Killed a ROM in a Classic II

[captainserial]

I have two Classic II's that I have been working on restoring. This is my first re-cap adventure.

I recapped one of the logic boards with tantalums, then cleaned it with an ultrasonic bath and PCB cleaner. When I put the ROM chips back, I accidentally plugged one of them (U25) in backwards, but didn't notice. When I booted it I got scrambled looking vertical bars. When I noticed the backwards ROM, I re-seated it correctly, but it still booted to the same scrambled bars. I borrowed the ROM chip from the other board, and it chimes. So I'm fairly sure I killed that ROM chip. Both boards are of the 4-chip variety.

Is there a way to program a new ROM? Has anybody done that successfully? I searched the forums here but couldn't find anyone who had actually done it, just some discussion.

I'm bummed I made such a stupid mistake after what was apparently a successful recapping.

 

[dochilli]

This may help:

https://web.archive.org/web/20190617000041/http://synack.net/~bbraun/classic2.html

According to this site a 27C010 or a 29F040 eprom could be a solution. Complete ROM images are downloadable from the net. If I understand it right, you can burn the image four times into the eproms. 

 

[Bolle]

You have to split up the ROM images that you can find on the net with the 1st, 5th, 7th and so on byte going into the first chip, 2nd, 6th, 10th... going into the second chip.

This can easily be done with srec_cat on about any unix like system.

Or you just read the contents from the working chip that you have, just reading it like a 27C010 and have the programmer ignore the manufacturer- and chip-ID because those usually don't match on mask ROMs.

Burn the contents to a fresh 27C010 afterwards and you're good to go.

 

[bibilit]

where are you based ?

maybe a damaged board somewhere with a good rom

 

[techknight]

ill have to travel through my junk box, I may have ClassicII parts board. Maybe. 

 

[captainserial]

This may help:

https://web.archive.org/web/20190617000041/http://synack.net/~bbraun/classic2.html

According to this site a 27C010 or a 29F040 eprom could be a solution. Complete ROM images are downloadable from the net. If I understand it right, you can burn the image four times into the eproms. 

This did help. Since I have a working #4 chip already, I am going to just copy that one onto a new chip, as Bolle suggested. I ordered a programmer and some blank 27C010 eproms. They are apparently still readily available in DIP32.

 

[captainserial]

where are you based ?

maybe a damaged board somewhere with a good rom

I’m in Reno Nevada. I have two with the same 4-chip board, so I’m going to try copying the known good ROM I have first, before I look for a donor board. Thanks for the help though.

 

[captainserial]

Well copying the known-good ROM onto a fresh AT27C010 fixed that issue, but now I have a problem where the recapped board boot loops once and then sad-macs with code 0000000F 00000001, no matter what ROM I use in it.

 

[captainserial]

I'm starting to think I killed the processor when I booted it with that RAM chip in backwards.

 

[dochilli]

Could be a problem with the harddiskdrive. Does the classic II have a HDD? First step could be to disconnect the HDD and to boot from a floppydisk. You need System 6.08L or higher. It is not so easy to get a bootable disk for 68030 macs. But there are some downloadable in the net. If it boots from floppydisk, the problem is the harddisk. Old SCSI hdds are often crashed.

Perhaps you can test to boot with disconnected hdd and without a floppydisk, then you should get the blinking questionmark.

 

[captainserial]

Could be a problem with the harddiskdrive. Does the classic II have a HDD? First step could be to disconnect the HDD and to boot from a floppydisk. You need System 6.08L or higher. It is not so easy to get a bootable disk for 68030 macs. But there are some downloadable in the net. If it boots from floppydisk, the problem is the harddisk. Old SCSI hdds are often crashed.

Perhaps you can test to boot with disconnected hdd and without a floppydisk, then you should get the blinking questionmark.

I wish that was it. I tried disconnecting the hard drive and got the same result. Then I tried disconnecting the floppy, then I tried disconnecting both, with no difference. Since I have two of these computers I still have a known-good logic board I can test with, and it boots fine with this hard drive.

I thought maybe since the caps were replaced it became more sensitive to the voltages being in range, but I checked them from the floppy port and measured the 12V at 11.88 and the 5V at 4.994, which seems fine.

Here is a video of what it does:

 

[captainserial]

Here is some pictures of the logic board after recapping and cleaning:

https://imgur.com/a/9C4ULXe

 

[dochilli]

When it reboots, it looks like there is an unstable voltage, but I have no idea how to fix it.

Perhaps Bolle or techknight can help.