How to find a failed capacitor on a iMac power/analog/video board

[Harry]

Hi! Im new here and I have a question.

On my iMac DV+ the screen starts to "pump" and shake, and after 5 to 10
minutes the screen makes a "blink" and the iMac freezes.

So far i found out (with the help of a service manual) thath the
power/analog/video board is broken, but i think it's more like an
broken capacitor who causes this problem.

So my question is

How to identify this capacitor, or do I need to replace every capacitor
on that board?

Thanks

 

[Jerry G.]

Use an ESR meter to test the caps reactivity, and to know if one is
shorted use an ohm meter (you must remove the cap from the circuit to
use the ohm meter). To know if the cap is on value, check it with a cap
meter (you must remove the cap from the circuit to use a cap meter).

To properly follow the schematics and have some understanding of what is
going on, you would have to have a strong basic knowledge of electronic
circuits, and how to properly read the schematics. To service monitors
and TV sets, it is best to have the basic training, service information,
and the proper tools to work on them.

--

Jerry G.
======

Hi! Im new here and I have a question.

On my iMac DV+ the screen starts to "pump" and shake, and after 5 to 10
minutes the screen makes a "blink" and the iMac freezes.

So far i found out (with the help of a service manual) thath the
power/analog/video board is broken, but i think it's more like an
broken capacitor who causes this problem.

So my question is

How to identify this capacitor, or do I need to replace every capacitor
on that board?

Thanks

 

[Richard]

Hi! Im new here and I have a question.

On my iMac DV+ the screen starts to "pump" and shake, and after 5 to 10
minutes the screen makes a "blink" and the iMac freezes.

So far i found out (with the help of a service manual) thath the
power/analog/video board is broken, but i think it's more like an
broken capacitor who causes this problem.

So my question is

How to identify this capacitor, or do I need to replace every capacitor
on that board?

Thanks

Hi,
I just had a 2000 iMac with exactly that problem. Using the take apart
I opened up the video board (the one on the back of the CRT neck) I
found an area where the soldering looked funky. Resoldering all the
connections in this area solved the problem. I ran it for 2 straight
days and no problelm.
All the customary cautions about the CRT voltage apply.

Richard

 

[Harry]

Hi, I just had a 2000 iMac with exactly that problem. Using the take apart
I opened up the video board (the one on the back of the CRT neck) I
found an area where the soldering looked funky. Resoldering all the
connections in this area solved the problem. I ran it for 2 straight
days and no problelm.
All the customary cautions about the CRT voltage apply.

Richard

Thanx for the tip,
I'l try this out.
Harry

 

[Harry]

Hi, I just had a 2000 iMac with exactly that problem. Using the take apart
I opened up the video board (the one on the back of the CRT neck) I
found an area where the soldering looked funky. Resoldering all the
connections in this area solved the problem. I ran it for 2 straight
days and no problelm.
All the customary cautions about the CRT voltage apply.

Richard

Hi, I opened the video board but could not find any bad soldering. All
looked 100% fine but the iMac still freezes after some time (38min
yesterday), so I have to look further.

Harry

 

[[email protected]]

Hi, I opened the video board but could not find any bad soldering. All
looked 100% fine but the iMac still freezes after some time (38min
yesterday), so I have to look further.

Harry

Dumb question, but do you know what a bad solder joint looks like?

A thermally fatiqued joint will look cracked when examined closely.
Sometimes a dry solder joint will look dull and just not right. Best
bet for finding bad joints is a bright light and a magnifying glass.
I've found ones that were barely noticeable and some that were so bad
the component lead was flopping around in the hole.

Bad caps are harder to find and an ESR meter definitely helps a lot.
Physically swollen or leaky caps need replaced. Dried up caps might
look fine, but have lost their value or built up a high series
resistence (esr).

-Chris

 

[Harry]

Dumb question, but do you know what a bad solder joint looks like?
A thermally fatiqued joint will look cracked when examined closely.
Sometimes a dry solder joint will look dull and just not right. Best
bet for finding bad joints is a bright light and a magnifying glass.
I've found ones that were barely noticeable and some that were so bad
the component lead was flopping around in the hole.

Bad caps are harder to find and an ESR meter definitely helps a lot.
Physically swollen or leaky caps need replaced. Dried up caps might
look fine, but have lost their value or built up a high series
resistence (esr).

-Chris

I took a close look at the solder joints, unfortunately, i don't have
one of those magnifying glasses with a light source. So i could miss
some tiny bad soldier joints. All caps looked fine, no swollen or leaky
ones, so dried out ones could cause this.

Unfortunately sending the iMac to a repair-shop is too expensive. More
and more It looks like my iMac is going to end up as a
iMac/ATX/external monitor/Borg kind of equipment.

Harry

 

[Richard]

I took a close look at the solder joints, unfortunately, i don't have
one of those magnifying glasses with a light source. So i could miss
some tiny bad soldier joints. All caps looked fine, no swollen or leaky
ones, so dried out ones could cause this.

When I was a repair tech, if there was a suspect board we would as a
matter of course redo every solder joint on it. this would fix about
20% of the cases.

Unfortunately sending the iMac to a repair-shop is too expensive. More
and more It looks like my iMac is going to end up as a
iMac/ATX/external monitor/Borg kind of equipment.

So have you done it with this iMac?

Here's some extra notes from a Mac repair person:

 

[Harry]

When I was a repair tech, if there was a suspect board we would as a
matter of course redo every solder joint on it. this would fix about
20% of the cases.


So have you done it with this iMac?

Here's some extra notes from a Mac repair person:

I did everything from the service manual. This includes the external
monitor test where the picture on the external monitor was normal (no
distortions, no "pupming"), i' have done the PMU reset. None of this
helped. The only thing to do before replacing the board is to replace
the battery. The battery is dead. But I can not imagine that a dead
battery can cause souch problems.I am the first owner of the mac, and it worked fine for 4 years. I only
noticed, from time to time, that the display occasionaly makes a "jump"
- eg. if the display vas set to display the desktop from screen border
to screen border is simply jumped so that there vas a gap of 5 to 10
pixel betven the desktop and the screen border on the left and the
right side but on the top and the bottom side the desktop vas by some
amount of the viewable screen area.

 

[Harry]

I did everything from the service manual. This includes the external
monitor test where the picture on the external monitor was normal (no
distortions, no "pupming"), i' have done the PMU reset. None of this
helped. The only thing to do before replacing the board is to replace
the battery. The battery is dead. But I can not imagine that a dead
battery can cause souch problems.
I am the first owner of the mac, and it worked fine for 4 years. I only
noticed, from time to time, that the display occasionaly makes a "jump"
- eg. if the display vas set to display the desktop from screen border
to screen border is simply jumped so that there vas a gap of 5 to 10
pixel betven the desktop and the screen border on the left and the
right side but on the top and the bottom side the desktop vas by some
amount of the viewable screen area.

I changed the battery, no change. The failure remains.