Viewsonic N3752W Tuner Woes

[mmartell]

This tv was dead and upon inspection was found to have just about every cap in the secondary blown so ordered a kit and replaced them and now set powers up fine.

When I do a channel scan there is two bars, one for AIR and one for CABLE. Presumably the first half of the AIR scan is for analog and the second half is for digital channels. The meter goes half way across and freezes at what is the beginning of the digital scan and never gets to the CABLE portion of the scan and so never completes.

I measured +30v and +5v at the tuner module but am unsure how to proceed. Any help is appreciated.

[mmartell]

Re: Viewsonic N3752W Tuner Woes

Some pics...

[fatcat]

Re: Viewsonic N3752W Tuner Woes

I have this same problem with the scan. The scan hangs halfway through the air scan. Did you ever get it fixed?

[mmartell]

Re: Viewsonic N3752W Tuner Woes

No. Still waiting for input.

You have the same set ?

[fatcat]

Re: Viewsonic N3752W Tuner Woes

Yes, the same tv. This one also has a dark spot on the screen. When I hook up the laptop through hdmi there is a pinkish hue to the screen. Pretty messed up. Not sure if it is worth fiddling with. The scan thing is frustrating. Using a satellite box works fine though. Anyway, I guess this thread got a bump so we'll see if we get any helpful advice. Thanks for the reply!

[mmartell]

Re: Viewsonic N3752W Tuner Woes

Hey fatcat does yours tune any cable or digital channels by direct entry ? Trying to determine if this is hardware or software/firmware related but I don't have cable nor the original remote so no "-" button for digital channel entry.

[mmartell]

Re: Viewsonic N3752W Tuner Woes

And have you tried the Eeprom Init in the Factory Menu ?

Menu-9-9-1, first entry. Will shut off and come back on after about 1 minute iirc.

Didn't work for me but seems to have worked for some from what I have read.

[fatcat]

Re: Viewsonic N3752W Tuner Woes

Thanks for those tips. I'll try later. I did figure out the pink screen. Needed to change the resolution down to 720 compatible. Works good now with the laptop.
I have a home made ota antenna that I'm trying to scan channels in with but it just hangs halfway like you said. I'll let you know if your tips help the situation. Thanks!

[fatcat]

Re: Viewsonic N3752W Tuner Woes

Well, I tried doing manual channel input using the - and I'm assuming the - replaces the . is that right? Didn't seem to do anything. Problem is, I'm at my brother in law's place and since he had cut his satellite I whipped together the hanger wire bow tie antenna thing but the scan didn't work so I'm not sure if the antenna is working at all. We are very close to a major city so theoretically it should bring in some channels. I would think the tv should still try to scan in the channels even if the antenna doesn't work and then just show that nothing scanned in. Very odd problem. Did the eeprom reset too but still the same. If it was my tv I would open it up to check for bad caps and go from there. Anyway, it's giving me something to fiddle with while I'm here.

[mmartell]

Re: Viewsonic N3752W Tuner Woes

No badcaps in mine, not visibly anyway and not after all the ones on the secondary of the power supply were replaced.

So you have not had the back off this set ? I bet your power supply is full of bloated caps. I was thinking this dirty power had maybe corrupted an eeprom and was causing us the same problem. Zero on the web about this

[mmartell]

Re: Viewsonic N3752W Tuner Woes

Ok so the analog tuner works. The channel was fed from the rf output of a sat box and was even found on the channel scan but froze again anyway at the start of the digital scan as before.

I think I need to find the atsc tuner ic if it is a separate unit as perhaps it has failed.

[mmartell]

Re: Viewsonic N3752W Tuner Woes

The only things in between the rf input and the main processor are the demodulator ic and an mpeg2 hardware decoder ic. I would think that ic rarely fails (it's in millions of dvd players) so the demod ic (mt5112) is suspect. That or some serious ripple in one of the supply voltages. I can test for ripple but don't have another ic to drop in. Stay tuned

[fatcat]

Re: Viewsonic N3752W Tuner Woes

Hey there. Glad to hear you are tuning in on the problem. Any news to share? I'm going to be back at the brother in law's so I need to find a way to get tv or I might blow a cap or two myself.

[mmartell]

Re: Viewsonic N3752W Tuner Woes

This one is on the back burner atm. When I get back to it I'm going to check the oscillator for functionality. Beyond that I might just zip it back up as the main boards are going for about $50 and that just doesn't seem worth it.

[fatcat]

Re: Viewsonic N3752W Tuner Woes

Well, I brought an external tuner box and with the little bow tie antenna I made it scanned in 19 channels so something is definitely not working right with the tv. Makes a good monitor type display.
Thanks for the help trying to troubleshoot the problem.
Merry Christmas to you if you are so inclined.
Happy New Year as well.

[mmartell]

Re: Viewsonic N3752W Tuner Woes

I'm hoping to have a look at this over the holidays as it needs to be finished one way or the other. Merry Christmas and a Happy New Year to you as well.