iMac slotload pincushion problem

G

G. Louie

Guest
I've got a sick iMac - raster is full screen, but too wide with severe
pincushion. Monitors control panel has no effect for width, keystone or
pincushion, but the other adjustments work. Actually, if width is set at
the very leftmost (00), there is a tiny affect, and then keystone and
pincushion also have a tiny effect. But nowhere near enough to get the
raster straight and narrow enough. Same effect with Apple Display Utility.

PMU reset, PRAM reset, etc. I'm told this happened suddenly. This model
has no VGA output.
 
The first slotload iMac 350MHz G3. Yes, the big cap has a bulged top. I
don't know what it does, but why would everything but the width and pin
amp work fine? The cap is 470uF 400V, I believe. Is this a known failure?
TIA.


In article <MTL8c.93321$1p.1412604@attbi_s54>,
William R. Walsh <newsgroups1@idontwantjunqueemail.walshcomptech.com> wrote:
Hi!

What clock speed or generation of machine?

Anything greater than a 350MHz G3 seems to cause enough heat that a very
large capacitor in the CRT area becomes badly bulged. I have quite a few
units with this seeming problem, but none seem to be "suffering" as of yet.

The capacitor sits on the right side of the picture tube as the machine
faces you. See if it's bulged...and if so, maybe it has failed and is
causing the problem you have.

William
Click to expand...
 
On 26/3/04 2:42 am, in article MTL8c.93321$1p.1412604@attbi_s54, "William R.
Walsh" <newsgroups1@idontwantjunqueemail.walshcomptech.com> wrote:

Hi!

What clock speed or generation of machine?

Anything greater than a 350MHz G3 seems to cause enough heat that a very
large capacitor in the CRT area becomes badly bulged. I have quite a few
units with this seeming problem, but none seem to be "suffering" as of yet.

The capacitor sits on the right side of the picture tube as the machine
faces you. See if it's bulged...and if so, maybe it has failed and is
causing the problem you have.

William
Click to expand...
Every cap I've seen like this on slot loading iMac's has been fine. The
black plastic disk bulges, but not the can. It's just cosmetic.

Steve Bell
 
On 26/3/04 1:51 am, in article c3vur8$e7s$1@nntp6.u.washington.edu, "G.
Louie" <louie@u.washington.edu> wrote:

I've got a sick iMac - raster is full screen, but too wide with severe
pincushion. Monitors control panel has no effect for width, keystone or
pincushion, but the other adjustments work. Actually, if width is set at
the very leftmost (00), there is a tiny affect, and then keystone and
pincushion also have a tiny effect. But nowhere near enough to get the
raster straight and narrow enough. Same effect with Apple Display Utility.

PMU reset, PRAM reset, etc. I'm told this happened suddenly. This model
has no VGA output.
Click to expand...
I've seen this problem, but not for some time and it was intermittent. It
was cured by a good solder up around the HOT and yoke return and EW
circuitry. It the faults solid you'll most likely have a component failure
in the EW modulator circuitry.

Steve Bell
 
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