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sirlemonhead

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  1. sirlemonhead

    Request from someone with 475/Quadra 605 and multimeter

    Thanks for checking that for me, I was like 90% sure but wanted to be certain
  2. Hi, I accidentally lifted a pad on my Performa 475 when removing the capacitors. I'm not sure how to repair this. I was wondering if someone with one of these machines (an LC 475/Performa 475/Quadra 605) could check some continuity on their board for me if they have a multimeter? I need to know if the two pads, highlighted in red here (https://www.dropbox.com/s/2eqwqyk749hj5gt/p475_pads.jpg?dl=0) are electrically connected or not? They're at the back left of the board. Thanks!
  3. sirlemonhead

    Dead Performa 475

    Yeah I'm running a 16meg SIMM at the moment which I figure will probably be fine! I have a bootable OS 7 Iomega ZIP disk thats working for now so I can at least confirm the SCSI system seems to be OK I've got a floppy drive on the way and I think I'll probably grab a SCSI2SD as buying a drive on ebay seems like it'd probably be a waste of time.
  4. sirlemonhead

    Dead Performa 475

    Yep 8, sorry
  5. sirlemonhead

    Dead Performa 475

    Thanks I just removed them. I don't have any spares and I have a bag of SIMMs hanging about.. I might just leave the onboard chips off.. unless there's any issue with that? I've just powered on the board again and it's now showing a floppy drive with the ? on it, so it's looking good. I am still concerned about those slightly darkened traces - scrape off and reapply some new conformal coating?
  6. sirlemonhead

    Dead Performa 475

    It's alive! My first ever hot air desoldering attempt was a 100% success. I removed the 10 onboard RAM chips. No pads lifted and with a socketed SIMM, now I have a grey screen with a movable cursor on it! no bongs of doom! I've no HDD or floppy drive so I guess that's why the machine doesn't do much else?
  7. sirlemonhead

    Dead Performa 475

    I've cleaned the board. It's now no worse or no better. I have been now able to get continuity on all 4 data lines for each RAM chip to the PrimeTime chip, so it looks like those traces are OK! Unless the problem lies between CPU and PrimeTime..
  8. sirlemonhead

    Dead Performa 475

    Yeah I was going to just use the pad for some physical stability - would definitely be easier to just run a wire! The board runs exactly the same without the big SMD caps. No video output with the PRAM battery installed. Does the board do the chimes of doom without the VRAM present? I'm wondering if that could be at fault...
  9. sirlemonhead

    Dead Performa 475

    So I got the caps off.... unfortunately lost a pad for one of the caps near the audio chip. When lifting it up, it dropped and adhered itself back down at an awkward angle. No matter how careful I was, it wasn't to be unfortunately. https://www.dropbox.com/s/5terj73dlq9gms2/p475_liftedpad.jpg I might try to glue the pad back on, and it appears as though it was connected to the + of the capacitor beside it.. which would mean the + of the right capacitor was connected to the + of the bad pad capacitor.. does that make any sense?? Here's the black traces: https://www.dropbox.com/s/h3vxov3fvv03184/p475_traces_1.jpg https://www.dropbox.com/s/rixu7e60tnvuam2/p475_traces_2.jpg This is interesting, as it shows blackened traces but these are the lines to the RAM address lines, I believe, and these are all showing continuity https://www.dropbox.com/s/tka2xt3klixxbo9/p475_traces_3.jpg So maybe it's not so hopeless.. Here's an example of the solder holes on the ROM socket, the topmost being dull grey https://www.dropbox.com/s/w4r8it6vjfvr7oh/p475_rom_corrosion.jpg
  10. sirlemonhead

    Dead Performa 475

    PRAM battery has been delayed - I forgot those can't go by air, I think? So I've got the caps but the PRAM battery should hopefully be with me by Friday. I guess I was putting off recapping because I figured since the current ones are OK looking that it might be a waste of money/time to recap it. I'll do it now though so we can eliminate it as a source of potential issues. I'll try get some pictures of the board. Maybe I could stick it on a flatbed scanner? My Dad has one of those I could use - I find photos with my phone always come out pretty dark. The board currently has NEC chips - these specifically https://randomsonicnet.org/workshop/42(S)4400_E70.pdf I have quite a few spare SIMMs though so I could probably salvage chips from those instead? Can the onboard slots only address a max of 4 megs? Also, just wondering - the capacitors are probably decoupling caps, right? Could the board be tested without them present? PS Thanks for the welcome
  11. sirlemonhead

    Dead Performa 475

    Hi, I picked up a really cheap Performa 475 on ebay as the board looked OK from what I could see of the screenshots. I'm an Apple newbie so even though the auction stated chimes of doom, I figured I might be able to get the board working correctly with little effort - not the case unfortunately. I have no SIMM installed and no PRAM battery, but I have two VRAM sticks installed. The machine turns on and does the initial BONG noise, then the 8 notes - 4 ascending and then 3 descending which is the chimes of doom I believe? I don't get any video output. If I do the flick on/off/on again trick, I still don't get video ram. I have a new PRAM battery on the way. The machine seems to have been kept in a damp/humid environment as the RF shield in the case was a little bit rusty, and the VRAM and RAM slots had a handful of corroded pins (somewhat greenish corrosion I think?). The included SIMM actually had most of the gold pins erroded on it's edge connector. The pins of the soldered in RAM chips were a small bit corroded and mostly cleaned up OK. Some traces near the VRAM and Ram underneath look dark in places but I can't be sure if they're gone or not - I can't get any beep from my multimeter in continuity test when I probe either end of a dark trace using it's via holes. Though saying that, I can't get a beep either from doing similar on a perfectly good via. PSU appears perfect. It's a Dyna Comp and the capacitors look good and each voltage rail is spot on. The capacitors on the board look perfect - the board was dusty and there was no evidence of cap leakage. Pads appear shiny. I haven't recapped yet but have caps on the way. I found this thread - https://68kmla.org/forums/index.php?/topic/24711-finally-back-with-some-news-475/&tab=comments#comment-260992, and started checking the pins on each of the on-board RAM chips. I can successfully get continuity between pins A0-A09, RAS, CAS, WE back over to the MEMCjr chip. VCC reads 5v on each chip. What I can't seem to find is where the data input/output pins are supposed to go - Do these also connect to the MEMCjr chip? or to the CPU? If someone could advise on that, I could start trying to find out of those are OK... Should I wait and recap the board, or should I keep probing?
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