Bizarre CRT bloom / wobble / shadowing on... all of my compacts?

[chiptripper]

I've been tearing my hair out troubleshooting an otherwise healthy SE/30. Adjusting brightness, either from the adjustment wheel or directly on the analog board, results in noticeable bloom (screen increases in size). When I click a menu or open a window, display shows slight horizontal shadow lines, and the left and right sides of the screen bulge slightly. If I dim the screen, the issue becomes less severe.

It has been meticulously restored. Fully recapped. Good voltages. Analog and neck board joints reflowed. I have swapped in a new flyback, new CRT, tested transistors / resistors / diodes, swapped ICs known to fail. Swapped every cable, tried different power cables, different outlets (GFCI and regular).

Probably just a random component I'm overlooking, right? Well, on a whim, I tested a non-recapped SE. It has the same issue! Then a Plus w/ recapped logic and analog board. Same! Next, Classic II I recapped years ago, has a spinning hard drive. Same.

This problem does not seem to affect my Color Classic or M1212 display. Just every B&W compact I've tested.

At this point I have to think there's an issue with mains voltage / ground in my house that these machines do not like. It's a 1950s place with two-wire outlets and (mostly) GFCIs. Does this sound plausible? Any suggestions for how to safely test this theory?

 

[ymk]

Are your outlets polarized and correctly wired? If not, the CRT, boards and frame could be hot.

Measure each AC wire against a water pipe to identify neutral and hot.

 

[Juror22]

Its a compact (with a handle built into the top) take it (along with a mouse and a power cord) to someone else's house with good power and try it there?

 

[joshc]

How strong is the power supply? I know you said it’s recapped but even then it’s good to read the voltages at idle and under load.

 

[pizzigri]

Big power appliances can make this happen, like refrigerators, compressors and the like. I was going crazy 30 years ago before realizing the grocery store below my apartment had huge fridges, A/C and similar. I moved the crt monitor out of my room in the dining room and that made all the difference. May be not your case but worth looking into. The Sony Trinitron TV we had at the time was NOT affected. That what sparked my memory

 

[Skate323k137]

Big power appliances can make this happen, like refrigerators, compressors and the like. I was going crazy 30 years ago before realizing the grocery store below my apartment had huge fridges, A/C and similar. I moved the crt monitor out of my room in the dining room and that made all the difference. May be not your case but worth looking into. The Sony Trinitron TV we had at the time was NOT affected. That what sparked my memory

I had a faulty AC unit, and a faulty dehumidifier, both bad enough to cause noticeable disruption to lights in the whole house until we hunted them down.

 

[chiptripper]

Are your outlets polarized and correctly wired? If not, the CRT, boards and frame could be hot.

Measure each AC wire against a water pipe to identify neutral and hot.

Good idea! I know the renovation by previous owner was not professionally done, I will check polarity.

Its a compact (with a handle built into the top) take it (along with a mouse and a power cord) to someone else's house with good power and try it there?

Bold of you to assume that I (a guy who spends all his free time fixing vintage Macs) have any friends! Haha no that's a very reasonable suggestion, I'll try that.

How strong is the power supply? I know you said it’s recapped but even then it’s good to read the voltages at idle and under load.

I tested while opening windows / menus, enough to make the display artifacts manifest. In that setting voltages were rock solid, but I suppose I could test under a heavier load. That said, I've now tested so many different compacts I'm not convinced it's a PSU / analog issue at all.

Big power appliances can make this happen, like refrigerators, compressors and the like. I was going crazy 30 years ago before realizing the grocery store below my apartment had huge fridges, A/C and similar. I moved the crt monitor out of my room in the dining room and that made all the difference. May be not your case but worth looking into. The Sony Trinitron TV we had at the time was NOT affected. That what sparked my memory

I had a faulty AC unit, and a faulty dehumidifier, both bad enough to cause noticeable disruption to lights in the whole house until we hunted them down.

Hmm, that's interesting. We don't live near any large commercial power draws, but I've noticed the transformer outside our house has been buzzing loudly. Also our washing machine causes the lights to noticeably dim. Would an isolation transformer shield my compacts from those kinds of disruptions, I wonder?

 

[joshc]

It does sound like it's being caused by the electrical installation of your house -- definitely worth trying the compacts at a different location to rule that out I think.

 

[ObeyDaleks]

Are both the bloom AND shadowing occurring on all (four?) compacts?

 

[Forrest]

If you have a UPS, you could unplug it from the wall and run your compact Mac to see if the problem disappears

 

[chiptripper]

Are both the bloom AND shadowing occurring on all (four?) compacts?

Definitely the bloom and screen bulging, but not positive the shadowing occurs on all four. That could be an issue specific to the SE/30.

 

[chiptripper]

Are your outlets polarized and correctly wired? If not, the CRT, boards and frame could be hot.

Measure each AC wire against a water pipe to identify neutral and hot.

I tested and a few of our outlets do actually have reversed polarity. I'm glad to know about that before someone gets a nasty shock, so thank you for the suggestion. However, the issue manifests even on correctly polarized plugs.

I also tried running a ground wire directly from the Mac to the breaker box (used one of those Japanese cables with a separate earth wire), then directly to a copper water supply pipe, but in both cases the wobble persists. Oscilloscope going on the Christmas wishlist.

Tonight I'll haul a Classic down to my wife's shop, which is newly constructed, and see how it runs there. Appreciate all the help!

 

[pizzigri]

I believe my problem was more related to a magnetic field rather than electric grid fluctuations. Otherwise, changing room would have yielded zilch.
have you actually tried taking one of your highly portable compact Macs to another place and turn it on?

 

[chiptripper]

I tested at another location. The issue persists.

Must be a component I missed, or a flaw in my rework process, or equipment. But what could cause this identical symptom across a Plus, SE, SE/30, another SE/30, and Classic II? I haven't done any work on the SE, either.

(It's gonna end up being something really dumb, isn't it...)

Am I simply misremembering how horizontally stable these displays are with brightness up? Attaching a video. (Ignore the raster lines, I turned the bright way up so the wobble is obvious on camera.)

 

[pizzigri]

Well, that has NOTHING to do with a magnetically induced "wobble". It is too regular and pulse like. Probably would have never even suggested it if I saw that earlier. But, what is it with the menu flashing ? Are you doing that, and the "wobble" is dependent on the activation of the menu?

 

[joshc]

Sorry if you already mentioned it, but are your voltages stable while the wobble happens? Seems odd that it's on every compact you have but could just be a coincidence.

 

[chiptripper]

Yes that's me opening the menu to demonstrate the issue. When a menu or window is opened, it bulges horizontally. When I adjust the brightness dial or the AB cutoff, the whole screen blooms. Seems to depend on brightness. If I dim the screen enough the problem becomes imperceptible. (I'll add a video of that tomorrow.)

Voltages were totally steady mid-wobble last time I tested, but I'll take more readings from different spots. Yeah it'd be quite the coincidence for this to happen on 5 compacts, but still plausible. Neck board resistor or diode maybe?

 

[ymk]

I think this is normal. Increasing the cutoff makes the screen brighter, but also larger.

At the point where retrace lines are visible, the picture content affects geometry.

 

[joshc]

Yeah, on my compacts, if cut off is too high, the screen is too bright and also bulges/increases in size. But it doesn't wobble.

 

[chiptripper]

Bloom isn’t very noticeable at average brightness with retrace lines invisible. But every time I open a window or menu the horizontal geometry wiggles and jumps, and at above average brightness the shadowing presents itself.

I’ve read up more on bloom, could just be a worn out tube or flyback or a flaw in HV regulation. But I’ve now tested on five compacts, six CRTs. All have this identical issue. Only compacts. I’m baffled!