DLP

[GregS]

Working on a DLP projector, no light. I don't measure any voltage
going to a lamp socket with lamp disconected. I looked for both AC and DC.
Looks like there is a ahole board for the supply with OSRAM parts.
Anything else to check ?

greg

 

[James Sweet]

Working on a DLP projector, no light. I don't measure any voltage
going to a lamp socket with lamp disconected. I looked for both AC and
DC.
Looks like there is a ahole board for the supply with OSRAM parts.
Anything else to check ?

greg

You could find the signal line that triggers the lamp driver to turn the
lamp on and make sure it's changing states when the lamp should light.

Be *very* careful probing the lamp sockets on these, a properly working
driver will supply pulses of several kilovolts to ignite the arc in the
lamp. You can easily fry your meter, or worse.

The drivers are essentially switchmode power supplies configured to supply a
constant current rather than a constant voltage. Standard SMPS
troubleshooting applies, taking into account the greater than usual high
voltage hazard.

 

[GregS]

You could find the signal line that triggers the lamp driver to turn the
lamp on and make sure it's changing states when the lamp should light.

Be *very* careful probing the lamp sockets on these, a properly working
driver will supply pulses of several kilovolts to ignite the arc in the
lamp. You can easily fry your meter, or worse.

The drivers are essentially switchmode power supplies configured to supply a
constant current rather than a constant voltage. Standard SMPS
troubleshooting applies, taking into account the greater than usual high
voltage hazard.

I used an old analog meter. There is a LED lamp on indicatior on the top of
the unit, and it does go on. Evn if I just had a bad lamp, I would imagine there would
still be a clicking or visable arc around the lamp. $435 for a new lamp, wow.

greg

 

[Jamie]

I used an old analog meter. There is a LED lamp on indicatior on the top of
the unit, and it does go on. Evn if I just had a bad lamp, I would imagine there would
still be a clicking or visable arc around the lamp. $435 for a new lamp, wow.

greg

Ha, Sounds like you have an RCA 61 inch? , that is what my DLP is. and
it cost that much for a replacement lamp assembly..
Your problem sounds like a ballast/driver problem.

 

[GregS]

Ha, Sounds like you have an RCA 61 inch? , that is what my DLP is. and
it cost that much for a replacement lamp assembly..
Your problem sounds like a ballast/driver problem.

Viewsonic, and I have to come up with a power cord.

greg

 

[GregS]

Common causes are the lamp failing, and or the lamp power supply
failing. Servicing the power supply is not easy. It will need a proper
test load, or the lamp to load it for taking measurements.

There are safely issues involved when working on these. The factory
service tech will start by changing the supply if a new lamp does not
work properly.

I took the thing apart. One of the worst assemblies I have ever seen.
Seems I can't find much info on Osram stuff. It looks like the whole
power supply is by Osram. There is a block on the board which runs the lamp,
designed specifically for that lamp. There is some detail in the wiring on the block
but its not entirely obvious. The block runs on AC but I was going to plug it
into AC, but the frequency is likely to be higher than 60 HZ.
http://www.viewsonic.com/pdf/us_eng/products/pj1075.pdf

greg

 

[jango2]

I posted a reply here and it vapourised. Then it wouldnt let me add a
lengthy reply to another post, what is usenet up to?
Find out from the customer if he saw a lamp timer warning before this
happened. If so u need to find the lamp timer reset sequence of key
presses at power up (from the op manual). Do NOT send the set back
with the old lamp after resetting timer, it will implode liberating
noxious gasses.

 

[GregS]

I posted a reply here and it vapourised. Then it wouldnt let me add a
lengthy reply to another post, what is usenet up to?
Find out from the customer if he saw a lamp timer warning before this
happened. If so u need to find the lamp timer reset sequence of key
presses at power up (from the op manual). Do NOT send the set back
with the old lamp after resetting timer, it will implode liberating
noxious gasses.

I was guessing the lamp "on" was OK since the lamp LED came on.

greg

 

[jango2]

Oops , sorry, my bad.Have you checked the thermal cut off on the lamp
housing?

 

[GregS]

Oops , sorry, my bad.Have you checked the thermal cut off on the lamp
housing?

No, but I looked for lamp voltage with an old meter.

greg

 

[jango2]

DC avlbl in ballast?

 

[GregS]

DC avlbl in ballast?

The Osram block is driven by AC. I have not measured anything yet on the power board.
There looks to be an AC generator which feeds the output block.

greg