Jump to content


  • Content Count

  • Joined

  • Last visited

Profile Information

  • Location
    Stockholm, Sweden

Recent Profile Visitors

The recent visitors block is disabled and is not being shown to other users.

  1. The Q9 was OK but I noticed a bad trace to the Q9. After reparing that the AIII is booting ( Apple III system utilities) and the keyboard is working, but there is a videoproblem. No text, only vertical lines. I have replaced the RAM on the 5V memory board but the same results. According to Apple III service reference manual it can be defects in several IC on the motherboard. Any suggestions Before I order a lot of new ICs?
  2. The Apple III is alive - partially The reason for it to wake up was a little suprise for me. I measured the 5V line at the motherboard when using the ATX PSU, it was 2.9 V but when I measured it at the cable at the PSU it was 5.0 V. The reason for the voltage drop was that I used thin, bad and cheap cables from the PSU to AIII. When I used new good cables and soldered them to the PSU cables. The voltages at the motherboard then was -12.7, -5.2, +5.3, and +12.4 V. When I turned it on, there was one beep from the speaker and this on the monitor. Its a blinking cursor at the left top
  3. I tested the motherboard (connected with memoryboard, keyboard and monitor) with different voltages from Velleman . Only 5 V line. The current is displayed on the PS. Resistance calculated from that. Output V Measured Amps Calculated resistance 0.5 11mA 45 ohm 1 120mA 8 2 518 mA 3.8 3 997 mA
  4. I tested with a Velleman programmable DC Lab Power supply. When set to 5.0 V it drains 2.0 A. Nothing is really hot on the board, the only thing thats warmer is the SY6522 ic at B6 thats 36 degr C. Also tested with a working PSU from a Apple II. All four voltages. Same results as the tests with ATX PSU, 5.0 V goes down to 2.9 V and no booting. AII PSU tested OK afterwards.
  5. Thank You techknight for that suggestion. I have an adjustable bench power supply but it can only deliver two voltages. Maybe I can combine with several PSU and all " 0 Volt" line connected. Is it dangerous not to feed the AIII with -5V or -12V? Can I test the motherboard without the memoryboard to see where its getting hot?
  6. Yes, probably. But its strange (at least for me) that the resistance between 0 and +5 on the AIII is 215ohm and that implies that there is not a constant short. Maybe a capacitor thats defect??
  7. I have an Apple III, A3S1 no 57901 motherboard 820-0043-00E 5V memory board. When I got it the power supply was dead. I´m trying to restore it but I have tried with ATX PSU unit that delivers -12, -5, +5 and +12V. Put in a new keyboard lamp. When I turn it on there no sound, no video, no reaction from the floppy drive or keyboard. The internal LED CR7 has a faint light. Otherwise no signs of life. I have tried two different floppy drives. It is obvious that someone has replaced some capacitors. The electrolytic caps C60, 61, 62, 63 and tantalum C1, C10, C12, C13, C71 l
  8. Hi nvdeynde and techknight. I got a defect Mac Plus (240V) that was dead. No power on the analog board so I started to check all components. It was exactly the same fault, R55 had no connection, completly open. It was 33k but I replaced it with a 20k resistor ( according to Larry Pina, Macintosh Repair & Upgrade Secrets) and its working perfect. Maybee should be 33k https://68kmla.org/forums/index.php?/topic/29763-macintosh-plus-analog-board-q12-replacement/&tab=comments#comment-575154 but its working anyway.
  9. Hi bibilit. That’s a little confusing for me. For Mac II-series machines with ROM SIMM slots, check to make sure the W1 jumper is removed (if a ROM SIMM is installed) or installed (if the ROM SIMM slot is empty). http://www.ccadams.org/se/pickle-faq.html According to BMOW , Mac IIsi: Insert a jumper at location W1 on the logic board if a ROM SIMM is installed. https://www.bigmessowires.com/romdrv/rominatorii-instructions.pdf When I got it it was no jumper, no ROM SIMM, no RAM SIMM, (not working). I have tested my MacIIsi board ( 820-0301-A, 630-0265) with and without jumper and w/w
  10. I have used an ultrasonic cleaner that I found on ebay, made in China. Its working fine. During cleaning it was like smoke coming up from the MB under the RAM chips. Cleaned with distilled water mixed with cleaning fluid. The MB looks like new but unfortunately the MB is not working. Same result as before cleaning. I will desolder and clean UB7 and UB8 , maybe that can help. Otherwise I dont know what to do.
  11. Thank You techknight and sigtau for Your comments. I will try to find a ultrasonic cleaner for a reasonable price. If not it will be the dishwasher..
  12. Yes, I cleaned the board with isopropylalcohol after removing the caps. Cleaned with q-tips with aceton were the caps had been. I have recapped SE/30 boards before and I think this one looked rather good. No battery leaking. No obvious destruction on the traces. But I realize that one should look for defects around the caps. All the fuses on the board are tested and are OK. A picture of the board before recapping..
  13. I got this Mac IIsi a year ago. Removed the battery and all caps then. Didn´t test it before that. Now I have started to get it working. All caps are replaced with tantalums, new axial caps. When I turn it on, the fan is working, HD is spinning. The screen is white with no mouse pointer. Only a click from the speaker but no other sound. The PSU is fine, I have also tested with o PSU from a working Mac IIci, same result. No RAM SIMMS, no ROM SIMM. pin W1 is enabled. I guess the IIsi should boot with the RAM on board. I have checked several times for corroded traces but not found any . Also ch
  14. I submerged the board in 99% isopropylalcohol for some hours. then cleaned with a toothbrush, high pressure air and dried for some hours. I checked the tracing You described, all Ok. The board looks very clean and nice, but its not working . Same error code. Time to replace the RAMs. I tested with a RAM card of 1 Mb installed. That is from a working portable. No change. I guess that the internal RAM must be OK to use the RAM card. The SRM20256 RAM on the board is 256k, is it possible to mix with 128K ???
  15. Thank You techknight for Your interest in this poor portable. In fact it was a poor picture with some dust on the board. After cleaning its looks like this today Previously I have resoldered that RAM, as the soldering did not looked perfect before. The Connections are OK now and no bridges between the pins. Maybe I will start replacing RAMs on row A-B as they are closest to C4- C5.
  • Create New...