Sony Service recently replaced the 100 watt UHP bulb in my GWIII rear projector. The new OSRAM bulb is much better (after 30 hours break-in) than the old Phillips.
These UHP bulbs need tender loving care. I observe the following rules:
1) Once the projector is on, it should stay on for at least one hour
2) Once the projector is off it should remain off for at least an hour
The bulb has a large effect on the color temperature. Misuse it and color temperature will suffer. The following excellent explanation is from the rear projector forum:
Hi guys, looks like I get to help out a little on this problem with my first post
First a little background, back in my younger and wilder days I worked in the Motion Picture industry for slave wages but outrageous cool factor. I dealt with MP lighting all day long and know this technology intimately albeit on a much larger scale, up to 18kw back in the day. Imagine the PJ you could fire with that lamp.
When I first started seeing these threads about the "buzz" in these new sets I instantly thought of a spark gap. After doing a little research at Philips web site and confirming that the lamp used in these sets is in fact an arc lamp I can explain what you are hearing and maybe even shed some light on why it is happening.
According to Philips the lamp used in these sets is a 100w UHP mercury halide lamp. These lamps are basically an arc welder inside a glass bubble filled with gasses that produce a specific color temperature when a specific amount of current is passed through the lamp turning the gas into plasma. Maintaining the the arc through the plasma once the lamp is lit is easy, making the first spark jump across the 1mm gap in these lamps is hard, it takes a 20kV (that's 20,000 volts folks) spark to jump the gap in a cold lamp. It also takes a fair amount of current to make the leap and start a path that can easily be maintained by the operating current. The easiest way to make sure you have enough voltage and current built up before you try and fire the lamp itself is to include and air gap in the high voltage line.
The cylinder described above is an air gap. It forces the 20kV firing circuit to have enough juice to jump that air gap before it tries to ignite the lamp, without this air gap the lamp would be immensely harder to fire when it's cold and impossible when it's hot. There are current sensing circuits in the ballast that fires and powers the lamp that cuts off the 20kV ignition pulse when it senses the steady current of a lit lamp. On a cold start you might not even hear the ignition pulse because it should be very short, it is much easier to start a cold lamp than a hot one. Short run times and hot restrikes are the absolute worst things you can do to an arc lamp. They both cause the lamp to become cloudy and shorten the lamp life.
There is a decent link to a care and feeing guide for your lamps if you Google care and feeding of arc lamps. I can't post a link yet otherwise I would. Although this references mercury lamps used in microscopy it is the same technology and probably very similar to the lamp used in these sets.
The relevant bits from the care and feeding guide:
In order for these arc lamps to function optimally, they need to be used properly. The following points should be observed for their use:
When an arc lamp is brand new and first fired up, it should be left on for two hours, whether observing specimens or not. This is to allow the arc to establish arcing points on the electrodes to which the arc will always go and keep the arc stable when the lamp is fired in the future.
The lamp should always be cold when it is turned on. Never turn an arc lamp when it is warm. This causes clouding of the glass in the bulb and both considerably shortens the life of the burner and decreases the burner's brightness. When the glass is clouded, the burner will heat up more and the lamp is more likely to explode.
Once a lamp is turned on, it should be left on for a minimum of twenty minutes (thirty is preferable). This allows it to warm up properly and will help prevent premature wearing out (clouding) of the burner.
Other than firing the burner when warm, turning the lamp on and off repeatedly (many warm-ups and cool-downs) is probably the worst contributor to shortening the life of burner.
With all of that said, how do we fix this problem? That depends. Since the lamp and its igniter come in a package from Philips we shouldn't have to worry about design mismatches. There is a slim possibility that Philips has a design flaw in their ignitor circuit, So we are left with a loose lamp housing as reported by some already, fast cycle times or low input voltage that are causing this problem. Even if it is just a loose lamp housing the lamp will already have sustained some damage and you can't fix that entirely once the problem has occurred although you can take some steps to minimize the issue and maybe correct some of the damage.
Possible low voltage problem:
Someone in another thread I think removed their set from the power strip that had all 12 outlets filled and plugged it straight into the wall and it fixed the problem. To me that means there was a voltage drop while powering on all of the components in his AV setup which lowered the strike voltage for the lamp. Solution, turn on the TV first and let the lamp get going before starting to power up everything else or move the set to its own power source.
Fast cycle times or short run times.
The only way you can try and correct for this is to leave the set running for extended periods of time to try and recondition the lamp envelope and the electrodes. I have had some success with this before on lamps that had been mistreated but you can never get it back to the same condition it would have been in had it not experienced the problem in the first place.
HTH
These UHP bulbs need tender loving care. I observe the following rules:
1) Once the projector is on, it should stay on for at least one hour
2) Once the projector is off it should remain off for at least an hour
The bulb has a large effect on the color temperature. Misuse it and color temperature will suffer. The following excellent explanation is from the rear projector forum:
Hi guys, looks like I get to help out a little on this problem with my first post
First a little background, back in my younger and wilder days I worked in the Motion Picture industry for slave wages but outrageous cool factor. I dealt with MP lighting all day long and know this technology intimately albeit on a much larger scale, up to 18kw back in the day. Imagine the PJ you could fire with that lamp.
When I first started seeing these threads about the "buzz" in these new sets I instantly thought of a spark gap. After doing a little research at Philips web site and confirming that the lamp used in these sets is in fact an arc lamp I can explain what you are hearing and maybe even shed some light on why it is happening.
According to Philips the lamp used in these sets is a 100w UHP mercury halide lamp. These lamps are basically an arc welder inside a glass bubble filled with gasses that produce a specific color temperature when a specific amount of current is passed through the lamp turning the gas into plasma. Maintaining the the arc through the plasma once the lamp is lit is easy, making the first spark jump across the 1mm gap in these lamps is hard, it takes a 20kV (that's 20,000 volts folks) spark to jump the gap in a cold lamp. It also takes a fair amount of current to make the leap and start a path that can easily be maintained by the operating current. The easiest way to make sure you have enough voltage and current built up before you try and fire the lamp itself is to include and air gap in the high voltage line.
The cylinder described above is an air gap. It forces the 20kV firing circuit to have enough juice to jump that air gap before it tries to ignite the lamp, without this air gap the lamp would be immensely harder to fire when it's cold and impossible when it's hot. There are current sensing circuits in the ballast that fires and powers the lamp that cuts off the 20kV ignition pulse when it senses the steady current of a lit lamp. On a cold start you might not even hear the ignition pulse because it should be very short, it is much easier to start a cold lamp than a hot one. Short run times and hot restrikes are the absolute worst things you can do to an arc lamp. They both cause the lamp to become cloudy and shorten the lamp life.
There is a decent link to a care and feeing guide for your lamps if you Google care and feeding of arc lamps. I can't post a link yet otherwise I would. Although this references mercury lamps used in microscopy it is the same technology and probably very similar to the lamp used in these sets.
The relevant bits from the care and feeding guide:
In order for these arc lamps to function optimally, they need to be used properly. The following points should be observed for their use:
When an arc lamp is brand new and first fired up, it should be left on for two hours, whether observing specimens or not. This is to allow the arc to establish arcing points on the electrodes to which the arc will always go and keep the arc stable when the lamp is fired in the future.
The lamp should always be cold when it is turned on. Never turn an arc lamp when it is warm. This causes clouding of the glass in the bulb and both considerably shortens the life of the burner and decreases the burner's brightness. When the glass is clouded, the burner will heat up more and the lamp is more likely to explode.
Once a lamp is turned on, it should be left on for a minimum of twenty minutes (thirty is preferable). This allows it to warm up properly and will help prevent premature wearing out (clouding) of the burner.
Other than firing the burner when warm, turning the lamp on and off repeatedly (many warm-ups and cool-downs) is probably the worst contributor to shortening the life of burner.
With all of that said, how do we fix this problem? That depends. Since the lamp and its igniter come in a package from Philips we shouldn't have to worry about design mismatches. There is a slim possibility that Philips has a design flaw in their ignitor circuit, So we are left with a loose lamp housing as reported by some already, fast cycle times or low input voltage that are causing this problem. Even if it is just a loose lamp housing the lamp will already have sustained some damage and you can't fix that entirely once the problem has occurred although you can take some steps to minimize the issue and maybe correct some of the damage.
Possible low voltage problem:
Someone in another thread I think removed their set from the power strip that had all 12 outlets filled and plugged it straight into the wall and it fixed the problem. To me that means there was a voltage drop while powering on all of the components in his AV setup which lowered the strike voltage for the lamp. Solution, turn on the TV first and let the lamp get going before starting to power up everything else or move the set to its own power source.
Fast cycle times or short run times.
The only way you can try and correct for this is to leave the set running for extended periods of time to try and recondition the lamp envelope and the electrodes. I have had some success with this before on lamps that had been mistreated but you can never get it back to the same condition it would have been in had it not experienced the problem in the first place.
HTH
