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mitchW

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  1. I just repaired (recapped and cleaned the PCB) a PowerBook 170 Power Adapter M5140Z (APS-20E). Needed all of the brown ELNA capacitor replaced. 47uF 50V, 82uF 16V, 180uF 16V and 1200uF 16V were all leaking in the bottom. I was lucky as the corrosion around the caps was still minimal, so I didn't need to repair any traces. I replaced them with 100uF 16V and 220uF 16V Polymer capacitors and the 1200uF 16V with a Rubycon ZL series (Low ESR) one. For the 47uF 50V I just used off the shelf normal cap. Few other caps were fine, so I left them in. PCB was cleaned with multipurpose degreaser/cleaner and plain water. I left it 3 days to dry up in the sun. Main problem was to get it open properly. I was compressing it with two F-clamps while spraying the seam with a brake cleaner to make the plastic a bit softer. Slowly, I got it to open without any damage. Last thing was to adjust the voltage, as it was outputting 7.9V, I corrected it to 7.65V and to glue it back. First two images are before recap and last two after.
  2. mitchW

    Recapped LCiii boot issue

    There was one capacitor on LC III models that was installed backwards from the factory. If you used ceramic capacitors, it wont matter, however if you used tantalum that capacitor may go eventually in smoke. See this thread: https://68kmla.org/forums/index.php?/topic/19752-lciii-recap-apple-design-fault-47uf-reversed/ Also wash the board and check your work. Also clean all the SIMMs.
  3. mitchW

    Manual inject floppy drive woes

    These Mitsubishi drives are very reliable, even with old capacitors in place, however do replace the capacitors, even if you do not see any leakage. Most of the drives had no signs of leakage around the capacitors, but when removed, there was almost always a small pool of electrolyte underneath it. In past, I repaired several dozens of Mac and PC floppy drives and most of the times there are problems with dust and dirty heads, but more commonly in last few years, there are problems with mechanical parts seizing up, even on "later" drives. I even managed to repair an 400K drive with a missing felt pad where the top head is on 800K drives. Last month had a PC floppy drive from 1993 386 machine. It was Mitsumi or Sony one, problem was that its heads only stepped for 1/3 of the distance then stopped. I put some lithium grease and half a drop of light oil on the rails where head assembly rides on and moved the assembly few times around with hand and it worked. I also put a bit of grease on the worm stepper drive while I was there. Cleaned the heads with a Q-tip and isopropyl alcohol and it worked as new.
  4. Huh, no replies? Well, I am still on a lookup for a suitable logic board for my PB G4.
  5. mitchW

    PowerBook G3 Pismo - main battery reset?

    Probably the suicide fuse is blow, it can be replaced with a suitable thin wire. Located on the main battery PCB. 3 pin device. Had this happen on two occasions.
  6. I recently acquired a near mint condition PB G4 A1052 17 inch. The computer was from a friend of mine and it ran fine until about 4 years ago, then it started to show problems with GPU, artefacts, random lines and so. Not long after, it completely died. I know for sure that the LCD was good and all other components worked, even the battery isn't that old. I inspected it and the logic board is toast and beyond economical repair. For anyone interested, it has a shorted ATI 9600 M GPU chip, that is unobtanium these days (I was actually interested in replacing the BGA chip itself). Even after removing the affected GPU chip, there is still some very low resistance on few components, so it may have more shorted components. I was looking around eBay for a replacement logic board and I could not find anything suitable. The current one is 820-1524-A. Can I use anything else? I don't care if it is an older or newer board, I would just be happy to see this work again. Or if perhaps someone has the suitable / compatible logic board here for sale, as I am prepared to buy it
  7. mitchW

    PowerBook 160 Battery

    I am thinking of 3D printing a battery pack that would contain 5 AA cell holders that would be accessible from the outside, so one could be able to use the cells they wish and change them on the fly. I think you could be also able to use alkaline batteries (include a switch for alkaline use that would put the pack in series with a diode, so you won't be able to charge them). I use my PowerBooks quite rarely and when I get to use it, the battery is almost always flat, so I need to charge it for few hours etc. But I keep 8 AA Eneloop cells always charged, so I would just put them in. Also, I was thinking of designing an Li-Ion to NiMH converter circuit, one that would take the charge voltage of PB and then limit it to 4.20V to charge lithium cells. Then use a boost converter to boost this voltage to around 6V so the PB would be happy. Perhaps add a variable output voltage function depending on the voltage of the input, so the output voltage would not be constant, and PB would then know how much juice remains and initiate a low battery alarm, etc.
  8. That would be the part to order: http://eu.mouser.com/ProductDetail/Littelfuse/1206SFS500F-32-2/?qs=sGAEpiMZZMsIz3CjQ1xegdajYV%252bSgOyhtRV3I06tmz0%3d
  9. I tore apart my parts Pismo and found a similar fuse there. It was located on charger board. This one is 5A and has Fairchild logo on it and also a "T" which means "Time Delay" or Slow-Blow. Replaced it with the one from Pismo and now it works. While I was there, I also measured 35V 100uF capacitor next to the fuse and sure enough, it had high ESR (about 0.6 ohms), so I replaced it with new one (ESR about 0.1 ohms). I think that in a matter of 5-10 years, all these iBooks and PowerBooks G3 might need capacitors replaced. Well, tear the thing apart and check continuity of the F1 fuse on the Charger Daughterboard (the one with battery connector).
  10. I am repairing a iBook G3 Clamshell that has blown fuse on the charger board (F1). This causes the known good battery not to charge, despite the orange light on the charger. Can anyone suggest what is the original specification of the fuse? It has "5" written on it. Considering my electronic knowledge, that would be 5A 32V Slow Blow? Thanks!
  11. mitchW

    Powerbook 520/540c Power Adapter repair/re-cap

    I would leave ceramic and plastic film capacitors alone for now. Except if these are actually paper caps you are referring to. You probably saw cracks in clear case capacitors near the AC input on 128k/512k analog boards. These are plain old paper (or paper in oil) capacitors (usually from company WIMA). They are placed across the line and from line and from neutral to ground. When new, these capacitors were one of the best for these type of applications, as the paper has excellent dielectric properties and has very low dissipation factor. However, after 20-30 years the paper will slowly begin to degrade and turn acidic thus the capacitor will start to turn into resistor (become "leaky"). The cracks in the case will only accelerate this. So these capacitors are now known to short and fail and sometimes explode. I replace them on sight with proper film X2 type or ceramic Y2 type ones. Commonly are present on older analog boards, but I remember seeing them also in Duo AC adapters. The proper test method is to use high voltage insulation tester, but if tested with a common capacitor tester they will almost always read high (0.1uF will read 0.14 uF, etc.), heating them with a hairdrier will cause them to read even higher, whilst a good film capacitor will stay at the same value across the all temperatures. Some universal component testers will also show voltage loss when there should not be any. Metallic film and polypropylene film capacitors will not fail as such even after many decades. I have some from late 1950s and they still test excellent with no leakage even at few thousand volts, whilst paper capacitors from same era are all junk.
  12. mitchW

    Aftermarket charger for the PB 160

    It works!! I got the charger today, it looks reasonably built, but still feather light compared to original one. It measures 7.80V at the output with no load. At first when I tried it, the barrel did not fit completely into the back of the plug, the insulating sleeve was too long. I then used x-acto to cut about 3 mm of the plastic sleeve off, and now it fits. The PB 140 then started up with ease. So I guess we now have a source of cheap aftermarket PB AC adapters.
  13. mitchW

    MiniScribe Repair

    I have two Miniscribe SCSI drives sitting on a shelf for more than I can remember. One of them worked, but it sounded like it was about to die. The other one was more or less dead, and I also used Silverlining, but it didn't help. Even when new, these drives were known for not being very reliable units.
  14. mitchW

    How Toasted is This Logic Board?

    I used to remove the capacitors by desoldering them, but I managed only to pull a pad every other time, which gave me headaches. Now I use the method of twist and pull with pliers, with that method, I never pulled a pad. You grab the capacitor with pliers and then you twist it left and right few times. Do not pull upwards! Usually they are so corroded underneath that they will break loose after one or two twists. You can also use SMD hot air station to remove them, but you will usually melt some plastic connector or something that is near the cap... About cleaning the board, rubbing alcohol is good, but when the board has a lot of corrosion or residue left, it would often not help much. Use vinegar or a limescale remover instead.
  15. mitchW

    iBook G3 SE 466 MHz restoration

    Thanks. I realise that the missing peduncle would be common on these iBooks. 2/5 iBooks that I owned in the past had this thing missing! About time for someone to start 3D printing them! The DVD-ROM drive works perfectly, about as good as it was new. It passed my scratched CD and DVD read tests. Too bad that the bezel is missing, though. Perhaps another idea to 3D print?
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