Quadra 605 adventures: repair, testing, and upgrades

[m1420owner]

I got myself another 68K Macintosh, because I find them fun to work on.

This time, it's a Macintosh Quadra 605 with a Motorola XC68LC040RC25B (25MHz w/o FPU), 36MB RAM, 160MB HDD, 1.44MB FDD (manual-injection), 512KB VRAM, and the only issue it has is the death chime and no video. I wired a series of AA batteries (3 of them) to the battery holder since the no video needs a PRAM battery, but the death chime was still present.

I cleaned the board twice and it still didn't work, but my BlueSCSI and floppy drive get power and I used my Performa 450's PSU since that was recapped and decided to take the old caps off to diagnose it some more.

However, at this time with the caps removed, 2 pads broke off for the caps and 4 others aren't too far behind. Yet, those 4 I can just use wire to patch them, which is a good thing. But for these two, I cannot tell if they interconnect to each other or not.



C149 (+) and C150 (+) are the two that are the ones I cannot tell if these connect to each other or not.

Anyone have any ideas?

My plan is to recap both the PSU and logic board, find a replacement top chassis for the system, upgrade to an XC68040RC33, swap the resistors for 33MHz, get a BlueSCSI V2 (internally), and upgrade the RAM to 132MB along with the VRAM to 1MB.

 

[killvore]

I love these things! I am lucky to have two LC475s in working condition and they are a joy to work on. I made an overview of the various upgrades I've done to mine.

- RAM might be too high, since it will increase the boot time unless you have a way to bypass the RAM check (think this needs a custom ROM)
- there is a software overclock option for the LC475, but not sure if this also works for the Q605
- depending on what you are connecting to you might want to bump the VRAM to 1MB. iirc 2x256kB (stock) will get you 256 colors at 640x480, but I wanted 256 grays for my portrait display
- I didn't like the fan noise, it was actually preventing me from using it, so I splurged on a Noctua A6x15 FLX. It fits perfectly. I also added the low noise adapter and now it is almost completely silent to my ears, running at 40MHz, with no stability issues.
- I prefer System 7.1 for 040 68k machines but you'll need to add system enabler 065 iirc to get it to boot on this one

Congratulations on your nice machine! Hope you figure out the capacitor situation

 

[Powerbase]

As already mentioned, there is a software overclock option avaliable now for these machines. You can probably take your current 25MHz 040 to 40MHz fairly reliably.

 

[finkmac]

schematics here

specifically, page 16

 

[Nycturne]

I see finkmac already shared the schematic.

I did something similar on mine, and those schematics helped a ton for making sure my work was correct. Probably will be helpful if you continue to get the death chime after this.

I also would consider removing the RAM SIMM when tracing down the problem, once you've got the capacitors replaced. Just to make things a bit easier (one less variable).

 

[m1420owner]

I recapped the system and no dice.

RAM installed/no RAM installed - COD
VRAM switched around and one module swapped - COD
SCSI drive and FDD installed/removed - COD
ADB anything connected/disconnected - COD

CPU resocketed - COD

I fixed some traces that were sketchy and I'm not sure if I missed any other traces.

 

[m1420owner]

And it gets worse. The TI 343S0135-01 A chip has broken legs and the pads are too small to solder wire to as legs.

 

[Juror22]

The TI 343S0135-01 A chip has broken legs and the pads are too small to solder wire to as legs.

Do you have a picture of this that you can post?
Also, how are you washing the board?

I had a no FPU 040 chip I tried and I don't believe it worked on mine - I don't recall the exact way it failed to work, but I can recheck that on mine and report back.

 

[Juror22]

I tried out the no-FPU 040 again today, to refresh my memory of the issue with it and it booted with a normal chime, but there was no video or apparent further boot processing, since the HD did not progress. After trying a couple of more reboots to make sure that was the only result, I swapped that CPU back out with original and it had the same reaction - boot chime and then nothing. After a second boot and a third confirmed the same, I started to get worried. Then I thought that maybe it had captured a setting and clearing it by removing the battery might help.

After removing and re-installing the battery, it started normally again, whew!
I don't know if this is always the case, but apparently mine had an issue with the CPU, and since there were no chimes of death, you likely need to continue your investigation. Please let me know the method you use for cleaning your board.