. No dice... hmmm. I then started to check for different things off the 4013 IC. Most things checked out, but the return signal from the system back to the 4013 to indicate power status didn't seem to have any activity. According to the 7800 troubleshooting flowchart, it states to replace the 4013 IC at that point. So I removed the original 4013, installed a socket and plugged a new 4013 into place. 
    No dice... still no power. I then started to check further along and found that no input voltage was getting sent to the 7805 voltage regulator. The input voltage switching is controlled by both the 4013 and another power transistor (MJE201). The 201 stands proudly on the edge of the mainboard between the heatsink of the voltage regulator and the power input port. Sure enough when checking the readings from it, I found it wasn't switching on to send the input voltage to the original VR.
    To test this I then hooked up my bench power supply, set it to 10v and connected it directly to the input pin of the VR and to ground on the main board. Turned on my bench supply and the 7800 came to life. So I knew I had the right component.
    So... what was the point of all of this text?! Simple... to document the basic troubleshooting process I went through to identify the problem component. Now, the 201s aren't exactly made anymore but there are equivalents. However, I don't have any of these modern replacements on hand (Because this is only the 2nd time I've had a 201 go bad ever). So I took the 201 off a donor parts 7800 board and installed that. The clients 7800 lived again. 
    I also ended up replacing the original VR with a newer 2A output rated one and installed new capacitors and new front panel switches for good measure. Client figured I was already inside the system and for about $10 in parts...why not?
    Mainboard picture. New capacitors, new front panel switches, new voltage regulator and replacement MJE201 just to the right of the heatsink near the power plug.

     
    Donkey Kong PK is a good game to use for burn-in testing as it has a demo mode and uses the pokey chip for new enhanced audio. So it is a good test for everything. And... tons of fun to play too!

     
    This 7800 was cleaned up and is already back in the hands of its owner and ready to be enjoyed and played for many more years to come!

  3. CrossBow
    Here is an issue that I've seen before in one form or another and I thought I would talk about it here while working on a earlier era 2600 heavy sixer last night. The system was sent in for refurbishment. In this case that is all the original electrolytic capacitors being replaced out, new DC power jack, new voltage regulator etc. But a problem was reported and confirmed during testing of the console.
    What was the issue? In this case it was an issue with the player 2 controls. Specifically, player 2's fire button was always registering as being pressed. Easiest game to demonstrate this was Air-Sea Battle as when you reset the game to start, player 2 is constantly shooting the entire time even without a controller plugged in. Part of the refurbishment process is changing some components near the joystick port per an Atari service bulletin from back in the day for ESD protection.
    It is the last part in regards to the ESD protection that needs focus, because it was found that static electricity from players hands when inserting and unplugging the joysticks, would cause static discharge to the joystick pins. Luckily for most this is pretty harmless but one component in particular on the heavy sixers is very sensitive to this and prompted Atari to create the service bulletin to address it.
    The specific component to be checked is labeled as A203 on the main board. While the original IC chip has an Atari PN labeled on it, the chip is a bog standard 4050 IC that was common on the 8-bit line, 5200, some 2600s and lots of other devices. So common in fact, that the 4050s are still made today. However, on the heavy sixers, the trigger lines (Fire button) goes through the 4050 chip and in turn relayed back to the TIA. The most basic way it works is that +5v is always present on pin 6 of the joystick port which is the trigger line for each controller. When you press the fire button, you ground this connection causing the +5 to drop to near 0. This is what is referred to as going from Hi to Lo and is how the system knows when controller inputs are being used. In the case of this 2600, pin 6 from joystick port 2 was not showing any voltage from it and as a result, this was being interpreted by the logic in the system as if the fire button was already being pressed down. The basic troubleshoot process here is to verify the traces from pin 6 back to pin 7 on the 4050 IC chip and ensure there are no broken traces. If that checks out, then the culprit is down to two component at that point being The 4050 IC or the TIA itself. 
    Anyway, per the service manual flow charts and because I found no issues with the traces on the board, I removed the original 4050 IC chip, installed a socket and new 4050. Let it burn in test for several hours last night and verified that player 2 is now behaving properly and not so short tempered.
    So in this case it was an easy fix but also a warning on why ESD was and still is an issue to this day. In this case, an errant spark from someones hand in the past damaged something internally in the 4050 IC causing it to no longer function properly in regards to the player 2 fire button.
    Replacement 4050 IC installed in new socket however, I did eventually replace this 4050 out also with a new Ti branded one as this on would cause graphic visual issues after a while.
     

     
    Just a pic showing the soldering work after installing the new socket and 4050 IC chip.
     

     
    Here is one of the new cap+diode component fixes applied to port 2 at location C237 as stated in the Atari service bulletins. There is another component set like this on the player 1 port C236 location as well.

     
  4. CrossBow

    The curse of the Saturn horizontal lines!

    By CrossBow,


    Service Work Stories
    This story starts a few years ago when I powered on my model 1 Sega Saturn and played a game for a bit and then powered the console off and back on to switch to a different game. But to my horror I discovered some strange horizontal white lines scrolling upwards on the screen? I powered the console off/on again and the lines were still there only now there were a lot more of them and they were scrolling much faster. Additional power off/on cycles would only cause the lines to change thickness and motion and scrolling rate. I don't have a picture of my actual console doing this, but here is one on youtube that demonstrates the issue very well. It is best to see it in motion anyway to get an idea of how annoying it really is..
     
    Reading up on the issue you find a few different fixes for the issue or no fixes at all. The most common fix thought to correct it, is to replace the caps in the PSU board. Saturn consoles have their PSUs internal inside them. Luckily they are all throug hole caps to not that big a deal to replace. But you have to make sure when ordering a cap kit, that you order the right one for your Saturn as it seems there over a half dozen different PSUs used on the various Saturn models and they all have different component layouts, different amount of caps needed, and of course different values of caps used. So that was the first thing I did was to recap my PSU. And at first I thought things were good... but nope. The issue would happen after about 10min of playing a game and when powering cycling the console again to change games, the white lines would be back?! Keep in mind the actual console continues to play normally but visually it is less than ideal.
    The next common fix for this issue that has worked for a few people, is to replace the main PWM switcher that is on the PSU boards. There were two main types used in the Saturns depending on the country it was being used in. For instance in Japan and NA. The PWM could handle between 100 - 120v. In Europe it was for their 220-240v ranges. The exact PWMs used are difficult to find but I did some sleuthing on this over a year ago and found a modern drop in replacement that can be used in all regions as it can handle between 100 - 240v by itself. These can be purchased from console5 if needed here:
    https://console5.com/store/top224yn-saturn-power-supply-pwm-75w-voltage-regulator-replacement-for-top102yai.html
    But sadly once again in my case, it was not to be the fix for mine. So I've just kinda lived with the issue now. Until last night when I remembered something and then tested it a bit.
    Remember when I said that powering off/on would cause the lines to be different each time on my console? Well, I also discovered that if I could quickly turn the console off/on enough to cause the screen to dim for a sec but not enough to cause the saturn or the game to actually shut off, that sometimes those lines would go away?! That got me to thinking... which, in all honesty can be a bad idea for me sometimes.
    The power switch changes the conditions depending on how quickly I'm actuating it. Or maybe the force used to power it on and off? So...
    I decided to take the switch apart. This was NOT an easy task. The switches used on these earlier model 1 units I believe are different than later made models. It has an additional power protection component soldered onto the AC input wires on the side of the switch. Wrapped with a bit of yellow electrical tape, and then a blue/green translucent colored rubber cap that was draped over it to protect everything. Once you carefully remove all of this (As you will want to reuse at least the rubber cap). Then you have to pry apart the steel housing that covers the top portion of the switch. Once you have done this, you have to be careful of 2 things. Both of which are springs that will do what springs do best. They will likely shoot out somewhere and you won't find them again if you aren't careful. My wife may or may not have a non functioning ball point pin in her pen holder as I type this...
    Once I got this figured out and was able to study the switch. I then found old yellowed colored grease inside the switch along with a bit of black carbon residue mixed into the grease. Similar to what we see on colecovision and atari toggle switches. I cleaned all of this gunk out and put it back together with some new dielectric grease. Once I got that switch back together. I crossed my fingers and turned on the Saturn. No white lines! But I couldn't get excited about it just yet because what I didn't mention is that most of the time on the first power on, the Saturn doesn't have those lines. It is only after it has been on for a bit and then I power cycle it that the lines would appear. So I played some Bulk Slash and got through a few missions and powered the console off to switch games. Turned it back on... and still no white lines?! This is a good sign. I continued to play several different games for at least another hour and half power cycling the console well over a dozen times in the process and those pesky white lines have not come back.
    So it would seem that power switches are another potential source for the white lines issue on Saturn consoles. I'm not sure why the first power on would always be good and it was only successive power on attempts after that would cause this, but for now it seems those issues might finally be corrected. I will have to play a bit more Saturn games to find out. What a chore... 😉 hehe.
    Here are some pics of the insides of my Saturn for those that might be curious. I recapped the entire thing several years ago and at the time only radial caps were in the kits so I had to install them in a similar manner to how it is done on Gamegears when replacing surface mount like caps with through hole radial type. And, it has a Hi-Saturn region free BIOS installed as well. Even with the Rhea configured to report every game as being NA/US, the Japanese games still wouldn't load right and would require me to use my Acton Replay cart to bypass. But as that cart becomes more and more finicky to use, I opted to just install the region free since in this model Saturn, it is literally a drop in replacement chip.

     

     

  5. CrossBow
    This one was quite tricky and I'm still not 100% convinced this was the full cause. However, grab a snack and a drink cause here we go...
    An older 2600 heavy sixer was sent for just a refurbishment and no upgrades. Basically just replacing out the components that come in a standard console5 refurb kit. But I immediately knew someone was off about this console before I even opened it up due the bulging I could see in the front facia switch section near the left side of the cartridge port?

     
    Upon opening it up I also found that whomever was inside this previously (and I know someone was), had also applied some very sticky foil tape around the RF modulator housing? I think this was done to improve the picture output as this H6 does have pretty poor RF output compared to most I've worked on.


     
    I actually removed this foil tape completely. Took the RF modulator from off the switch board and disassembled it. I then removed and applied new solder to all components on the RF board as much of the solder was looking pretty old and I could see what looked like old joints with some possible hairline cracks starting to form. This along with the refurb kit has improved the RF output a little but not as much as I've seen in the past. I suspect the RF modulator itself has some other issue going on but as it is the 3pin version, they aren't that common for replacements. Also the tuning coil in these appears to be locked in place as this one just didn't want to move and I didn't want to chance cracking the core trying to force it. So it is stuck in the position it was given from the factory around the channel 3 area. Some of my TVs did have issues locking onto this console's signal but of course the CRT downstairs had no problem with it.

     
    So what about the power issue that this Blog is titled for? Well, after doing all of this, the console still had a strange issue where sometimes when powered on, I would just get a blinking screen of snow and black...snow....black...snow...black. Something I hadn't seen before. Since you always ASAP electronics issues I first checked the input power which was given me a steady 13.2v on the input side. This would drop to about 12.4v when the console was powered on which, is to be expected for the additional load once the rest of the circuit is active. 
    It was when I checked my voltages on the new voltage regulator that was also installed that I found something very odd! I was getting a 12.3v reading on the input pin of the VR which, again is quite normal, but what wasn't normal was that the output pin of the VR was showing 11v ?! It was then, using my meter that I found that somewhere the input and output pins of the VR were shorted. How this console worked in the past is beyond me because 11v off the output pin of the VR would also be getting sent to the mainboard in the metal housing and that can't be good! In looking at the old schemes for these boards the only spot I could see that might cause this was taken up by this rather large guy here:

    That is a 2w Allen Bradley style resistor. According to band colors, this is a 68Ω 5% resistor. I took it out of circuit and sure enough the short I was getting between the input and output pins of the VR went away. But the resistor was reading 71 - 72Ω which is within the 5% tolerance spec. But taking a chance I powered on the system without it and it came right up and appeared to be working just fine. I then left the system running moon patrol for about 8 hours yesterday to make sure everything was good. And it was fine. 
    My understanding is that this resistor was added to reduce the current on the input going into the VR so it wouldn't get crazy hot. But the VR was replaced and I drilled a hole into the heatsink so I could use a screw and nut to secure the heatsink to the VR vs the clips that were used on these originally along with new thermal paste. That 8hour session of moon patrol did get the heatsink warm but not enough to burn as I could keep my fingers around it without it getting too hot for me to touch. So perhaps the older VRs couldn't dissipate the heat as well and this is why these large resistors are only present on the very early model H6 units. It might even be the first one I've seen that has one as most of the others I've worked on I don't recall seeing it present. 
    Anyway, I'm going to power on and test this system again today to be sure it is still working properly but hopefully it is good to go, and ready to go back to its owner.

     
  6. CrossBow
    Here at the Ivory Tower, I get quite a few requests for console services. It might be an actual repair to get a console working back to full factory function or refurbishment of a working condole to ensure it works for another 40+ years into the future. But by and large most of my requests are to enhance a console in some way. Usually through audio/video upgrades etc. But on more rare occasions, I will be sent a system that has already had work done to it either by the original owner or from another and requested to further enhance. 
    Because of just how I am... In such requests I usually undo most of what has been done before when it requires it. Sometimes I will use existing wiring and just trim it up or tighten loose AV jacks that have been installed. But in this particular instance, I had a Sears Intellivision console sent that had been prior upgraded with a composite video output and had an earlier RGB board installed into it. It was requested to give the entire system a once over and correct any wrongs found while also upgrading the current RGB with one of the newer offerings. 
    I'm writing this blog because some might feel that with a console already having been prior worked on before and semi working already, that the amount of work required to upgrade what has been done before might be less work than doing it on a console that hasn't been touched or modified in the past. In most cases... this is far from the truth as you will see with this particular Intellivision.
    First let me show you some pics of what it looked like inside when I first opened it up. I do not know exactly who did the original work, but it is pretty representative of the kinds of work I find in these systems sent to me to fixed and upgraded further.
    This is a picture of the power supply board when I first opened up the system. Nothing horribly an issue here, but it would seem that whomever was in this before did apply new thermal paste on the VRs, but they used too much as you can even see it on the legs of the VRs below. They also didn't replace out the high wattage 12Ω resistor that is the grey tube thing near the center. You can see on the left hand side it is starting to show signs of breaking down as it is starting to flake. To be fair, it might not have been this way when it was last worked on.

    This is the original composite video upgrade that was done in the past. My only issue here is that the wires these older kits from the guy in Turkey used, are a bit thin and break easy. The wiring was also not tided up and left long. Likely so the main board could still be removed in the future but some tidying would have been nice to see.

    Here are the original RCA jacks that were installed as part of this kit. Again, the wiring is left long and not secured in any way. Also, the RCAs had worked loose and were free spinning. This results in dimming picture output because the ground connection is off those metal tabs. If they jack is free spinning, that means the ground tab isn't very secure and is barely making contact.

    This is what I found when I removed the controller tray. That PCB is the older 'Fred' RGB board. It was not attached at all and was loose inside this section of the Intellivision. First, this area is NOT for installing boards like this. This area is empty because it was thought you would store the power cord inside this section when the console wasn't in use. So if someone had done that here, they very likely would have pulled something loose off this RGB board or started to fray the AC cord. Either way... this is NOT acceptable in any situation and should have been installed elsewhere in the system. 

    Because of the board laying in here loose, it stands to reason that the RGB output jack is here as well and yes it is. This isn't too much an issue but again not idea. For starters, it is a bad idea to route any AV outputs near power sources and we have that large AC transformer just a few inches away. But mainly bad because as you can see, the wiring is again loose here and would have separated easily over time. The RGB jack was epoxied into place and I do not have any issues with that since that is really the only option you have for these type of panel mount jacks and is something I do myself.

    The RGB board gets its signals from the U10 color IC chips, the same way the current RGB boards do. But in this install a separate breakout PCB was used where the original IC was removed and installed into a single wipe socket on the breakout PCB. The PCB was then stuck into the original single wipe socket that the IC chip was originally in. This seems overly complicated since it is just as easy and provides a better connection to just solder to the bottom of the PCB to the pins where this chip is located. My main issue here is the cheap single wipe sockets of the original not being replaced out with higher quality, and the use of single wipe on the PCB breakout board.

     
    Now for what I has been corrected and redone... First is the power supply board was recapped and new high wattage 12Ω resistor installed. I also cleaned up the VRs and redid the thermal compound with higher grade stuff.

    The older composite only board was completely removed as composite output was being replaced by the new all in one board combo that I installed. This is Crayon King's older v5 RGB board with one of his separate expansion boards on top. This provides not only RGB that is of much better quality and compatibility to the older board, but provides the best composite I've seen from an Intellivision, plus a really excellent s-video output as well! Here is the new RGB board combo installed on the main PCB with all the new wiring in place.

    I installed a new AMP brand dual wipe socket for the U10 color IC chip and attached it back onto the mainboard. As a result, the wiring needed for the new RGB now attaches at the bottom of the PCB to the pins that are connected to the U10 color IC chip. The scorching in the lower right is quite normal and is a result of the stupid amount of heat that the two 3906 transistors in that part of the board experience. It gets hot enough to discolor the PCB. I always replace these transistors as part of any Intellivision model 1 refurb because the originals are ticking on their last lives at this point. Can't do anything about the heat, but at least with new ones, they should last as long as the originals have to this point. The other wires from cartridge port are for a power LED that is being added to the console at the owners request. That is actually the exact same method INTV used when they added the power LEDs to the Super Pro System and INTV III consoles.

    The RCA jacks were redone using star lock washers to hold them in place more securely. I also added in an additional Red colored RCA for dual mono output so the owner of this console doesn't have to keep using an audio splitter. This also allows for a future stereo upgrade later should a nice kit come along that provides that. You can also see the new s-video panel jack that has been added since that is available, why not add it? A switch was also installed to allow for palette switching on the new RGB board since it comes with 2 different palette options. 

    Since the original RGB output jack ended up having bad internal pin connections anyway and was giving video drop outs, I had to crack out the original and replaced it with a new matching type. To help with keeping things more tidy, I used a breakout board for the jack and secured the wiring more.

    Here is what the entire rear of the console looks like at this point. Have to keep in mind that the Red RCA, the s-video jack to the right of that, and the RGB on the far right have been replaced. You can see the toggle switch used for the palette change here as well. I have it facing downwards as there is plenty of room for it, it makes it easy to find and flip and doesn't protrude beyond the normal width of the casing. I add colored boots to the switches so they don't seem quite as obvious. 

     
    And that is all I have at the moment as I'm still finalizing this console. But everything is tested and as you can see in these pics, I use connectors for all wiring that is attached to the case shell so that it is easier in the future to remove the mainboard for servicing completely from the shells. The point here is that just as much work and maybe more goes into working on a system that has already had work done in the past and it shouldn't be assumed that because some of this stuff was already in place, that it results in less labor being needed to upgrade further.
  7. CrossBow
    This might require its own thread but I actually was working on an NTSC 7800 that was eating my lunch most of the weekend. It was sent in for just a basic composite mod installed into it. When I used the diagnostic roms everything was fine with this 7800. But then not long after I got the composite board installed and tested it again, I noticed some odd flashing lines of colors across the screen. It seemed to do this badly on Dungeon Stalker and Ballblazer. In the case of both games, it would flicker around with the color like this for anywhere from a few minutes to about 10min and then just abruptly lock up or got to a black screen?! It was also doing it through the RF when I put everything back in stock condition and reinstalled the original components I had removed. I replaced every single one of the main ICs without any luck starting with the Maria as it wasn't doing this in 2600 games. I did try to install my cap off the A15 line in a similar fashion as my other video I did about this,  but that didn't change anything either. You know what removed 90% of the flickering color bars on the screen and stopped it from locking up?
     
    The freaking crystal! (Y1) I removed the one in it and replaced it from one of my 2 parts donor 7800 boards. The first one I popped in the flashing colors were only occasional on the game ballblazer but didn't happen at all with dungeon stalker or any other games I tried. And more importantly, it didn't lock up either and BB and Dungeon Stalker both ran for several hours before I finally shut them off. I did try other crystals to see if I could get the slight flicker to go away completely but that only took it back to the way it was. So obviously something in the crystal I installed from the other 7800 seem to mesh better with this 7800. I also replaced every single one of the 3904s starting with Q3 and Q4 as both of those were installed. In fact this 7800 was kinda strange. Seem to use a later revision board, had C64 for the extra timing circuit on it, but was missing the rest of the ICs you usually find in that circuit? It also had all of the caps and resistors installed, whereas most of them show some removed at the factory by clipping them out or just not being installed in the first place. It also was using Sony 10ns speed RAM in it but no resistor installed on the bottom RAM chip as I normally see with most of the Sony RAMs. (BTW replacing RAM didn't do anything and in fact just gave me a black screen).
     
    So all I can say is that timing on the 7800 doesn't have much room for tolerance it seems and that all of the components we find installed into the consoles was done so at the factory in what seems like a case by case basis? 
     
    BTW when I put it all back together and replaced all the RF shielding, the flickering seemed to go away completely at that point? I'm still not 100% sure it is 'fixed' but it is a strange issue for sure and one I hadn't yet come across.
     
     
    View the full article
  8. CrossBow

    IMP TIA = BAD TIA!!!

    By CrossBow,

    Had a pre-modded 7800 sent to me with a UAV that had good s-video but was producing some ugly jail bars in composite. But it was ONLY doing this on 2600 games. I at first suspected something in the wiring of the UAV or the UAV itself and first redid all of that and replaced the UAV. No change. It was then I started to look at things more closely and noticed that this '84 main board all socketed chip board appeared to have a TIA I'd not seen before. The company branding on it is IMP and it had a mid year 1988 date stamp on it indicating it was not likely original to the 7800 to begin with. Since I was able to disconnect the TIA color signal and get crystal clear black n white with the jail bars, I knew it had to be in the color signal. And since the UAV is tapping that signal straight from pin#9 off the TIA there was really only one culprit. I had another semi working 7800 with a more normal looking AMI branded TIA on it. Pulled that and put it into the socket on this troublesome 7800. Sure enough the jail bars are gone! I'm guessing this is a late revision TIA and it likely a CMOS part as it doesn't seem to heat up like most TIA chips do and it just feels a bit different. In any event...stay the hell away from these TIAs in and think about replacing them if you find them in your 2600s or 7800s. Especially if you plan to use composite upgrades or a UAV as it does produce jail bars. I also noticed that color trimmer has to be adjusted but a full 180 between the two chips. So there are some obvious internal differences in how they are designed and made. I've attached some pics to show what I was getting and between the two TIA chips.
     
    Here is the section about halfway on the edge of the ColorMatch screen on the Colorbar generator program. You can see the jail bars on the slightly different hue of green on the lower half. Upper half is fine.

     
    Here is the green purity screen with the bad TIA. Again, you can see the jail bars and while this is on green, they are present on all colors pretty much.

     
    Here is the colorbar screen from the bad TIA IMP branded chip. Again you will see that most of the colors exhibit noticed jail bars on them. It is quite distracting and unusual to see from a UAV board.

     
    Here is the actual IMP branded TIA chip that was causing the headaches above:

     
     
    Now here is the colormatch screen edge with the good AMI branded TIA chip.

     
    Here is the green purity screen with the good working TIA. Quite a difference here.

     
    Here is the colorbar screen on the AMI TIA. While there is still come color bleeding and other artifacts normal with composite on an LCD, you will see that the colors don't have the jail bars as they did with the other TIA chip.

     
    And of course, this is what the common AMI branded TIA looks like in most 7800s I've encountered:

     
    So if you have nasty jail bars from your composite video out signal, you might look at the TIA as the possible cause.
     
    Ivory Tower Collections
     
    View the full article
  10. CrossBow
    Not a video to share this time, although in hindsight I should have made one as a quick tech video. But recently I decided I would get some replacement filter caps for use in standard wall wart power supplies like those used with our Atari, Sega, etc. consoles from back in the day. As I have quite a few of them on hand and wanted to test them out I decided to start with a few Sega Genesis power supplies. I decided to look at three different supplies last night. I first checked the voltages from all of them and they were all pretty normal. One reading about 14v, a model 2 supply reading 13.5, another model 1 reading about 13.8v. Nothing out of the ordinary from such old transformer supplies that don't have a load on them. Still, they are all well over 20 years old so I figured why not.
     
    Now, many of the sega power supplies require a small 4mm hex bit to open them up and that was the case with one of the model 1 supplies I had. I didn't have this tool so I ordered it online. The other two I had actually required a small #5 security torx bit similar to what is used on TurboGrafx and PC engine systems. But that bit I had on hand and with that I was ready to crack them open and get to work.
     
    The first model 1 PSU is one I've been using for a few years on my workbench as a go to PSU for several systems. I've created adapters so that I can use it with several other classic consoles I work on so I don't have to keep a bunch of different ones on hand at the ready. So it has gotten quite a bit of use over the past few years. It required the small 4mm hex bit I had to order. No issues once I got it opened up. Looked okay and had that ages electronics smell but nothing out of the ordinary. Removed the old large 3300µf at 16v capacitor. It seemed to be in good shape still with no evidence of bulging or leaking. Still it is over 20 years old and would hurt to change it out. Did that and working just dandy!
     
    Then I looked at the second one and this one is where I first discovered that the 4mm hex nut driver I'd gotten wouldn't work and I needed to use my #5 security torx instead. Opened it up and it noticed it seemed to be glued shut as the two halves wouldn't separate as easily as the last one had. Interesting..worked on it a bit and was able to get it to come loose on one side. It was right about when I started to grab for a small flat blade screw driver help pry open along the sides that the smell hit me... 
     
    If you aren't aware, the old electrolyte used in these older caps smells very much like fish and has an oily consistency to it. And it is very distinctive and not at all like a normal electronics type smell. This wasn't a good sign as that smell would indicate that I was about to discover something nasty inside. Once I got the two halves of the PSU case apart, the smell really hit me and I could see it. A shiny surface on the top of the small PCB around some of the diodes on the PSU and where the output wires are soldered in. I removed the PSU assembly from the case housing and this is what it looked like on top.

     
    Now it is hard to see, but you can make out the shiny look on the PCB and also where it is a darker color. But the large filter cap looks okay physically right?

     
    Well not quite because once I removed it you can see near the negative lead of the cap, where it has stained the PCB from electrolyte that has been leaking from the capacitor over the years. Also hard to make out but the bottom of the cap itself was also coated in the oily residue of the leaking electrolyte. Now this doesn't seem like a big deal right? Just clean that off and put in a new cap and your good to go? Well, the bottom side of the PCB where the traces are, has a very different story to tell and shows you the results of what leaking electrolyte does on a PCB over time.

     
    Here you can see where there is a mottled almost moldy look the left half of the bottom of the PCB here. Well, that is where the cap was and where the electrolyte over time has seeped onto the bottom of the PCB and started to corrode the upper layers of the PCB masking and copper traces under neath. This is essentially cancer on a PCB slowly eating away at the board. If this had been something with much smaller traces to components, it would likely be a lost cause or at least require quite a bit of small and time consuming trace repair work. Luckily the traces on most PSUs like this are large and thick. So how do you clean this up? I took my electrical grade 99.9% alcohol cleaning solvent and a toothbrush and went to work to clean and neutralize the electrolyte. In the process of this, the top green layer coating started to flake off exposing the copper traces underneath it since the electrolyte had so badly ate into it. There were also dark patches on the copper itself underneath. This required me to also use my fiberglass pen to remove the remaining layer protecting the traces to fully expose them and also remove the corrosion. This is what it looked like after cleaning and removing most of the corrosion.

     
    Still a few dark patches left behind that has pitted into the copper traces but it shouldn't get any worse than it is now since it is cleaned up. So what now? Well I installed the new replacement filter cap and the used lots of flux and solder to apply a new layer across the traces to protect the copper underneath going forward. This was following up by a lot more cleaning with both a PCB board spray cleaner and lots more high grade alcohol. I then left it out overnight exposed to fully dry out before testing and reassembly.

     
    The third PSU was for a model 2 genesis and also required the #5torx security bit to open it. It was like the first PSU in that the capacitor in it wasn't leaking and everything appeared to be fine inside. Just replaced that cap the same way as the first, buttoned it back up and it works just fine. 
     
    But the moral of this is that just because a power supply works, doesn't mean that everything inside it is okay and good to go. That second PSU with the leaking cap would have eventually died on me as the traces would have continued to corrode and eventually sever from the rest of the circuit and possible start to lift from the PCB itself. This means that with this wonderful discovery, I need to now try and open up all other PSUs that I'm able to open up easily and inspect them for similar cleaning and possible repairs.
     
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  11. CrossBow
    In this 3 video series, I go over the basics and understanding of the Roland MT-200 sound module. It is an excellent multifunction sound module that can act as both a sequencer and sound module. This means that in addition to being a very nice general MIDI and Sound Canvas sound module, it also has the ability to record MIDI songs from the MIDI in port and save them to diskette to be played back in a standalone fashion later, making it a MIDI Jukebox as well!

    The first video goes over the basic overview of the module itself in what it is, what it can do, how to access the hidden diagnostic functions, and their uses.







    In the second video I go over the advanced diagnostic functions in how to set the internal date and time along with how to use the diskette drive functions.





    In the third and final video in this series, I go over the basic hardware needed to connect the MT-200 for use on a modern day computer. I also cover how to get the software drivers along with how to configure ScummVM and DosBOX for using an external MIDI device. Finally I demo how I have my MT-200 connected to my modern day Windows 10 PC along with my Roland MT-32 connected through MIDI Pass-thru. I then demo how I use the two modules in DosBOX on the game Space Quest 1 (VGA Remake). The audio is heavily compressed on this part as Geforce Experience software compresses the audio to mad levels for streaming. But you get the idea on how it works all the same.




    Thank you for viewing these as it has been a lot of fun learning about this wonderful sound module and understanding its uses and secrets! Enjoy!View the full article
  12. CrossBow
    As some might know by now, I've got an MT-200 that I picked up over a month ago now. Really cool little device from Roland that was originally intended for use in teaching music. But these devices have the ability to play back midi files through built in disk drives that use IBM formatted 3.5 inch disks. They can also be used as sound modules and with modern day computers can still be made to be used with ScummVM and Dosbox for classic gaming. Anyway I was getting frustrated with my disks seeming to work one day and then a week later suddenly given me read errors. So I read up on using one of these cheap Gotek floppy emulators into mine. But information on actually making one work with my MT-200 wasn't to be found. I did find Gotek's pre-configured to work with devices like my Roland MT-200 and its variants on eBay, but at $80 + shipping that seemed crazy to me. So I bought a generic Gotek with the intention of figuring out how to make it work in my Roland MT-200.

    I was quite successful and it turned out to be MUCH easier than I thought it would be. I did a video last week on the process of which jumpers are needed, the installation, and the software I found to make it all work in my Roland MT-200. I now share this knowledge in my recently released YT video so that you don't have to pay those crazy prices on eBay either and can hopefully find this useful:


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  13. CrossBow
    I am only a hobbyist and NOT an electrical engineer. As such I'm sure my terminology and explanations of things will be off or perhaps completely wrong. As such, please let me know in comments on such mistakes as it helps me and all others who might view this video to learn.

    With that, this is my basic intro to my BK 1474 O'scope that I got some time ago and some ways it can be used. This video is only meant for fun and not as instructional as most of my other videos are. Enjoy!



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  14. CrossBow
    Been doing a few composite AV mods on client intellivisions. Though I would video the process I go through for doing a capacitor replacement. I'm working on trying to get the videos down to be more watchable in smaller amounts of time but perhaps too much compression on time is used in this video?
     
    Big special thanks to Adan Toledo for his permission to feature some of his music from the CollectorVision homebrew release of Sydney Hunter & the Sacred Tribe for the Intellivision!
     
    - Order your official OSTs for Sydney Hunter and Mecha 8 from Adan himself here: http://adan.eu5.net/europe.html
    - Order your copy of Sydney Hunter & the Sacred Tribe plus other homebrews from CollectorVision here: http://collectorvision.com/
     
    Comments always welcome and much appreciated!
     

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  15. CrossBow
    Replaced the original 7805 regulators from my atari 5200 recently and installed a pair of DC/DC switching converters in their place. In this video I show the power measurements from the original 7805 and from the DC/DC converters. Next up with be the Intellivision once I get additional parts in.


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