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  • Posts

    • Great news! Despite his screen name, @EvilCapitalist has sent me a parts SE/30 board to scavenge an ASC from. Thank you very much, @EvilCapitalist!   Let's have a look at the damage.     Yep, Maxell bomb. How about the ASC? That's what we're after here. A bit of corrosion was present, but it looked salvageable to me.     I decided to scrub down the whole board with some vinegar to try to stabilize things a bit. I was a bit too vigorous with the toothbrush though, and knocked an IC right off the board. I think this is a RAM muxer?       After a rinse under tap water, and hitting it with the air compressor, it was time to desolder the ASC. I don't have a hot air station, so we'll have to use another method.     First, a generous amount of paste flux. There's a lot of corrosion to burn through.     Next, I heated up the pins with the iron, and fed in a generous amount of desoldering alloy. A brand name of this stuff is Chip Quik. It's basically solder, except the melting point is super super low, so it stays molten for a very long time. Here, you  can see it in a molten state, even though I've put down the iron and grabbed my phone to take a photo!     One lesson I did learn with this: you need to get the pins nice and warm before adding the desoldering alloy. If you don't, the alloy will just follow your iron around instead of sticking to the pins.   After coating each side in desoldering alloy, I began raking my iron back and forth across all sides. I kept the iron moving pretty quick, rake-rake switch. Rake-rake switch. Rake-rake switch. After a few passes... pop! Suddenly, the IC moved off of the pads and was free to pick up with some tweezers!     I used the iron to reheat the pins on the chip (super fast and easy) and the solder sucker to remove the excess from the pins. A quick scrub down in some Isopropyl alcohol:     The board looks pretty good too! Here's what it looked like. After this is cleaned things up with some desoldering braid. Not that this board will ever work again... but it's great for practice. You may have noticed that I removed the caps earlier - I will certainly keep it around for parts, or for a reference board, so I wanted it to be stable for storage.     Hopefully tomorrow, I will desolder the ASC from the good board, and solder down this new ASC. I sure hope it works!
    • Congrats on the Color Classic! I think this is a moot point since you have a hot air station... but I now exclusively use the "twist and push" method to remove caps. On the ~6 boards I've done like this, I've only broken one pad off. But like I said, moot point for you...   Looking forward to seeing how this one comes together. Would love to see lots of photos (with surrounding context) as I haven't actually seen a Color Classic in person since I was in kindergarten! I've been watching for one... it's the "unicorn" that I've been trying to track down to finish up my compact Mac collection!
    • https://archive.org/details/dr_dobbs_journal_vol_10/page/n721/mode/2up ?
    • While @switch998 said, "Don't worry about cleaning it", I couldn't help myself. This is the 6115CD after dishwasher detergent, scrubbing with a brush, a lot of Goo Gone, and some paper towel + baking soda scrubbing. The only thing I didn't do was bust out the flat razor to try to scrape away all of the crusty sticker residue that the Goo Gone didn't cut through.   I figured I'd share, just for closure.                  
    • I've updated the spec to fix a few mistakes, and I've also added some sample code to operate the ROMBUS from the Mac, which I'll reproduce below:  ROMBUS Spec.pdf #define SIGR_WR ((short*)0x41FFE0) #define CSR_WR ((short*)0x41FFD8) #define CSR_RD ((short*)0x41FFD0) #define RXR_RD ((short*)0x41FFD2) #define RXR_RD_SH8 ((short*)0x41FFD4) #define TXR_WR ((short*)0x41FFDA) #define TXR_WR_SH8 ((short*)0x41FFDC) void rbus_enable { *SIGR_WR = 0xC1AD; } void rbus_disable { *SIGR_WR = 0x0000; } void spi_select() { *CSR_WR = 0x8000; } void spi_deselect() { *CSR_WR = 0x0000; } char spi_transfer8(char x) { *TXR_WR_SH8 = x; return *RXR_RD; } char spi_transfer8_slow(char x) { char ret; int i; for (i = 0; i < 8; i++) { // Shift MISO into return value ret <<= 1; ret |= (*CSR_RD >> 13) & 1; // Pulse clock hi then lo *CSR_WR = 0xC000; *CSR_WR = 0x8000; // Clock out MOSI after clock goes lo *TXR_WR = (x << (8 + i)) & 0x8000; } return ret; } char delay_100us() { __asm__ __volatile__ ( " move.l #100, %%d0 \n\t" "1: subq #1, %%d0 \n\t" " bne 1b \n\t" : /* out */ : /* in */ : "d0" /* clobbered */); } This code is designed to provide the HAL layer for Elm-ChaN's SD/MMC library, making it easy to integrate that open-source, well-tested code into a future ROMBUS driver.     Edit: Also the boards for Macintosh Plus and Macintosh 512/128 are finished: We will be sending these to production in a few weeks once we release the 2MB and 8MB Mac II ROM SIMMs.