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  • Posts

    • Don't forget that the drives internal transfer rate is slightly different for reading and writing. AV drives were optimized for writing data, consumer desktop drives are optimized for reading data. You also have different real world speeds depending on if you have data on the inner tracks or outer tracks (empty vs full drive).
    • Wasn't this also known as the "internal transfer rate"? If so, most drives did have this published. Check out the pages of hard drive specs at stason.org: most of them have it listed in the first few lines (assuming they're accurate). According to the info there, for example, an HP C3325A (2GB, 5400RPM) supports a 10MB/s external SCSI interface but only transfers internally at 5.5MB/s. A Conner CFA-1080S (1GB, 4500RPM) supports the same 10MB/s externally but has only a 4MB/s internal transfer rate. A Conner CFP-1060AVW (1GB, 5400RPM, supposedly AV-rated) has a 20MB/s fast/wide SCSI bus for external transfers, but still only rated for 4MB/s internally. Ouch. Not buying that one. IBM's 0662-S1D (1GB, 5400RPM) has a 10MB/s external SCSI bus and transfers internally at 5MB/s. Surprisingly that HP drive is supposedly the fastest of these and the only one to exceed 5MB/s internally. I did not expect this. I actually have one of those, and I guess I'll have to stick that on a fast SCSI bus in a late-model Mac rather than use it to upgrade a stock Quadra or something. Is there anything that can saturate that SCSI bus though? Ah, here we go: IBM DCHS-39100DEF20W (9GB, 7200RPM) has a 40MB/s Ultra Wide SCSI interface and a 15.4MB/s internal transfer rate. This drive is more than a match for the fastest SCSI buses built into Macs and would nearly saturate the 20MB/s Fast/Wide SCSI bus of a JackHammer, depending on file sizes and how well the caches were utilized.
    • The photo seems to show a black mark on top of LF1, if that is a burn mark then maybe LF1 has a short. Also, is the hightlighted resistor burnt or just black in colour?     If all good then my next step would be to desolder the switching transistor (and remove it from the heat sink), then switch on the power and see if the fuse pops or not. If it does, then it is likely you have a fault somewhere from the AC input to the 170V rail.     If not, then most likely the switching transistor (yellow circled in photo above) and/or associated circuitry is shorted out.        
    • Hi Will. You mentioned the previous owner had connected it to 240v instead of 120v, and that had blown the fuse. I think it likely that some other component has been fried before the fuse went. I checked the failure mode of X2 and my money is now on that:   When a Class-X capacitor, also referred to as an "across the line capacitor"—the capacitor placed between line and neutral—fails because of an overvoltage event, it is likely to fail short. This failure, in turn, would cause an overcurrent protective device, like a fuse or circuit breaker, to open. Ref: https://www.allaboutcircuits.com/technical-articles/safety-capacitor-class-x-and-class-y-capacitors/   I’d test for a short across X2’s pins next...it might be new looking but you didn’t replace it, right?   JD
    • Yeah I'm pretty sure at least 3/4 of the vintage computer people (myself included) are more on the hardware side than software. I mean if you only want to use old Mac software you'll just download mini vMac or Basilisk or Sheepshaver or whatever emulator, not futz around with ancient finicky mounds of increasingly brittle plastic and metal that take up loads of space and require regular maintenance to continue operating and that cost tons of money to fix when they inevitably break (or if you want something like an original XCeed card, for which most people would have to sell one or more children for medical experiments to be able to afford). So here we sit, heads filled with grand ideas and fully realized hardware mods and nobody to write anything that uses it. Tragic. Good programmers are hard to find.   People love these old things but so far they've basically been limited to the original mid-80s experience (read: slow and monochrome) or a mod (several people have gutted classic Macs to use the cases to house iPads or minis with small LCDs). Once this project is released an unintended side-effect may be to drive up the cost of SE/30s since now you'd be able to do modern things at a reasonable speed, all in the comfort of your authentic vintage Mac. I'm just glad that I bought six of them before your case project was released to the world.