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SE/30 screen distortion when HDD/floppy activity

8bitbubsy

8bitbubsy

6502
Is this normal? My SE/30 is recapped and everything looks good.. Even the PSU is recapped.

I get noisy scanlines that runs downwards when there's heavy motor activity (hard drive/floppy drive head moving). The aspect ratio of the screen is stable, it doesn't change. It's just a scanline distortion, it's not extreme but it's there for sure. I suspect that the screen is picking up noise from the +12v rails used to power the motors, but how would I go ahead and filter this away? First I need to know if all SE/30's act like this... Maybe it's related to the recap I did? All caps have the same farad ratings, and same or higher voltage ratings. I did not use very low ESR caps, though they aren't hi-ESR either.

I can't take a good picture of it, sorry.

 
That isn't normal. So you re-capped the power supply? You might try cleaning the connectors between the power supply and analog board and between the analog board and motherboard. Also check for cracked solder joints on the analog board. This sounds like you might have a poor ground connection somewhere.

 
I recapped everything that was electrolytic capacitors. Exact same microfarad ratings, and +105 celcius rated (higher quality caps).

There's not a single cracked solder joint, I've been through the entire machine for hours checking for dried/cracked joints. I did find some initially, but they're all restored now. Restored as in fully remove old solder, clean up flux, add new leaded w/ flux solder. I've also checked that the thick green ground wire going from the PSU case to the SE/30 chassis is good.

I'll try cleaning the connectors, I'll keep you updated on how it goes.

 
I cleaned the connectors, especially the SCSI and floppy connector, they were dirty. Now they're super shiny.

However, the problem still occurs the exact same way. But I want to rephrase the problem, it's actually happening under heavy read/write from either the HDD or the floppy drive, so I assume it's some kind of data bus noise instead of motor/mechanics voltage noise.

This confuses me :(

 
If both the PSU and Analog board are recapped and both +5 and +12v lines keep stable when the FDD is used, then it's probably the bourns filter.

Do you still have the stock hard drive or a larger high rpm model ? If the latter, it can be drawing more power the PSU can handle.

Disconnect the hard drive and boot from the floppy drive as test.

 
Do you think a problem with the bourns filter could cause interference all over to the display signal in the motherboard connector??

Sounds very unlikely to me, but oh well...

 
I have come across almost the exact same problem om my classic a few days back...

except that it very very rarely comes up by itself without the machine actually reading from the hdd or floppy.

it stays on for like 3 seconds and then everything is good again.

i have NOT yet recapped the analog board, i did recap the logic board with success.

i also want to know what is causing this... could it also be a bourns filter in my case?

 
For the Classic it's likely the Analog board as the capacitors used are of very poor quality.

The capacitors there are in worse chape than those on a Mac 128K Analog board.

 
Yeah i was kinda afraid for that.

Really amazing how the inside of a classic looks so much cheaper made when you compare it to an SE.

 
It's hardly surprising. The SE was an expensive high end machine, the top of the line compact Mac when it came out. The Classic was a cost reduced consumer machine, bottom of the line, cheapest Mac available when it was released.

 
The Classic was a cost reduced consumer machine
Click to expand...
Yes, the Classic was more or less a new version of the Macintosh Plus, and was marketed with the Macintosh LC an IIsi in the Low Cost range.

 
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