68kMLA Classic Interface

This is a version of the 68kMLA forums for viewing on your favorite old mac. Visitors on modern platforms may prefer the main site.

Click here to select a new forum.
Got A BBB Problem: Boots W/ Black Bars
Posted by: K55 on 2015-12-20 12:29:57
Image is worth a thousand words here:

Got this se/30 recapped from uniserver (thanks btw, great work 🙂 ) and everythings been fine and dandy until last night.

I left the system on overnight to unpack system 7.5 and I came back this morning to what you see above, boots fine, but displays the black bars above.

I thought it might be UE8 -> UC6/7 becusae of the video lines, so I checked the connections, didn't see anything, but soldered patch wires to make 100% sure that wasnt it and.....it didnt work 🙁 . Any ideas on what could be wrong?
Posted by: techknight on 2015-12-20 14:25:16
UE8 bad or trace broken. 
Posted by: K55 on 2015-12-20 16:32:22
Well I patched all the traces so the chip is most likely bad. 🙁 I wish I knew someone in NJ that did smd work, but all anyone does these days is phones :-/ .

Does Uniserver do small smd jobs like this?
Posted by: takimoto on 2015-12-20 19:44:08
Hi K55.

I think you can make narrow the situation by using voltage meter.Video data lines between UC6/7 -> UE8 were 2.05v or 2.36v when my SE/30 is showing ? icon.If there is line sticking 0v or 5v,video memory is dead,or trace is dead or touches another line.make sure have a look both UC6/7 side and UE8 side,If trace is broken,there will be difference(sounds like not this case,you patched lines...)

If all lines show you good voltage,I think UE8 is dead. 

Cheers!
Posted by: K55 on 2015-12-20 20:12:47
Just reporting in before I sleep, checked the line voltages, all of them were 2.39V except for 2 lines that were at 1.86V which makes sense because the minimum TTL input level is 2 V so the 2 inputs on the UC6/7 chips are never going high. It seems like UE8 is borked.

Thanks for the tip! 🙂

Posted by: K55 on 2015-12-20 21:04:26
Specifically the problem is with the lines that go to UC6, VID4 (2) and VID6 (5) are lower than on UC7 as are lines D(28) and D(31), Do the D lines have anything to do with the video signal?
Posted by: takimoto on 2015-12-20 21:22:10
Data lines bring video data only when video ram is selected,otherwise bring instruction and data and everything.so we can't tell something comparing them.I thought Data lines to video rams are good because if there is problem,whole system won't be working.but is there possibility there is cut just before video ram?
Posted by: uniserver on 2015-12-20 22:22:25
hey there how long before it started doing this, just curious?

UE8 is a common fail point with the SE/30, but usually it proves it self to be bad with in the 2 hour burn in.

I charge 25 to replace the UE8 if you want to send it over i can swap that out.

If it would have went bad on me here i would have swapped it out here and saved you the hassle...

Oh well Murphy's law… 
Posted by: uniserver on 2015-12-20 22:41:44
or just replace it with this:

http://www.mouser.com/Search/ProductDetail.aspx?R=SN74HC166DRG4virtualkey59500000virtualkey595-SN74HC166DRG4

if you want to invest in a hot air station they are pretty reasonable these days!

http://www.ebay.com/itm/858D-110V-Hot-Air-Rework-Station-LED-Solder-Desoldering-Tool-w-110V-Stand-USA-/301828051023?hash=item46465a904f:g:yjYAAOSwk1JWchd9
Posted by: K55 on 2015-12-21 08:26:19
Morning all!

Quick post before going back to work.

hey there how long before it started doing this, just curious?

UE8 is a common fail point with the SE/30, but usually it proves it self to be bad with in the 2 hour burn in.

I charge 25 to replace the UE8 if you want to send it over i can swap that out.

If it would have went bad on me here i would have swapped it out here and saved you the hassle...

Oh well Murphy's law… 
Yeah Uniserver I was thinking about getting a hot air setup for future smd work, at some point the cost of repair/shipping everything to you will balance out with doing some of the repair work myself 😉 .

In terms of run time before it failed? Maybe 30 hours tops. I'll poke around a bit more tonight but I'll probably ship it to you for repairs.

Data lines bring video data only when video ram is selected,otherwise bring instruction and data and everything.so we can't tell something comparing them.I thought Data lines to video rams are good because if there is problem,whole system won't be working.but is there possibility there is cut just before video ram?
Nah all the traces are fine, its probably because the 2 video lines from UE8 are bad its causing some weird stuff on the D bus, the system works fine otherwise.
Posted by: takimoto on 2015-12-22 07:23:40
OK!

Hope you get this SE/30 fine!
Posted by: K55 on 2016-02-01 19:17:23
Fixed :^)



Replaced the shift register and we're back in business. Probably will get a hot air gun for the next time.

Used some gallium solder but it doesn't work so good on older solder joints like these.
Posted by: Elfen on 2016-02-01 20:11:40
Wash the board with some ammonia & distilled water and then chase it down with alcohol to get rid of any remaining cap goo. Dry with compressed air or a hair dryer.
Posted by: K55 on 2016-02-01 21:21:40
Don't worry Elfen, Uniserver did that already (pretty sure he gives every mobo a bath with his re-caps 🙂 ).

Pic isn't cap goo but excess flux I cleaned up after that picture.
Posted by: uniserver on 2016-02-02 09:37:07
it looks like before you replaced the ue8 you ran some lines to the vram first. 🙂

cool man.  hey it works.. so that is good!
Posted by: K55 on 2016-02-02 13:26:36
Trust me it was easier to rework the shift register than it was to solder the lines to the vram 😛

1