Macintosh Classic II blank screen after recap

Any status with this? Looks like fallen had found a troubled spot under q1. And under the rp on the flip side of the board.

Sorry that is u1 not q1, But looks like there might be some cap goo crust under U2 chip, might want to also look at.

Seems like with these classic ii's. Short out the sound, the whole thing is dead, and that I think is because the sound dac just like in the se30 controls system reset as well.

I am returning to this board after 2 months, the situation is the same.

I've pulled all the small chips, U1,U2,U3,U4,U5,U6,U7,U10,U11,U12,U15, but it will only display checkerboard wihtout U10 present (Egret). Others don't make any difference in operation. I also did the RC1, RC2, RC3 - no difference.

Underneath the chips, all the traces are intact, as this is probably the cleanest old Mac logic board I've ever seen (in the start, there were no leaking capacitors).

Is possible that the other Egret chip is also dead? The other one was pulled from a dead LC III board.

Ok, I've swapped the Egret from another Classic II (Rev. 1) board, but it didn't help at all. The Egret chip was definitely okay, as it works okay on the other board.

Also when I tried the working board with the Egret chip removed, it was completely dead, the exact opposite of what the broken one does, as the broken one does checkerboard without the Egret.

I am running out of ideas, I've already spent about 20 hours on this thing.

Only thing that might help are the schematics, but as for the most of the Macs they're unavailable.

In reviewing this, I read that the egret chip was swapped out several times with other egret chips with the same result. So unless everyone of those egret chip is bad, the problem is not there. It has to be elsewhere. So what's holding down the reset pin on the Classic II? I think the chips other than the Egret chips Uniserver is pointing too are the key, even if the chips are good, their traces and VIAs could be bad and cap goo shorting out traces as well. So start checking traces and VIAs as well around the 'usual suspects'.

It also good to dunk the board in a 3 to 2 parts mixture of distilled water (3) and ammonia (2), and slosh it around for a couple of minutes. This will eliminate what cap good is under the chips. If this liquid turns color (I noticed that it would turn green in many cases), that there was cap goo it eliminated. Then rinse out the board with distilled water and then high proof isopropyl alcohol (I use 70% or higher) Then dry the board with compressed air; if you don't have an air compressor, use a hand held hair dryer set to high air flow and high hot heat. DO NOT USE compressed air in a can.

I know that with an Apple II, if you flex the board back and forth slightly to loosen up chips that are in sockets, you start to break connecting traces at around where sockets are soldered to the trace.

Thanks,

The Egret is fine.

Well, I would be glad if there was any cap goo, but as I said, this board was very clean. And trust me with that, as I recapped at least 50 old Mac's boards, so when I find a clean one, I know it. I cleaned it with a mixture of degreaser and distilled water about 4 times, so I don't think that there is any goo left. Dried in oven at 80 deg. C for 1 hour after every cleaning. Also for the traces and vias, I doubt that there is one broken or shorted, but if it is, I don't think it is from cap goo. I have a feeling that this computer was retired early in its life, as the case is still snow white and the board was extremely clean. Possibly retired from an error that it troubles me now.

I lifted the reset leg from the Egret chip, so now the line stays high. Now it will sometimes boot to the checkerboard and sometimes not. I talked to my electronics friend and he said that if that chip is reseting itself, there must be a problem with something connected to this chip, also my logic says the same.

Before a recap, if I recall correctly, there was checkerboard at all times.

I have the classic II schematics,  but its the 4 rom chip variant. not the 2 rom chip verison.  I think they are pretty close though.

you can pm me if interested.

I finally made some progress. I managed to get the chime and white screen. It looks like there is a broken trace or perhaps a component that likes heat.

If I heat the board with the heatgun in the area underneath the Egret chip it will chime sometimes, sometimes it will do a jailbar pattern, sometimes it will do the checkerboard, and so on. I still have the reset pin lifted from the Egret, so I guess something must be wrong in this area. I checked it with the magnifying glass and removed the chokes for the ADB and audio, but I can't see any signs of anything broken...

eaten trace. 

It must be in a layer you can't see.

Yeah, however I thought that these boards are only 4 layer (bottom, ground, power and top plane)... If it is in a layer that I can't see, is it even possible to repair it somehow?

I also reflowed the capacitors on the bottom side, but it also did nothing. Also replaced the memory chips... It will chime when it is warm (not just under Egret, but also under sound ASIC area), but it freezes immediately after that, so if I reset it, it will do a chime of death and picture will still sometimes come, and sometimes won't after resets. Sometimes it will do a jailbar and sometimes a checkerboard. Also very commonly these two patterns are a bit scrambled, but not much, just pixels shifted a bit...

Any thoughts on that?

Not that this helps, but i registered because I recapped my classic II 2 years ago, when i pulled it out for use after working for 8 hrs or so i got the lines down the screen and no chime, so I ended up taking the board out and scrubbed it real good put it back in and its working fine, I must have missed some corrosion.

These guys arnt 4 layer, I believe they are 6 layer. But, the SE/30 its hard to tell if its 4 or 6, but they definitely run traces on the inner layers. But, its also possible it is a 4-layer, but they only use 1 layer for ground fill, and they use a 2nd layer for VCC traces, and regular traces. 

Only way to tell is take a sacrificial/battery acid board, strip it down to the bare PCB only, and grind/shave it off. one layer at a time, and document. 

is it even possible to repair it somehow?

Click to expand...

sure with a patch wire and the schematics.

uniserver said:

sure with a patch wire and the schematics.

Click to expand...

That def. seems like something someone would send to you rather than try themselves. On the other hand, maybe I'm just a wuss. I just prefer professionals fix my stuff, I love my compacts too much to risk them on my own repairs.

ill tell you guys what... i have seen some battery destroyed boards fixed by techknight. with traces/pads and VIA's complete shot... 

and wires ran all over like spaghetti that techknight fixed,  That man has some sickening patience.