Horizontal lines on SE/30 Display

[mmaseda]

I’ve been working for a while trying to determine the cause of very faint horizontal lines that move from the bottom to the top of the CRT every few seconds. While I can see them perfectly with my eyes I’ve had a hard time documenting them in a photo or video. Here is my best attempt to capture them in a short video. I don’t have a good camera where I can fine adjust the shutter speed so this was just done on my iPhone. I can reproduce this on several SE/30 and SE computers and I have an idea what might be causing it but would rather not get into that at this time until I can get someone else to confirm they have also noticed this.

Manuel

 

[ArjenCNX]

Video ram comes to mind here, check the Vram chips and make sure there is no capacitor spillage around them, and that the Vias are OK, a few gentle taps on the board can sometimes expose bad connections.

 

[mmaseda]

Thanks but that isn’t the problem. I can recreate this problem on multiple computers each with a different logic board. At this point I’m just trying to see if anyone else has every noticed the problem before.

 

[ArjenCNX]

yeah, that solidly excludes that option indeed, just considering the way it works, it would be possible that there is a soldering issue on the motherboard somewhere along the video signal as in comes in, some percussion there may show you something, as could cooling things down with some canned air. other then that i'd have to have the unit in front of me to say much more useful things. Best of luck though!

 

[mmaseda]

Since nobody else seems to have the problem I just tell you what I found. Turns out to be an issue when using a Sony power supply. Don’t see the problem with Astec supplies. Have tried multiple Sony and Astec supplies on several different computers and the problem is always there with the Sony supply.

 

[Mark_W]

Not on a se30 but I got this problem on a color classic, alternating white and dark lines are constantly moving from top of the screen to the bottom. Check the video and if you look closely you can see them crossing the bottom edge of left window at the beginning and around 3-4s. Hard to capture it in the video but it's more apparent to naked eyes.

https://imgur.com/a/W6skH6X

Btw this is the color classic I posted earlier with a dead logic board power supply, which I repaired by hacking in a standalone 5v/12v power supply. It's sitting right next to the tube and I believe it's some interference caused by the switching frequency of PSU. Tried to wind the output wire on a ferrite ring for a few turns, it helps a bit but the scrolling lines are still there. Anyway I just ignore them for now, till I can come up with a better solution to isolate the PSU.

 

[Steve Rieck]

Since nobody else seems to have the problem I just tell you what I found. Turns out to be an issue when using a Sony power supply. Don’t see the problem with Astec supplies. Have tried multiple Sony and Astec supplies on several different computers and the problem is always there with the Sony supply.

Have you recapped it? JDW has an excellent video on YouTube about recapping that particular power supply (Sony CR-44)

 

[mmaseda]

have you recapped it? JDW has an excellent video on YouTube about recapping that particular power supply (Sony CR-44)

Yes it was fully recapped. I tested with 3 different Sony power supplies of which 2 were recapped. Results were always the same. Also I tested with multiple logic and analog boards that had also been recapped. Bottom line those horizontal lines were there when Sony power supplies were used and not there when Astec power supplies were.

 

[Steve Rieck]

interesting. that does seem weird. Did you test the exact voltages on the +/- 5 and 12V rails for each power supply? That might tell you something. I have three SE/30s all with Sony power supplies and not seeing that issue.

 

[mmaseda]

Yes, all rail voltages were fine. I also scoped all the rails and the Sony supplies do have a higher amount of high frequencies noise on the 12 volt sweep supply but not significantly more than the Astec. I’ll just use an Astec supply for now since it works fine. I’ll probably in the future change out the power supply with one of those that use the Mean Well modules like sold by Baby Face Electronics and TT Designs.

 

[Steve Rieck]

how many Sonys do you have? And did you recap and reassemble them all yourself? The only thing I can think of is some sort of grounding issue or interference but since it's common to all the Sonys it makes me think it might have something to do with the reassembly process like not getting some ground connected or maybe one particular component that is common to all three having some sort of issue.

 

[mmaseda]

I have 3 Sony power supplies that I used for testing of with 2 were recapped. I also have 3 Astec power supplies of which 2 were recapped. Always the same result. I’ve also verified that there is no interference being generated within my house and I have thrown all the breaker in my house and tested with only the computer connected and still see the issue.

 

[Steve Rieck]

sorry if I didn't read all of the above comments but did you test with another SE/30 logic board? Same results? just wondering how that particular logic board might be interacting with power supplies. If it were unique to that logic board of course that would give you something to work from.

 

[mmaseda]

Tested with multiple logic and analog boards.

 

[Steve Rieck]

Tested with multiple logic and analog boards.

Just curious and I'm not sure this is gonna tell you that much but does it only do it with SE/30 boards? Would you happen to have a regular SE board you could test? I guess if it did it with the SE board you could definitively say this is something about how the power supply is interacting with the analog circuitry.

also, same results with different CRT's?

 

[mmaseda]

Beat you to it. Also tested with a SE SuperDrive. Same results. I’m going to break out the spectrum analyzer today and look closely at the AC artifacts on the 12 volt sweep rail. I already looked with a scope and didn’t see much difference except the Sony appeared to show a little more noise.

 

[Steve Rieck]

with multiple CRT's, analog boards and logic boards, I wonder if the Sony's are somehow having an issue with the power in your home? anything suspicious plugged in nearby? Have you tried this at a different location?

 

[mmaseda]

It doesn’t appear to be anything generated from within my home as I have shut off all the breakerexcept the computer. I just finished my spectrum analyzer testing. The Sony supplies generate a large frequency spike at around 38.7 kHz with subsequent harmonics at 77 and 115 kHz. I suspect I’m seeing the switching power supply frequency which is supposed to be at around 40 kHz. Checked on multiple Sony supplies.

Do not see this on the Astec supplies. Perhaps they are doing a better job at filtering out these frequencies. Again checked on multiple Astec supplies.

I have also previous tried to isolate out both power supplies from earth ground with no difference in results

 

[Steve Rieck]

that's really interesting. I've got six compact macs with Sony power supplies... when I get a chance I'm gonna go through them and see if any are demonstrating those horizontal lines. I may not have even noticed.