Well, I got it home and started testing it further and discovered it would shut itself off after an hour or so and wouldn't come back on unless I power-cycled it (unplug, replug). Next time it would shut off sooner than an hour, indicating to me a heat problem. I tried contacting the seller but he was unresponsive, leading me to believe he knew the unit had problems that he did not disclose to me prior to the sale. So I am not even certain now that the new bulb story is true.
I also began to note, during my testing, an audible whirring sound when I would power it on. My first supposition, not knowing a whole lot about these TV's, was that a cooling fan might be going out. Since then, however, I've begun to believe the problem is more likely the color wheel. That is because the unit will now no longer power on: that whirring sound starts when I hit the power button, fluctuating a few times before the unit emits an LED error code. The code is the same as the one I saw when the unit would shut itself off: 3 green, 2 yellow. The manual indicates this error code means "Lamp ignition failure, Lamp failure, blaster error, Lamp shut off unexpectedly. (The system will shut down main power go to standy mode.)"
As far as steps I've taken thus far, I first tried making certain the lamp door shut-off switch was not malfunctioning. I did that by adding a little material to the end of the cylinder that depresses the switch when the door is closed. That did not resolve the problem. Then I removed the back panel, thinking a would try turning an fan on the insides to test whether the problem I was seeing was a cooling issue. That made things worse: it was after I'd done that that the unit stopped powering on. I put the panel back in its place, but the unit still will no longer power on.
I'm pretty frustrated with this because, though I probably have adequate skills to repar this unit (I've built quite a few computers from components), I did not buy it thinking I was going to have to repair it. I really don't have much time at this juncture to work on a project like this. But because I'm faced with the prospect of finding some way to dispose of it, I decided I should at least get a second opinion on whether to try reparing it. Which is why I've come to this forum.
So, any opinions on whether this TV will be worth spending any further time and money on? I've looked a bit at the parts market, and it looks like parts for this (and maybe other DLP's) are hard to come by. And when found, they can be expensive. And they don't seem to last very long. Needless to say, I'm not going to spend anywhere near what an LED/LCD TV of this size would cost: I've seen used sets in my area going for under $200. And I'm already more than 1/4 of the way there. So this might be a lost cause.
Feedback will be appreciated.