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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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iMac slotload pincushion problem
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. |
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iMac slotload pincushion problem
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 |
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iMac slotload pincushion problem
Hi!
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. I do not know that it is a known failure--to me it just looks like trouble. I have a G3-500 unit here in dark blue and the cap is bulged to where it looks like it might explode. It runs fine and the picture on screen is very good (albeit very slightly out of focus at the edges...) so I don't know if this is the problem you are having. I think the machine is too dark blue for me to get any kind of a picture, but if you'd like I can try. But if you can, you might try replacing that cap and most all of the others in the monitor assembly. Given the heat they are exposed to it cannot hurt. William |
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iMac slotload pincushion problem
"G. Louie" wrote in message ... 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. If the cap is bulged, by all means replace it first, even if the unit is working fine, it's very possible for quite a bit of damage to be done if the cap fails catastrophically. |
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iMac slotload pincushion problem
On 26/3/04 2:42 am, in article MTL8c.93321$1p.1412604@attbi_s54, "William R.
Walsh" m 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 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 |
#6
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iMac slotload pincushion problem
On 26/3/04 1:51 am, in article , "G.
Louie" 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. 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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