On Tuesday, December 18, 2018 at 10:54:00 PM UTC-5, wrote:
got a monitor chassis with a bad ka3842. i have a tl3842, but am not well versed enough to compare via datasheets. can i do the substitution?

thanks

Not telling you what to do (and I didn't go through every parameter), but they're close enough where I'd try it.

I might disconnect the output to make sure it doesn't cause an over volt in case the feedback is different.