SE/30 Whiteout!

[CC_333]

Hi,

Sorry for the whimsical title, but it's true, one of my SE/30s has somehow broken in such a way that the screen is white with permanent scan lines (adjusting the cutoff doesn't get rid of them).

I have refreshed just about every solder joint on the analog board (which I figured couldn't be bad anyway), and touched up a few joints on the logic board because it would momentarily cut power if moved a certain way (which I figured meant an intermittent connection in the connector somewhere; I assume I have fixed it, since this particular behavior no longer occurs).

It all seemed to start when I broke the CRT after discovering a broken solder joint on the video board. I subsequently replaced the CRT with a severely burnt-in, but working spare, and repaired the broken joint.

I turned it on, and it worked for a few seconds, perhaps a minute. Then, as I was reaching over to adjust the image, it displayed a Sad Mac (death chimes and all). So I reset it.

After that, I have been unable to get the thing to work properly.

I suspected the video board was damaged somehow, so I replaced it with a spare. Same problem.

Then I re-soldered almost everything on the analog board. I got a faint and highly washed out picture with the cursor, but then it faded away to solid white after a few seconds.

When this problem first arose, I noticed some disturbing arcing going on between the lower right (from the front) CRT mounting lug and the internal frame. Could that have damaged something?

I doubt a broken logic board could cause this problem, though.

Any ideas?

c

 

[JDW]

Since you appear to have access to SE/30 spare parts, you might for good measure swap out the entire analog board, since you may have destroyed not only the flyback transformer but other components on the analog board too.

I doubt the PSU is damaged, but you ought to confirm it anyway with a digital multi meter, testing all the respective 5v and 12v outputs.

 

[CC_333]

Hi,

I was afraid the arcing might have destroyed something

I can put the logic board in another machine to see if it's OK (it chimes, so it's not damaged too badly, I hope).

I guess the analog board's a loss, then (unless I can test and confirm whether the flyback and supporting parts are bad or not).

I have a lead on some flybacks, so I'll look into replacing it to see what happens (or will other damaged stuff ruin the new flyback?)

Oh, well. I had essentially relegated this machine to the parts heap anyway.

This is sad :'( It was working fine before the CRT broke!

c

 

[JDW]

After putting your logic board in that other machine and confirming nothing is wrong with it, you could also take your suspect analog board out and put it in that machine too. If you have the same video problem in that machine, then such would be proof that the problem lies in your analog board.

 

[CC_333]

Hi,

OK, I'll do that.

Here's a silly question: Could the suspect A/B damage the CRT in the test machine at all? That seems unlikely to me, but one never knows...

Thank you for your help!

c

 

[JDW]

I honestly do not think so. But if you're really worried about it, and if you have a lot of free time, and if you don't mind the extra effort involved, you could swap CRTs and check to make sure that your CRT is okay. Then once you confirm that it is okay, you can swap out your analog board. Then again, if you swap out your CRT and confirm that it's okay, there's really no need to swap and test your analog board, since that's really the only thing left that could be broken.

 

[uniserver]

looks like board #1 that technight did, had an (all white screen) with his first attempt at fixing this mainboard.

in this case the issue was the motherboard.

 

[nvdeynde]

If the logic board is working fine, check resistor R20 on the Analog board. It should be 100K. If this one is open, you get an all white screen and the brightness cut-off doesn't work. I've had this issue with one of my SE's a few weeks ago.

If you haven't recapped the PSU and Analog board, it's definately recommanded as most capacitors are degraded due to age as they are over 22 years old now.

 

[JDW]

Although what you say is true about the need to recap virtually any electronics where the electrolytic, fluid filled capacitors are more than 20 years old, the fact is I've never heard of any serious SE/30 problem that pertains to the analog board or PSU because of leaky/aging caps on them. In almost every case of problems with an SE/30, it usually goes back to bad caps on the logic board. Of course, in the case being discussed in this particular thread, the circumstances are a bit extraordinary — it looks like the user may have shorted something and destroyed components. Therefore, the problem most likely lies on the analog board, and it's doubtful that problem has anything to do with aging caps on it.

 

[CC_333]

I honestly do not think so.

That's good.

But if you're really worried about it, and if you have a lot of free time, and if you don't mind the extra effort involved, you could swap CRTs and check to make sure that your CRT is okay.

I don't think I'll bother with that. I might as well use the analog board from the test machine in the problem machine (less handling of the fragile CRT, of which I've already accidentally broken one so far > )

looks like board #1 that technight did, had an (all white screen) with his first attempt at fixing this mainboard.in this case the issue was the motherboard.

This is different, I think.

If the logic board is working fine, check resistor R20 on the Analog board.

Okay, I'll do that. If it is blown, is there a chance that everything else is OK?

If you haven't recapped the PSU and Analog board, it's definately recommanded as most capacitors are degraded due to age as they are over 22 years old now.

I thought of that (since I have some), but I didn't want to waste any more time than I already have unless I can determine without a doubt the board isn't a lost cause.

the fact is I've never heard of any serious SE/30 problem that pertains to the analog board or PSU because of leaky/aging caps on them.

Perhaps not, but it's still probably a good idea, especially if there's evidence of leakage (I have a flaky SE/30 power supply, and it smells like electrolyte, which probably means the capacitors have leaked and failed). By the way, I have noticed that they (SE and SE/30 A/B's and P/S's) are particularly sturdy compared to, say, the 128-Plus A/B.

it looks like the user may have shorted something and destroyed components.

Hopefully, any damage I have accidentally caused is easily and inexpensively fixable.
Thank you all for the suggestions!

c

 

[techknight]

Try another CRT. an H-K short will cause this.

 

[CC_333]

Try another CRT. an H-K short will cause this.

What exactly is an H-K short?
c

 

[JDW]

What exactly is an H-K short?

Something pertaining to stock sales in Hong Kong? |)

 

[CC_333]

Something pertaining to stock sales in Hong Kong? |)

I don't think that's what he meant
c

 

[techknight]

Known as a heater to cathode short. its a term carried over from the old CRT TV servicing days.

 

[uniserver]

Ah so the tube its self, Hummm

 

[CC_333]

Hi,

Interesting!

Perhaps, if I do determine that it's the tube itself (I didn't know they could go bad like that), I'll recycle it (which is something I need to do much more of, I'm afraid :-/ ).

I'll install the suspect A/B in a machine with a known good CRT and see what happens.

Any chance a damaged CRT could cause damage to other components? Logic says yes, but I want to be sure.

c

 

[JDW]

Any chance a damaged CRT could cause damage to other components? Logic says yes, but I want to be sure.

I would say that there certainly is "a chance," but to find out exactly how much risk there is, I have posted a query in this thread:

viewtopic.php?f=7&t=477&p=191182#p191182

Now, going back to capacitor replacement, you said you might wish to replace all the caps on the Analog Board. I personally have never taken time to do that because none of my analog board caps are leaking fluid all over the Analog board, nor have I experienced any serious problems that I would attribute to the analog board. Nevertheless, you do have a good point about replacing the old caps on those Analog boards. But rather then take all the time and expense to replace everything, you might save some time and money just by using an ESR meter. Although the following YouTube video is talking about the repair of an LCD monitor, the use of an ESR meter in that video is very applicable to capacitor replacement in any vintage Mac computer.