Jump to content

Cinan

6502
  • Content Count

    50
  • Joined

  • Last visited

Everything posted by Cinan

  1. Yes I have already tried that. I have used this LB with a 128k analog with same response and the 128kbLB with this AB and it works fine. So it's something on the LB.
  2. No change unfortunately, I used a tantalum and then an electrolytic. the sequence is as follows : 1. power on - vertical bars 2. reset switch - boot ok with bong. 3. power off 4. power on - boots ok with bong 5. power off 6. power on - boots ok with bong point 4& 6 only work if they are within a few seconds of 3&5 leading me to believe that there is a capacitance issue somewhere as once the charge has been lost it goes back to point 1. I can't see other capacitors on the schematic that would be causing that. So unless there
  3. I have taken C9 out of the board to test it. it is just showing an open circuit on the multimeter when I test for capacitance. I have a spare non-working Mac Plus board, is there a glass bead cap on here that I can transplant, too hard to read so I need some experience to tell me - please. If I can't transplant can I replace C9 with an electrolytic or a ceramic cap ? On the schematic it looks like it is polarised but on the board there is no +/- marking, help !!!
  4. Have done some of my own research. Glass bead caps it appears. I assume I can replace this with a ceramic cap of 4.7uf 35v ?
  5. So I replaced LM311 without any change. I am now thinking it might be C9 as per the image above. In my understanding if C9 isn't working properly then the -ve won't be presented to pin 3 and therefore LM311 won't create the reset signal. But if the reset switch is pressed (SW2) then it will complete the circuit and the negative presented to P3 and hence LM311 creates the reset signal when I press SW2 and the CPU reboots ?? is that logic right ? My eyes aren't the best but C9 looks to be a non-polarised 4.7uf 35v on the schematic but on my board C9 looks more like a diode than a
  6. I would start with the chips that have traces passing by any caps so UK11, UK12, UJ11, JI12, UG12, UE11. these should all have D and A connections and pass but eh group of caps around C9. I started with identifying any visual damage, and then looked at the traces around that and started there. Also built a spread showing pin on origin chip and pin on destination pin for easy lookup while holding the multimeter probes.
  7. Yes they have been replaced and the analog board is fine.
  8. I would also check traces between components not just between components and CPU.
  9. I had a similar problem see link below. Check your Dxxx and Axxx data traces between IC's. I see you ahem recapped the board, mine was caused by a broke trace near C9.
  10. Agree. I have ordered a new LM311 chip so lets see what happens. I did some more testing last night and it seems that after resetting once and then using a multimeter on pin 7 to see what was being sent, the machine then started working normally after a few times of on/off's but then resorted to not starting. I also got the FloppyEMU working when using System 2.0 as the system disk. Some strange behaviour but at least it is showing signs of life. Does anyone have a spec sheet of the smaller components - Especially the Diodes on the 512k board as I may need to replac
  11. And yes Sound is working ok to give a bong. I will do testing on the LM311 today to see what it is doing at startup.
  12. Found it here - http://www.digibarn.com/collections/diagrams/mac-512klogicboard/index.html
  13. Assume it's the LM311 chip.
  14. Thanks this makes sense. Just need to find now what pulls RESET and HALT low creating the RST circuit. On the schematic it looks like the circuit above the IWM chip on the Schematic but it is too fuzzy to read. Does anyone have any clarity on this ?
  15. So some progress but only accidental. I have checked all the connections coming off the CPU and traced them to other chips and performed some general continuity testing across the Logicboard today from what I can read on the very fuzzy Schematic of the 128/512k board. (Note : I actually found an error in the schematic on pins 45 & 46 on the 8530 chip, they read D14 & D12 but should be D15 & D13 !) I had all but given up and thought I would try the interrupt switch at the vertical bars, nothing. Then I tried the reset switch and I got a bong and a Mac scr
  16. Thanks this is really helpful, I will study over the weekend. brings back many memories of Assembler coding at university ! Any easy way to test the CPU without a scope ?
  17. I am trying to diagnose a problem with vertical bars on a 512k and want to know if anyone has seen a documented boot sequence for a 128k/512k Mac so I can work through the sequence. I don't have any visual issues on the logicboard so I am down to trying to work out which chips may have problems. The fuzzy schematics I have been able to find aren't that helpful - or readable. What I am after is the triggering mechanism from when the power is turned on to get to a "bong", somewhere in there I have a problem. Details can be found over here - unfortunately it seems to have been take
  18. Some interesting updates. I have tired the 512k Logicboard with he 128k Analog board (same result) and I have tried the 128k logic board with the 512k analog board and it works ok, so the 512k analog bard is good. I have then swapped the ROM's from the 512k to the 128k and the 128k works ok, so the 512k ROM chips are ok. I have tired the 128k ROM's in the 512k but it still does work, so the 512k board is the issue not the ROM's or the Analog. I am assuming at the 128k ROM should work in the 512k board ?
  19. I have acquired a 512k 120v model. On first inspection the fuse was blown and diode at CR24 was burned out, I have replaced these and done a complete recap of the electrolytic on the analog and logic board plus the RIFA CAP at C38. On start up I get no bong and vertical bars as per the photo. This is usually associated with a ROM issues, I have pulled and reseated the ROMS and also re-soldered the ROM holders on the under side of the board with no change, I will try with a logic board etc of a 128k but thought it worthwhile asking this group. One peculiar point is the top of
  20. I will pull the power board out and send an image of that as well over the weekend.
  21. Any link to the pinouts on the boards ?
  22. Thanks all some good ideas to check. I have wired in a AAA vision of 4.5v for the PRAM battery and tried to start with the power key on the keyboard. Absolutely no sign of life. Will try probing around on the weekend.
  23. Hi all, I have a Performa 5260 that is dead on power on, no noise, no smells. no activity. I am more used to Compact Mac's so this is new territory for me. I was going to start with a complete recapping of the power board and video board and see if anything changed. I have pulled a few resistors and checked, they seem fine, I am also thinking C801 and C804 are Rifa caps so may replace them as a matter of process, I have also checked the fuse at F801 and it is fine. Are there any other obvious areas where these suffer and would cause it to be completely dead ?
  24. BTW, the trace fix also fixed the lack of sound.
  25. Hi all, I have a Performa 5260 that is dead on power on, no noise, no smells. no activity. I am ore used to Compact mac's so this is new territory for me. I was going toast with a complete recapping of the power board and video board and see if anything changed. I ave pulled a few resistors and checked they seem fine, I am also thinking C801 and C804 are Rifa caps sp may replace hem as a matter of process, I ahem also checked the fuse at F801 and it is fine. Are there any other obvious areas where these suffer and would cause it to be completely dead ?
×
×
  • Create New...