On Dec 10, 11:14 pm, (Brad) wrote:
Hi,

I have a Magnavox (Philips) TV model 27MS3404/17 ch L01.1U AC-7638
(mfg 08/04) in my shop. The TV will turn on with picture and sound, but
anywhere from a few seconds to a couple minutes, the horizontal sweep
shuts down, which looks like the TV turned off, but the SMPS is running
"Full" and the TV on light (front panel) is lit. Note: I replaced C2455
47/25 in the horizontal driver circuit, but that didn't fix this problem.

HV measures 27KV (aok). Note: I "fixed" a problem like this on a
similar model several months ago by reducing the "Picture" (contrast) and
Brightness that was set too high, but doing the same on this TV did not
"fix" the problem.

could be any number of things.
measure the b+. see if theres any variation from cold -warm-hot. may
indicate bad caps.
you may have a bad line output transformer, i have seen this happen if
the transformer is bad; check for any minor arcing in a darkened
room.
the CRT going duff may also cause this shutdown.

and of course there is good ol' bad solder joints!

-B,