Magnavox TV tunner trouble

[liammc00]

I have this Magnavox TV from 1996. The TV was found in a barn so it ant perfect (the TV was put into storage broken). The TV won't stay tunned on a signal the picture cuts in and out about every second and audio pops with the picture. I think there is problem in the tunner but I'm not sure. I have tried a VCR and RF modulator and nether of them make a difference. This YouTube video will show the problem better then I could explain the problem in words or pictures. The TV is RF only and thanks in advance for any information or help you might have

Link removed

[JohnCT]

Originally Posted by liammc00

I have this Magnavox TV from 1996. The TV was found in a barn so it ant perfect (the TV was put into storage broken). The TV won't stay tunned on a signal the picture cuts in and out about every second and audio pops with the picture. I think there is problem in the tunner but I'm not sure. I have tried a VCR and RF modulator and nether of them make a difference. This YouTube video will show the problem better then I could explain the problem in words or pictures. The TV is RF only and thanks in advance for any information or help you might have

https://youtu.be/qi1sTFdUmb4

Whew.. racking my brain trying to remember here.. IIRC, the problem with those is the SAW filters - I believe there's one for the picture and one for the sound.

Depending how bad it is, you can probably tweak the AFT adjustment in the IF section and get it to stop hunting. I recall this adjustment could "fix" the problem or get it to the point where it's watchable with a bit of mistuning evident.

I also recall that the parts became unavailable towards the end of the service time for these models, so finding the filters could be problematic.

Post a chassis number and let me see what I can find out.

John

[liammc00]

Originally Posted by JohnCT

Whew.. racking my brain trying to remember here.. IIRC, the problem with those is the SAW filters - I believe there's one for the picture and one for the sound.

Depending how bad it is, you can probably tweak the AFT adjustment in the IF section and get it to stop hunting. I recall this adjustment could "fix" the problem or get it to the point where it's watchable with a bit of mistuning evident.

I also recall that the parts became unavailable towards the end of the service time for these models, so finding the filters could be problematic.

Post a chassis number and let me see what I can find out.

John

The chassis model is 19X603-00AA

[jbattles]

there's a i.c by the tuner that controls it. that i.c is bad i cant remember what it is called post a pic of the chassis and i could tell you where it is at.

[zeno]

Looks like the AFT is bad so the set isnt stopping tuning.
Try easy first. Go into menus & set the band to "AIR" & the AFT
to "NORMAL". See if that helps. After that a chassis pix may help.
You can also lightly tap around the tuner, micro & jungle IC &
maybe get lucky with a cold joint.

73 Zeno
LFOD !

[liammc00]

Pictures of the chassis. I also checked for cold soldier joints didn't find any. The TV is set to antenna mode and haven't found a way to change the AFT.

[zeno]

Under the antenna input there is an area on the PCB that looks
greenish. Also the input looks rusty. Anyhows clean up that green mung
with a brush & 91% isopropyl alcohol & a brush & try when dried.
Looks like water damage...

73 Zeno
LFOD !

[JohnCT]

Originally Posted by liammc00

The chassis model is 19X603-00AA

On the X6 series chassis, the AFT adjustment should be L210. This will be a small silver can (like a transistor radio IF) with an external knob you can use your fingers to adjust. Don't go more than a quarter turn max either way and mark where you start from. If there's no improvement, put it back where it was. When you adjust it, move it a few degrees *then* hit the channel select. If it doesn't help, move it a bit more and repeat. The adjustment may not bring in the AFT while it's hunting. You might need to adjust it then command another channel change to see if the adjustment works.

Also, I recall there was an open resistor from the sweep sourced 33V line that fed the tuner for tuning voltage (independent of the 5V the tuner used for processing). There were one or two 15K resistors, one of which will open up and cause all sorts of tuning weirdness. I believe the numbers are R360, or 361 or both (can't remember exactly). I remember a lot of guys condemning tuners when this resistor was the culprit.

These resistors are not near the tuner itself IIRC but somewhere between the flyback and about halfway across the board.

John

[liammc00]

Thanks for the help. The TV is at my dad's house and won't be back until Friday. I did clean some of the corrosion off after the pictures was taken. This was at my grandpa's and was stored for years in old travel trailer along with bunch of stuff and couple of years ago he moved the stuff to the barn. So it wasn't stored very well.

[liammc00]

I tried adjusting the AFT it made no difference. I did also checked R361 and it tested good. R360 is not populated on the circuit board on this set.

Ended up being the jungle IC and since the TV was not stored in the beast place I decided not to continue on. The TV is now a parts set.