Been asked to repair this , if possible, unlikely, but I will at least look.
DLP type.
Never looked in a projection TV before, currently red LED falshing ,
supposed to indicate blown bulb. No light at all on switch on .
Prior to that , not seen by me , only reported, there was a slightly
diagonal shadow across the very right hand edge of the screen, but still
being used like that.
Only 2 wires to the bulb , is it filament type ? if so open circuit, but no
obvious blackening or anything.
The whole inside is covered in dust, including a very dusty reflector on the
bulb. Would it be safe to blow out the dust, from the whole iside of the
casing, with a 1KW blower or is there anything like the rotating filters
likely to be dislodged or damaged.?


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

N_Cook wrote in message
...
Been asked to repair this , if possible, unlikely, but I will at least
look.
DLP type.
Never looked in a projection TV before, currently red LED falshing ,
supposed to indicate blown bulb. No light at all on switch on .
Prior to that , not seen by me , only reported, there was a slightly
diagonal shadow across the very right hand edge of the screen, but still
being used like that.
Only 2 wires to the bulb , is it filament type ? if so open circuit, but
no
obvious blackening or anything.
The whole inside is covered in dust, including a very dusty reflector on
the
bulb. Would it be safe to blow out the dust, from the whole iside of the
casing, with a 1KW blower or is there anything like the rotating filters
likely to be dislodged or damaged.?



Looks as though the shadow is a stock fault due to something coming adrift
inside the light guide from the rotating colour wheel.
Can't find details about the bulb though


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

The actual lamp is marked SHP58 Hg so presumably a mercury discharge lamp ,
so what sort of voltage and ballast to check that ?


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

"N_Cook" wrote in message
...
Been asked to repair this , if possible, unlikely, but I will at least
look.
DLP type.
Never looked in a projection TV before, currently red LED falshing ,
supposed to indicate blown bulb. No light at all on switch on .
Prior to that , not seen by me , only reported, there was a slightly
diagonal shadow across the very right hand edge of the screen, but still
being used like that.
Only 2 wires to the bulb , is it filament type ? if so open circuit, but
no
obvious blackening or anything.
The whole inside is covered in dust, including a very dusty reflector on
the
bulb. Would it be safe to blow out the dust, from the whole iside of the
casing, with a 1KW blower or is there anything like the rotating filters
likely to be dislodged or damaged.?


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/


These people will help you
http://www.soundandvisionav.co.uk/

Discovered what the original problem was.
A rectangular tunnel between the colour wheel and the first lens, going
across the airpath of a fan. Made of silvered microscope slide glass , 4
pieces forming a rectangular tunnel about 6 x 8mm but the glue at the
corners failed with time or heat and the retaining spring pushes one edge in
a bit.
Removing the spring and the tunnel collapsed, i'm surprised the fan air
didn't totally disloge them.


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

N_Cook wrote in message
...
Discovered what the original problem was.
A rectangular tunnel between the colour wheel and the first lens, going
across the airpath of a fan. Made of silvered microscope slide glass , 4
pieces forming a rectangular tunnel about 6 x 8mm but the glue at the
corners failed with time or heat and the retaining spring pushes one edge
in
a bit.
Removing the spring and the tunnel collapsed, i'm surprised the fan air
didn't totally disloge them.


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/




Before wasting my time rebuilding the 30mm long 4 x 3.7mm internal bore
light tunnel I need to establish whether the bulb is actually failed or a
problem with the drive .

Putting a 50 watt floodlight mercury discharge lamp across the feed, either
way round produces nothing.
Putting a 110V neon across the feed there is a constant orange glow but no
initial flare - too short to be seen ?.
Putting a 150 watt spotlight discharge lamp there, nothing.
Even tried a 9 inch standard fluourescent tube in all orientations.
Anyone know what the trigger voltage duration would be? I'm loathe to
connect up a scope in such circumstances, how to check there is a high V
trigger pulse ?

Would you expect to see black colouration in the active part of the original
lamp or some other sign of problem ?


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

I've removed the ps board. The high power, LV, side of the lamp drive looks
ok, despite some varnish browning around some wide format 1K SM resistors.
But on the assumed HV section, the inverter size and type of hf transformer
measures weird.
4 segments to the wiring , 1 thick wire and 3 fine wire all the same fine
gauge.
secondary coil 115 ohm
primary 0.1 ohm and another coil, presumably for control/feedback, now trace
cut on the pcb to confirm, connected to the primary. This measures 16.7K
despite my twisting of the transformer frame/ light prodding.
1.6K is about the most I'd expect to see on such a transformer and that on
the HT side. You'd never get 20,000 turns or so of this gauge wire on such a
bobbin.
Still a bit hidden from view as sreening/heatsinking still in place but on
the far side of one of the fine coils seems to be a bit of broken copper
wire sticking up, colour of copper wire and resists a needle probe in such a
manner.
Anyone know of a representative/generic schematic for these gas discharge
drivers ?


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

No 12V is getting to the HV circuit of JRC 2901 quad
comparator/transistors/inverter transformer, because the B764 pass
transistor is held off by an isolated line from the video board. Taking the
output of the opto isolator low by 330R the HV circuit works.
Explains why the colour wheel motor is not spinning. I somehow don't expect
to fault find a complex graphics board.
I don't suppose anyone has any ideas? surely does not need a video feed to
check the menu functions etc, not bothered connecting one so far. Surely not
a chicken and egg problem?

I now know that a standard 50W floodlight mercury discharge lamp will work
on this circuit as will a 9 inch fluourescent tube and more diagnostically
380V neon runs fine but nothing without the HV circuit, 110 V very bright
and a low output without the HV , just the 62V power sustain voltage.


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

N_Cook wrote:

I don't suppose anyone has any ideas? surely does not need a video feed to
check the menu functions etc, not bothered connecting one so far. Surely not
a chicken and egg problem?


Many projectors do require a video signal before you can access the menu.


--
Tim Phipps

replace "invalid" with "uk" to reply by email

Tim Phipps wrote:
N_Cook wrote:

I don't suppose anyone has any ideas? surely does not need a video
feed to
check the menu functions etc, not bothered connecting one so far.
Surely not
a chicken and egg problem?


Many projectors do require a video signal before you can access the menu.


I don't think that's true of most Infocus; but I don't know every model.
More commonly there are simply menu functions, like keystone
adjustment, that are unavailable. I usually use the menu for rough
focus and initial setup.

jak

Found out why so much dust on the bulb reflector - breakdown product of the
chop-strand fibre reinforcement (asbestos?) making up the high temperature
plastic surround to the lamp combined with nicotine as sticky agent.

To get some more hours out of the bulb, ie defeat the counted-out lifespan
of the bulb its a matter of pressing both volume switches on the switch
panel for 10 seconds , so full drive resumed to the colour wheel. lamp drive
and all else. Rewinding the 3 primary coils of the inverter transformer
worked, so now reliable startup now the control from the video board is
resumed.

Now a matter of sticking those fiddly 4 bits of light tunnel together.
Will bend back the part of the spring plate that holds the one of the
vertical bits of mirror in place and just rely on the top force to hold all
4 together, in its cradle, if/when the superglue fails due to the heat. That
way there will be no sideways pressure to push in the side piece and so stop
down the light tunnel.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/