Jump to content

AlexTheCat123

6502
  • Content Count

    64
  • Joined

  • Last visited

Profile Information

  • Location
    Columbia, South Carolina

Recent Profile Visitors

448 profile views
  1. All of the PSU voltages seem to be fine.
  2. I checked/reseated the connectors and they seem to be making contact just fine. What should I try next? I'm guessing the problem has something to do with the lack of the 300V and -100V voltages or the 5V bus that is too low.
  3. I have replaced all of the capacitors as well as the TDA1170 chip and nothing changed. I'll check the connectors right now to make sure that they're making contact. Do you have any tips on getting a multimeter probe down on the bottom part of the video board? It's really hard since there's a CRT in the way.
  4. I have an Apple Lisa 2/5 that was working fine up until about a month ago. The screen started randomly collapsing to a horizontal line and eventually got to the point where it was unusable because it was a horizontal line all of the time. After a few weeks of troubleshooting, I found that the problem was a bad trace on the CPU board that made the vertical sync signal intermittent, but after fixing this trace, the screen now displays nothing at all. The heater in the neck of the tube is glowing, but there is nothing on the screen. When measuring voltages on the video board, I discovered that th
  5. I just received a Color Classic with a Performa/LC 575 logic board (https://www.ebay.com/itm/Apple-Macintosh-Color-Classic-MYSTIC-computer/233213293063?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649) and I am trying to get it running again. I tested the computer with my standard Color Classic logic board and the rest of the machine works great, with the exception of the Mystic board that it came with. Nothing happens when I try to power the computer on from the keyboard, so I pulled the 575 logic board out to investigate. I noticed that there were a few bent pins on the lar
  6. That is very strange. The link still works fine for me.
  7. Thanks pcamen. That's what I was thinking, but I wanted a second opinion just to make sure.
  8. I am currently repairing a Mac Classic II that I picked up a few weeks ago and I have found a capacitor that appears to be burned on the bottom of the logic board. Of course, I need to replace the cap (C39), but the schematic for the logic board shows a weird symbol after stating the value of the capacitor. A picture of the symbol can be seen in the attachment below. The symbol looks sort of like a combination of a P and an F, so would it be correct to assume that this means picofarads? I can't seem to find any other mention of this symbol on the internet anywhere. Thanks! Ale
  9. Unfortunately, there is not. Five or six of the pins are broken off entirely and several of the pads on the motherboard have been completely eaten away by the corrosion.
  10. Really? If that is that case, then it would be really cool if someone could program a microcontroller to emulate the PRAM chip.
  11. Darn. I guess I won't be able to get the Quadra working after all because replacement RTC/PRAM chips seem to be pretty much impossible to find.. Thanks for all of the help!
  12. I am certain that the SCSI drive has a compatible OS on it because it is running System 7.5. According to my research, U92 is the RTC and PRAM chip, so that shouldn't have anything to do with the SCSI bus, right? It is a relief that the green tint is probably not a problem with the computer itself. I was sort of nervous that I had yet another repair problem on my hands.
  13. I tried desoldering and resoldering U92, even though it is missing some pins, and to my amazement this caused the computer to boot to the blinking floppy disk screen. It will boot just fine from floppy, but I now have two more problems. 1. The screen has a greenish tint to it. What is causing this? Is it my monitor or is it a problem with the computer? 2. The computer will not recognize or boot from a known good SCSI hard drive. At the blinking floppy disk screen, the drive's activity light flashes briefly every second or so, but the machine will not recognize the drive
  14. I have now replaced all of the parts that were missing, with the exception of C61, which I have not ordered yet, and U92, which is only hanging onto the board by only a few pins. I now get a startup chime when I turn the computer on and the reset and interrupt buttons seem to work fine. However, when I hooked the computer up to a monitor I saw that it had a sad mac error with the code 0000000F 00000001. Is this likely caused by the absence of U92 or is it something else?
  15. Thank you for the pictures! I agree that it appears to say IA5. I believe this means that it is a 0.1uf capacitor.
×
×
  • Create New...