DavidMil Posted February 2, 2019 Share Posted February 2, 2019 I have a 1220XL that the color keeps going in and out and lately the PC is always locking up. I have traced it back to the clock circuitry. First I thought it was one of the transistors but changing them out didn't resolve the problem. When I put my scope on the crystal, it was not stable and moved all over the place. Sometimes up to 4MHz but mostly down around 2.xxxMHz. So my question arises from the fact that I don't have C061090 crystal, but I do have a C016010 crystal. Can I use the C016010 (from a 2600) in the 1200XL? They both seem to have the same frequency. Thanks, DavidMil Quote Link to comment Share on other sites More sharing options...
Rybags Posted February 2, 2019 Share Posted February 2, 2019 Probably... I needed a 14 MHz one for my 800XL with VBXE. In it's case you retain the colour gen crystal for the PAL machine and use the 14.1 which the VBXE divides down to provide the master system clock. I got mine from a 7800. Then replaced the one from the 7800 with a generic NTSC 14 MHz crystal which I got from some old PC expansion card. Weird that the clock would be all over the place. Maybe the quartz has a fracture or something? Generally the tolerance of these things is pretty tight. Quote Link to comment Share on other sites More sharing options...
Keatah Posted February 2, 2019 Share Posted February 2, 2019 What's the output of the oscillator circuit like? Not the crystal.. Quote Link to comment Share on other sites More sharing options...
+mytek Posted February 2, 2019 Share Posted February 2, 2019 David I'm just wondering if you are trying to attach the scope directly to the crystal? Doing so would cause great instability in the frequency, which is what you say you are seeing. It would be preferred to scope it on the output side of the associated transistor oscillator circuit. An easy place to do that would be to scope pin-28 of the GTIA chip. 3 Quote Link to comment Share on other sites More sharing options...
_The Doctor__ Posted February 2, 2019 Share Posted February 2, 2019 you beat me to it, Mytek for the win! 2 Quote Link to comment Share on other sites More sharing options...
DavidMil Posted February 2, 2019 Author Share Posted February 2, 2019 David I'm just wondering if you are trying to attach the scope directly to the crystal? Doing so would cause great instability in the frequency, which is what you say you are seeing. It would be preferred to scope it on the output side of the associated transistor oscillator circuit. An easy place to do that would be to scope pin-28 of the GTIA chip. Pin 28 of the GTIA chip was where I first discovered the problem. The 1200XL field service manual is so poor I use the 800XL manual for trouble shooting. It says that no color or bad color (which I started having first) could be the clock circuitry. It was like the oscillator circuit was 'skipping a beat' every now and then. The scope would have these random very short 'flat lines' (where the voltage didn't move). And then it would start up again. And yes I was putting the test lead directly to the crystal. Thank you for the new knowledge! Ok, I'm open to suggestions here... David Other things: This was my first 1200XL and the boys played it for hours every day. I know for sure that it was dropped at least once. But there is now telling what kinds of torture a couple of boys could do to a computer over the course of several years. I've done the 'simple' trouble shooting (swapping all the chips including the delay chip) with known working chips in my other 1200XL. The problem stayed with the bad 1200XL. VRegs are solid and stable. Game cartridges work fine except there is no color (or just a flicker of color every once in awhile), at least until the machine locks up. DM 1 Quote Link to comment Share on other sites More sharing options...
_The Doctor__ Posted February 2, 2019 Share Posted February 2, 2019 You know the story, especially if dropped and tortured by kids, time for the complete clean and re seat, look for failed sockets, cracked joints et al. While it is rare for a crystal to go bad, it can happen, rough treatment or not, I've had to resort to hot and cold machines for testing already for a couple of machine that no one could figure out, literally acted one way in the cold another in the warmest room. Turned out to be a complex issue, some components were failing at the edges of the operating temperature ranges, yet sort of worked at normal temperature so it was a moving gremlin. replaced a socket, a transistor, and a support IC that were all supposedly good, but were marginal in reality. Problem solved on that one. Same deal sort of but not quite with a crystal, depending on the temperature it worked perfect or would become erratic (I suspected it was cracked inside and would either contact fully at one temp and not so much at others. Sometimes swapping stuff just because, after all else had failed works... I just had to know why so I dedicated way to much time on such science experiments... Quote Link to comment Share on other sites More sharing options...
DavidMil Posted February 4, 2019 Author Share Posted February 4, 2019 Well so much for my Crystal solution... I don't remember what I was doing but I pressed down on the board just a bit to the right of R13 and the screen went black and the computer locked up. So I guess I'm going to reflow every thing around R13 and then I'll break out the wife's high powered magnifier to look at components. Also I'll have to connect the leads to end points of all traces around there and press on the board again to see if I get any open traces. It's a good thing I enjoy (well mostly enjoy) figuring out these kinds of problems. David 1 Quote Link to comment Share on other sites More sharing options...
DavidMil Posted February 11, 2019 Author Share Posted February 11, 2019 The saga continues... After reflowing all the components within an inch of R13, I decided to do the GTIA chip too. When I pulled out the chip, part of the single wipe pin from position 21 fell out of the socket too. I thought I had discovered my problem but when I desoldered the socket several other pins fell out of the plastic before I could even turn the board back over! Not good, not good. So I decided to look at the ANTIC socket too. Yes, several of the pins were very loose there too. Only two pins fell out while desoldering that socket. One fell out of the CPU socket too. So now I've decided to replace every socket on this 1200XL. I don't have enough 40 pin sockets to replace all of them now, so tomorrow I'll call Brad and order some more. I have a special feeling for this old computer, or I swear I'd pull all the chips out and drop the system board in the garbage at this point! DavidMil Quote Link to comment Share on other sites More sharing options...
_The Doctor__ Posted February 11, 2019 Share Posted February 11, 2019 This is becoming all too common, bad sockets, either too weak to make good contact or swipes literally falling out or rattling around... Quote Link to comment Share on other sites More sharing options...
+mytek Posted February 12, 2019 Share Posted February 12, 2019 Jameco has nice machine pin sockets for a reasonable price, that would be far better then the stock ones, and also better for upgrades to plug into. Jameco Part no.: 41136 40 pin $1.69 each 2 Quote Link to comment Share on other sites More sharing options...
+Stephen Posted February 12, 2019 Share Posted February 12, 2019 Always use the proper crystal! Especially for 1982 era equipment. Then your Atari will launch that football over them mountains. 2 Quote Link to comment Share on other sites More sharing options...
DavidMil Posted February 16, 2019 Author Share Posted February 16, 2019 Jameco has nice machine pin sockets for a reasonable price, that would be far better then the stock ones, and also better for upgrades to plug into. Jameco Part no.: 41136 40 pin $1.69 each I do like those machined sockets. Here is a picture of all the sockets that I had to replace. Quote Link to comment Share on other sites More sharing options...
DavidMil Posted February 16, 2019 Author Share Posted February 16, 2019 The post before this one locked up and I can't do anything with it, so I just added the picture here. Like I said, I do like machined sockets. DavidMil 2 Quote Link to comment Share on other sites More sharing options...
DavidMil Posted February 16, 2019 Author Share Posted February 16, 2019 (edited) Always use the proper crystal! Especially for 1982 era equipment. Then your Atari will launch that football over them mountains. After I changed out all the sockets and the machine quit being 'flaky', I tried swapping out the crystals. You would think that .0009 MHz wouldn't create any problems, but it was enough that the 1200XL came up and worked without any problems... Except there was no color, only a black and white image. Like you said Stephan," Always use the proper crystal." DavidMil Edited February 16, 2019 by DavidMil 1 Quote Link to comment Share on other sites More sharing options...
+Nezgar Posted February 16, 2019 Share Posted February 16, 2019 Beautiful work there! Love seeing all those big 40 pin machine sockets in place. That would take me ages with my lowly thumb-press suction pump. Maybe one christmas I'll get one of those fancy desoldering stations I recently stocked up on these machine sockets... https://www.aliexpress.com/item/10PCS-Round-Hole-IC-socket-Connector-DIP-6-8-14-16-18-20-24-28-pin/32888818828.html Grand total of $11.11 (free shipping) for 40 sockets: 20x28 pin, and 20x24 pin sockets. Took about a month for delivery. Then from eBay: https://www.ebay.com/itm/18214423022210PCS DIP40 40Pin SIP Round IC Sockets Adaptor Solder Type gold plated machined10 for USD $3.51, Free shipping 2 Quote Link to comment Share on other sites More sharing options...
DavidMil Posted February 16, 2019 Author Share Posted February 16, 2019 Beautiful work there! Love seeing all those big 40 pin machine sockets in place. That would take me ages with my lowly thumb-press suction pump. Maybe one christmas I'll get one of those fancy desoldering stations Thank you Nezgar. If you can swing the $120 or so dollars, it's really worth it. I removed all those bad sockets in a little over an hour. David 1 Quote Link to comment Share on other sites More sharing options...
Keatah Posted February 16, 2019 Share Posted February 16, 2019 Which desoldering station did you get for $120? Quote Link to comment Share on other sites More sharing options...
DavidMil Posted February 16, 2019 Author Share Posted February 16, 2019 Which desoldering station did you get for $120? Google ZD915 desoldering station. You'll find them on eBay for about $10.00 less than Amazon. DavidMil 1 Quote Link to comment Share on other sites More sharing options...
Forrest Posted February 16, 2019 Share Posted February 16, 2019 After I changed out all the sockets and the machine quit being 'flaky', I tried swapping out the crystals. You would think that .0009 MHz wouldn't create any problems, but it was enough that the 1200XL came up and worked without any problems... Except there was no color, only a black and white image. Like you said Stephan," Always use the proper crystal." DavidMil David, The chroma line was not connected to the monitor port on the 1200XL. How are you connecting the computer to the monitor? Quote Link to comment Share on other sites More sharing options...
DavidMil Posted February 16, 2019 Author Share Posted February 16, 2019 I've modified all of my 1200XL's with a video upgrade from a guy named Bob Woolly. I use his ClearPic 2002 upgrade. The improvement is really amazing! Especially when using S Video. I don't know if he ever did another improvement to this upgrade... Anyone Know (hint, hint Bob)? DavidMil Quote Link to comment Share on other sites More sharing options...
+DrVenkman Posted February 17, 2019 Share Posted February 17, 2019 I missed this thread until now - dude, next time make it clear it's a 1200XL in the subject line! Yeah, the stock Atari single-wipe sockets suck donkey balls. I had to replace three of the 40-pin sockets in my Ugly Duckling 1200XL during my restoration of that machine. Note pin 19 on this one: broken right off at the bend. Bah. 2 Quote Link to comment Share on other sites More sharing options...
DavidMil Posted February 17, 2019 Author Share Posted February 17, 2019 (edited) I missed this thread until now - dude, next time make it clear it's a 1200XL in the subject line! Yeah, the stock Atari single-wipe sockets suck donkey balls. I had to replace three of the 40-pin sockets in my Ugly Duckling 1200XL during my restoration of that machine. Note pin 19 on this one: broken right off at the bend. Bah. Pin19.jpg Sorry DrVenkman. Here's a picture of all the bad/loose pins: Don't know why but the pins in the PIA chip were fine. I don't think I every replaced it before... DavidMil Edited February 17, 2019 by DavidMil 2 Quote Link to comment Share on other sites More sharing options...
+bob1200xl Posted February 17, 2019 Share Posted February 17, 2019 I modify my 'working' 1200XLs by removing R63, C115, and L15, and replacing them with wire (1 ohm resistors, actually). Add a wire from the left side of R186 (looking at the component side of the PCB) to the empty pin of J5 (the video DIN). This is a CHROMA pickoff. You can also either remove C60 or replace it with a smaller value, like 39pf. This affects your noise/bandwidth - sharp characters or noise in the background. Bob I've modified all of my 1200XL's with a video upgrade from a guy named Bob Woolly. I use his ClearPic 2002 upgrade. The improvement is really amazing! Especially when using S Video. I don't know if he ever did another improvement to this upgrade... Anyone Know (hint, hint Bob)? DavidMil 3 Quote Link to comment Share on other sites More sharing options...
DavidMil Posted February 17, 2019 Author Share Posted February 17, 2019 I modify my 'working' 1200XLs by removing R63, C115, and L15, and replacing them with wire (1 ohm resistors, actually). Add a wire from the left side of R186 (looking at the component side of the PCB) to the empty pin of J5 (the video DIN). This is a CHROMA pickoff. You can also either remove C60 or replace it with a smaller value, like 39pf. This affects your noise/bandwidth - sharp characters or noise in the background. Bob So you don't remove Q8 and all the other components from the 2002 upgrade anymore? David Quote Link to comment Share on other sites More sharing options...
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