Mirage Electronics AD-1700 REV:F Problem

[Alembic]

Hi Everyone

Hope someone can help.
Troubleshooting the AD-1700 Mirage board
at the moment.
The fault is as follows: Screen fires up for approx
3-4 mins - although this period can be shorter- then
cuts out and can flash on randomly.
When screen is on there is also a slight vertical jitter and
a hint of interference.
I suspect some kind of thermal issue but not too
sure.
Changed all the caps,changed the 12v Reg as I felt it
was getting pretty hot.
Disconnected the BLights and powered them from another
unit and display is normal and steady so looks like the
VGA logic board is okay.
Looks to be only the inverter side of the board that is "Playing up".
went over all the solder joints on the usual suspects but
can`t seem to resolve this problem.
Could the PWM chip be the issue? The fact there is also
"jitter" on the display makes me think there could could be
some kind of ripple at a supply point -purely guessing here.
Only have a DMM to play with (Novice hobbiest)
Any input gladly received.
Thanks.

[PlainBill]

Re: Mirage Electronics AD-1700 REV:F Problem

Hi Everyone

Hope someone can help.
Troubleshooting the AD-1700 Mirage board
at the moment.
The fault is as follows: Screen fires up for approx
3-4 mins - although this period can be shorter- then
cuts out and can flash on randomly.
When screen is on there is also a slight vertical jitter and
a hint of interference.
I suspect some kind of thermal issue but not too
sure.
Changed all the caps,changed the 12v Reg as I felt it
was getting pretty hot.
Disconnected the BLights and powered them from another
unit and display is normal and steady so looks like the
VGA logic board is okay.
Looks to be only the inverter side of the board that is "Playing up".
went over all the solder joints on the usual suspects but
can`t seem to resolve this problem.
Could the PWM chip be the issue? The fact there is also
"jitter" on the display makes me think there could could be
some kind of ripple at a supply point -purely guessing here.
Only have a DMM to play with (Novice hobbiest)
Any input gladly received.
Thanks.

Congratulations for coming up with an unusual problem!

A couple of questions come to mind.

Changed all the caps

. Did you change the caps on the power supply / inverter, the video board, or both. What brand and series of cap did you use?

The symptoms seem to indicate a regulator that is running very close to dropping out of regulation. I'd suspect one of the regulators (or it's filtering caps) on the video (logic) card.

PlainBill

[Alembic]

Re: Mirage Electronics AD-1700 REV:F Problem

Hi

Only on the power supply / inverter, I figured the fact the display
is steady and stays on firing the BLights from an outside source
would rule out any issue with the logic board.
The only cap I did`nt change was the 100uf 400v.
I checked the Voltage across that cap in "fault mode" and it
is steady at (if memory serves) 339Vdc.
Replacements used: Hitano 105deg
Thanks for reply.
Alembic.

[PlainBill]

Re: Mirage Electronics AD-1700 REV:F Problem

Hi

Only on the power supply / inverter, I figured the fact the display
is steady and stays on firing the BLights from an outside source
would rule out any issue with the logic board.
The only cap I did`nt change was the 100uf 400v.
I checked the Voltage across that cap in "fault mode" and it
is steady at (if memory serves) 339Vdc.
Replacements used: Hitano 105deg
Thanks for reply.
Alembic.

Hitano makes several different series of caps rated for 105°C Not all of them are low ESR. What series did you use?

The inverter will generate a lot of noise on the power supply lines (especially the 12 Volt line). Using an external power supply for the inverter isolates the logic card and display from this noise.

From personal experience, I had a Viewsonic monitor that would work well at all resolutions except it's rated 1600 x 1200. It would work perfectly when used on an external supply. Recapping the power supply and inverter didn't help. Recapping the main board solved the problem.

PlainBill

[Alembic]

Re: Mirage Electronics AD-1700 REV:F Problem

Hi PlainBill

Series used: EXR 105°C - vent 9L10.

Using an external power supply for the inverter isolates the
logic card and display from this noise:
The external supply
is purely powering the CCFL`s. The original Power/Invertor
board is powering the Logic/main board.(with the exception
that the CCFL`s are disconnected.)
Interesting point about supply noise though. As I pointed out,
in the original post, of there being a slight interference along
with vertical jitter, I can only describe it as when a car passes
and causes interference on TV,not as heavy but akin to that.
Thanks for assistance.

Alembic

[PlainBill]

Re: Mirage Electronics AD-1700 REV:F Problem

Hi PlainBill

Series used: EXR 105°C - vent 9L10.

Using an external power supply for the inverter isolates the
logic card and display from this noise:
The external supply
is purely powering the CCFL`s. The original Power/Invertor
board is powering the Logic/main board.(with the exception
that the CCFL`s are disconnected.)
Interesting point about supply noise though. As I pointed out,
in the original post, of there being a slight interference along
with vertical jitter, I can only describe it as when a car passes
and causes interference on TV,not as heavy but akin to that.
Thanks for assistance.

Alembic

At a quick glance I would say those are fine. They are definitely rated for this type of application.

PlainBill