Katheryn's Macintosh SE/30 saga

[alectrona2988]

So out of paranoia I replaced all the RAM muxes and a few of the logic gates, and now I get a black screen... I also don't get a little 'pop' from the speaker when I turn it on, so I suspect the power supply is going bad? I know I didn't do a full recap on that...

 

[Phipli]

So out of paranoia I replaced all the RAM muxes and a few of the logic gates, and now I get a black screen... I also don't get a little 'pop' from the speaker when I turn it on, so I suspect the power supply is going bad? I know I didn't do a full recap on that...

The pop is normal - that's the sound buffer being set up I think

Black screen is worse than stripes, so re-visit what you've done today.

 

[Phipli]

I know I didn't do a full recap on that...

What voltage is the 5th from top left pin on the floppy port? (Poke a paperclip in it)

 

[alectrona2988]

If you'll please excuse the RAM slots (I got combined slots, and tried cutting them in half and ultimately screwed up), here's what my board looks like. Anything that I did wrong? I know it does need a good cleaning but I'm not sure what would be best right now. Yes, the SWIM is not installed, I know. It does seem like it powers on but nothing happens, though the PSU and analog board work fine.

 

[alectrona2988]

Okaaaaayy, I may have a suspicion as to why it doesn't work right now. At one point I had soldered on one of the two SN75175DE4 chips that was the only one surviving, and recently I removed it. Can't remember where I put the chip when I removed it and the second one was damaged because of capacitor leakage.

 

[Phipli]

Is that UC12 and UB12?

Once you get further I'm not sure it will be happy about not having a SWIM either? Or is that OK?

 

[alectrona2988]

Yes those would be UB/UC12.

 

[alectrona2988]

Okaaaaay, I think I found my issue. It's the fact that I didn't clean the board like I should have. The solder paste seemed to have stayed near the contacts where I applied it to for putting my components on, and I had to clean it off with IPA. Don't know if it works yet but I think this is the cause for most of the issues I seem to be having.

 

[alectrona2988]

Yeeeaaah I still get a black screen. Could anyone give me any ideas as to what could be causing it specifically?

 

[finkmac]

is there a chime? i assume not. a black screen could be.... anything.

break out the multimeter and start beeping out your solder work.
break out the scope and check the clocks...

 

[Phipli]

Given it was doing stripes before you did some work on it, I really would revisit those areas.

 

[alectrona2988]

no chime, and no display... idk what i did, all i had done was replace 80% of the muxes. i might see what's going on with it another day, i really need to focus on life right now... :/

 

[alectrona2988]

just bought a microscope from amazon and i'm putting this on hold until it arrives, and until i have the courage to fix whatever i broke. meanwhile i have resources to build some 1MB SIMMs, i think. still have 22 chips left over from a tube i bought from ebay to use on my iisi's motherboard, and i have some dead 2/3-chip SIMMs.

 

[alectrona2988]

welp... already finding a lot of things i screwed up on. this doesn't seem like its totally bridged, but theres quite a shocking amount of paste that didn't get heated through. yeaaaahhh definitely invest in a microscope for one of these projects. if you're doing it without one, you'll screw up something like i have. also what would be a quick and easy way to get all the flux off of here? is there a good flux remover out there?

 

[Phipli]

View attachment 72717
welp... already finding a lot of things i screwed up on. this doesn't seem like its totally bridged, but theres quite a shocking amount of paste that didn't get heated through. yeaaaahhh definitely invest in a microscope for one of these projects. if you're doing it without one, you'll screw up something like i have. also what would be a quick and easy way to get all the flux off of here? is there a good flux remover out there?

Slightly depending on type, most of the time a little bit of flux shouldn't matter. Some parts of a circuit can be sensitive to contamination, but it isn't common.

Only thing I can think of is the sound circuit in LCs and similar is hyper sensitive.

I wouldn't call a bit of flux a screw up, best to get it off for the long term, and it tends to be easier to remove when fresh.

There are dedicated flux removers but I use IPA and scrub if I'm only using a little... My brother... Not even sure I should say this... Uses a brake cleaner in a spray can... It gets rid of flux, I'll give him that. I worry it is too agressive.

 

[obsolete]

There are dedicated flux removers but I use IPA and scrub if I'm only using a little... My brother... Not even sure I should say this... Uses a brake cleaner in a spray can... It gets rid of flux, I'll give him that. I worry it is too agressive.

Modern non-chlorinated brake cleaner is mostly a cocktail of acetone and methanol with some other light aromatic hydrocarbons thrown in just for fun.

I use a water-soluble flux, so I wash boards in two steps--first distilled water with a soft brush, then isopropyl alcohol to get any residue left behind and dry out the water faster.

 

[Phipli]

Modern non-chlorinated brake cleaner is mostly a cocktail of acetone and methanol with some other light aromatic hydrocarbons thrown in just for fun.

I use a water-soluble flux, so I wash boards in two steps--first distilled water with a soft brush, then isopropyl alcohol to get any residue left behind and dry out the water faster.

Yeah, I don't use acetone on PCBs in case there are any susceptible plastics on there. I own a tub of acetone, but I mostly use it for plastic welding ABS and degreasing metal!

 

[alectrona2988]

i think for one thing my attempt at fixing the original board last year had done some damage to the chips because i know the solder paste i used then was crap... thankfully i've already watched some replacement chips on ebay so i'll buy those when i have a more disposable budget.. lol. not sure about the custom ICs, and i REALLY hope my GLUE chip isn't fried...

 

[Phipli]

i think for one thing my attempt at fixing the original board last year had done some damage to the chips because i know the solder paste i used then was crap... thankfully i've already watched some replacement chips on ebay so i'll buy those when i have a more disposable budget.. lol. not sure about the custom ICs, and i REALLY hope my GLUE chip isn't fried...

The other day you had strips - that means loads of stuff was working

To show stripes, the video circuit has to work, as well as lots of chips. But the processor probably wasn't running code from ROM to fill the VRAM with the right stuff.

 

[alectrona2988]

yeaaaaahhhh.... i hope i didn't screw up the video PAL. speaking of video... has anyone recreated the micron xceed card stuff? i'd love to have one because the SE/30 deserves better than 512x342 at 1 bit color...