Mac SE/30 only sees 1024kb of ram regardless of the ram attached on either bank?

[naruse]

hey everyone, so I am trying to get back my SE/30 back to working order after full recapping everything (logic and analog boards, and PSU) and today when I turned it on out of nowhere it only sees 1mb of ram?; is there any reason why this could happen?

I have tried everything, adding 4mb on bank A, 4mb and 4mb on Bank A and B and regardless it only sees 1mb or ram


FWIW TL071 died on me so I took it out and I now don't have sound on the speaker -- yet on the headphones it chimes correctly -- I can boot to System 6.0.8 and see it reported on the finder.

This has me quite puzzled on why this started to happen and I am not sure what to even check on as I havent seen this before (not that I am an expert on this, I am just starting)


also, bonus question to whoever knows -- Can the Mac SE/30 start without UB11?

(the sound chip connected to the reset signal but not the main PLCC sound chip (UE10))

 

[dv-]

There’s a chip responsible for detecting ram simm size; it was called out in a recent repair video Adrian’s Digital Basement did on YouTube but I don’t remember which one it was. If you zip through his last video on the se/30 he was repairing it’s in the second half I think.

 

[Chopsticks]

You can boot the se/30 without ub11, it’s been awhile since Ive done that myself but I believe you might need to manually trigger reset. Pin 5 of ub11 is the reset signal, it’s active low so grounding it momentarily should work

tl071 is an OP-amp used to boost the line level audio signal for the internal speaker so it’s audible. It’s actually connected to pins on the headphone out jack that gets deactivated when you plug in a pair of headphones. It’s common for the contacts inside that 3.5mm jack to get oxidised over the years preventing internal sound working. when you replace the op-amp if the internal speaker still doesn’t work trying some contact cleaner in the headphone jack.

while I haven’t seen Adrian’s latest se/30 repair videos I suspect @dv- is referring the the GLU chip and the SIZ0/SIZ1 pins used to detect ram sizes. Consult the schematics for the exact pins but they should connect back to the cpu somewhere. It should be direct connections as there’s no buffers on the logic board.

 

[cheesestraws]

Check that A10 (? if I've got my maths right) is going to the right places and isn't being pulled down or up by anything.

 

[naruse]

ha! -- I havent checked the latest video of Adrian, I will follow up on that one next! thanks @dv- .

Also great to know that I could boot with UB11 because most of the time "it just boots" and sometimes it doesnt and I could boot it by manually triggering ping 5 to ground on UB11 as @Chopsticks mentinoned.

It’s common for the contacts inside that 3.5mm jack to get oxidised over the years preventing internal sound working. when you replace the op-amp if the internal speaker still doesn’t work trying some contact cleaner in the headphone jack.

interesting, I will use then some Deoxit on it, thanks!

Finally -- I will be delving into the schematics to look into SIZ0/SIZ1 to confirm they are going where they are supposed to go and will also look into A10 as @cheesestraws proposed.

Thanks Everyone for the leads! -- i will follow up with what I find

 

[naruse]

Hey guys! I SOLVED IT!

Again thanks for all the feedback -- I ended up checking Adrian's video and as I was planning to check the signals -- oddly enough if SIZ0/SIZ1 signals would mismatch with the actual ram I believe the computer wouldn't work YET, that was the lead I was needing!.

Turns out while I was checking for the pin numbers in the GLUE chip a microscopic sized blob of solder was in between 2 legs, I removed it, started the machine back again and wohoo! 8mb automatically recognized by the system!

I would have never thought such a tiny blob could cause me so much trouble but at least I managed to figure out what was the issue -- Lesson learned and I will be checking with more detail from now on every time I solder / desolder stuff.

Many thanks to everyone for the suggestions and the leads!

 

[JYewman]

Hi guys, sorry to revive this thread but I'm experiencing exactly the same issue with my SE/30, I have 4 x 1mb sticks installed (as well as 4 x 256k) stick and my SE/30 only reports 2MB! I have checked the traces for SIZ0/SIZ1 and they are both fine, I've also reflowed the GLUE chip and I'm still getting the same issue. I have completely run out of ideas. "HELLPPP!!!".

 

[naruse]

Hi guys, sorry to revive this thread but I'm experiencing exactly the same issue with my SE/30, I have 4 x 1mb sticks installed (as well as 4 x 256k) stick and my SE/30 only reports 2MB! I have checked the traces for SIZ0/SIZ1 and they are both fine, I've also reflowed the GLUE chip and I'm still getting the same issue. I have completely run out of ideas. "HELLPPP!!!".

I would check for microscopic traces of solder balls touching pins, that was my case. good luck !

 

[noe]

I would check for microscopic traces of solder balls touching pins, that was my case. good luck !

Where did you find the solder balls exactly and how did you detect it? Knowing it would help, because I have the same problem and I have verified all lines with the multimeter and I have not found any problem.

 

[naruse]

The micro ball was between two pins behind a SMD IC. It’s not about the traces, the balls where stuck between two legs on the ICs

 

[JYewman]

pins behind a SMD IC. It’s not about the traces, the balls where stuck between two legs on the

Was it on the GLUE chip?

 

[naruse]

Was it on the GLUE chip?

hard to recall but could be? -- it was one of the larger ones