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Yes, it definitely must be the international modem card. My Portable originally was bought in Netherlands, so it be.

It looks like the the internal ExpressModem card from PowerBook 100 series. There is an additional localtalk-like port to which connects the external modem dongle. Never thought Apple had one for Portable those times.

I’ve got a working Macintosh Portable with the strange modem card installed. The part number is 670-4267-A, Designed by Apple Computers in 1989. It has a standard RS-422 port outside. Looks like an early version of Apple ExpressModem. I tried to search by the part number with no success. Just...

Well, I was curious if the system could be showing all the memory but using only a part of it. Sounds stupid, I know. Ok, I’m gonna clip the resistor when I unscrew the case next time.

Yes, the battery is new.

Hi all, I have a perfect working Macintosh SE which came to me with 4mb of memory installed. System 6 shows all 4 megabytes in the “About this Mac“ correctly. The main question is: do I still need to cut the R35 resistor as it is documented for my revision of the motherboard?

Finally, I solved this problem by simply pushing some chips on board. I believe it was cache and ROM ones. Perhaps some of them had bad connection. Now my board starts without a problem. Thank you so much for your patience and assistance!

Early revision, 820-0163-B

The board was cleaned, old axial capacitors were replaced, new power switch button was soldered. I checked the board several times. Sometimes it starts normally, sometimes no reaction except powering on the power supply.

My troubled Macintosh II board continues to surprise me. This time it boots, however, one time the process is normal, other times it is not. When something goes wrong, the board starts with the only short click out of the speaker, and nothing more happens. No boot chime, no error chime, nothing...

We found a cause, one of the axial capacitors started to leak and made a shortage, making the power controlling transistor always on.

Good point, thank you! I'll check it.

Yes, exactly so.

Yes, I’ve already done this check and got the motherboard staring each time when I’m powering my setup. As I have an explanation of schematic I’ll do the check of NAND gates and transistors down the circuit.

Yes, I’m pretty sure. It was de-soldered again to check if the board could power on normally. No way, it continues to fire up immediately even without the switch

I de-soldered power switch and checked the board without it. It continues to power on each time I plug a power cord. Before repairing it behaved correctly. I don’t know what could be broken since that time

yep, it’s a genuine Mac II board, early revision. The problem is I don’t understand what was broken after the power switch was installed on board. It was the only modification I performed.

After replacing the broken power switch my Macintosh II motherboard begins to startup immediately after power cord is connected. I tried to de-solder and remove power switch to restore the previous working state with no luck. My board turns up every time when plugged to power. It seems like the...

Next trouble: suddenly the motherboard begins to startup immediately after connecting power cord. It looks like starting circuit is always on. What should I pay attention first?

Thank you for answering. I’ve got all RAM modules and NuBus cards out and started a motherboard with the boot chime sequence coming again. Then I manages to get a working set of four 256kb SIMMs to boot the machine. The motherboard needs couple of fixes yet It is in great condition and running.