I am working on this LCD computer monitor. It trys to power up,
flickers and then the backlite goes out. The display seems to
still be there so its a back lite issue.

Took the inverter out. ESR'ed the 100/25 caps. They seem to be OK.
no bulges. resoldered the board. Still does the same thing.
Seems to be going into current limit or such?

Anybody work on one of these or have a link to a inverter
schematic?

Seems to be a common problem with this unit.
There is a aftermarket inverter available, buts its $100
which makes it not feasible with this old of a unit.

bob


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On Sat, 26 Jul 2008 11:01:27 -0500, bob urz put
finger to keyboard and composed:

I am working on this LCD computer monitor. It trys to power up,
flickers and then the backlite goes out. The display seems to
still be there so its a back lite issue.

Took the inverter out. ESR'ed the 100/25 caps. They seem to be OK.
no bulges. resoldered the board. Still does the same thing.
Seems to be going into current limit or such?

I see several posts that suggest that replacing those 4 caps fixes the
flickering problem. Why not just replace them anyway?

Anybody work on one of these or have a link to a inverter
schematic?

Seems to be a common problem with this unit.
There is a aftermarket inverter available, buts its $100
which makes it not feasible with this old of a unit.

bob

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

On Sat, 26 Jul 2008 11:01:27 -0500, bob urz
wrote:

I am working on this LCD computer monitor. It trys to power up,
flickers and then the backlite goes out. The display seems to
still be there so its a back lite issue.

Took the inverter out. ESR'ed the 100/25 caps. They seem to be OK.
no bulges. resoldered the board. Still does the same thing.
Seems to be going into current limit or such?

Anybody work on one of these or have a link to a inverter
schematic?

Seems to be a common problem with this unit.
There is a aftermarket inverter available, buts its $100
which makes it not feasible with this old of a unit.

bob


Are you sure all the lamps are turning on? Most inverters will shut
down if one lamp fails to start. This is usually caused by the
inverter, but a broken lamp will also cause it.
Andy Cuffe

Franc Zabkar wrote:
On Sat, 26 Jul 2008 11:01:27 -0500, bob urz put
finger to keyboard and composed:


I am working on this LCD computer monitor. It trys to power up,
flickers and then the backlite goes out. The display seems to
still be there so its a back lite issue.

Took the inverter out. ESR'ed the 100/25 caps. They seem to be OK.
no bulges. resoldered the board. Still does the same thing.
Seems to be going into current limit or such?


I see several posts that suggest that replacing those 4 caps fixes the
flickering problem. Why not just replace them anyway?


Anybody work on one of these or have a link to a inverter
schematic?

Seems to be a common problem with this unit.
There is a aftermarket inverter available, buts its $100
which makes it not feasible with this old of a unit.

bob


- Franc Zabkar

When i get another parts order in i may just do that.

Visually, the caps look fine. No bulges, no leaks. ESR looks good
in circuit. The other monitors i have fixed showed obvious
ESR problems or bugles and leaks.

I started to draw a schematic, buts its going to take some time.
It drives three lamps with one inverter and three lamps with
the other. Both are controlled by the same OZ controller chip.

Bob


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On Fri, 01 Aug 2008 00:11:36 -0500, bob urz put
finger to keyboard and composed:

Franc Zabkar wrote:
On Sat, 26 Jul 2008 11:01:27 -0500, bob urz put
finger to keyboard and composed:


I am working on this LCD computer monitor. It trys to power up,
flickers and then the backlite goes out. The display seems to
still be there so its a back lite issue.

Took the inverter out. ESR'ed the 100/25 caps. They seem to be OK.
no bulges. resoldered the board. Still does the same thing.
Seems to be going into current limit or such?


I see several posts that suggest that replacing those 4 caps fixes the
flickering problem. Why not just replace them anyway?


Anybody work on one of these or have a link to a inverter
schematic?

Seems to be a common problem with this unit.
There is a aftermarket inverter available, buts its $100
which makes it not feasible with this old of a unit.

bob


- Franc Zabkar

When i get another parts order in i may just do that.

Visually, the caps look fine. No bulges, no leaks. ESR looks good
in circuit. The other monitors i have fixed showed obvious
ESR problems or bugles and leaks.

One post suggests that those 4 caps are connected in parallel. If so,
then an in-circuit ESR test may be inconclusive, as one good cap could
mask three bad ones. Is it possible that the supply to the inverter is
bad, in which case you may want to check the caps in the main PSU ???

I started to draw a schematic, buts its going to take some time.
It drives three lamps with one inverter and three lamps with
the other. Both are controlled by the same OZ controller chip.

Bob

The O2 Micro web site doesn't have any datasheets. It seems they are
only available to O2 Micro's "partners". All we mere mortals get is a
brochure with a skimpy "application diagram".

http://www.o2micro.com/prods/prod_intelliglting.html
http://www.o2micro.com/prods/o2m_int_ltg_brochure.pdf

Having said that, you may still be able to get an idea how the OZ
devices work by referring to the US patent at the bottom of each page.

For example, the description of the OZ9921 part refers to US patent
#7,057,611.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.