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About tf_hh

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  • Birthday 10/11/1970

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    Microelectronics, Atari 8-Bit Hardware, Atari 16-Bit Hardware, ATMEL Microprocessors

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  1. Ok... now it´s clear - and simple. One of the both SHIFT keys are permanently pressed down by failure. Remove the caps from the keys and check if there´s some dirt between. Which keyboard type you have? Best is to make a picture from both sides.
  2. Check this little program out (see above). The reason why I let test it: Maybe one of the datalines to ANTIC is faulty (ANTIC reads from memory, D5 = defect). ANTIC fetches the ROM for character set (typical $E000) and the RAM for screen memory and it´s program - called Display List. When a normal "A" (BIN: 01000001) is printed, but a "0" (BIN: 00110000) not, then maybe bit 5 is defect. This bit is mostly not used in the Graphics 0 Display List. You would have some less or more empty lines at the screen´s top, but the human eye wouldn´t see that. ANTIC might work in Graphics 0 "normal" except wrong screen memory contents.
  3. Yes - and no 😋 - You´re absolutely right, my power PCB has also 9.1K at this place. But Atari did something weird, R204 two time exists - one at the power PCB (with 9.1K) and one left side of the variable inductor on the mainboard. This one was the one I meaned, and it´s 75R as shown in the FSM, too. From memory I didn´t recall when writing this above, that R204 should be on the mainboard, not on the power PCB. R204 at the power PCB is connected to the modulator mixed video/audio input and ground. I would like to know HOW this could be burned this way...
  4. If you want to use this monitor / TV anyway, then change of the 500k color pot (lower left corner of your 800XL) might be worth a try. Sometimes after warming up these pots are changing their resistor significantly and this also forces some monitors / TVs to make a wrong colored picture like in your 2nd picture. It´s a standard pot, 500k, linear, 10mm pitch. Take a closed case one like Piher PT10 or so. It´s just a buck or less.
  5. R204 should be 75 ohms. It is the major pull-down resistor for the chroma (color) amplification around transistor A104B. The way it´s burned the only possibility is that somebody has sometime put a power supply to the monitor jack of this Atari 800. Sometimes Atari has built here 130 or 390 ohms in, but this is wrong. The correct impedance for video is 75 ohm. I would suggest to check all parts twice if there are any more burned components. Also take a look at the solder side, specially around the connector to the power board, maybe a trace is burned also.
  6. I´m pretty sure something went defect. Probably ANTIC, maybe GTIA, or a very strange issue with RAM. Try following. Switch the computer on with no devices attached, no key pressed. BASIC is started and you should get a READY prompt. Now enter BLIND. Don´t look at the monitor, just type it in: 10 PRINT "! 1234567890 ABC XYZ" 20 GOTO 10 Enter "RUN" and look what happens. When there´s repeated output on the screen and it won´t stop after a few seconds, the memory should work. What you´re reading on the screen when this BASIC program runs?
  7. Hi, it´s an absolute standard part. The one shown in the picture is the 1 MHz version, working fine in any 1050. When you order them from one of these chinese sellers on eBay etc., keep in mind, that 50% of the delivered ones have failures. Sometimes these are faked, too.
  8. Hi, some hints... 1. Yes. The CPS1050 test runs only with genuine Atari firmwares. For example, when a Speedy is installed, the inserted disk will be formatted during the main tests 😋 2. & 3. Does the motor start spinning anyway? Did you test with a well-known working mechanic? Most issues around spin motor fails or step motor fails are based on instable voltages. First check if the output of the 7812 linear voltage regulator is stable between 11.90 and 12.10 volts, even when any of the both motors starting action. Best is checking with an oscilloscope to see if the input (approx 25 volts DC) and output (12 volts) is stable and show a flat line. When the input shows sine curves, replace the three big caps (C67, C68, C71) immediately. In rare cases one of the six major rectifier diodes is bad. When input and output voltages are clean and stable, replace the four caps involved in the 12 volts motor power circuit. These are: C70, C21, C42 and C43. In mose cases the spindle motor starts now flawless. Now use CPS1050 tests with a fresh single-density formatted disk (you should never use the CPS1050 disk for these tests...). Format the disk in a well-known working 1050. Step motor issues could be of course a defect step motor or typically a defect at one of the both 5713 chips. Also have a look at the 47R resistors R56, sometimes it was slightly burned, visible by a brown/dark smokish surface. Good luck!
  9. It´s meaned this way, that for installation of the SCCC there´s no need to drill extra holes in the case nor scratch any traces or so at the mainboard. Most owners of Atari 400 / 800 computers won´t do such destructive things. Changing the whole CPU card isn´t any kind of "destruction" - Atari wouldn´t design a changeable CPU card if they won´t have thoughts about new or better CPU cards for the system (specially with the also changeable personality card of the Atari 800) in the future. In some rare cases the video quality of the SCCC might be a little bit better than using the seperate UAV rev.D Plugin-Board for example. I´m using a two-staged voltage regulation on the SCCC. First there´s a highend, very low drop (LDO) voltage regulator from the +12 volts rail to +5.0 volts down with max. 0.8 amps load. The "new" 5.0 volts are used for the video circuit involved chips needing 5.0 volts (NCS2563 video chip, the 74HCT74 for PAL color clock generator etc.). These clean 5.0 volts are again reducued to 4.5 volts using the exact same LDO voltage regulatur found on the UAV rev.D boards to meet Bryan´s specs. The difference is now, that the "new" 5.0 volts feed at the SCCC is absolute clean and free of any disturbances caused by CPU, ANTIC and GTIA (and at last all other chips using the standard 5.0 volts rail at the whole computer), so called independent from system load and capacitance. IMHO the picture is sometimes a little bit clearer and sharper than using UAV rev.D in an Atari 400 or 800.
  10. Sorry, not beeing often online here this time. So much trouble in reallife these days. Diagnostics over long distances are hard. The DRAMs used at this board are not known for often failures, but never mind, RAM failures are the most probable issue followed by bad CPUs... normally. My personal experience the last 2 or 3 years shows me, that more and more other chips went bad, too. Not only RAMs or CPUs, I got more and more defects with ANTIC, GTIA and the MMU, which is a standard PAL16L8 labeled with Atari markings. Also bad O.S. ROMs follows. It´s a mixture of culprits these days, and remembering the fact that nearly all chips were producted 35 years and more ago, it´s no wonder that the amount of failures over all chips raises. If you have an oscilloscope, check out the usual points. Pin 7 of the CPU - is there execution of opcodes or not? What about CAS (pin 15 of all DRAMs), is the RAM accessed or not? Check CAS_Inhibit (Pin 16 of MMU), or also check Pin 6 of the MMU - there must be a toggle from high-low-high during power-on, this is when the selftest is mirrored for a short time. If this won´t happen, the memory size test fail and the O.S. hangs up. Much more possible, but without a scope there´s no real chance to check the major points.
  11. I didn´t understand polish language and the google translator doesn´t work fine with that forum without login. But, independent - the "manual" from Lotharek is... non existent. Maybe it´s forgotten. But what I can say from years of experience with several speeders is, that with these four capacitors only POKEY divisor 9 or more (higher the divisor, slower the transmission speed) works flawless. The Speedy 1050 is also working at divisor 6 in Highspeed-copy-mode, and this requires the removal of the caps. Also the Happy 1050 Highspeed XFER-test will only pass with removing them. If you have more than one 1050 connected to the SIO buss, the problems gets more worse. Finally: Take a Happy 1050 and you have a not so flawless speeder, but it works mostly with the caps installed. AtariMax offers a solderless version of a Happy 1050 clone. All other speeder requires the removal of these for caps IMHO.
  12. Do you mean the "1050E" from Lotharek? This one needs also the removal of the four caps, otherwise you get a lot of transmission errors in highspeed mode. I´ve tried with capacitors, doesn´t work flawless. Without caps, works mostly fine (except some firmware issues, as you already mentioned).
  13. That´s the reason why I like to order at Mouser. They´re not the cheapest on the planet, but - from my sight - the fastest. More than one time I place an order at the weekend, at finally on Tuesday or Wednesday the FedEx driver knocks on my door. The goods are always shipped from Memphis, TX to Germany. A lot of german or european electronic dealers are much slower than Mouser - from over the pond! 🤗
  14. Maybe it´s part of the holder/arm for the UV LED used for the write-protect light barrier?
  15. Take a machine-head precision socket, plug the defect chip in, fill the intact legs with solder, so that nothing can move even for a nano-meter 🙂 - Then take a little piece hard wire, plug in into the unused hole where the broken leg is. let flow some solder into the hole of the socket. Place this "new leg" against to piece from the former leg of the chip and solder again. This way I salvaged some ANTIC, GTIA and other from disposal.
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