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Macintosh Plus. Very vertical image at startup

ferol

Member
Macintosh Plus .very vertical image at startup

Hi everyone from Spain,

Recently the capacitors have been replaced on the analog board of my Macintosh Plus since there were problems with electrical tension.

Now, when the computer starts, it shows a very stretched image vertically, after a minute, the image is normal.
Do you know what could be the problem?

attached video

Thanks a lot.
 

Attachments

  • Mplus.mov
    6.2 MB · Views: 7

Byrd

Well-known member
Hi ferol,

I'd guess dry solder joints on the analogue board need reflowing - do this around the CRT adjustment pots, and cable going from the yoke to the analogue board connector - you might see some scorched solder joints here, double check the cable itself too for arcing/corrosion.
 

ferol

Member
Thank you very much for your quick response.

the welds were checked. It has also been tried with another cable.

the cause of the defect must be something else, I suppose.

Could this be a flyback problem?
Because as it heats up the image stabilizes.

thank
 

cheesestraws

Well-known member
Go back and check them again. Especially check things like solder joints around the image height potentiometer. Those boards are notorious for cooking themselves, which breaks initially good solder joints. Do not think this is just the solder joints you made.

I would very much not expect it to be the flyback.
 

ferol

Member
Thank you very much Cheesestraws,

We have followed your instructions, but unfortunately there are no changes.
 

desertrout

Well-known member
Welcome! Some thoughts:
  • Did you replace C1? If so, what did you use?
  • Check R1, should be 220 OHms
  • Inspect / reflow pin 4 of J1 (the top one) --- does the connector look burned?
  • inspect / clean the yoke connector pins and socket (at the back of the tube)
 

ferol

Member
Dear Desertrout

Thanks a lot. I answer your questions. the defect continues.

Did you replace C1? If so, what did you use? ----3,9mfd 35v
Check R1, should be 220 OHms------------------Done
Inspect / reflow pin 4 of J1 (the top one) --- does the connector look burned?--Done and NO
inspect / clean the yoke connector pins and socket (at the back of the tube) --Done
 

desertrout

Well-known member
Thanks for verifying. I'm assuming that the width adjustment pot is working correctly (L2 - sometimes it needs a cleaning), so maybe check /reflow the solder joints on the flyback, specifically pin 2 (for the horizontal sweep)...

EDIT: rewatching the video, this actually looks like something on the vertical sweep, not horizontal as I was thinking... so perhaps you should be focusing in that section of the circuit, starting with a good test and clean of R55:

Screen Shot 2022-06-17 at 12.13.44 PM.png
 
Last edited:

ferol

Member
I will get the components that I miss to change those that are in the list of your diagram. To be continued. Thanks
 

ferol

Member
I changed all components in the list (and more):
L2,R55, CR2 to CR7, CR8, CR15, Q1,Q2, Q4 and Q5 from a working analog board. They are no changes.....
 

ferol

Member
yes, like I said, it's a working analog card, and the Mac Plus worked perfectly with this card.
 

desertrout

Well-known member
My apologies - it wasn't clear to me that you had tested the tube with the other analog board. Well, I guess try the flyback then just to rule it out. If that doesn't solve it, my first thought is a voltage regulation issue that might be discerned by measuring voltage at the floppy port and the pins on J1 during boot up and comparing that to the working board. That might reveal a pathway to troubleshoot (instead of just swapping in parts randomly).
 

ferol

Member
It is I who apologize, sometimes my answers are a little evasive, not precise enough and I thank you for your attention to my problem. What type of voltage should I find on J1? How do I adjust my multimeter? What cable should I check? I cannot change the FlyBack: that of my analog card is not the same model as the card which does not work well.
 

ferol

Member
Comparatively, between a Plus working and the Plus with problems, there are no differences in the voltage of the J1 cables: Red and blue = 5.10 V, Yellow and green = 0.12V from power on to 10mn of use.
 
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