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lowlytech

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  1. Just got the power supply and analog board completely recapped and was reassembling it when the darnest thing happend. I was putting the flyback plug back on the CRT and the little teeth or hooks that connect under the suction cup just fell out on the bench. There was a very small bit of wire present still in the cup, so I tried to dab some solder in there and reconnect, but now because of the tight space I have managed to blacken the area inside the rubber ring and can't really tell if I have indeed soldered the main cable back. I tried to ohm out the clamp to any of the pins on the transformer, but I get no beeps on the meter. I would just see if it turned on, but I still have my logic board without half of its caps and a few other items completely un-soldered from it. I went ahead and turned on the mac to see if I would see a raster or some sign that the CRT was indeed powered on, but it was completely dark even when fiddling with the brightness control. The neck of the tube did have the orange glow but I thought I would ask on a hunch if you powered on a compact mac with its logic board removed, what behavior does the CRT have? Thanks and hope I didn't just break my flyback, as I don't know how to strip more wire, as it looks to be completely molded to the suction cup.
  2. lowlytech

    SE/30 RP12 replacement part, bourns filter

    Found this reference that matches the datasheet that has capacitors inside the filter. http://jerome.vernet.pagesperso-orange.fr/SE 30/Repair Mac.html#NoPointer The mouser part I ordered 652-4120R-601-250/201L definitely does not test the same for resistance and/or capacitance from the original yellow 115-0002; c 5SB filter that was there, assuming the original part is still good.
  3. lowlytech

    SE/30 RP12 replacement part, bourns filter

    I take it that the L vs LF on the part number 4120R-601-250/201 should be an okay substitute? The last post from that thread was in 2013. Throughout that thread it sounded like they had some issues locating stock. The 2nd post shows a datasheet with capacitors within the filter. I am not seeing this on the current datasheet, however the part numbers seem to indicate the same chip. I think I will end up installing a 20 pin DIP socket and that way I can easily swap the chip, assuming the one I have now won't let the magic smoke out of the board.
  4. lowlytech

    SE/30 RP12 replacement part, bourns filter

    Well not sure what is different, but the original filter I pulled now tests 44.8~45.2 ohms across all the pins except the four on the ends which are common ground. The new filter I got today (4120R-601-201L) tests 50.0 ohms across, with the same four pins on the corners as a shared ground. Will 5 ohms make a difference in this application? I guess I could put the original filter back in, but after trying to clean it up the legs are still pretty much tarnished with green/black. One other thing, mouser lists this as 20 pin 200ohms. Am I measuring wrong since I only get 50 ohms?
  5. lowlytech

    SE/30 RP12 replacement part, bourns filter

    I do recall in my google searching, running into a post somewhere that showed someone subbing a 16 pin filter for the original 20 pin one. That or maybe apple themselves changing to a 16 pin later in the SE's lifetime? So is this filter just a resistor network, or is it suppose to have capacitors in it as well? The original filter I pulled out shows typical ohm readings on the middle most pins, but a few act like something is discharging as the value fluctuates.
  6. Couldn't find a general section for this question so since it was an SE30 thought I would post here. I have about 8 or so traces that still appear to have the protective layer on them and they do ohm out okay, but the trace is corroded looking underneath. What is the proper way to handle this? just make sure you soak the board in a mild acid to neutralize the cap goo, or do I need to take off the protective layer to clean the trace before re-applying with an overcoat pen? Just don't want to overthink or do unnecessary things that might end up causing more damage.
  7. lowlytech

    Se/30 have to bang the box to get a screen

    I can also reinforce what already has been said with cold solder joints. I got a new to me SE30 this week and one pin on the P1 connector on the analog board had completely broke away from the solder.
  8. RP2 on my SE30 has a case of the green legs on both sides and there is about 4 bad traces in that area. Pulled up the RP12 last night to get a better idea on repairing the traces and thought I would replace the chip while I have it out. Checking if this is the right replacement part from Mouser.. https://www.mouser.com/ProductDetail/652-4120R-601-201L
  9. lowlytech

    Need help hunting the other end of a trace on a SE/30

    Thanks Tattar8 for explaining what the numbers/markings referred to. When I get home I will have another look at the schematics to try to follow that logic and make the connection on how to read and understand the schematic fully between pages. Appreciate the time and help with this. Hopefully I don't find too many more questionable connections. Will keep everyone posted on the progress. Hopefully we can get this SE/30 back up and running.
  10. lowlytech

    Need help hunting the other end of a trace on a SE/30

    Thanks Bolle for that info, I wasn't quite sure if I was counting in the right direction. This is really my first time tracking down pins on IC's that isn't in a DIP package. I checked pin 41 on the schematic and it looks like it is in the same group as pin 10. It labels pin 41 as A0. Looks like it goes to (1-6) A (0.31). What point is this on the board so I can make sure I have a good connection? I visually tried to follow the trace but it looks like it ducks underneath the Y2 oscillator crystal.
  11. Got my first SE/30 this week and have been looking over the traces after getting the battery and caps off the board. I have a questionable pin on UE10 that I believe is pin 10. The schematic shows this line connecting to something off screen. Can someone help me find a test point to check for continuity from this pin in the picture? Also have a question on the same schematic file (SE30_P7.GIF). I appear to have two broke lines on UC12 Pin 1 and 2 going to RP2 pin 18/17. This schematic shows a break in those lines. Is this a mistake on the schematic as I don't get continuity from these two test points, but I do get continuity from RP2 18/17 to R42 and R43 on the back of the board.
  12. lowlytech

    Apple IIGS keyboard with bad key switch

    Thanks AkwardPotato, I got those ALPS switches you had posted in yesterday, and got them installed and they work like a champ.
  13. lowlytech

    issues with 5.25 drive on a IIgs

    Got the drive back together and it works. What may have been the issue was there was a cardboard type paper that I put back the way I found it, which was I believe on the wrong side. This no doubt caused the shorted condition, smoke, and the drive just not wanting to read anything. Keeping an eye on it, but I think for now it is good to go.
  14. lowlytech

    Apple IIGS graphic glitches

    Still glitch free, maybe it was just a pin on the cpu not making good contact. Diagnostics ran for two days in a loop, no errors in that time.
  15. lowlytech

    Apple IIGS graphic glitches

    Well I am knocking on yellowed plastic here, but since reseating the CPU I have power cycled this poor GS about 50 times and haven't once had the glitches. Now with my luck the minute this post goes up it will glitch, but right now it is behaving. Thanks for all the input and info on this issue i was experiencing. I will get the diagnostics to run in a loop overnight and see if anything interesting happens. Are the best diagnostics the actual Apple GS ones I assume? Didn't know if there was a better more detailed option out there I wasn't aware of. Thanks again..
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