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  1. J

    Need help pointing to strange video problem on SE/30

    The problem could also be in the shift register itself, I've had logic ICs fail in such a way that inputs were dead, as well as some interesting internal faults that caused the outputs to not behave the way I expected. Occasionally I'll take a probe connected to Vcc or Gnd via a 100 ohm-ish...
  2. J

    Using Modern Hard Drives on Old Macs?

    Personally I prefer the pan-style brackets that mount the drive from the bottom over the bracket style. The advantage is that there's room for rubber noise isolation bushings to make the drive really quiet. If you enlarge the holes in the pan slightly, you can fit rubber grommets in them and run...
  3. J

    Macintosh Plus video gave out

    Tapping fixing it is a sure sign of bad joints. Often the fault will be visible to the naked eye as a crack all the way around the pin. It will often arc a bit when the connection opens up, and eventually this burns away more solder and it gets bad enough that tapping it won't fix it. Not only...
  4. J

    Anyone Have a Dead L2 Adjustable Inductor?

    They're made of powdered ferrite held together by a resin binder. The resin, like most plastics, deteriorates with age, heat, ozone, etc and becomes brittle. Also the former it screws into can shrink or warp slightly causing binding making it easier to break. I haven't had to replace one myself...
  5. J

    Caps! -- LC I / II / III

    They may have put those pads there to enable the use of 2x as many chips of half the capacity. It's also possible that they were in anticipation of future production upgrades, quite possibly requiring a different memory controller chip or other changes. You might try tracing out the circuit. I...
  6. J

    Thanks for Warning on PRAM Battery Exploding!

    Most seem to last about 10 years, it varies by usage and storage temperature though and YMMV. I would definitely recommend removing the battery from anything that is not going to be used for a few months or more. I have a IIfx that was completely destroyed by both batteries exploding. There are...
  7. J

    Mac Plus turns off after short time

    It's a fairly common problem. It's likely just a poorly shielded VGA cable and one of the signals is close to a multiple of the frequency you were tuned to. I was recently playing with a FPGA board and found that it emits quite a lot of RF leakage, stomping over my reception of the 128.000 MHz...
  8. J

    Anyone Have a Dead L2 Adjustable Inductor?

    Isn't this the horizontal width coil? Almost every CRT display has something similar. You can also get ferrite cores from other coils, or if you can find all the bits, they can be glued back together.
  9. J

    LCIII Recap - Apple design fault -47uF reversed!

    I noticed the same thing when I re-capped mine. I happened to be looking at the traces and thought something seemed odd, so I measured it and sure enough, the marking on the board is backward. I had already removed the old capacitor so I'm not sure whether it was installed correctly or not...
  10. J

    Moving Caps-n-Coils - Electrical Complications?

    The thing you will want to watch for is parasitic inductance and resistance in the leads. That looks like a switchmode regulator which can have very high peak currents at high frequencies. Notice the parts are clustered tightly together connected by big fat traces. You can *probably* get away...
  11. J

    Multilayer Ceramic Capacitors MLCC - SMD/SMT

    I've used them, they install nicely, actually even easier than tantalums because they conduct heat nicely and the solder flows easily. They're smaller too so it's easier to get at both sides with an iron to install them in tight places. An added perk is they are non-polarized so you don't have...
  12. J

    Mac Plus turns off after short time

    As some have mentioned, it's fairly common for these to fail, sometimes rather spectacularly. As long as the replacements are X2 rated, of equal or greater voltage rating, and similar capacitance they will work. You don't need to find exact replacements although it's nice when you do. As a...
  13. J

    Anyone Have a Dead L2 Adjustable Inductor?

    Easier to measure the inductance and select a similar standard part. Should be able to salvage something that will work from a junk TV or monitor. The wire doesn't have to be identical, anything close will work as long as the core is similar. In a pinch you can make Litz wire by twisting...
  14. J

    Mac newbie & SE30 vid prob...not another one!

    If it's a connection to an internal layer, there's not really much you can do besides running a wire. I use kynar insulated wire-wrap wire, it's the same stuff that was occasionally used in the factory to repair traces or rework errors. It's not uncommon to see a few bits of it stuck on...
  15. J

    Multilayer Ceramic Capacitors MLCC - SMD/SMT

    They work just fine, in fact they are arguably superior to tantalum in terms of performance and reliability. Only reason I've mostly used tantalum is that they are roughly half the cost of the ceramics. Either one is vastly superior to the original parts. The original SMT electrolytics are...
  16. J

    LC PSU Board inside an Apple IIe PSU (Power Supply)

    You'll probably be fine as long as you stick to simpler/newer peripherals. Some of the old RAM cards were real power hogs, particularly those that used a big pile of early generation low capacity power hungry chips.
  17. J

    PCB Design, ART?!?!?

    I definitely consider the appearance when I lay out a PCB. I will see it, and other engineers will see it, and I know that when I look inside a product, I can usually tell something about the engineering that went into it by looking at the PCB layout. There is also the fact that layouts that...
  18. J

    Using Modern Hard Drives on Old Macs?

    Crap, I probably just single-handedly quadrupled the price of these things, I guess I should have bought a few more for myself first :) I've never had to replace a Powerbook drive so I don't know. As someone else mentioned, the length may be an issue although with enough determination one...
  19. J

    Prototype Transparent Mac SE

    That's awesome! I love these transparent prototypes. I have a transparent prototype of a force feedback steering wheel game controller from a previous employer, it's not nearly as cool as a transparent vintage Mac but maybe some day I can sell it for a fortune and retire. Yeah not likely :)...
  20. J

    How to remove corrosion from color classic motherboard?

    I usually use a little squirt of Deoxit, let it soak for a few minutes and then scrub it with a Magic Eraser (melamine foam) and it usually makes a big improvement. For more severe corrosion you can try a green scouring sponge but take care as it will scrape up the PCB. Dental type picks are...
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