the test with RF modulator was useless basically from the beginning because the composite signal was already bad when sent directly to the monitor. Loved the rest of the troubleshooting.
Thank you. Yes, I agree that in retrospect it was useless. I just just grasping straws in case there was something "slightly" incorrect about the composite signal and somehow the RF modulator would be less sensitive to it than the TV.
I had long wondered how PAL Apple IIs worked considering what I knew about how they generated their colors, but, "we just hacked some stuff on top of the existing NTSC hardware" was not at all what I would have guessed. Great vid!
This is the first video I've seen on your channel and I have to say the quality is excellent in every way. Impressive. Good job solving this problem. I spent many hours back in high school at the keyboard of these Apple IIs. It was a very exciting time for me. As you say, the circuitry is odd and hackish. This is because Apple never wanted to use a custom IC when off-the-shelf parts could be made to do the same job. While that can be seen as an inefficient use of space, it means that there's almost nothing in these machines you can't easily replace with new components that are readily available to this day. 40 years later, this design is paying dividends.
Thanks so much! I'm really glad you like it. I also love computers made mostly out of off-the-shelf parts. You know you can always fix them, not matter what happened. It's almost the same thing with early ZX Spectrums and Amstrads (except for the pesky ULA). But once you get to ASICs and things like that... things get more complicated.
Quite ironic that the modern Apple now deliberately use custom chips to perform functionality easily available from off-the-shelf parts, in order to discourage or prevent repair!
Thanks so much for explaining the A2 PAL circuit. I'm about to dive into my machine to fix a PAL issue. This was super helpful! 👍 (And subscribed... 🙂)
Noel, I’m really surprised with every single video that you publish. It’s a really hard job and more than a lesson for all of us that enjoy your publications. I much really appreciate your free contribution. 👌
Things which I didn't expect to happen today - learning how PAL signals actually work. I knew some basics, but not in this depth. Quality content as usual. Sad that the video schedules have to get relaxed, but good luck with your game project!
Thank you so much for all the details on how PAL/NTSC "work", this was a lot of fun to watch. I think all the Apple haters who didn't watch the video missed out on a VERY education episode! :)
I actually own one of these rare 8-bit classic Apple computers. I had the pleasure of helping to develop some c&c software for it back in the early 1980's and I just love the architecture of the early Apple systems. The only problem I have now is that the "gold brick" power supply is in serious need of a re-cap and service, not a task for the fainthearted as it was one of the earliest switching power supplies, quite tricky to work on and easy to blow up if you aren't careful...
Thanks. Glad you liked it. It took me a while to dig all the way there, although it's one of those things that once you figure out what it is, it seems like it couldn't have been anything else :-)
@@NoelsRetroLab Aaand... I spent most of my time finding out most of the info about PAL composite video on my Apple //e myself... the problem I have is similar, mine shows yellow only, and seems to be in color mode even when it shouldn't (e.g., in text mode). I just started studying how the 6600 works, but looks like you have quite a good description here (and way better schematics than the one I have!) I'll rewatch your video soon, with the board in one hand and the oscilloscope in the other :)
@@marco_foco Make sure you read the PAL section in Understanding the Apple IIe (linked in the description). There are two crucial pages about it which helped me immensely following the logic and tracking this down.
@@marco_foco What you're describing is really weird though. Yellow in text mode? I doubt it's generating the color burst in that mode (easy to check), and if it isn't... that sounds more like a TV issue. Drop by the Discord if you want and we can chat there. Easier to post pictures and stuff like that.
@@NoelsRetroLab That's the problem, or at least one of them: it is generating the color bust in that mode. The color is greenish/yellow in text mode, in graphic mode you can see random pink/green patterns sometimes, and the black isn't really black but often very dark red. As you did in your video I tested with several devices and adapters (a TV, a portable projector, and a screen with a composite to HDMI adapter, exactly like yours, but white :)), they do have some differences, but the problem is always there. I even tried to swap one of the transistors (Q9) that seemed bad in circuit, but revealed good once removed, and the variable capacitor (which broke in two when I tried to move it). Absolutely no change. Unfortunately I didn't have time recently to check it again, I hope I'll have some time on Sunday.
TIP: When you have a stuck part like that I always cut the pins away from the part, then de-solder each pin. This puts the least stress on the PC board pads and plated through holes. Of course you destroy the chip or part but in this case a TTL chip is pretty cheap. Also the subcarrier frequency is quite critical. I don't remember 4.43mhz PAL specs exactly but NTSC is 3.579545hz +/- 10hz so I expect PAL would be the same tolerance. That's actually a much better color system than the NTSC Apple 2. I guess they had no choice but to use a real subcarrier quadrature modulator because of the PAL phase alternating line requirement. We don't have that need in NTSC so you can have much simpler crude color circuits. Just mix a subcarrier with the luminance at a different phase than the burst. No quadrature modulator needed. Just a feed the subcarrier into tapped delay line and a CMOS six part inverter chip plus some capacitors does that nicely. Of course this approach is hardly broadcast quality but good enough for early computers.
Yes, you're right. I'm in the habit of taking them out without cutting them because many times I'm either not 100% sure the IC is faulty, or it's an interesting chip that I want to keep for future tests. But in this case it's just a dumb 74xx, so yeah, that would have been much better.
Another absolutely splendid Noel video! =) Really excellent explanation of the circuitry as usual. I'd never given any thought as to how PAL Apple IIs generate video, though I'm familiar with Woz's famous NTSC method.
@@NoelsRetroLab Before the integration on the PAL IIe mainboard they essentially made a very similar expansion PAL card for this. The older European Apple II+ was also called "Europlus" back then.
If the phases of alternated lines are not inverted, the results is the substraction of color information on them. Then, it shows as black and white because all the color information is interpreted as noise and suppressed. The PAL standard was designed to use this method to be immune to the problems on color shift of NTSC system.
Noel! I was just brewing some tea (for iced tea) and thought of you! :-) I spent a lot of time behind Apple ][s in the late 70s and 80s. :-) So this is what you're up to now!
Well done! Instinctively I would not have suspected a flip flop in this case. But it shows that with the schematics you can use an analytical approach. If everything goes well my first ever Apple IIe comes in tomorrow. It was, as you said in the beginning, not easy to find I in Europe. But I guess during all these everlasting effing lockdowns people clear up their attics and gems turn up. I also managed to grab an SX64 a few months back - I’d been looking for one within the QWERTY area of the EU for ages.
Thanks! I don't have enough of an instinct developed for the Apple IIe to be able to tell where faults are located, so I just had to take the brute force way and follow the whole color-generating circuit. Which in the end was really interesting and learned a lot, so I'm glad I did it. Good luck with your Apple IIe! It's a fun system!
Great video as always! I have only a small tip for you: You may want to invest in a "Trimming Potentiometer Adjustment Tool" made of plastic for future adjustments, especially in such high-frequency circuits (relatively speaking). Metal screwdrivers can sometimes introduce new problems.
What an excellent video of the inner video hardware details! I wished you would bring more with this computer. I might be biased though, as i have exactly this model in a running condition and had an apple// clone, when i was a child. So many memories. :) Greetings from germany.
Thank you! I'm glad you enjoyed it. I'm really bummed that I haven't been able to get more Apple IIe content, but I've been swamped with other things. I have a few things planned though, so it'll reappear for sure 👍
Not even my good Hakko FR-301 can get all the solder off some of these Apple boards. Also, even when it does, the parts stick to the plated-through holes (or, more maddeningly, the small pads on the top, which have traces I can peel away if I get too impatient) more often than not. I always make sure to put a socket in after this kind of repair. I'd never thought of bringing the soldering iron topside to help free the part. That will save me a load of cursing as I struggle to free it from the lumpy thing.
I always wondered how the hacky Apple II NTSC color circuit had been modified to do the much more complicated PAL color. Of course... they used a flip flop on the horizontal sync.
Your knowledge is really astounding. If you are a game developer you probably know Witcher 3. This is the first game that really knocked me off the plinth. Sky, Clouds, Sun, and the shadows that are cast to ground according to the moving clouds is just mind blowing. The buildings the light, everything is unbelievable. The play mechanics on the other hand is crap and buggy.
2:00: "This model specifically is from 1982, and that's even earlier than some of the other computers that we're seeing, like the Amstrad or ZX Spectrum." Actually the Speccy came out that same year.
I’ve worked on dozens of these machines, but they were all NTSC units. It’s nice to learn about the PAL model. But either way, an RGB card will fix all these problems!
By an RGB card do you mean a generic card that takes composite and generates RGB, or is there an Apple II-specific expansion that generates an RGB signal. I'd love to check that one out.
@@NoelsRetroLab There are RGB cards for the IIe that fit in the aux/80col slot, including one sold by apple itself. They were available with digital or analog RGB signals.
Cool video, again! May I ask you something: CD-ROM, in a quick search, will be refered as being launched to the market on 1985, and I can read CD-ROM word on the Apple IIe board. Can you talk a little about this? If the unit was built in 1982, how can CD-ROM be read on the board?
I did not see any problem with the first time you put it on LCD. And among the last sentences of the video i finally understood why and what was wrong with it. Red. Red signal not getting interpreted. And greens aare in signal coded into both red and blue channels. I'm red/green colorblind. The image seemed a little bit off but if you showed me bot the correct and that i would not be able to tell which was wrong.
Hmm, that must be a replacement keyboard. That style wasn't around until post-83 iirc. The stock '82 keyboard (on US versions anyway) would have still had white lettering.
Interesting! I don't know much about Apple IIe history and details like that. I would imagine the European models could have been different. Also, maybe the board says 82, but the model itself was a later one? Apparently this one was rescued from a big bonfire (!!!!) pile many years ago, so we have no idea of its history.
Great video! Well done on figuring out the problem and fixing it! I wonder if a similar fix would work on the PAL Apple //c? I used to have an Apple Colour monitor connected to one as a kid using the composite connector and it showed full colour. However connecting the composite out to a tv showed only black and white. Similarly and weirdly connecting a PAL colour signal to the composite in on the Apple monitor would only give a black & white image. I’ve read about an adapter made by Apple (A2M4023) for getting colour out of the seperate 25pin monitor port on the //c but they are rare and expensive when it seems clear that the composite out is capable of colour anyway. I think Apple’s method of converting NTSC to PAL was a bit off and perhaps the monitor had extra circuitry to decide the PAL colour composite signal? Any chance you might take a look at a PAL //c? I still have mine but no special monitor and would like to fix it if possible.
I don't have any experience with Apple IIc, but from what I can read about it, it seems very similar to the IIe. I did also read problems with Apple PAL monitors showing as black and white only, so it seems it's not an unusual problem. If I get my hands on a IIc I'll definitely check it out and make a video from it. These old Apple computers are really neat from an architecture point of view.
Yeah the IIc is nearly identical to a IIe, just has 128k of ram and a built in 80 column card and disk drive and more ports, that’s about it. I could get full clear colour on an AppleColour monitor just using a single composite cable. So the information must be in that signal for colour. Interestingly I read that the AppleColour monitors automatically switched to black and white for 80 column text mode. So perhaps that’s why they only showed monochrome for other video signals?
When it's a shitty 74ls chip you're fighting to desolder, which you don't care to keep in a working condition (especially if it's faulty to begin with) It's much simpler to just cut the leads and remove them one by one.
That's very true. I'm in the habit of desoldering them without cutting them because half the time I'm desoldering potentially damaged chips or valuable ones that I want to keep even faulty (to run experiments with them). But in this case you're right, I would have been better off snipping it off.
Hmm if the quartz oscillates there's a very low chance it has issues. OTOH, if it didn't, you'd need to make sure it's not the oscilloscope probe that's loading it too much and stopping oscillation. On my thinkpad'd ethernet PHY I had to jumper another one in parallel to see that it was broken… well almost, when started sometimes it kept oscillating, just wouldn't start on its own.
Yes, that's a good idea. I usually don't do it because I'm never 100% sure that the chip itself is faulty (sometimes it can be shorted from somewhere else) and there's something satisfying about testing them after you desolder them to confirm they're indeed faulty. But yes, that's a much more practical approach, especially with cheap ones like this.
How is it that the Apple II composite colours are so different from the CGA composite colours? Is that just a function of the particular choice of resistors used at some point in the circuit?
CGA has actual color information built into it (analog RGB) which can be displayed directly on a CGA monitor or encoded in some other form (composite). The Apple II didn't really have any color information in the signal. It was a monochrome signal with high frequencies and timings in such a way to trigger color artifacts. The Apple II didn't control the palette of possible colors, it's just whatever NTSC produced, whereas CGA did at least make some (bizarre) color choices.
@@NoelsRetroLab That's a little hand-wavy. Also, what mode are you referring to with that explanation? Mode 4 on composite? I was actually referring to the not-super-officially documented but common 160x200 composite mode, which needs bits 4 and 1 set in the 03D8h register. And in that commonly known and not excessively tweaky composite colour mode, the CGA does fundamentally the same thing as the Apple II: It uses 640x200 "monochrome" data ("b/w" by default) to generate a composite colour image via NTSC artifacting. Yet if you look at the 16 colours which composite, 160x200-mode CGA produces by default (w/o further tweaks and 1337 hacks), you'll see that the CGA's palette is very different from the Apple II's default composite colour palette. (No hardware? Just look at the corresponding Wikipedia articles; they both have palette pics.) So that unexplained difference between both systems' respective composite palettes is what I asked about, and if anyone can give a non-hand-wavy answer, I remain very interested in hearing it. It is a given that I do of course know that both 160x200 mode CGA and Apple II use composite artifacting to create their chrominance info out of little more than "thin error" (if you'll forgive the pun).
Everything about monitor television signals is about precise timing. Chrominance information is effectively sent on a the phase of a subcarrier mixed onto the luminescence signal. The angle represents the vector between the Y-R and Y-B for a particular color. Color artifacting works by sending digital signals on the chrominance subcarrier during the duration of a particular pixel.The monitor/television's color decoder interprets these signals as having a particular phase based on some PWM/PDM filtered result of those bits and specific timings. The computer doesn't generate the colors, it just generates bits at randomish times and the monitor interprets those as colors based on it's color gamut. As long as the signals are always generated with the same phase referenced to the color burst signal, a series of bits will always be interpreted as the same color -- but the computer has no idea what color that will be. The Apple ][ and the IBM CGA graphics cards both use a similar method to generate color; but, their timings are completely different. While Apple displayed 140x192 pixels do to other timing constraints on the Apple ][ board, CGA displayed 160x200. The vertical and horizontal intervals were therefore different and different in reference to the colorburst. Thus the timings of when phase the digital signals were sent over the chrominance signal were completely different. Therefore, the palettes of the machines are also completely different.
I couldn't care less about Apple computers, but your videos are so engaging! Well done repair. Also, is there a source of information about games you were/are working on?
Haha thanks! I'm glad you enjoyed it in "spite" of being about an Apple computer. Here's the list of some of the games I've created since I went independent: www.snappytouch.com/ The new one isn't announced yet though. I'll probably mention it in the channel whenever we announce it though.
You are a game developer too?! Would you consider making an autobiographic video about your background, what you do professionally, when you started with computers, what was your first computer, how/when you learned about electronics, etc? I am a software developer myself with some background in system administration, but with no knowledge of electronics to speak of. I am about your age (even have a daughter about the same age as yours) and I watch your videos almost as a window to alternative reality of who I might've been. 😁
Yes, I'm a game developer. You can read some stuff I wrote about gamedev on my web site gamesfromwithin.com/. I don't know if i'll go as far as making an autobiographic video though. It might be a bit too much navel gazing :-) As for the electronics, I did study Computer Systems Engineering, but I really learned all practical electronics by myself when I started repairing my own computers a few years ago. So it's never too late to get started with that if it's something you're interested in.
DO service the psu , mine came from Oz.. previous owner didn't tell me about it.. got a nice smell of RIFA caps :( . also if you don't have one, I really like the w/drive for it :) . you can get a vga out card by the bulgairan woz , which I should get :)
Definitely! That was the first thing I did with this one when I got it a couple of years ago. And it was totally cracked, ready to burst too. The wDrive is awesome. That's what this video was originally going to be about until I ran into the no-color issue. So I'll have a video about the wDrive coming up soon :-)
Thanks! Actually, if you start with the premise that you can't change the video circuitry from NTSC to keep everything compatible, this was remarkably clever. I'm still kind of amazed that it works the way it does! :-)
The scope I usually run it at 10x precisely to avoid that and being able to see the signal coming from crystal oscillators. The metal screwdriver... there you got me. I still haven't gotten a plastic one yet! 🤷♂️😃
@@NoelsRetroLab Even at 10x the probe still introduces some capacitance which de-tunes the crystal. Normally you want to find a buffered output when tuning while measuring. It's all good I'm just being nit picky. You do a nice job finding the faults. You really need to get a bit nicer scope IMO however. Something with a gradient display and faster update.
@@jeffm2787 Agreed...a crystal should be measured after a buffer. The PAL crystal freq is 4.43361875MHz. The colour burst is ten cycles of subcarrier which changes phase by 180 degrees every line. PAL is a lot more involved than one might expect but Noel did a good job explaining the problem and fixing it.
Haha, you had me go back and look at the video to see if it really showed I'm wearing shorts and flip flops (which I probably was) and then I realized what you meant! Well played 👏 👏 👏 🤣
True! I'm based in Spain at the moment and there don't seem to be any around here. I'm planning to work on some Dragons, which are pretty similar though.
@@NoelsRetroLab Thank you for all the repair videos, always excellent. A nice touch having a diagram inset where you are setting the probes for testing. Thank you again.
whilst you could likely play choplifter on a an apple 2 e i suspect you are likely going to see similar to same resolutions as a vic 20 or c64 i don't think the game was designed to run on a apple 2 e
Agreed. I usually don't do it because the desoldering gun does such a great job. I think I stuck with it because I wanted to have the option to go back and test the faulty chip afterwards.
Since theres a switch inside to switch between B&W & color, that means it can sending a color signal, wich means you cannot get color from a B&W signal to a color tv, no matter how you regroup pixels, it’s just bogus.
the test with RF modulator was useless basically from the beginning because the composite signal was already bad when sent directly to the monitor. Loved the rest of the troubleshooting.
Thank you. Yes, I agree that in retrospect it was useless. I just just grasping straws in case there was something "slightly" incorrect about the composite signal and somehow the RF modulator would be less sensitive to it than the TV.
This channel deserves more subscribers.
I had long wondered how PAL Apple IIs worked considering what I knew about how they generated their colors, but, "we just hacked some stuff on top of the existing NTSC hardware" was not at all what I would have guessed.
Great vid!
This is the first video I've seen on your channel and I have to say the quality is excellent in every way. Impressive. Good job solving this problem. I spent many hours back in high school at the keyboard of these Apple IIs. It was a very exciting time for me.
As you say, the circuitry is odd and hackish. This is because Apple never wanted to use a custom IC when off-the-shelf parts could be made to do the same job. While that can be seen as an inefficient use of space, it means that there's almost nothing in these machines you can't easily replace with new components that are readily available to this day. 40 years later, this design is paying dividends.
Thanks so much! I'm really glad you like it.
I also love computers made mostly out of off-the-shelf parts. You know you can always fix them, not matter what happened. It's almost the same thing with early ZX Spectrums and Amstrads (except for the pesky ULA). But once you get to ASICs and things like that... things get more complicated.
Quite ironic that the modern Apple now deliberately use custom chips to perform functionality easily available from off-the-shelf parts, in order to discourage or prevent repair!
Thanks so much for explaining the A2 PAL circuit. I'm about to dive into my machine to fix a PAL issue. This was super helpful! 👍 (And subscribed... 🙂)
Glad it helped!
I watch a lot of vids and I have to say that this was the most informative I have seen in a long while, thanks!
Wow, thanks! That means a lot!
Noel, I’m really surprised with every single video that you publish. It’s a really hard job and more than a lesson for all of us that enjoy your publications. I much really appreciate your free contribution. 👌
Another excellent video showing how an oscilloscope is a great tool! Very logical. Thanks!
Most of the time I have no idea what are you talking or doing about...yet somehow I watched the whole video.
I have to say, this one of the best retro diagnostic videos I have seen in a long time.
Really happy to hear that! 😃👍
Things which I didn't expect to happen today - learning how PAL signals actually work. I knew some basics, but not in this depth. Quality content as usual. Sad that the video schedules have to get relaxed, but good luck with your game project!
Thanks! I'm glad you enjoyed it even if it was unexpected :-)
Thank you so much for all the details on how PAL/NTSC "work", this was a lot of fun to watch. I think all the Apple haters who didn't watch the video missed out on a VERY education episode! :)
You're welcome! I'm glad you found it useful!
I actually own one of these rare 8-bit classic Apple computers. I had the pleasure of helping to develop some c&c software for it back in the early 1980's and I just love the architecture of the early Apple systems. The only problem I have now is that the "gold brick" power supply is in serious need of a re-cap and service, not a task for the fainthearted as it was one of the earliest switching power supplies, quite tricky to work on and easy to blow up if you aren't careful...
Fascinating. I would never have found that in a million years!
Thanks. Glad you liked it. It took me a while to dig all the way there, although it's one of those things that once you figure out what it is, it seems like it couldn't have been anything else :-)
@@NoelsRetroLab Aaand... I spent most of my time finding out most of the info about PAL composite video on my Apple //e myself... the problem I have is similar, mine shows yellow only, and seems to be in color mode even when it shouldn't (e.g., in text mode).
I just started studying how the 6600 works, but looks like you have quite a good description here (and way better schematics than the one I have!)
I'll rewatch your video soon, with the board in one hand and the oscilloscope in the other :)
@@marco_foco Make sure you read the PAL section in Understanding the Apple IIe (linked in the description). There are two crucial pages about it which helped me immensely following the logic and tracking this down.
@@marco_foco What you're describing is really weird though. Yellow in text mode? I doubt it's generating the color burst in that mode (easy to check), and if it isn't... that sounds more like a TV issue. Drop by the Discord if you want and we can chat there. Easier to post pictures and stuff like that.
@@NoelsRetroLab That's the problem, or at least one of them: it is generating the color bust in that mode.
The color is greenish/yellow in text mode, in graphic mode you can see random pink/green patterns sometimes, and the black isn't really black but often very dark red.
As you did in your video I tested with several devices and adapters (a TV, a portable projector, and a screen with a composite to HDMI adapter, exactly like yours, but white :)), they do have some differences, but the problem is always there.
I even tried to swap one of the transistors (Q9) that seemed bad in circuit, but revealed good once removed, and the variable capacitor (which broke in two when I tried to move it).
Absolutely no change.
Unfortunately I didn't have time recently to check it again, I hope I'll have some time on Sunday.
TIP: When you have a stuck part like that I always cut the pins away from the part, then de-solder each pin. This puts the least stress on the PC board pads and plated through holes. Of course you destroy the chip or part but in this case a TTL chip is pretty cheap. Also the subcarrier frequency is quite critical. I don't remember 4.43mhz PAL specs exactly but NTSC is 3.579545hz +/- 10hz so I expect PAL would be the same tolerance. That's actually a much better color system than the NTSC Apple 2. I guess they had no choice but to use a real subcarrier quadrature modulator because of the PAL phase alternating line requirement. We don't have that need in NTSC so you can have much simpler crude color circuits. Just mix a subcarrier with the luminance at a different phase than the burst. No quadrature modulator needed. Just a feed the subcarrier into tapped delay line and a CMOS six part inverter chip plus some capacitors does that nicely. Of course this approach is hardly broadcast quality but good enough for early computers.
Yes, you're right. I'm in the habit of taking them out without cutting them because many times I'm either not 100% sure the IC is faulty, or it's an interesting chip that I want to keep for future tests. But in this case it's just a dumb 74xx, so yeah, that would have been much better.
Fantastic video Noel, really enjoyed this one as I work my way through your backlog.
Glad you enjoyed it!
Man, you rock! That is quite a detective work, in addition to the usual electronics skill show. Congrats! Really nice video.
Thank you Chema! :-)
Another absolutely splendid Noel video! =)
Really excellent explanation of the circuitry as usual. I'd never given any thought as to how PAL Apple IIs generate video, though I'm familiar with Woz's famous NTSC method.
Thank you! Yeah, it's kind of crazy they managed to build a circuit to emulate the results on NTSC. I was blown away when I learned that.
@@NoelsRetroLab Before the integration on the PAL IIe mainboard they essentially made a very similar expansion PAL card for this. The older European Apple II+ was also called "Europlus" back then.
If the phases of alternated lines are not inverted, the results is the substraction of color information on them. Then, it shows as black and white because all the color information is interpreted as noise and suppressed.
The PAL standard was designed to use this method to be immune to the problems on color shift of NTSC system.
Really good insight on that. I hadn't thought about it that way. Thanks!
Noel! I was just brewing some tea (for iced tea) and thought of you! :-) I spent a lot of time behind Apple ][s in the late 70s and 80s. :-) So this is what you're up to now!
Hi Roland! Good to see you here. Yeah, I've been doing this as a hobby on top of my normal gamedev. Really fun!
Wow, I would never have found that!
Great job Noel! We look forward to you getting back to the lab :)
Very interesting. I would guess that this is probably one of the more complex PAL adaptations of an NTSC computer.
seriously it's a pleasure to watch your videos
En serio es un placer ver tus videos
Even after fixing that Apple, I'll still give you a thumbs :p
Well done! Instinctively I would not have suspected a flip flop in this case. But it shows that with the schematics you can use an analytical approach.
If everything goes well my first ever Apple IIe comes in tomorrow. It was, as you said in the beginning, not easy to find I in Europe. But I guess during all these everlasting effing lockdowns people clear up their attics and gems turn up. I also managed to grab an SX64 a few months back - I’d been looking for one within the QWERTY area of the EU for ages.
Thanks! I don't have enough of an instinct developed for the Apple IIe to be able to tell where faults are located, so I just had to take the brute force way and follow the whole color-generating circuit. Which in the end was really interesting and learned a lot, so I'm glad I did it.
Good luck with your Apple IIe! It's a fun system!
That's why I used to enjoy working on macs and then came the imac !!! Goddamned spudgers !!!
Great video as always!
I have only a small tip for you: You may want to invest in a "Trimming Potentiometer Adjustment Tool" made of plastic for future adjustments, especially in such high-frequency circuits (relatively speaking). Metal screwdrivers can sometimes introduce new problems.
Thanks! And yeah, good point. I've been meaning to get one of those for a while. I'll bump it up in my priority list.
That was great detective work! I hope your game development project goes really well.
Thanks! Much appreciated.
What an excellent video of the inner video hardware details! I wished you would bring more with this computer. I might be biased though, as i have exactly this model in a running condition and had an apple// clone, when i was a child. So many memories. :) Greetings from germany.
Thank you! I'm glad you enjoyed it. I'm really bummed that I haven't been able to get more Apple IIe content, but I've been swamped with other things. I have a few things planned though, so it'll reappear for sure 👍
Not even my good Hakko FR-301 can get all the solder off some of these Apple boards. Also, even when it does, the parts stick to the plated-through holes (or, more maddeningly, the small pads on the top, which have traces I can peel away if I get too impatient) more often than not. I always make sure to put a socket in after this kind of repair.
I'd never thought of bringing the soldering iron topside to help free the part. That will save me a load of cursing as I struggle to free it from the lumpy thing.
I always wondered how the hacky Apple II NTSC color circuit had been modified to do the much more complicated PAL color. Of course... they used a flip flop on the horizontal sync.
Yeah, kind of amazing they managed to pull that off with such a simple circuit actually.
A simple error, and so mutch work to locate it. 👌
Looking forward to your next edu video next month.
Thanks! Yes, it's often that way: Lots of searching and then the actual fix is really simple :-)
Good debugging. I bet you're a great programmer too.
The trim cap should be set to achieve maximum signal amplitude (to tune into the resonant frequency of the crystal).
Thanks! As you could tell, I wasn't sure if there was a specific ideal setting.
Your knowledge is really astounding. If you are a game developer you probably know Witcher 3. This is the first game that really knocked me off the plinth. Sky, Clouds, Sun, and the shadows that are cast to ground according to the moving clouds is just mind blowing. The buildings the light, everything is unbelievable. The play mechanics on the other hand is crap and buggy.
Good luck with the project mate, I'll miss the regular videos...
Thanks! The plan is to still be around and release videos, just not as many of them.
2:00: "This model specifically is from 1982, and that's even earlier than some of the other computers that we're seeing, like the Amstrad or ZX Spectrum."
Actually the Speccy came out that same year.
I’ve worked on dozens of these machines, but they were all NTSC units. It’s nice to learn about the PAL model. But either way, an RGB card will fix all these problems!
By an RGB card do you mean a generic card that takes composite and generates RGB, or is there an Apple II-specific expansion that generates an RGB signal. I'd love to check that one out.
@@NoelsRetroLab There are RGB cards for the IIe that fit in the aux/80col slot, including one sold by apple itself. They were available with digital or analog RGB signals.
Great videos! Found your channel through that comment you made on one of Adrians videos.
Thanks! Glad you found it :-)
Good detective work! Really enjoyable video.
Thanks! I'm glad you enjoyed it :-)
Cool video, again! May I ask you something: CD-ROM, in a quick search, will be refered as being launched to the market on 1985, and I can read CD-ROM word on the Apple IIe board. Can you talk a little about this? If the unit was built in 1982, how can CD-ROM be read on the board?
I love this video! thrilling to the end and so happy to see the resolution. Apple iie was my first computer = )
Thanks! It's very satisfying when I manage to fix what I set out to do, which is not always the case :-)
If you can do a video about apple iic pal. it is the most strange machine when it comes to color
Oh really? That's really intriguing after seeing how convoluted the IIe PAL color was. Now I'm really curious. I'll have to see if I can find one 👍
Great video, thanks for the very informative explanation!
Thanks! Glad you liked it!
I did not see any problem with the first time you put it on LCD. And among the last sentences of the video i finally understood why and what was wrong with it. Red. Red signal not getting interpreted. And greens aare in signal coded into both red and blue channels.
I'm red/green colorblind. The image seemed a little bit off but if you showed me bot the correct and that i would not be able to tell which was wrong.
Hmm, that must be a replacement keyboard. That style wasn't around until post-83 iirc. The stock '82 keyboard (on US versions anyway) would have still had white lettering.
Interesting! I don't know much about Apple IIe history and details like that. I would imagine the European models could have been different. Also, maybe the board says 82, but the model itself was a later one? Apparently this one was rescued from a big bonfire (!!!!) pile many years ago, so we have no idea of its history.
Great video! Well done on figuring out the problem and fixing it!
I wonder if a similar fix would work on the PAL Apple //c?
I used to have an Apple Colour monitor connected to one as a kid using the composite connector and it showed full colour.
However connecting the composite out to a tv showed only black and white.
Similarly and weirdly connecting a PAL colour signal to the composite in on the Apple monitor would only give a black & white image.
I’ve read about an adapter made by Apple (A2M4023) for getting colour out of the seperate 25pin monitor port on the //c but they are rare and expensive when it seems clear that the composite out is capable of colour anyway.
I think Apple’s method of converting NTSC to PAL was a bit off and perhaps the monitor had extra circuitry to decide the PAL colour composite signal?
Any chance you might take a look at a PAL //c? I still have mine but no special monitor and would like to fix it if possible.
I don't have any experience with Apple IIc, but from what I can read about it, it seems very similar to the IIe. I did also read problems with Apple PAL monitors showing as black and white only, so it seems it's not an unusual problem.
If I get my hands on a IIc I'll definitely check it out and make a video from it. These old Apple computers are really neat from an architecture point of view.
Yeah the IIc is nearly identical to a IIe, just has 128k of ram and a built in 80 column card and disk drive and more ports, that’s about it. I could get full clear colour on an AppleColour monitor just using a single composite cable. So the information must be in that signal for colour. Interestingly I read that the AppleColour monitors automatically switched to black and white for 80 column text mode. So perhaps that’s why they only showed monochrome for other video signals?
When it's a shitty 74ls chip you're fighting to desolder, which you don't care to keep in a working condition (especially if it's faulty to begin with) It's much simpler to just cut the leads and remove them one by one.
That's very true. I'm in the habit of desoldering them without cutting them because half the time I'm desoldering potentially damaged chips or valuable ones that I want to keep even faulty (to run experiments with them). But in this case you're right, I would have been better off snipping it off.
Hmm if the quartz oscillates there's a very low chance it has issues. OTOH, if it didn't, you'd need to make sure it's not the oscilloscope probe that's loading it too much and stopping oscillation. On my thinkpad'd ethernet PHY I had to jumper another one in parallel to see that it was broken… well almost, when started sometimes it kept oscillating, just wouldn't start on its own.
interesting but video signal circuits can be a darn headache - thats why the had specialist tv guys in the day :P
With stubborn chips like that, I usually cut the pins and remove them one by one.
Yes, that's a good idea. I usually don't do it because I'm never 100% sure that the chip itself is faulty (sometimes it can be shorted from somewhere else) and there's something satisfying about testing them after you desolder them to confirm they're indeed faulty. But yes, that's a much more practical approach, especially with cheap ones like this.
¡Choplifter! ¡The first game I've got on MSX!
How is it that the Apple II composite colours are so different from the CGA composite colours? Is that just a function of the particular choice of resistors used at some point in the circuit?
CGA has actual color information built into it (analog RGB) which can be displayed directly on a CGA monitor or encoded in some other form (composite). The Apple II didn't really have any color information in the signal. It was a monochrome signal with high frequencies and timings in such a way to trigger color artifacts. The Apple II didn't control the palette of possible colors, it's just whatever NTSC produced, whereas CGA did at least make some (bizarre) color choices.
@@NoelsRetroLab That's a little hand-wavy. Also, what mode are you referring to with that explanation? Mode 4 on composite? I was actually referring to the not-super-officially documented but common 160x200 composite mode, which needs bits 4 and 1 set in the 03D8h register. And in that commonly known and not excessively tweaky composite colour mode, the CGA does fundamentally the same thing as the Apple II: It uses 640x200 "monochrome" data ("b/w" by default) to generate a composite colour image via NTSC artifacting. Yet if you look at the 16 colours which composite, 160x200-mode CGA produces by default (w/o further tweaks and 1337 hacks), you'll see that the CGA's palette is very different from the Apple II's default composite colour palette. (No hardware? Just look at the corresponding Wikipedia articles; they both have palette pics.) So that unexplained difference between both systems' respective composite palettes is what I asked about, and if anyone can give a non-hand-wavy answer, I remain very interested in hearing it. It is a given that I do of course know that both 160x200 mode CGA and Apple II use composite artifacting to create their chrominance info out of little more than "thin error" (if you'll forgive the pun).
Everything about monitor television signals is about precise timing.
Chrominance information is effectively sent on a the phase of a subcarrier mixed onto the luminescence signal. The angle represents the vector between the Y-R and Y-B for a particular color.
Color artifacting works by sending digital signals on the chrominance subcarrier during the duration of a particular pixel.The monitor/television's color decoder interprets these signals as having a particular phase based on some PWM/PDM filtered result of those bits and specific timings. The computer doesn't generate the colors, it just generates bits at randomish times and the monitor interprets those as colors based on it's color gamut. As long as the signals are always generated with the same phase referenced to the color burst signal, a series of bits will always be interpreted as the same color -- but the computer has no idea what color that will be.
The Apple ][ and the IBM CGA graphics cards both use a similar method to generate color; but, their timings are completely different. While Apple displayed 140x192 pixels do to other timing constraints on the Apple ][ board, CGA displayed 160x200. The vertical and horizontal intervals were therefore different and different in reference to the colorburst. Thus the timings of when phase the digital signals were sent over the chrominance signal were completely different. Therefore, the palettes of the machines are also completely different.
@@timharig Thanks for the detailed explanation. Your last paragraph resolved one of (retrocomputing) life's little mysteries for me. :)
I couldn't care less about Apple computers, but your videos are so engaging! Well done repair. Also, is there a source of information about games you were/are working on?
Haha thanks! I'm glad you enjoyed it in "spite" of being about an Apple computer. Here's the list of some of the games I've created since I went independent: www.snappytouch.com/ The new one isn't announced yet though. I'll probably mention it in the channel whenever we announce it though.
@@NoelsRetroLab Thanks for sharing.
You are a game developer too?! Would you consider making an autobiographic video about your background, what you do professionally, when you started with computers, what was your first computer, how/when you learned about electronics, etc?
I am a software developer myself with some background in system administration, but with no knowledge of electronics to speak of. I am about your age (even have a daughter about the same age as yours) and I watch your videos almost as a window to alternative reality of who I might've been. 😁
Yes, I'm a game developer. You can read some stuff I wrote about gamedev on my web site gamesfromwithin.com/. I don't know if i'll go as far as making an autobiographic video though. It might be a bit too much navel gazing :-) As for the electronics, I did study Computer Systems Engineering, but I really learned all practical electronics by myself when I started repairing my own computers a few years ago. So it's never too late to get started with that if it's something you're interested in.
DO service the psu , mine came from Oz.. previous owner didn't tell me about it.. got a nice smell of RIFA caps :( . also if you don't have one, I really like the w/drive for it :) . you can get a vga out card by the bulgairan woz , which I should get :)
Definitely! That was the first thing I did with this one when I got it a couple of years ago. And it was totally cracked, ready to burst too.
The wDrive is awesome. That's what this video was originally going to be about until I ran into the no-color issue. So I'll have a video about the wDrive coming up soon :-)
@@NoelsRetroLab you in the apple 2 group on FB ? few euros are in it.. not loads though haha
I believe so (unless there are many different ones). I posted this video on a couple of them.
It’s only North American systems that give COLOR.
PAL systems use a far more sophisticated system called COLOUR. 😉
Check out the Yellowstone card
Nice catch on the flip-flop. That video circuit seemed a bit over engineered.
Thanks! Actually, if you start with the premise that you can't change the video circuitry from NTSC to keep everything compatible, this was remarkably clever. I'm still kind of amazed that it works the way it does! :-)
I didn't even know PAL Apple II exists
wow, nice work
Great video, as usual!!!👍🏻
Thanks!
Buen trabajo! You should be teaching electronics in a school/university if you are not already. :)
Haha, thanks! No, I'm a game developer, not a teacher :-)
Scope probe loading down the crystal, metal screwdriver on the trimmer cap. Like your video's but that was painful.
The scope I usually run it at 10x precisely to avoid that and being able to see the signal coming from crystal oscillators. The metal screwdriver... there you got me. I still haven't gotten a plastic one yet! 🤷♂️😃
@@NoelsRetroLab Even at 10x the probe still introduces some capacitance which de-tunes the crystal. Normally you want to find a buffered output when tuning while measuring. It's all good I'm just being nit picky. You do a nice job finding the faults. You really need to get a bit nicer scope IMO however. Something with a gradient display and faster update.
@@jeffm2787 Agreed...a crystal should be measured after a buffer. The PAL crystal freq is 4.43361875MHz. The colour burst is ten cycles of subcarrier which changes phase by 180 degrees every line. PAL is a lot more involved than one might expect but Noel did a good job explaining the problem and fixing it.
Wearing his shorts and flipflops must be going to the beach. :)
Haha, you had me go back and look at the video to see if it really showed I'm wearing shorts and flip flops (which I probably was) and then I realized what you meant! Well played 👏 👏 👏 🤣
You are a Master!
I notice you never work on CoCo's !
True! I'm based in Spain at the moment and there don't seem to be any around here. I'm planning to work on some Dragons, which are pretty similar though.
impressive !
Merci! That means a lot from an Apple II expert like you! :-)
I don't know how they could say the Apple II was colour. It was just accidental. Any mono computer could do that with 320 or so across mono output.
True. I guess they were one of the first (if not the first) to do it? I'm not sure what the historical sequence was there.
@@NoelsRetroLab Thank you for all the repair videos, always excellent. A nice touch having a diagram inset where you are setting the probes for testing. Thank you again.
whilst you could likely play choplifter on a an apple 2 e i suspect you are likely going to see similar to same resolutions as a vic 20 or c64 i don't think the game was designed to run on a apple 2 e
Actually Choplifter was developed for the Apple II, then ported to the other systems.
Easier to clip the legs from LS74 package and remove each leg individually.
Especially for 74 series chips which are easily sourced.
Agreed. I usually don't do it because the desoldering gun does such a great job. I think I stuck with it because I wanted to have the option to go back and test the faulty chip afterwards.
Since theres a switch inside to switch between B&W & color, that means it can sending a color signal, wich means you cannot get color from a B&W signal to a color tv, no matter how you regroup pixels, it’s just bogus.
Right. That whole circuit is only active when the switch is on the color setting.
Hi
I’ve sent you a message on Facebook regarding Apple 2 GS monitor recaping.
Can you reply? Thanks
Oh Apple, why don't you want us going inside and doing things these days? :P
0:08 No, IIe. Not IIb ;P Harharhar.
:-b
The days when 🍏 let you upgrade and fix things.
Seriously! 😕
Just cut the pins next time you get such a difficult chip.