My SE/30 hates 16mb ram sticks

[Aeroform]

You don't, you replace them all. That is what I do. I don't question it anymore as I got tired of messing with dodgy chips.

You can sit there for hours chasing your tail to figure out where the bad one is based on a logic analyzer or you can just replace them and save a whole bunch of time.

Based on the good looks of the area / chips (no battery leakage whatsoever), would you still consider it possible there could be a faulty chip there? Or would you recommend replacing UD8 / UE8 first and see (although I'm unsure those chips could cause that error to start with)?.

Really appreciate all input I can get as I don't really have any skills in this department.

 

[techknight]

Based on the good looks of the area / chips (no battery leakage whatsoever), would you still consider it possible there could be a faulty chip there? Or would you recommend replacing UD8 / UE8 first and see (although I'm unsure those chips could cause that error to start with)?.

Really appreciate all input I can get as I don't really have any skills in this department.

YES. physical appearance has nothing to do with electrical operation, at all

The behavior is death chimes with additional RAM? then that is a major yes.

 

[Aeroform]

YES. physical appearance has nothing to do with electrical operation, at all

The behavior is death chimes with additional RAM? then that is a major yes.

Ok, thanks. Behavior is works perfectly with all sim slots populated as long as the individual ram sims is less than 16mb. With 16mb sims it gives death chimes and jailbar pattern on boot, irregardless of being installed in bank A or B.

 

[techknight]

Ok, thanks. Behavior is works perfectly with all sim slots populated as long as the individual ram sims is less than 16mb. With 16mb sims it gives death chimes and jailbar pattern on boot, irregardless of being installed in bank A or B.

likely because of an address line not being muxed right. one of the 74F253s is bad. Find the one with the highest address lines and repalce it.

 

[Aeroform]

likely because of an address line not being muxed right. one of the 74F253s is bad. Find the one with the highest address lines and repalce it.

Thank you so much! That REALLY speaks torwards UE8/UD8 which I suspect as these F253’s look poor. All F258’s visually at least looks 100%. I’ll have those swapped and will report back. Thanks again!

 

[Aeroform]

I’m trying to track down replacement chips for the F253’s, but there are so many variants and they all look the same? Does anyone know which ones would be correct? I’ve found:

SN74F253D
SN74F253DR
SN74F253DRG4

Thanks

 

[demik]

I’m trying to track down replacement chips for the F253’s, but there are so many variants and they all look the same? Does anyone know which ones would be correct? I’ve found:

SN74F253D
SN74F253DR
SN74F253DRG4

Thanks

It's just packaging difference IIRC (tube vs reel etc). They are all the same.

 

[trag]

You can sit there for hours chasing your tail to figure out where the bad one is based on a logic analyzer or you can just replace them and save a whole bunch of time.

Yes, at less than $1 per chip, one must ask whether it's worth the time to test, vs. just replace the lot. Excellent point, techknight.

 

[Aeroform]

It's just packaging difference IIRC (tube vs reel etc). They are all the same.

Thank you for confirming. Will get an order in!

 

[joshc]

@Aeroform Did you ever get to the bottom of this?

 

[Aeroform]

@Aeroform Did you ever get to the bottom of this?

Not yet unfortunately. I got some help with swapping the F253’s but unfortunately there was some miscommunication and he only replaced the ones that visually looked bad / corroded. And that did not help, but from what I could understand from the schematics that did not include the ones for the high address lines (haha ofc) - soooo, I still suspect a faulty F253.

It’s still on the ToDo to swap the remaining ones and test some more. But I struggle with finding time between my two small kids and work currently, so it might take a while. I also have another fully working SE/30 and other toys to play with so it’s not the highest of priorities haha.