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max1227

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  1. Yes I suppose it is! However any sort of valuation would be greatly appreciate. I presume these machines are desirable.
  2. Does anyone have an idea of the approximate value of this Umax clone?
  3. Thanks for your messages. Yes I have learnt that you can be much more forceful with these drives than one might expect. I since have acquired two more widgets and have opened up all 3. Now on all 3 brakes release and all 3 have the glass optical grating intact and stuck down. One I think has a bracket holding it in place which incidentally is also a low serial number and a 4 layer controller. The two additional widgets I acquired were also broken but I managed to fix them both. Easy cases of stuck platters and one had a faulty Z8 which I worked out through swapping boards and IC's
  4. Thank you both for your help. A while back I ordered a ESR meter and it arrived today (took absolutely forever but I'm glad that its finally here). So I tested the capacitors C33 and C46 two capacitors involved in some shape or form from what I can tell with the +5B2 trace (I could be wrong here). Both capacitors tested fine and were good according to the meter. I then check most of the larger (in physical size) axial electrolytics on the board also and they too were fine. I then compared the readings to a working 2/10 I/O board and the values obtained were very similar.
  5. Again silly question, are these electrolytic caps? I only have a store of surface mount electrolytics for recapping Mac logic boards which obviously wont work with the design of the Lisa I/O board.
  6. Thank you both for your replies. I have tested this 2/10 I/O board and you're both absolutely right. The Lisa works fine with the 2/10 I/O board powering off and on normally therefore the problem is verified to be on the 2/5 I/O board. Will all traces verified as working in the affected area on both sides of the board I'll have to wait until the ESR meter arrives to test the capacitors.
  7. Thanks for your reply. Just made a quick post on the forum to see if we can get a consensus. I feel this information may be of use to other Lisa 2/5 owners attempting to repair their I/O boards.
  8. Hi Lisa enthusiasts, I have a 2/5 which has I/O problems due to the corrosion and myself and a fellow member are trying to diagnose. I need to find out if the I/O board is the fault or potentially the edge connectors or traces on the motherboard. I don’t have a spare I/O board unfortunately. Is it possible to interchange a 2/10 I/O board for a 2/5? This will require use of the same 2/5 motherboard, CPU card and memory boards although the latter 2 I believe are interchangeable between any Lisa system ROMs dependant I suppose if you have the Mac XL screen mod and 800k drive.
  9. Fab thank you so much! I have ordered an ESR meter the same as the one you have as I really need one that works in circuit as so many of the capacitors around the COP’s chip have corroded solder joints so I cannot easily desolder them. In the meantime I was wondering if electrically speaking a 2/10 I/O board is compatible at all with the Lisa 2/5 motherboard, CPU and memory boards? I saw a post of the Lisa FAQ which says they are but you have to make modifications to the Lite Adapter. I don’t wish to do this so if I unplug the lite adapter and leave the twiggy cables unplugged can
  10. If this is after a period of inactivity and it is left plugged in so the +5V standby is on the Lisa will always start up correctly If this is after a period of inactivity and it is NOT left plugged in so the +5V standby is off the Lisa will always startup without the soft switch being pressed. The crowbar mechanism is okay I think as to test this I adjusted the pot beyond the specification of +5V (probably not recommended) and it activated and the Lisa when tick tick tick tick when plugged in and power switch pressed. So the +5V is good and that safety mechanism is working nor
  11. So I tested all those traces for continuity and they are all good measuring almost zero ohms. I also swapped the COP421 chip (no difference) and swapped the 6522's (no difference). Really not sure where to check next as all the traces appear to be working normally. My only thought, and again, really not sure if any of this is logical thought, is that the Lisa is always on when plugged in and switched on at the wall. Therefore that +5V is running continuously when plugged in. My Lisa without fail will not start-up correctly when plugged in and switched on at the mains after a period
  12. Fab thank you very much! I will check those pins for continuity Just to confirm is pin 1 and pin 2 the 7417? Your board looks quite good actually Lots of the traces around the COPS chip look the normal colour.
  13. This is a really silly question but where is U7F? Is it part of the COP421 chip?
  14. Another interesting find. The resistance of the trace between Q11 and pin 20 on the COP421 chip is reading as 15.2K, is this normal? Looking at the schematics I can’t see how this is. But as mentioned previously there is probably some component that I don’t understand how it works. But testing some other boards reveal similar readings...
  15. It was actually just a coincidence that the Lisa did what I said it did in my previous message. But it was a very convincing coincidence as I unplugged the parallel cable (stopped working) replugged it in (started working). I did that a couple times and it repeated the former perfectly every time. Although just retested it again and it's now exhibiting a different problem. After leaving the system alone for a while it always without fail reverts back to switching on automatically. But then after a few minutes to warm up it will start working properly again. I tested the parallel cable and conn
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