Recent content by mitchW

Anyways, I found the problem and actually repaired it. One of the lines (ENBL1) from the IWM was reading just 150 ohms to ground. On the other board, this line measures about 3M ohms! As it passes through the RC filter (FILTER2 / 115-0002), I figured I should first isolate it first. I sucked the...

Thanks, but I don't see any values of the resistor packs in this PDF. It mostly covers analog board repairs / upgrades. I did find schematics for 512K board and I am including a floppy controller part here. Any suggestions what I should measure first?

Yes, 1.4MB floppy does work in Mac Plus, but only as 800K drive. The original cable has a red stripe, but previous owner cut the 2 lines (pin 9 and 20), so essentially this converted it into yellow strip cable. But if I am not mistaken, this modification was only required for some early 800K...

I am having an issue with my recently restored 512K. That 512K was upgraded (RAM, SCSI, Mac Plus ROMs, etc.) - so it is essentially a Mac Plus., but I am not sure if upgrades are the culprit. Original 800K drive was beyond repair (bent heads), so I managed to find and repair a 1.44MB drive...

Thanks! I checked my parts bin, and I actually have 18 of 41256 ICs (not tested though) and a 74F253! Other missing parts, I can order :) But now I found some photos of the fully populated Dove MacSnap 5.0 on ebay, but it seems it has and additional snap connector for one chip on top of the...

Here, I snapped few pics of the card :)

Thanks, I did use a special "gentle" rust remover cleaning product that I usually use for corroded stuff and it turned all green corrosion into dull grey metal. I will try white vinegar if it will make it any better

I am restoring a Mac 512K with a 512K Dove MacSnap 5.0 RAM Upgrade card + SCSI. This upgrade card brings the Mac RAM to 1MB. But I've seen some other Dove MacSnap RAM Upgrade cards that contain 1MB or 2MB of RAM. Is it possible to upgrade my upgrade card to 1MB or even 2MB? Also, one of the...

I got my Mac Plus this way. A 120V unit was brought over to Europe and plugged into 230V. If I remember correctly, it blew one of the 100uF 200V caps and a fuse. So after 5$ of parts, it was all happy again (with step-down transformer of course). I did end up replacing both 100uF 200V caps and...

Hey can anyone please provide me with the value for the R36 NTC inrush thermistor? Thanks

I also replaced UC3843 on mine, but it didn't help. Possibly it was also fried.

If you have +5VSB and nothing happens when you connect it to the PS_ON pin, then it could be the LM339 chip - it was dead on my PSU. Also worth checking all diodes and transistors for shorts. YMMV

This is the first thing to check... if you have experience in electronics repair, then this will be easy for you

Are you getting +5VSB? If not, this is the first thing to get sorted then. Those units don't get bad caps as such, my two PSUs both still run perfectly with all original caps. Sadly not much is known about common failure points on those. One of mine had blown standby power circuit and also a...

I am using 8500 PSU on 8100 and it doesn't work :) And not one, but two!