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Hello fellow.

 

First congratulate you for having this forum so fabulous.

 

About a month ago came into my hands my first Apple computer, nothing more and nothing less than a Mactintosh SE/30 :)

 

I did the typical operations of cleaning and change the capacitors and the computer began to walk.

 

Currently it has a problem that I have not managed to resolve :(

The upper area of the image does not appear and the typical menu of Apple is hidden.

 

It is not a problem of adjusting the potentiometers, because although you make with them the lower image, the image appears incomplete too.

 

48.jpg

 

I've changed all the electrolytic capacitors of the board but without any result.

 

Sorry for my poor English and if I skipped any standard correct me, please.

 

Thank you.

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Huh, if a part of the image on the screen is missing, I'm inclined to think that a certain section of the RAM where that part of the video data is stored is damaged or the trace to it has been destroyed and thus it is not being rendered on-screen. You'll notice that part of the image seems to be completely missing from the screen, not just the menu bar, because the corners are square. On a properly rendered mac screen/desktop, the corners are always round, like the bottom of your screen/desktop.

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If you look carefully, you can see the burn in where the menu bar usually is, so maybe the display *is* being rendered correctly, and it's simply a function of a corrupted System file or something?

 

Maybe??

 

Try reinstalling your System Software. That might help?

 

c

Edited by CC_333
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The burn-in could easily be from before damage to the logic board occurred due to leaking caps, etc...

 

From that video, its clear its not even rendering the area for the menu bar, its stopping right at the sharp corners.

Edited by Paralel
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Maybe you do not appreciate too well in the video, but  the upper horizontal scan lines are more abundant.

 

Is this normal in a " healthy" screen?

 

See if someone can test with your mac increasing the brightness screen .

 

Thank you.

Edited by Sinclair
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There's two adjusters for screen brightness most compacts. (except the Classic line of Compacts where they no longer sport the front brightness knob). The external one you can interact with and one on the analog board that you have to take the back cover off to reach.

 

If you set it too high the scanlines become visible. Even a healthy system would do this and it's a general habit of all CRTs if you adjust brightness too high. Most newer CRTs don't let you set brightness high enough for scanlines to appear. But the older ones like the compact macs can if you adjust the internal brightness meter too high which then allows the front brightness knob to send brightness to high causing the scanlines to appear.

 

The worst you'll get from running a mac like this is shorter run time for the phosphers of the CRT and the chance of burn in occurring at a quicker rate. I would say you should avoid that.

 

I adjusted mine so it gets the highest brightness without the scanlines appearing.

 

Though I don't usually have it that high on the front brightness knob. I just tightened it up a bit so I have the option of going max brightness. :p

 

As for the screen. You should take video of it rebooting. Are the screen corners rounded during boot but once Finder comes up, they vanish or are they present even during the happy mac boot screen?

 

If the corners are cut off even at bootscreen, a hardware fault like bad VRAM or trace to VRAM will cause that.

 

If it's a vram/trace issue, the menu bar should still be present. Did you try and move the mouse beyond the area being drawn on top? It should be easy to tell if the menu bar is actually gone or if it's a video problem. Move the cursor to where you think the Apple Menu will be. (assume the menu bar is above the visible screen area in this instance)

 

If the mouse actually stops at the edge of the visible screen perhaps it is a software issue. But since you haven't shown it rebooting, we can't rule out hardware fault.

Edited by Apache Thunder
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nope. not CRT. 

 

I dont think its the analog board either. Because if it was a vertical issue, you would see the menu bar and mouse pointer in the "foldover" section, appearing as a brighter line. 

 

But because you dont have that, tells me the logic board is the ACTUAL fault here.... probably related to one of the PAL/GALs. 

 

The only ever chance it could be the analog board, is if the back porch pulse is too wide and driving the CRT into cut-off for too long, thats generated by the flyback and feeds the vertical stage in a feedback format. 

 

But, since the scan drive is generated by the logic board, that sorta rules that out... Goes right back to the logic board... If you noticed in your video, the vertical raster period isnt on long enough. Back to the logic board!

Edited by techknight
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Could be, but again.. it goes back to my previous post. 

ok, but you say too :

 

The only ever chance it could be the analog board, is if the back porch pulse is too wide and driving the CRT into cut-off for too long, thats generated by the flyback and feeds the vertical stage in a feedback format. 

 

 

TDA-1170N?

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but the likelyhood of that is fairly small. Still possible, yes... but small... the circuitry is way too simple. Now if this were a color monitor, all bets are off... 

 

You need to try and find another logic board, even if its a regular SE. This will help point yourself in the right direction, otherwise I see you chasing your tail in circles all day long. 

 

Without that, the only other option is using a scope and watching the signals coming from the logic board, but then you need a known good board to compare the waveforms to. 

Edited by techknight
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