On Monday, November 5, 2018 at 11:30:28 AM UTC-5, Jeff Liebermann wrote:
On Mon, 5 Nov 2018 07:19:38 -0800 (PST), John-Del
wrote:

On Monday, November 5, 2018 at 12:47:37 AM UTC-5, Jeff Liebermann wrote:
On Mon, 05 Nov 2018 15:02:48 +1100, Lucifer
wrote:

The Samsung LA19R71B is a 19" LCD TV.
I was using it with the RF output of my Commodore C64C.
Channel search works but no channels are detected.

For the C64, make sure the tuner in the TV is set to OTA (over the
air) and NOT to CATV (cable television).

That actually won't matter. 2-13 on CATV or analog OTA are the
same frequencies assuming he's looking for channel 3 or 4 which
just about every modulator in the U.S. used. If the modulator's
output was in the UHF band, then selecting OTA instead of CATV
would be necessary.

Oops, your right. Bad guess(tm):
"CATV FREQUENCY ASSIGNMENT"
http://www.annsgarden.com/telecom/CATV.html

Probably has a bad tuner.

Maybe. It would be nice to know what "Channel search works" really
means. Does it find and display any other OTA stations? If it does
find and display other stations, then the tuner is not broken.

Could still be a bad tuner. Since the dawn of time (or at least the dawn of TV), we've seen plenty of tuners that would work on one band, but not on others. Before cable boxes, we'd see plenty of tuners that had no 2 to 6 (VHF low), no 7-13 (VHF hi), or no mid band or high band CATV (can no longer remember the line of demarcation of the those), or UHF. Today, we add digital OTA functions to the legacy bands.

So even if he scanned OTA with a cheap antenna and received one or two digital TV channels, it still wouldn't prove his tuner was OK.

BUT, if his modulator works on any low band VHF channel, he can enter the number manually as you suggest if he has a remote, or if the menu allows it (doubtful on newer TVs).