Weird issue with starting up

Question

iMac Intel 17"

1.83 GHz Core Duo or 1.83, 2, or 2.16 GHz Core 2 Duo A1208 (EMC 2104/2110/2114/2124)

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tr121 @tronke

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crwdns2931729:0crwdne2931729:0: Sun 30, 2019

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Weird issue with starting up

I’m having an issue with this hand-me-down iMac I got a while ago. It will only start up if the screen is disconnected from the logic board and if I hold the power button down while it is starting up.

iMac starting up when screen is disconnected:

iMac starting up when the screen is connected

This completely baffles me. I have still yet to try connecting the iMac to an external display, but here is what I have tried:

Reseating the RAM (the RAM is known-good)
Replacing the PRAM battery

Does anyone have any ideas of what could be going on here? I’m leaning towards either a logic board or a display issue.

Alright so I played in the guts of this iMac and snooped around looking for swollen or leaking caps. I found none that appeared to be too swollen but there were definitely some caps that were a teensy bit bigger then the rest. Have we found the root of the problem?

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mayer @mayer

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MacHale Enterprises

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crwdns2931729:0crwdne2931729:0: Sun 31, 2019

crwdns2933897:0crwdne2933897:0

Examine the capacitors on the logic board (cans). Look for leaking and/or swollen ones.

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crwdns2944067:012crwdne2944067:0:

Quick question, not trying to shoot you down here but wouldn't the capacitors be on the power supply instead of the logic board?

crwdns2934271:0Sun 31, 2019crwdnd2934271:0 tr121 crwdne2934271:0

What are the diagnostic LEDs on the center of the logic board telling you? The reason I want you to look at the capacitors is that it is a very well known issue and i have seen a lot of these. Yes the power supplies do fail a lot on these but your symptoms indicate the caps.

crwdns2934271:0Sun 31, 2019crwdnd2934271:0 mayer crwdne2934271:0

Alright, thanks for the clarification. I’ll take a look at the caps on the L-board and the PSU once I get home. Are the diagnostic LEDs in the videos not the ones we are looking for?

crwdns2934271:0Sun 31, 2019crwdnd2934271:0 tr121 crwdne2934271:0

@mayer updated answer

crwdns2934271:0Sun 31, 2019crwdnd2934271:0 tr121 crwdne2934271:0

Your picture shows a failed or failing capacitor.

crwdns2934271:0Sun 31, 2019crwdnd2934271:0 mayer crwdne2934271:0

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Quick question, not trying to shoot you down here but wouldn't the capacitors be on the power supply instead of the logic board? — tr121
What are the diagnostic LEDs on the center of the logic board telling you? The reason I want you to look at the capacitors is that it is a very well known issue and i have seen a lot of these. Yes the power supplies do fail a lot on these but your symptoms indicate the caps. — mayer
Alright, thanks for the clarification. I’ll take a look at the caps on the L-board and the PSU once I get home. Are the diagnostic LEDs in the videos not the ones we are looking for? — tr121

iMac Intel 17"

Weird issue with starting up

Update (01/31/2019)

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