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Mac newbie & SE30 vid prob...not another one!

genie_mac

genie_mac

Well-known member
Hi there,

I'm new to the forum and Macs in general. I always wanted one around the late 80's but could never afford one, so when I was bitten by the retro bug last xmas I started looking for one. That's when I realised that buying old Macs is like getting the bus: you wait for ages and then 3 come along at the same time. So after 3 months of searching I am now the proud owner of an SE, SE30 and Classic II in various states of repair, and the proud owner of some big problems!

So here it goes: SE30 video problem regular vertical bars as in linked image



I have done the following so far but no difference whatsoever.

-Board cleaned with IPA.

-Logic boards swapped between SE and SE30. Same problem with SE30 logic board in SE and SE logic board works fine in SE30,so must be prob with logic board.

-Simms (ROM and RAM) cleaned and reseated.

-PRAM battery replaced .

-RAM simms replaced with known good ones.

-Board recapped (except large electrolytics C2 and C11).

-Continuity of replaced caps checked and OK.

-Board visually inspected and two wires soldered in where corrosion had destroyed track (around DAC UE10 and UE12).

-Voltages on floppy connector checked and OK.

I think I'm going to try and analyse the bars on the screen and see if I can come up with an idea of what's going on...getting my head around that video interface is going to be a daunting task!

So I would be grateful for any info / tips.

Cheers! :b&w:

PS: Sorry about posting another topic on SE30 video problems but I have been reading most of the other threads on SE30 vid problems but bar one with a faulty demux (iirc) I think there was never a real solution.

 
genie_mac

genie_mac

Well-known member
Hi,

as I can literally see the tumbleweed blowing across this thread, I thought may as well post the first reply.

Just a quick update on my problem: I have now managed to boot the SE30 (see pic) off the floppydrive (good!) but I had to disconnect the harddrive (bad). Could the SCSI chip be gone? Sound is OK.



Looking at the bars and their pretty regular appearance I have tried to come up with a possible cause for this. I'm probably way off but how about the output (pin7) of the first mux in UD8 (the 74253) being stuck at 1 (aauming the VRAMS chips are ok)? This seems to supply the least significant bit to the address decoder of the VRAM, which could (???) create the 8 pixel wide bars on the screen. Am I right in assuming that the VRAM is interleaved between the two chips (lower 4 bits from UC7 and upper 4 bits from UC6) which are then going to the serial shift register (UE8)?

I would really be interested in what the experts think about this.

Cheers!

PS: Does anyone know how the VRAM is tested on boot-up? Could it be a checkerboard test which may explain the shape of the bars (10101010 on first line versus 01010101 on the next line)?

 
J

jwse30

Well-known member
As far as the RAM SIMMs being a possible cause, wasn't it a common troubleshooting tip way back when to rearrange the SIMMs into different sockets so if there was a trace of corrosion on a pin it wasn't likely to touch the exact same spot on another SIMM. This might be something to try as the sockets could be less than spotless after all this time.

Just remember that the SE/30 uses two banks of RAM; so if you're using two different types of RAM, make sure they are all in the same bank.

Hope this helps (and isn't just an urban legend)

J White

 
genie_mac

genie_mac

Well-known member
Some progress updates but more problems now.... :(



I managed to fix the video problem :) :) :) . Seems I was right about my initial diagnosis, I traced it back to a faulty via. Tried reflowing it but no good so I had to run a wire. Man that board is staring to look like a plate of spaghetti...

What's the best way to fix those vias? There is continuity between top and bottom of the via but the internal layer is not connected.

So MAcTestPro Ok'ed the logic board but I still have no SCSI. Harddrive works OK in my SE, but SE30 doesn't see anything on the bus.

Looks like this is going to be a bit trickier to diagnose than the video prob, 'cos I don't know what's wrong. Back to the schematics I suppose!

Any idea would be much appreciated.

Ta!

Ps: three cheers to the person that originally uploaded those SE30 schematics. Legend! :cool:

 
J

James1095

Well-known member
If it's a connection to an internal layer, there's not really much you can do besides running a wire. I use kynar insulated wire-wrap wire, it's the same stuff that was occasionally used in the factory to repair traces or rework errors. It's not uncommon to see a few bits of it stuck on production boards from that era. PCBs were so expensive to build at the time that it was cheaper to rework them by hand than to scrap a faulty board.

 
genie_mac

genie_mac

Well-known member
Will post some pictures tomorrow, was busy fixing up my external HDD until now...works fine now and will try with the SE30 tomorrow hopefully.

Also haven't had the chance to have a look at the other SE30 thread yet, not enough hours in the day :)

For running connection wires I also use wire wrapping wire, find it the easiest to work with. Yeah I remember some reworked boards like that too. Still have a few old PC boards lying around with them on it. I pity the poor guy that had to solder them all day... ;)

 
genie_mac

genie_mac

Well-known member
Ok here are pictures of work done so far.



The two wires are bridging tracks that were corroded away. Ones is going to the Sony sound chip and the other one to the Bournes filter (so nothing to do with my graphics problem).



One wire to fix the graphics problem. Ran out of wirewrap at that point hence the crooked wire, nah probably just too lazy...

SCSI still not working but I found two more faulty vias associated with the SCSI chip...everything else checked out OK.

Bed time now though |) , might have a go at it tomorrow.

 
genie_mac

genie_mac

Well-known member
Ladies and Gentlemen, we have SCSI! Meaning I managed to get SCSI going on the SE30. It was the two faulty vias between the SCSI chip and the glue chip.

I tried everthing I could think of to test the system (both internal and external drive, formating, disk copy between two drives, bad block checking etc) and it seems stable, so that's grand.



Next on the list are serial ports, I reckon there may be a problem as well as there are a lot of badly corroded vias around that area. We shall see...the saga continues.

 
genie_mac

genie_mac

Well-known member
Looks like I've now got a healty (but pretty fragile) SE30 on my desk (not bad for a pensioner). Serial ports checked out OK, did Zmodem transfers, dial-up stuff and it seems OK. Printing on LocalTalk OK as well so I'm a happy camper now. Max speeds of 57600baud on the serial port with ZTerm only though...takes a while to fill that 80Mb external drive with games....

PS; will post pictures of board as soon as I have opend it up again...

 
uniserver

uniserver

Well-known member
i feel like apple should have spent 50 extra cents and filled the VIA's with solder like they did later on.

 
T

trag

Well-known member
i feel like apple should have spent 50 extra cents and filled the VIA's with solder like they did later on.
Click to expand...
On my IIci, the vias being filled with solder did not help. The capacitor goo ate the solder too. The vias still *looked* okay, but a little probing with a dental pick revealed that the metal fill was soft and crumbly.

 
genie_mac

genie_mac

Well-known member
Ok, as promised here is an image of the "final revision" of my SE/30 board, the back of the board hasn't changed, see a previous post for that.



Also upgraded RAM to 20 Mb, but there is one thing I'm not sure about. It shows 20Mb but I thought the SE/30 had 24 bit addressing (giving a theoretical max of 16Mb). I believe in System7 you use Mode32 but what about 6.0.8? Could someone enlighten me?



Cheers!

 
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