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Could be a problem with the ROM. Clean and reseat the ROM or use a known good.

Do you hear a chime? If not it could be a problem with the ROM. Clean and reseat the ROM. I would do the same with the RAM. Do you have 8MB? Did you measure the voltages at the floppy port? Should be 5 and 12 V.

Check the voltages at the floppy port. Should be 5 and 12 V. Shows the LB the stripes in the working classic? Then the LB is the problem. Could be a problem with the ROM too. Reseat and clean the ROM.

ROM download: https://www.macintoshrepository.org/7038-all-macintosh-roms-68k-ppc- Sometimes must be splitted up into 2 or 4 Files. The 2 ROM version of Classic II can use 2 27c400 EPROMs (100ns or faster; 150ns won't work). The 4 ROM version can use 4 27c010's (AFAIK).

In this video you can see the gear (around 20 min).

I used the adafruit board and got the same result as with the sparkfun. Two sd cards worked, two not. The non working are shown on the left side in the photo. One of the non working cards showed a very short red LED flash and then nothing, the other showed the LED on the whole time. The working...

There are a lot of parts on classic AB that can be defect: DP3 and DP4 (1N4148), TDA4605, CNY17G, IRFBC40.

Removing the pull up resistor did not solve my problems with some SD-cards. I think that the spark shifter board could be the problem. I will try another board with some cables as connection to the tashtwenty...

I built a 1.1 tashtwenty and have some problems with sd cards. Only with a 4 GB intenso card I had success. A 16GB sandisk ultra worked sometimes but then stopped. A philips 16GB did never work. In one of the first posts in this thread you showed a picture that the mac formated a sd. How did you...

Did you check the 12V, when you have 5.1 V?

You need 4.85 V. With 4.5 you get a checkerboard. You could try to turn pp1, but check the 12 V, when you turn the poti!

And recap the LB and the AB. Search for cracked solder joint on the LB/AB connection and the neck board (CRT).

I would remove the rust with some vinegar. After that you can see a little bit more of the damage. I had one board that has the same problems and I could rescue it.

Use 25V position. Put the red cable to pin 8 and the black cable to one of the screw (ground). Then you should measure about 12 V. Do the same with pin 6 for 5 V. If you measure 0 V, your analog board has a problem. Did you check the solder joint of the power connector?

Did you measure the voltages at the floppy port? Should be 5 and 12 V.

Yes, 4.86V at the level shifter board. I downloaded MPLAB 8.92 and now I can build the HEX-File. A Pickit3 is ordered. I had a Pickit2 but it will not work with the 1825. Now I am waiting for the pickit3... Thanks for your help!

Thank you for the link to the HEX-File. I tried to flash the 1825 with a TL866plus, but a mac plus with a 6.08 boot disk does not see the HD20. I used the image with two drives. The SD-Card has 4.86V at VCC. I think that there is a problem with flashing the 1825. Up to now I only worked with...

I have some questions: 1. Where can I download the HEX-files for the firmware for the 1825? I am new to PICs and tried to compile the firmware with MPLAB X IDE but I get an error with the file P16F1825.inc and the build stops. 2. Which IDE and compiler do you use to compile the firmware?

Yes, 03 is bad RAM, but FFFF means that all chips are bad! Usually the subcode is used for the identification of the bad chip: https://udcf.gla.ac.uk/~gwm1h/Error_Codes/Sad_Mac_Codes.html

You could try THINK Pascal 4.5. It is a nice development tool. Pascal is easy to learn and there are a lot of books available. Apple developed a lot of software for macs with Pascal. https://www.macintoshrepository.org/1550-symantec-think-pascal-4-5 If you want something newer than Pascal you...