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WombatPredator

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  1. I didn't think of that. I've been trying a couple of ROM SIMMs with the same results, and close inspection of the slot led me to believe that it was fine (no corrosion, nothing bent). But I didn't really consider that the problem might be simply mechanical. I'll take another look. Thanks for the idea!
  2. I think that for the specific use cases of the denizens of these forums, it has a very good price / usefulness ratio. This little box should be able to happily sample the fastest 68k Mac of all times (the 840AV), which is a 68040 running at 40 MHz. Also, it's being actively reverse-engineered and integrated in the sigrok project (specifics for this model are here) which means that alternative (and potentially better) interfaces exist, and that it will remain useful in case its manufacturer drops it. If you can afford it, I think it will cover a lot of your needs for a long while.
  3. I have received the logic analyzer and I've been able to poke around a little with it. Once you get your head around the basics, it's quite straightforward and, so far, it's been like shining a flashlight all over the dark corners of the board. I get the feeling that, instead of my current approach of "let's take a wild guess at what could be wrong and hope I find something", I should be able to methodically start ruling things out and pinpoint the source of my troubles. So, the model I got is an InnoMaker LA2016 (which seems to exist under a bunch of different brands, including "K
  4. Thanks for checking the headphone jack! That really helps! I've ordered some tape as you recommended, that should diminish the stress levels I've also received a little logic analyzer. I picked a 200 MHz model because I need it to keep up with the wicked fast 40 MHz of the IIfx, and the recommendation seems to be that the analyzer should run 4x or 5x faster than the thing being analyzed (to ensure that nothing is missed). A lot of these analyzers seem targeted at Arduinos and serial ports and, let's face it, we're looking at the quickest piece of hardware this side of
  5. Thanks for the tips on the desoldering. Sounds feasible / terrifying. I also have a cheap air station* (huge time saver for the 14+ caps of the IIfx) so I could definitely try the removal that way. But I'll try your second idea first, I think And I assumed that the speaker was good because plugging in headphones gave me the same popping sound as the speaker. But thanks to your comment, I now realize that it doesn't really prove anything because I don't recall if the chimes are played in the output jack. It could still be the speaker, or the whole sound circuit th
  6. Thank you for the suggestions. C7-C9 is indeed the location where noticeable damage was noticed and I may have missed something there. And I'll try to reflow the new ones. Would you know what UB16 (a black cube with 4 metallic lines running across its top) is? I wonder if something oozed underneath. I have replaced the radials. I don't think they were leaky but I did it anyway. I'll re-check those too. And I dread replacing UI18 and UJ18 a little. I haven't replaced a multi-legged thing yet I wonder if I should get a logic analyzer (I was shocked by how che
  7. Well, reflowing the weird traces didn't help. And after another thorough cleaning of the board with IPA and a toothbrush, still nothing. I've also been checking Gamba's diagram and checking every connection in the startup circuit and nothing seems amiss there either. Corrosion seems minimal. To illustrate the depth of my despair, I got pretty excited when I found a flake of flux straddling two legs on a chip I'm starting to wonder if I should start desoldering chips in the vicinity of the old caps, in case corrosion got underneath (although it seems unlikely judging by
  8. <smacks forehead> Of course. And the fact that the ROM-inator II has a custom chime should have been a clue to that. Thanks for pointing it out! Back to testing with the ROM in then, and to including the ROM has a potential cause for my troubles. I've been redoing some continuity testing around the areas pointed out by JRotar above and, previously, I was only paying attention to the beep (easier when your eyes are glued to a microscope). However, a couple of traces take longer to beep and show 5 Ω (where most of them are at 0.3 Ω or less). I'll reflow them an
  9. No leaking cap that I can see. But good thing to check once I get there! Right now, I'm aiming for the death chimes. I'm running the board without RAM, without ROM* and without any card. The only things plugged in are the speaker, the batteries and the PSU (obviously). * It's my understanding that the machine chimes when it's done powering up and before it looks at the ROM but I might be mistaken. I'm looking at page 244 of the "Guide to the Macintosh Family Hardware 2nd Edition" (it's on archive.org) but I don't see mention of chimes, which is a shame because it's a us
  10. Thank you very much for your reply. I'll take a closer look in that neighborhood. I may have overlooked some of those legs. The hugeness of the IIfx motherboard makes it difficult to maneuver under a microscope without constantly bumping into the boom stand. It's sometimes tricky to look at something under different angles, and things might end up unnoticed. And thanks for drawing my attention back to Gamba's diagram. I had looked at it in the past but it's now obvious that, judging by the symptoms I'm experiencing, the issue lies somewhere there.
  11. Hello everyone, I'm currently trying to bring an old IIfx back to life. It powers on using both the back switch and an ADB keyboard but goes no further. The speaker makes a little popping sound (I assume this means it's getting power) but doesn't chime. There is no video on my known-good original Mac display, using either of the NUBUS cards I have kicking around. NUBUS is getting power however, because my Ethernet card is happily flashing green on power-on. Here's what I have done so far: - New batteries. - Replacement of the electrolytic condensat
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