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  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
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