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NE555

6502
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  1. NE555

    another simasimac

    all data lines from the floating processor to ROM are good. My CPU is not socketed
  2. NE555

    another simasimac

    It can't be more boring than some of the videos that are on youtube at the moment. I can't find any traces that are OL. But I am getting the feeling that even if a trace might not be bad It might have a resistance that makes it useless? As I said I would like to see a video like this just to be able to compare to a baseline. Maybe someone testing the board with an oscilloscope even. check between CPU and anything else sounds extremely generic. How many have actually fixed a Simasimac SE/30? And I don't mean one that just needed C6 and C7 replaced
  3. NE555

    another simasimac

    I wished someone would make a youtube video of that process
  4. NE555

    another simasimac

    thank you for that info.
  5. NE555

    another simasimac

    I recapped the SE/30 logic board. then upon start up , there is no bong, no error chime. just a Simasimac screen. I have been trying to trace things out and found a whole bunch of vias without solder in them. Been trying to fill them with solder and a piece of wire. So far the Simasimac persists. I keep finding more and more empty vias. I am not sure if what I am doing is actually helping in any way. All the rails seem to get the proper voltages. LS166 has been replaced already. what's next?
  6. NE555

    SE/30 with graphics issue

    Oh ok , that makes sense then. I thought you meant it booted regardless of no RAM
  7. SO yes Even without RAM I will get a fast chime. The green pattern comes up with a ROM in the socket and internal video and RAM. I didn't try a NUBUS video card. well I did. But I am not sure that card is actually good. I can take a high res picture, but there is nothing prominent. I even looked it over under the microscope About the ROM, I tried with an SE/30 ROM https://www.ebay.co.uk/itm/Apple-Mac-SE-30-ROM-64-Pin-SIMM-Macintosh-820-0241-02-630-4339-Vtg-SE30-/362591668923 The other is a toshiba ROM SIMM it has a number 7788A1. Not sure if that's a SE/30 simm
  8. NE555

    SE/30 with graphics issue

    Am I reading this correct? You said you got the Computer to boot without RAM? I didn't know that would work... Actually I'm pretty sure that wouldn't work. Hmmmm ...
  9. I used a couple of 512k ROM . They should boot or at least show a gray screen? I also tried the RAM of a good board. to the same effect. If the onboard ROM is bad then using a 512k Should do the trick or not? PSU is known to be good, too.
  10. No broken traces under or near the battery tray. I noticed that having the RAM in or not doesn't seem to make a difference. But taking the ROM jumper out causes the board to do nothing at all.
  11. there is no prominent damage from battery acid. But I'll look at the traces and vias in that area. thank you for the advise.
  12. When I turn on the board I get a fast error chime, no video. When I install a ROM sim I will get a green striped screen. Jumper is in . All memory populated or 4 RAM populated makes no difference. swapped for other RAM it makes no difference, either. The Power up circuit seems fine. So what is next to check out?
  13. NE555

    Apple III issues

    tried that... no go... I was thinking that maybe one is sticking on? not sure ... would that not affect the reset, control OA combo?
  14. NE555

    Apple III issues

    The Keyboard connector seems to be seated correctly
  15. Last time I turned on the apple III it worked perfectly. Today I noticed that upon start up , the keyboard doesn't function. Or better Most keys don't. Reset , control and open apple seem to work. But I can't enter any keys to start memory check for instance. any advise on that?
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