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Just replaced the lamp on my Toshiba 52HM84 and it seemed to

work fine for the 1st...
Just replaced the lamp on my Toshiba 52HM84 and it seemed to work fine for the 1st few days but it occasionally would cycle on and off trying to ignite the bulb. It would eventually ignite and all would be well. The last few days it would not ignite and I would have to remove it and replace it and after a couple of hit and misses it would work. last night it would not turn on but simply cycle on and off where the sound comes one but after a few seconds of trying to ignite the bulb it powers down and makes another attempt at it. I've made sure that the power cord was disconnected before replacing the bulb and made sure the door to the bulb unit chamber is replaced to trip the internal switch. Other then the "New" bulb having a problem I cannot visually see ( and it worked perfectly once it did ignite ) I am at a loss. Have to wait till Monday to call the company I bought the bulb from to discuss a replacement for it.
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Answered in 17 minutes by:
3/21/2009
Chuck Williams
Chuck Williams, Technician
Category: TV
Satisfied Customers: 3,810
Experience: Over 25 years of experience servicing AV electronics to component level, ISF and THX Cert.
Verified

Hi!

 

Very odd. I know Toshiba has had many lamp and lamp power supply issues.

 

When you say the set attempts to fire the lamp, how do you know? What I tell customers to look for (listen for, actually) is to see if they can hear a buzzing sound coming from the lamp compartment at turn on that lasts maybe 3 seconds. That's the sound of the lamp being fired. If it doesn't light, it usually tries again.

 

Another trick is to remove the bulb, and while looking at the ballast (the power supply for the lamp), see if you can see a tiny blue arc of electricity near where the wires for the bulb come from. There is a spark gap there, and if you see that, that usually means the ballast is OK.

 

Remember that this will not work if the lamp cartridge has a sensor switch that is opened if the lamp is removed, and also won't work if the lamp compartment door isn't secure. There's definitely a sensor switch to detect that.

 

Let me know what you think!

 

Chuck

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Customer reply replied 8 years ago
Hello Chuck,

Thanks so much for answering my ???
Yes I do hear the sound the light makes for the first few seconds before it normally would light up. This will normally be followed with dim TV picture and within a few seconds it brightens up to full brightness. Tipical mercury light behavour right?
In this case I just just hear the noise - almost like a small fan reving up and then it throtles back to almost silent during normal operation. I get TV sound to whaever channel the set box is set at, just after a few seconds more the green light to the left of the main power light starts blinking, followed by a restart attempt.

In order for me to perform the check you suggested, I would have to pull out the lamp housing but in doing so, it would disconnect itself from the electrical built it poweer plug.

I tried externally depressing the micro switch that the lamp compartment hatch door depresses and didn't really see much of an ingnition attempt from that vantage of looking directly at the rear of the lamp housing. I unplugged the set for about three hours and still no joy. Since I purchased the lamp from a third party distributor I may have to call them on Monday. I just know their are going to blame it on the set and not on their product. It does have a 6 month guarantee though.

I have replaced lamps on other TV before and never had this odd problem.

I have to go out this evening and after returning will test it by manually depressing the hatch switch so I can observe the housing in a darkened room as it attempts to power up. With the door removed it normally goes into a blinking mode on the Red ( power ) and the blinking green ( code ) light.

I hope between us we can solve this or at least figure out where the problem may be coming from. I realize that it could be anything but if you could help me to troubleshoot this I would be eternally gratefull. This is really a great resource.
Customer

I understand that if you pull out the lamp cartrige, the lamp will be disconnected, that's why I would be curious if you can see that tiny blue arc of electricity. Actually, you should be able to see it with the lamp installed unless the lamp is shorted, and that's not likely. That spark has to happen somewhere, and if not the lamp itself (where it should happen), then on the spark gap on the ballast.

 

The way these lamps work, by the way, is that the ballast initially applies about 2000 volts to the lamp to ionize the gas inside, then reduces the voltage to about 80 volts, and the lamps conducts electricity. So it's the initial 2000 volt and its blue arc we are looking for.

 

All the other noises you describe are normal.

 

Good luck, and let me know how it goes!

 

Chuck

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Customer reply replied 8 years ago
Nope. I did not notice any sort of spark faint or otherwise. I manually tripped the hatch microswitch so the TV would stop blinking. Turned on the TV power with the remote and watched the bulb housing and did not see any type of indication of a spark. I did it with the room darkened to help me to see if the spark did occur.

This lamp is new and it did work for a few days with a few false starts that eventually would ignite the bulb.

Nothing works now and the bulb looks a new as it did when I originally installed it.

Jtoolman

Then it has to be the lamp power supply, called the ballast. It's possible that you are missing the roughly 330 volts DC that supplies power to the ballast, and if you are comfrotable taking the set apart and have a voltmeter, you should check that. It shouldn't be too difficult to do. You can also probably replace the ballast yourself, and if you want to try that, I might be able to give you some tips.

 

Let me know if you want to go down that route!

 

Chuck

Chuck Williams
Chuck Williams, Technician
Category: TV
Satisfied Customers: 3,810
Experience: Over 25 years of experience servicing AV electronics to component level, ISF and THX Cert.
Verified
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Customer reply replied 8 years ago
No I rather not. You have a clue what that would run to have somebody fix it?

Thanks

I would expect the ballast to be in the $200 range, and a tech to be in the $150 range. Get a tech who is either Toshiba authorized, or knows the problems with this set. As I said, this TV has a history of lamp and ballast problems, so a Toshiba tech will know all about it.

 

Chuck

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Customer reply replied 8 years ago
Thanks
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