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Shymon184

[HELP] Macintosh Plus Checkerboard screen

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My Macintosh Plus has many hardware issues, but I would like to address this one today. This checkerboard appeared one day and alongside that, the sound stopped working. I already replaced electrolytic capacitors on both logic board and analogue board. I recently upgraded my Macintosh from 2.5Mb of RAM to 4Mb of RAM and the checkerboard changed. I would appreciate some help with this problem because I tried many solutions and none have worked.

 

Before 4Mb upgrade:

IMG_0871.thumb.jpeg.310baba562ade57e916c58c068976fed.jpeg

After 4Mb upgrade:

IMG_0915.thumb.jpeg.a02e7f361cdcf611479e552cb2428e27.jpeg

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8 hours ago, LaPorta said:

Have you checked continuity of the actual pins for the sockets as well? That could also possibly do it.

Yup, I checked the pins before installing the 1Mb sticks, they seemed fine to me, all lined up perfectly.

Edited by Shymon184
spelling

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I forgot to mention that the checkerboard screen disappears after few seconds and normal boot sequence occurs. Other important thing is that if I select "Restart" in the Special menu, there's no checkerboard when the Mac restarts. This leads me to believe that this issue is not related to RAM per se.

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That would point to some sort of loose or poorly soldered connection that improves when the machine heats up. You could try and find it, or what’s probably easier is just resoldering all of the socket pins. Also, make sure that the socket fingers are making good contact with the RAM sticks.

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8 hours ago, LaPorta said:

That would point to some sort of loose or poorly soldered connection that improves when the machine heats up. You could try and find it, or what’s probably easier is just resoldering all of the socket pins. Also, make sure that the socket fingers are making good contact with the RAM sticks.

Resolder the logic board? That's a no no for me, I can barely resolder the analogue board, I guess I'll have to find someone who's gonna do the job...

Also other weird thing that happens with the picture is that over time, the picture just becomes wider, you can't see it expanding, you will only notice it when you use the Mac for a few minutes. Any pointers for that?

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8 hours ago, techknight said:

Or, the voltage is low on your analog board, 

That is more likely I think, but I can't quite figure out what went wrong, I adjusted the voltage to 5V and nothing has changed. Maybe the high voltage power supply is failing (I read something along those lines in Macintosh Repair and Upgrade Secrets or Classic Mac Repair Notes, can't remember which).

Edited by Shymon184
spelling

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high voltage power supply wouldnt have anything to do with this. 

 

Big thing is making sure the 5V, 12V, and -12V voltages to the logic board are on target. 

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8 hours ago, techknight said:

high voltage power supply wouldnt have anything to do with this. 

 

Big thing is making sure the 5V, 12V, and -12V voltages to the logic board are on target. 

Like I said, I adjusted it, but I can check again...

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22 hours ago, techknight said:

high voltage power supply wouldnt have anything to do with this. 

 

Big thing is making sure the 5V, 12V, and -12V voltages to the logic board are on target. 

I checked the voltage and I got these results:

  • Upon startup the voltage (both 12V  and 5V) started fluctuating, the 12V ranged from 9.n/aV to 12.08V and the 5V never went below 4V and for a second was 5V.
  • Once the Mac got to the insert diskette screen, the 12V stayed on 12.08V and the 5V stayed on 4.98V (which is strange because I adjusted it to 5V a few months ago).

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8 hours ago, techknight said:

And there is your problem. You still have power supply issues that you need to Iron out. 

So, you're telling me that fluctuating voltage isn't normal? Well that's a start, now let's find the problem! What could go wrong with the power supply?

I'm no expert in electrical circuits, but my tip is on the T3 transformer, last time I checked, it looked kinda fried up.

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8 hours ago, Shymon184 said:

So, you're telling me that fluctuating voltage isn't normal? Well that's a start, now let's find the problem! What could go wrong with the power supply?

I'm no expert in electrical circuits, but my tip is on the T3 transformer, last time I checked, it looked kinda fried up.

 

No, it is most certainly NOT normal. Voltages should climb up nearly instantly and remain steady at all times. There are many things in this power supply known to cause issues, and I remember running into a handful of threads where stability issues were being caused by a specific component that other members were trying to find functional substitutes for. I forget which threads they were, its been years. 

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8 hours ago, techknight said:

 

No, it is most certainly NOT normal. Voltages should climb up nearly instantly and remain steady at all times. There are many things in this power supply known to cause issues, and I remember running into a handful of threads where stability issues were being caused by a specific component that other members were trying to find functional substitutes for. I forget which threads they were, its been years. 

> I forget which threads they were, its been years.

Oh well, that's unfortunate, but at least I know what's wrong with my Mac. This narrows down the list of possible problems a lot, so thank you very much. :))

I'm reading The Dead Mac Scrolls at the moment and a lot of symptoms (especially the audio ones) point to the flyback transformer. I'm gonna do more research now.

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9 hours ago, Shymon184 said:

I'm reading The Dead Mac Scrolls at the moment and a lot of symptoms (especially the audio ones) point to the flyback transformer. I'm gonna do more research now.

The Flyback Transformer is a high voltage component. This is powered by the lower voltage PSU which sounds like it is broken. I think that you need to fix the power supply before doing anything with the Flyback Transformer. At a minimum, I would recommend thoroughly inspecting the components on the PSU and looking for anything that looks burned up. Of course, this might not be the case, and something could be broken without looking different from normal. Are you able to post some pictures of the Analog Board?

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8 hours ago, davidg5678 said:

The Flyback Transformer is a high voltage component. This is powered by the lower voltage PSU which sounds like it is broken. I think that you need to fix the power supply before doing anything with the Flyback Transformer. At a minimum, I would recommend thoroughly inspecting the components on the PSU and looking for anything that looks burned up. Of course, this might not be the case, and something could be broken without looking different from normal. Are you able to post some pictures of the Analog Board?

Sure, here are some pics:

It's an International analogue board btw.

Ignore the C1, it's an equivalent replacement and it also handles the heat a bit better. :D

P.S. if you want any specific pics, don't hesitate to ask.

IMG_0919.thumb.jpeg.c4f567b2ee99bb571eaffd849a53d875.jpegIMG_0920.thumb.jpeg.2c04547cc1bc331a18ccccedb4d95528.jpegIMG_0917.thumb.jpeg.29bc9efd978a22b05b6531b1935369f9.jpegIMG_0918.thumb.jpeg.e88cf9c3f1592f6ce357ca2f85f3deaf.jpeg

Edited by Shymon184
clarification

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I'm certainly not belittling your work here, but, are you sure that C1 equivalent is tolerating this? Those things look awfully small and tiny.

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8 hours ago, LaPorta said:

I'm certainly not belittling your work here, but, are you sure that C1 equivalent is tolerating this? Those things look awfully small and tiny.

No offence taken ;) but this is why I did it:

Quote

A suitable replacement capacitor can be a little difficult to locate on occasion, however, so if you don’t mind altering the appearance of the board, you may substitute a parallel combination of four or five 1.0μF ceramic disk capacitors, rated at 50V breakdown or more (there’s plenty of room; build it up as a module of four caps, and use two pieces of bus wire to connect it to the pc board; secure with hot glue if you wish). Ceramic capacitors are readily available and inherently nonpolar. What’s more, the parallel combination reduces the overall ESR to lower values than the commonly suggested replacements. Plus, whatever heat they generate is now spread out among the separate capacitors, reducing still further any temperature rise. This somewhat un-aesthetic solution is extremely robust.

This is written in Classic Mac Repair Notes 2.

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I am afraid that the T3 transformer is actually melting, here are the pics:

I don't need circuitry knowledge to see that it really shouldn't be in this shape, also the bottom terminals in the first picture seem awfully fried/burned.

IMG_0921.thumb.jpeg.1e7f0e4a001ac5b022a0c49a8ef68687.jpegIMG_0922.thumb.jpeg.a7dcab65d1da009393aab3f1051aeda6.jpegIMG_0923.thumb.jpeg.ad063f919d8eb28096bf32fc058c34ca.jpeg

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Granted, yes, Pina has said that will work. I just thought it was multiple points of failure that could go wrong. Maybe it works great!

 

As far as the transformer, I am no expert on this, but they are all coated in that goop. That looks pretty standard for all the boards ive seen. Doesn't mean it might not be bad.

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8 hours ago, LaPorta said:

Granted, yes, Pina has said that will work. I just thought it was multiple points of failure that could go wrong. Maybe it works great!

 

As far as the transformer, I am no expert on this, but they are all coated in that goop. That looks pretty standard for all the boards ive seen. Doesn't mean it might not be bad.

That might be true, but let's be realistic, the material seems like plastic and if you look at the analogue board pictures above, you can see the other corners look alike, but the bottom left corner is out of shape, this leads me to believe that it was made to handle certain amount of heat and on that one corner, the amount of heat exceeded the operating temperature and it just melted. So something happened that should not happen normally.

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