Plus / 512: smiling Mac surrounded by black screen

[superpantoufle]

Hi!

I had a Plus with a dead CRT, and a 512 with a dead mainboard. I thought of building a working Plus out of those two dead bodies, since I read that upgrading kits for the 512 were sold at the time, consisting of a Plus mainboard and a new rear case…

So I easily put my Plus' mainboard in the 512, plugged it to the wall and turned it on.

It starts up well (beep!) and shows the usual question mark floppy, only surrounded by a whole black screen. I put in a system floppy; it shows the smiling Mac and I can hear it booting well from the floppy, only still the smiling Mac surrounded by the black screen.

Any idea? Thanks in advance, and sorry for my bad english, I hope someone could understand what I tried to write!

 

[JDW]

A black "border" around the video area of your Mac's CRT is normal, within a certain limit.

Can you please post a photo so we can better see what you are describing?

 

[superpantoufle]

You're right, a picture will help… because as you said, a black "border" is normal, within a certain limit, and that limit is obviously over!

Actually I've seen similar screens on Macs along a death chime, but displaying the sad Mac and an error code.

Here the Mac is booting fine, as I can clearly hear the floppy drive.

Thanks for any advce!

 

[MultiFinder]

Wow, that's a new one. Seems that something awful odd is going on there; wish I had more useful info. You say it chugs at the floppy and boots; does it stay on the happy mac screen or go to a desktop?

 

[superpantoufle]

You say it chugs at the floppy and boots; does it stay on the happy mac screen or go to a desktop?

No welcome screen, no desktop, no nothing… It will stay on after booting, displaying nothing else than what you can see in the pictures.

As I said before, it's the chassis, CRT, analog board and floppy drive from a 512k, with the logic board of a known-working Plus. I've read those « upgrades » were possible; am I right?

Edit: I know the CRT is working fine, and by the way the smiling Mac icon is perfectly well drawn, pixels are sharp and on focus, and one can see the usual grey pattern behind the floppy and the Mac icons, around the edges…

 

[superpantoufle]

Some news:

Out of curiosity, I just took my working Plus apart, and put its logic board in the 512. Works well, boots just fine!

So it seems my issue is related to that specific Plus logic board. Well, still strange! I had never seen this, so I hoped someone around herre would have…

 

[Dennis Nedry]

I've seen that before on a plus I think. I believe it is a glitched out version of the sad Mac. Do you have any other boot floppies you can try? It could be a problem with the system files that prevents a plus from booting but not a 512k.

If you don't put in a boot disk, does it have the disk with blinking question mark on a normal checkerboard background? That info could help distinguish between a hardware and software problem.

edit

Upon re-reading the original post, it seems that it always has this blackness even before inserting a disk. This would point to a hardware problem with the logic board.

Your dead CRT may be fixed easily, a lot of us here have fixed old Macs that were dead by simply resoldering a connector or replacing a capacitor. There are a few likely culprits if you care to try to revive the one that isn't working. If the glass picture tube itself is broken, though, there's little you can do.

 

[JDW]

Thanks for the photos.

Goodness, I've seen that before, many years ago. I just cannot recall what caused it other than the Mac had been upgraded somehow. And that particular happy/sad Mac is not in any of my Larry Pina books either. But it is a problem that others have seen.

This will take some deeper digging, I can see.

 

[superpantoufle]

Your dead CRT may be fixed easily, a lot of us here have fixed old Macs that were dead by simply resoldering a connector or replacing a capacitor. There are a few likely culprits if you care to try to revive the one that isn't working. If the glass picture tube itself is broken, though, there's little you can do.

Sure. « Dead » CRTs often mean dead, or ill analog boards. But on that particular one, the tube's neck has been obviously broken. No hope on that side; that machine has been used by tons of girls and boys from a public school. It has a big « 16 » mark on the side from an inventory sticker, it's completely yellow and the switch area is dirty as hell. So I would have been glad to be able to use its logic board, but otherwise I don't really care about the case and repairing the analog board…

So, a faulty logic board is sure enough the issue. Doesn't matter a lot, since I'm really too bad at the soldering iron to try anything…

By the way, thanks for the help!

 

[JDW]

I can't give up on this. I've seen it before with my own eyes years ago and it kills me NOT to know the exact cause.

After an hour of Googling this evening, I found another case (open the page and search for "happy"). But the situation seems different than yours, and alas, no one in that thread responded to that poor fellow's call for help. Here's yet another case, but that thread wreaks of pure apathy toward researching the problem intelligently. It is interesting though that this problem seems to be linked to the Plus (as opposed to other compact models).

My gut tells me that someone on the logic board is non-stock. Could you post a crisp photo of the top of your Plus's logic board for us?

Also, have you tried other floppies?

I suppose you could pull the ROM chips, then carefully reseat them. Ditto for the RAM SIMMS (known good SIMMs, of course).

 

[Dennis Nedry]

I believe that the Radius Full Page Display card required a resistor to be cut on the logic board. It snapped on top of the 68000 chip and also there was another connection that had to be made with a spring. I remember trouble with this when I tried removing the card from my Plus.

My Plus also had 4MB of RAM, I seem to remember that somehow also required some hardware modification.

If you can, inspect the logic board for any cut resistors.

 

[superpantoufle]

Ram, ram, ram, it's all about ram! :b&w:

Thanks to JDW who asked for a close inspection of the logic board and Dennis who suggested hardware modifications depending on the Ram amount, I think I got it solved…

I had that page in my bookmarks for a while. It's in french, but it's basically a descriptive page about the Plus' specs. But the small table at the bottom got my attention, and it shouldn't be too difficult to understand, even if it's in french. A resistor in R8/R9 has to be cut depending on the Ram configuration. With the ports facing up, it's on the left edge of the board, at the same height than the analog board connector.

The resistor is cut on both of my Plus boards, so it means, according to the table, that I can have either 2x 1Mb in bank A and 2x 256Kb in bank B, or 4x 1Mb.

And it appears that I had messed up my simms one way or another, the faulty board was simply loaded with 4x 256Ko.

Good news: both of my boards works fine, all I have to do is look through my stuff for 6 more 1Mb simms, and they'll be fully loaded!

Bad news: During my heavy board switching I've done something wrong and killed the sound: no more startup beep, no more system beep, only silence! That's strange, since I haven't touched neither the analog board not the speaker cables… >

Anyway, thank you all for helping solve my first issue posted around 68kmla so quick!

 

[superpantoufle]

EDIT: no audio again. Thought it was solved, but no luck. I thought it would be better to open another topic on the audio issue here

So, to summarize the topic: A Mac Plus whoose Ram configuration doesn't match with the resistor's position in R8/R9 will « kind of boot », but displaying a completely black screen but the smiling Mac

Good to know, I guess.

The resistor's positions are as follow:

- resistor in R8, R9 empty => 4x 256Ko simms => 1Mb total;

- resistor in R9, R8 empty => 2x 1Mb simms in bank A, Bank B empty => 2Mb total;

- no resistor in R8/R9 => 2x 1Mb simms in bank A, 2x 256Ko simms in bank B => 2,5 Mb total, OR 4x 1Mb simms => 4Mb total. That's it!