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About MacinPosh

  • Birthday January 20

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  1. I finally got some time to replace R1 and U1. Unfortunately it doesn't seem to have made an improvement Are there any other common problem components I can look into?
  2. Thanks lisa2 I’ll replace these and report back asap.
  3. Thanks again for the ideas. I've had the card out a few times to inspect it and always made sure everything was connected back up, but i'll check again. Going on the assumption that as BU406 is hot, maybe something in the Horizontal drive circuit is failing, i.e. Row A of the schematic. I'm definitely not an expert in CRT circuitry/flybacks, if anyone has some insight into this it would be most appreciated. I've started looking at the biasing passives but they've all checked out so far
  4. A very good point, although I went through and recapped it when I first got it in 2018. I don't think they'd wear out that quickly?
  5. I recently brought my Lisa 2/5 back out of the cupboard to have a tinker during lockdown. Unfortunately after a few minutes the contrast goes very dark and the image starts to shrink on the right hand side. I haven't dared to leave it on long enough for something to go bang... The BU406 is quite hot, but probably within normal limits. Any ideas would be much appreciated I've attached the video board schematic for reference.
  6. I haven't found any shorts around the ROM pins, and the same issue happened to two different ROM chips, so I don't think the ROM is the issue. As I mentioned in my previous post, the ROM now only boots to death chimes and B&W Stripes in my other working machine
  7. I was in the process of cleaning and recapping an SE/30 logic board which had been subjected to a battery leakage. I've checked and rerouted all the rotted traces (totalling about 15) between the RAM, ROM, VROM and GLU but when I was satisfied enough to attempt a boot, pin 63 on the ROM burnt out (causing pin 64 to fall off, but pin 63 was definitely the offender) leaving me with a dead SE/30. Any ideas what might have caused the sudden burning on the ROM? I've checked it in another machine and now it only boots a grey screen with death chimes. Maybe there is a short I haven't
  8. Following up on this after a long time. After a lot of head scratching and component swapping, I went back to basics and discovered that the problem was in fact with two capacitors on the Hard Drive's analog board that had gone short circuit. (Shown in the RED box in the photos, compared to the original in the GREEN box) After replacing them, the drive span up and "promptly" booted to MacWorks. I learnt the typical lesson of check for the common simple issues first!
  9. Unfortunately I don't think that's the correct schematic for the board. The component is from the small daughter board connected to the Astec Power Supply AA11770
  10. Inspecting the Profile power supply board, I noticed a very burnt resistor that had cracked into two pieces. I'm having trouble identifying its value. Can anyone help me out? It looks like Brown-Grey-Orange-Grey-Brown? Thanks
  11. I recently acquired a 5MB ProFile drive in an unknown condition for use with my Lisa. I promptly replaced the power supply caps in hope that the drive would be operational. Powering the system on resulted in a high pitched whine but nothing else, but when I disconnected the internal data cable between the controller board and the hard drive, it did begin to spin up. Any suggestions on what to try next? I've tried reseating all the chips. Are any particularly prone to failing? Is there any way to narrow down whether the controller board or the drive analog board is at faul
  12. I've finally got round to looking at these Pluses, and interestingly/unfortunately the analog boards are working fine as they boot up the logic board borrowed from a working plus just fine. Larry Pina suggests the 5v regulator or the TSM chip is to blame for logic board related flupping. I've tried replacing both of these with no success. Are there any other "usual" suspects or is it a case of checking for bad traces? Swapping ROMs and RAMs doesn't seem to help either Thanks
  13. These are all great suggestions. I'll order up and replace parts sequentially and post my results ASAP Thanks
  14. Good afternoon all, I have acquired two Mac Plus units of which neither want to boot. I've started with the usual logic and analog board cleaning and recapping to no avail. The most promising combination of boards only achieves a white horizontal line accompanied by noise from the speaker, as seen in this video: Other combinations of board only achieve a flupping noise at various speeds with a blank screen. Nothing seems particularly broken on any of the boards, except scorching underneath the 5W 1Kohm resistor on both of the analog boards, both of which tested open and ha
  15. Hi Everyone, I recently acquired a Mac Plus with a temperamental analog board which would only display a picture briefly whilst being tapped on the left side. I tracked this problem to a failing flyback which I have replaced, but I now get horizontal scan lines across the display which I cannot get rid of (whilst also maintaining the video brightness) by adjusting the brightness knobs. The Mac itself is otherwise working I've tried replacing R5 but to no avail. Any suggestions? Thanks
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