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  1. Macintosh Plus Analog Board Q12 replacement

    Maybe the following can help to understand the circuit better, is part of the powersupply schematic does anyone have the schematics for the international version of the analog board?
  2. Classic II beyond repair?

    The challenge you have is not the caps but the repair of the traces, the board will not work until you repair these. there are a number of traces which have the capacitor island in the middle so the connection is broken. Also for example the trace which runs between the islands of C5 and goes to U8 has to be repaired. Add the caps when yo have checked (and repaired) the traces around and under the caps.
  3. Macintosh Plus Analog Board Q12 replacement

    tried some other resistors, 1K5 is too much (unstable), 1K , voltages too high. 1K1 and 1K2 work this is using a BRX49, don't have other BRX4x to test. You have to regulate the 5V to get as close as possible to the desired 5V value, too high or too low => crowbar.. Still looking for a beter solution...suggestions...
  4. Classic II beyond repair?

    I don't think you "need" any of the caps to boot. The most important thing is to clean the board to remove alle the leaked cap fluid. c15 connects to the pins as shown in the picture
  5. Classic II beyond repair?

    I always use tantalums to recap. C15 is connected between 2 pins op 344S1033-01, if you don't connect it the sound does not work, but the mac will
  6. Macintosh Plus Analog Board Q12 replacement

    Ok , changed R50 to 1K1 (2x 2K2 piggyback) Voltages are 5.1V and 12.25V Have to find the sweet spot...
  7. Macintosh Plus Analog Board Q12 replacement

    Thanks for your replies. Put a 10K potmeter in place of R50, the mac is stable at 1K, so I replaced R50 with a 1K resistor. Problem is I have very little regulation on RPx to adjust the 5V, voltages are 5.2V and 12.35V Mac is working ok but don't know if this is the best solution.
  8. Macintosh Plus Analog Board Q12 replacement

    Am also looking for a replacement for the E0122YA _ _ | x | |_ _| | | | | | | 1 2 3 E0122YA (K G A) tested the foillowing replacements: BT169D (K G A) flupping set P0102DA (K G A) flupping set BRX49 (A G K)reverse! mac starts but is not stable According to the other post, it may be possible to tweak the power supply (alter some resistors) to accept the replacement. Think it's R50 but can someone let me know and the value to change it to? Altered the schematic from Larry Pina's book to the international version of the analog board. R45 390 R46 4,7 R47 1K R48 39 R49 1,5 R50 2k2 R51 220 R53 1,2 R54 15 R55 33k C42 470uF C45 470uF Q10 2SC3153 BCE Q11 2N3906 EBC Q12 E0122YA KGA
  9. Macintosh Classic Ram problem

    does pin 4 connect to to pin 26 UI4 ? could you complete the following list so all pins are checked (don't have a schematic myself) UH6 pin 1,13,14 to pin 17 UI4 BBU pin 2 to pin 9 UL1 pin 3 to pin 15 UF3 pin 4 to pin 26 UI4 pin 5 to pin 3 UL1 pin 6 to pin 7 to pin 4 UL1 pin 9 to pin 5 UI6 pin 10 to pin 5 UL1 pin 11 to pin 12 to pin 15 to these seem to be correct (schema is incorrect) UL1 pin 6 to UI4 pin 15 UL1 pin 7 to UI4 pin 18
  10. Macintosh Classic Ram problem

    Hello Macalle, you have to check the connections from the pins of UH6 all the way to the CAS PAL UL1 and also to VLSI UI4 The must be a broken connection there In my case the connection was broken from UH6 to the via, but in your case may be somewhere else on the line.
  11. Macintosh Classic Ram problem

    had the same problem once
  12. Classic II strange problem

    Will replace the opto, have a number of them in stock. disconnecting the HDD is same result Does not explain that the board wih another analog board has the same problem. And another mainboard with both anolog boards is working ok..
  13. Macintosh Plus display problem

    have you tried adjusting the brightness on the front?
  14. Classic II strange problem

    Pressing the reset switch does not help. Tested the board yesterday again. tuned the voltage back to 12V and 5V (as close as I could get) installed a PRAM battery (empty don't have a charged one) Measured the voltages, go up to the 12v / 5v in seconds and stay stable (cool boot). Was measuring arond and suddenly the mac booted.... After reset still booting. This morning tried again (without the pram battery) and got the garbled screen again. After waiting 30 seconds the mac did a reset (on its own) and started working. The problem is slightly changed that I get the garbled screen on cold boot and after 30 seconds it reboots and starts ok. Anyone suggestions/
  15. Classic II strange problem

    checked the voltages at the hd power connector, 4.96V and 11.97V Boosted the voltages a bit to 5.08V and 12.20V problem seems to stay about the same. For the reset line, how do I check this?