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Sway in AppleColor Composite Monitor IIe

T

tezza

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Joined
Oct 1, 2007
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Location
New Zealand
Hi,
I’ve got two problems with this AppleColor Composite Monitor IIe.

One I know about and I know how to fix. It’s the same problem Lorne had in another thread i.e. the image is slightly tilted to the right. I’ve identified what to turn and I just need to prise away the glue and get the right tool to loosen the clamp.

2009-10-24-applecolour-monitor.jpg


However, there is another problem and this is where I need some suggestions. The display sways. There are no lines or distortions, but it just sways back and forth. Not dramatically, but enough to be irritating. I’ve seen this symptom before in screens that are close to an external power transformer, but this happens when the screen is well away from anything else.

The annoying thing is that this second symptom wasn’t there until I removed the case to check if I could fix the first issue! When I reassembled the case, suddenly the display wasn’t only tilted, it swayed as well.

Any ideas? I don’t have a technical manual for this screen so if you know of any PDFs on the net, please let me know.

Thanks!
Tez
 
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Odd; with the clamp and the glue how do those yokes manage to rotate, unless someone played with it previously and clamped and glued it like that...

The 'swaying' is usually interference or 'beating' between the vertical sweep and the line frequency, either magnetic (external transformers, motors etc.) or electronic (poor filtering of the DC voltages, AC in places where it shouldn't be); can't think of how you'd cause either one by just opening and reclosing the case though, alas. Maybe some wire carrying AC current moved a little closer to the CRT neck than it was? Check the DC voltages for ripple?
 
You sure you didn't adjust anything (contrast, brightness, etc) when you opened the case?

That swaying sounds like it could be quite peaceful - like ocean waves on a beach. Maybe you'll learn to like it :)

If not; from that same document that Per provided a link to, for my video problem:

Jittering, vibrating, or unstable picture.


Most likely causes: External magnetic interference or power line noise, hum in various power supply voltages resulting from dried up main filter capacitor(s) or other capacitors, resistors out of tolerance - all affecting power supply regulation.
  • Interaction of adjustments. For example, turning up the brightness results in a loss of sync or a wavy raster.
Most likely causes: Poor power supply regulation due to bad capacitor, resistor, regulator, or other component - or bad connections.

Adjustment or picture interactions
This describes problems such as turning up the brightness causes a loss of sync or adjusting height also affects width or produces a wavy raster. Or, a bright picture or opening a bright window results in a significant change in picture size or wiggly edges. Or, the monitor simply decides to shut down!
These may be caused by poor regulation in one or more low voltage power supplies or and interaction between the high voltage and low voltage power supplies - possibly a dried up capacitor if it is relatively old, bad connections, or another faulty component. Measure the B+ to the horizontal deflection (to the flyback, not the horizontal output transistor). If it is changing with the problem, then a regulation problem is confirmed. If this voltage is solid, you will need to check the others to see which one is actually changing.
 
Thanks guys,

I will investigate and report back any developments.

Actually I was using the monitor last night. The tilt and the sway aren't TOO bad. The average person would hardly notice them.

The rational part of me is saying to just leave them alone. But then, when did I even listen to that! :)

Tez

P.S. Yes I DID fiddle around with the brighness/contrast/other knobs when I opened the case.

P.P.S No one's got a digitised manual for these things have they?
 
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Just a follow up. I've found a user manual on the web. However, it's the technical manual I'm after, if such a thing exists in the wild.

Looks like I have a use for Philip Avery's (pavery's) scope again (he left it with me). I want to make sure I'm measuring the right piece of circuitry though.

Tez
 
Hi! I too have the exact same problem on my monitor. Going down the left margin is a rolling pin effect - quite subtle with about half of the time I can't tell its happening. The other half of the time the rolling effect is giving me a headache. Any documentation you could share please? Have sent a tweet in case this thread is missed. A capacitor reference would be great if such a document exists.
 
A quick search is not turning up a schematic. A couple possibilities come to mind for floating AC hum bars. One is the AC mains filter cap or caps. Typically the largest capacitors in the power supply like 100mf 250V.
Or if the degauss coil circuit is defective, it can cause a floating hum bar. One way to determine that is unplugging the degauss coil to see if the wave disappears.

Larry G
 
simple non pro tip, if 30 year old shit is giving you trouble, replace electrolytic and tantalum capacitors
 
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