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electronizer

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Everything posted by electronizer

  1. Yes, that is interesting considering the disk I got with it has C-64 software on one side and the Atari driver on the other side. There was no special software for the Atari, instead, the driver disk just allows you to use the Learning Keys keyboard in place of the Atari’s keyboard. When it was working, it worked pretty well with Hodge Podge, where pressing a different letter gets you a picture of something that starts with that letter (e.g. “K” gives you a koala).
  2. Thank you both for the quick replies. There is no other circuitry visible and the panel looks like it would be damaged beyond repair if I tried to peel off the keyboard layer. The keys are raised pads and definitely have tactile feedback, different from the non-key area. No calibration is required, however, the driver disk can detect whether the keyboard is connected to the joystick port. So, it must be looking for a particular resistance at the paddle inputs.
  3. StickJock, good guess! Looks like it’s using pins 7, 5, and 9, which would be +5V and both paddle inputs. Resistance from pin 7 to 9 is 11Mohm, and it doesn’t change when I press the keypad. Pin 7 to 5 appears to be open, again with no change when pressing the keypad. The Doctor, any thoughts on how I would reconnect the stapled traces? I’m thinking I would almost have to rip out the staples, add conductive paint, and then put new staples in before it dries.
  4. I got one of these a few years ago. From the start, it worked intermittently—sometimes the letters worked correctly, sometimes the rows were shifted so that e.g. when I pressed Q, it registered as K (the letter above it). Eventually it stopped working altogether, to the point where the driver disk wouldn’t even detect it. I took it apart to find “reject” stamped over the “QA Approved” stamp (uh-oh), and two flat Mylar cables coming out of the panel. I used a pencil eraser on the traces where they connect and they cleaned up nicely. However, only one Mylar cable connects to the joystick cable. The other one is connected by two “staples” that pass through the traces on both cables. When I measure the resistance between these staples and the contacts on the cable that connects to the joystick cable, one is high (several megohms), and the other is open—no connection. So, I’m guessing this is where the problem is. Anyone have any ideas about how to repair this stapled connection between the cables?
  5. Pictures of the keyboard, disk, and insert with instructions for Atari owners:
  6. I had two more pilot units—unfortunately I only had the case for these. DA000092 and the other one looks like DA000145. I gave both of these to bob1200xl.
  7. In a previous post I wrote about troubleshooting my Atari 820 printer. It’s been working solidly for more than a week now so I figured I’d post the solution. The failure mode is that the printer won’t do anything after you turn it on. The power LED comes on, but the paper advance button doesn’t work, and nothing happens when you try to print from the computer. Every once in a while, the printer may work when you turn it on, or it may work for a short time and then stop responding (no paper advance or lprint). Assuming you’ve already tried the standard “reseat the ICs” solution with no success, the fix is to replace capacitor C109, a 1uF electrolytic capacitor that forms part of the reset circuit. My guess is that this capacitor hasn’t aged well in many of the 820s out there, either losing some capacitance or developing a leakage current. Because of its small capacitance value, even a slight worsening causes the reset circuit to function poorly, and therefore the ICs in the printer may come up in an unknown (and non-functional) state. In my printer, I chose to replace the capacitor with a 2.2uF part to increase the reliability of the circuit. I tried values up to 4.7uF and the printer still powered up and came out of reset fast enough that it wasn’t noticeable. A capacitor with axial leads would be best, but I made do with the radial lead part I had. Here’s a picture of the fix: I attached the capacitor between R106 and R110. The R106 connection is a little tricky because there’s a via right next to the resistor lead and you need to be careful not to bridge the pads. I also clipped out the old capacitor in case it was passing a leakage current. You can see the empty pads at the left of the picture. The nice thing about this fix is that you don’t have to disassemble the printer, though you’ll need a small pair of precision diagonal cutters to get the old capacitor out. I laid the new capacitor on its side so that the RF shield would still fit. If anyone has an 820 that still works reliably, I’d be interested to know if it uses the exact same part for capacitor C109. Mine had a blue Nichicon rated at 50V. Let me know if your printer has a different one!
  8. Some time ago I got a Muppet Learning Keys "keyboard." This colorful flat membrane keyboard (similar to the 400's keyboard) connects to joystick port 2 and has a kid-friendly layout. For example, in one corner of the keyboard there is a chalkboard with letters in alphabetical order instead of the usual QWERTY layout. The keyboard came with a disk that had C-64 application software on one side, and an "Atari Adapter Disk" on the other side. The adapter disk isn't a game, rather, it loads drivers that map the keys on the membrane keyboard to actual keys on the Atari. It then pauses to allow you to switch disks, and will boot whatever you insert with the drivers resident so that you can use the keyboard. I used it with "Hodge Podge" as suggested in this post and it works very well! One neat feature is that there is a row of "paint pots" on the keyboard in standard colors, and pressing a paint pot will change the background color of the screen. I did some searching for an ATR of the adapter disk and couldn't find it. It may be out there somewhere, but I digitized my copy and will post it here in case anyone is looking for it. MuppetKey.atr After playing around with the ATR in an emulator, I discovered it requires an XL or XE computer, and will check to see whether you actually have a Muppet Learning Keys connected. If you know of any other games for kids that work well with this keyboard, I'd love to hear about them! Most keyboard-based games should work, but I think Hodge Podge is particularly nice since pressing a letter does something related to that letter (e.g. pressing "C" gives you a picture of a cat, "V" gives a volcano that erupts, etc.)
  9. Finally got a chance to test my theory. First I hooked up an analog voltmeter to the reset line and turned on the printer. It does stay low for a little less than a second before going high, which seems like expected behavior. However, the pointer wiggles slightly as if there is some noise before rising to 5V. Then I clipped a 10uF capacitor in parallel with the existing 1uF cap (10uF was the smallest value I had on hand that would make a difference). This time it took 4-5 seconds for the reset line to go high, but when it did, the printer worked! I was able to repeat this behavior over multiple power cycles, so my confidence that I’ve identified an issue is rising. My new theory is that there is some noise on the power line that couples to the reset line when the power is ramping on the printer, and if the chips aren’t held in reset long enough, this noise causes the chips to come up in an unknown state. I went to the parts store and picked up some smaller values to try (1, 2.2, 3.3, and 4.7). Smaller is better since larger values will mean a longer wait time after turning on the printer before I can start using it. Once I find the smallest value that seems to work reliably, I’ll solder it in and use the printer for a while to see if the issue has gone away. Doctor, to your point about other issues, I was fairly certain those weren’t the case because I had already reseated/replaced ICs. Also, I figured those parts were good because every once in a while, the printer would work fine when I turned it on. But always good to reseat ICs as a first step You mentioned a reset fix, were you referring to the tech tip?
  10. Thanks hunmanik! ”We are not aware of any service problem...” I was hoping there was a service problem with a suggested fix. My printer won’t work even when it’s been off for a long time before I turn it on. I’ll still try increasing the capacitance in the reset circuit to see if that makes a difference.
  11. Still no luck finding the tech tip. Here's the reset circuit: If I understand this correctly, C109 and R106 form an RC time delay circuit of around 1 second. The charging current flowing through C109 and R106 causes Q102 to initially turn on, pulling pin 1 of the 6507 and pin 34 of the PIA low (grounded through R134) to hold them in reset. After C109 is charged, Q102 turns off and pins 1 and 34 go high (+5V through R108, 4700ohm resistor). This also causes Q103 to turn on, and a current flows through R110, Q103, and R134 to ground. This raises the voltage on the emitter of Q102, causing it to go further into cutoff and ensuring it is no longer trying to pull the reset pins low. The next thing I'd like to do is look at the +5V supply and reset pins on an oscilloscope; the +5 supply should be stable before the reset pins go high. If it isn't, I imagine that using a larger capacitor (maybe 2.2 or 4.7uF?) to increase the time delay would give the supply enough time to stabilize.
  12. Thanks for the offer! I did a close inspection of the print head and discovered it was just dirty. I was eventually able to get it working again. I can also update on the platen tape—I talked to Brad at Best Electronics and he thought it was probably teflon tape. He sent me a piece and it worked very well to replace the old peeling tape. The printer now works fine! Now if I could only find the Macrotronics interface that works with this printer (uses joystick ports 3 and 4, mentioned briefly in Analog #2, page 42). Since my original post I also acquired a Trendcom 200 (80 column thermal printer). Macrotronics published some screen printer software that works with the 200 and it would be fun to try doing some screen dumps. From what I read, these would have been some of the earliest printers available to Atari users.
  13. Got the regulators soldered in place, installed the boards and cables, turned on the drive and inserted a disk. Turned on the computer and it booted on the first try! The Doctor said it well...the Grass Valley upgrade is the debug Now the only thing wrong is the power LED—it doesn’t light up. I followed the debug flowchart and it led me to CR107. On closer inspection, there’s a capacitor there when it’s supposed to be a 5V zener diode. Makes me wonder if there are other errors on the side board, but I guess if the drive reads disks ok it must be fine. I’ll put the correct part in and if the LED starts working, I’ll call it good. Now I have two working 810s—no more swapping when I want to duplicate disks
  14. Ready to go. Good thing the local Atari Service Center is well stocked
  15. Found two analog boards. One of the boards had test results printed: Last tested on April 27, 1983 and...as of a few minutes ago! Verified working on my known good 810 analog drive. The other analog board worked too. Guess these are just more reliable than the old design. Time to perform the upgrade; the only thing I haven’t tested is the power supply board. Off to find a 12V regulator...
  16. For comparison since I happened to have all three: On the left is rev 1 of the Grass Valley power supply, the middle is rev 2. On the right is rev 8 of the older rear board. I will probably install the rev 2 Grass Valley board. Apparently it last worked on Oct 6, 1982...coming up on 37 years!
  17. Thanks for the additional advice Doctor! I confirmed the mechanism is fine by swapping it into a known good drive (the newer analog drive, incidentally). It does have the felt pad. So, the only possible place left for the problem to be hiding is the rear board. I’ve already reseated and then replaced all the chips. I suppose it’s possible that one or more of the rear board headers are faulty... I do have a couple of newer power supply boards and an analog board; at this point it’s so far disassembled that I’m thinking about just doing the Grass Valley upgrade. Though it would be fun to have working examples of each version, if the old version is so unreliable I wonder if it’s worth it to debug the issue...
  18. Good find Allan! I’ll have to compare some of the other pages when I get a chance...
  19. Michael Current's Atari Library lists a collection of service bulletins, including the following: Does anyone have this tech tip? I have long suspected that my 820 doesn't work because the processor isn't coming out of reset properly. Even the paper advance doesn't work if the printer isn't working after I turn it on, though I can see that the paper advance signal is making it to the IC. However, the chips seem to be good because if I power cycle the printer, once every 100 or so cycles it comes up okay and will both advance paper and print. It gets tedious to switch on, press paper advance, switch off, switch on, press paper advance... I would be interested to see what the tech tip says, or whether anyone has solved the issue with 820s that only seem to work every once in a while.
  20. Thanks for the advice Nezgar! I thought maybe RPM too, so I tried turing the pot to change the speed. I could clearly hear and see the motor speeding up and slowing down, but no change in boot activity. 12V seems solid, it measures 12.4 at the pass transistor when nothing is happening, and drops only slightly to 12.3 when the disk starts turning. The 24V feeding the pass transistor drops much more significantly, I measured around 18-19V when the motor was turning.
  21. Years ago I found an 810 disk drive in the trash along with an 800, a 1200XL, and a box of disks. I've restored the 1200XL and am finally getting around to the 810. This 810 has the old-style rear board, and I know that the problem must be either with the rear board or the drive mechanism itself because I'm using a known good Rev C side board with data separator. I also verified 5V and 12V on the rear board; I had to replace the 12V pass transistor because it was shorted and passing 24V! So far, I've tried swapping out all the ICs on the rear board, but no luck. The drive goes through the normal power-up sequence, but when I insert a disk and turn on the computer, it alternates every few seconds between trying to zero the head (pushing against the stop since the head is already there), and beeping once with a "boot error" message on the screen. Any advice on what to try next? I do have an oscilloscope if it would help to look at some signals.
  22. You might find this post interesting: http://atariage.com/forums/topic/242227-calling-all-800s/page-1?hl=+800%20+serial Assuming the serial number is 949 4420, that would mean your 800 was made in the 49th week of 1979, making it a very early model indeed (and one of the oldest on the serial number list linked above). The CTIA and IC dates would seem to confirm the manufacture date. Nice find!
  23. I have two 810 side boards with what look like ROM upgrades, using piggybacked chips. One has a data separator board, the other doesnt: I also have a side board with a windowed FDC: Are these of any interest for ROM dumps?
  24. I recently got an Apple II+ with a clone of the Saturn 128 memory card installed. I have it connected via composite video out to a modern LCD TV. With the memory card installed, there is a lot of red and blue color bleed around text on the screen, and a bunch of vertical blue dashed lines that are continually pulsating. Without the memory card, the text is crystal clear. Interestingly, whenever I load a program on disk, the bad text and vertical lines clear up while the disk drive is running, then come back. Bad: Good (while disk is running): Is there any way to fix this? Should I find an official Apple 64k upgrade card and replace the clone Saturn card? Do I even need a memory upgrade? Im guessing yes because a lot of the games Id want to play probably require 64k.
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