SE FDHD Restoration

[LaPorta]

I did not patch the red trace because it still had good continuity all the way. If you think I should totally bypass it, I could do that.

im going to try all of your other suggestions as well. I can try the ROMs in a good MB I have.

 

[LaPorta]

Update: get good +12 and +5 V signals from the floppy port where I should be. Testing ROMs next.

 

[LaPorta]

ROMs/IWM work just fine in another, working SE board that I have without issue. If you can, please explain to me how to check chip voltages: each pin to ground? How do I know what each one should be? Also, more practically...how does one do that with the thing hooked up to the rest of the machine? It's not like I have a long-length AB to LB cable.

 

[BadGoldEagle]

each pin to ground?

That's basically it. 

My unit was made in Ireland so it has the longer AB to LB cable. The only solution to effectively create a test bench is to hack up a 24 pin ATX cable. Just make sure you cut it in the right spot as it's keyed.

The serial chip shouldn't prevent it from booting. A bad SCSI controller wouldn't allow it to go past the grey screen before the floppy/question mark logo. Something else must be bad on this board but what?? On my board, a few other traces near the ADB controller were bad. I have no idea how acid got there... Might be worth checking elsewhere for damage? 

 

[LaPorta]

I have been meaning to either find or make cables for both the 128k-Plus and the SE series to make a test bench for these machines. What are the voltages supposed to be on these things, is there a list somewhere?

 

[BadGoldEagle]

It's only standardised +-5V and +-12V


Pin


Color


Function


1


Black 


GND


2


Black 


GND


3


Black 


GND


4


Black 


GND


5


Black 


GND


6


Blue 


-5V DC


7


Green 


-12V DC


8


Black 


GND


9


White 


VIDEO (starts 11.2 usec after falling edge of HSYNC, lasts about 33 usec, first data line is 1.26ms after falling edge of VSYNC)


10


Purple 


HSYNC (square wave, falling edge triggered, 45 usec per line)


11


Gray 


VSYNC (square wave, falling edge triggered, 60.10 Hz / 16.64 ms per frame, 180 usec low)


12


Orange 


+5V DC


13


Orange 


+5V DC


14


Yellow 


+12V DC



source: https://trmm.net/Mac-SE_video

 

[LaPorta]

Oh ok just at the connector? I thought you said at each of the chips...perhaps I misunderstood.

 

[BadGoldEagle]

My bad, I thought you meant what were the voltages on the connector, not on the chips. Most of them will be 5V.

 

[LaPorta]

Thanks, at least this way I can check and see if certain chips are not receiving 5v as they should. I assume that if one has no voltage at all on any terminal, I should start to look there.

I appreciate the help, tracking down problems is new to me.

 

[BadGoldEagle]

You can find the pinout of most of the non Apple chips online (the Sony sound chip, the Bob Baily Unit BBU, the VIA, the RTC etc are all specific and pinouts aren't available).

 

[LaPorta]

Ok thank you very much. I also very much need to find a tutorial on using my oscilloscope just so I know what to look for. Any recommendations on a good book?

 

[jimjimx]

Well, I can start you (and anybody else reading this) off with.....

When using a DMM, put the positive (red) lead on ground, and probe with the negative (black) at the chip, therefore your probe won’t try to power up the chip, or chips!

O scope.....  yeah. Someone else chime in...

 

[LaPorta]

I got the connectors I needed, made a much longer connector, and set up a test rig. Now I can track the traces and test the voltages in-circuit:

 

[jimjimx]

Do you have links to the connectors?  I’d like to make some of those too.

 

[davidg5678]

Do you have links to the connectors?  I’d like to make some of those too.

Me three!

 

[LaPorta]

I managed to find it on Mouser:

https://www.mouser.com/ProductDetail/Molex/39-01-2145?qs=%2Fha2pyFaduiTiUTfcatyVrJcToNOagaAZzV5BuQq9ia5fzwjuTay7g%3D%3D

 

[jimjimx]

I managed to find it on Mouser:

Thank you for doing that!

What about the male connector? Got links?

A lot of people talk about fixing / repairing their machines, a lot of people help them, a lot of people question...........

..... And then that person comes back with “I found it at “parts supply” & fixed it, Hey thanks!”

But never give information on the part, or replacement part....

Yeah, we can all look at “parts supply” .com, but xxxx, don’t tell me “I found it at “part supply .com”! Give us a link, or more information about it..

Damn, looking up parts, even in the age of internet, can take days (and many brain cells).

Thank You!

I wish more people would give exact part #s..

I’ve thrown exact part #s at people many times, and I love it when they say “ 

Thanks, it’s working again”.

 

[LaPorta]

Yes, what happened was that I was rifling through the digital parts manual and said "Geez, there are so many and they all look alike...I'll never find this thing." So, I went to a somewhat local parts store with my original cables, and the guy found the identical piece in about 30 seconds. I used his part number to match to what he had on his website, and found the manufacturer's part number, which I then tracked online. The sad thing for the parts store guy is that, as helpful and awesome as he is, he sells the connectors for about $3 a piece, while Mouser has them for about 79¢ each...

I was willing to purchase to have them on hand (and get you guys part numbers), but in the long term, if I buy a good number of components at once, saving $7.99 on shipping vs pickup will not offset his high prices.

I did not purchase the male version, as I did not need one. However, usually via the data sheet PDFs on Mouser for each part, there will be a section that will say "Use With..." and give the part number of the exact male counterpart.

As for the Mac 128k-Plus style, I got a 12-pin version of the same (instead of 11 that it is), but it can be clipped off. I am still looking for the equivalent part online.

Hopefully soon enough, I can actually start tracing what the heck is wrong with this logic board!

 

[LaPorta]

Man, I really have almost had it with this thing. I’m just not sure what the issue is. I’ve been checking voltages all over the board, and they are within spec with regard to my reference board. I’m going to keep checking all the vias for continuity. Any more suggestions, I would really appreciate it.

 

[AwkwardPotato]

I've never heard of it failing, but maybe try swapping that big socketed VLSI chip next to the CPU, just to rule it out (just be very gentle to prevent cracking the socket). Also, maybe there's a rotted trace under the SCC or SCSI chip?