Montgomery Ward (Sylvania chassis, OEM NAP) Tuner Trouble

[liammc00]

First off I'm pretty ignorant when comes tuners especially the ones in TVs as I have not had to mess with them much. The last thing I need to fix is tuner on this set. Please look at videos provided in link. Video 1 is what happened when I first got the set. Since than I have repaired a bunch of cold solder joints and capacitors that had gone bad. Yes I did open the tuner it's self and there was one bad capacitor and made sure not to touch any of the coils. On video 2 which is test after service(sorry in advance for poor camera work). If anyone has any ideas wear I should I be looking at IF on main board or is it problem in the tuner module itself. I will continue to look around and with Sam's im going to check the voltage on the pins on IC601.

https://drive.google.com/drive/folde...cv5ecr0ODXEvBy (also a copy of service manual and chassis is 26C616)

https://archive.org/details/36112731...93729186_n.jpg

[old_tv_nut]

If you're getting snow like that, it seems the tuner and IF amplifier are working.
Guesses: May be a problem with AGC or sync (which could be on the same module as the IF), or a connection between modules, or a ground connection.

[liammc00]

Originally Posted by old_tv_nut

If you're getting snow like that, it seems the tuner and IF amplifier are working.
Guesses: May be a problem with AGC or sync (which could be on the same module as the IF), or a connection between modules, or a ground connection.

IC601(NTE1413) in the IC functions in the Sam's it says that IC601 does these things sync demod, IF amplifier, AGC DET/Noise INV, White Spot Inverter, video preamp, AFT sync demod, and REF amplifier. I did test the voltage on the pins that the Sam's (2660 folder 2) in troubleshooting the IF/AGC with a signal attached from a VCR out putting a blue screen as my signal. I did mark the adjustment pot for the RF AGC and no matter were I moved it. The results were barley noticeable after that I put the pot back at the factory spot.

Results:
Pin 3 .7v the Sam's says .6 volts
Pin 4 11v the Sam's says 4.7volts ( 4.5 -11volts ) RF AGC range
Pin 14 12v the Sam's says 7volts ( 6.7- 11volts ) IF AGC range
Some other pins were reading not what the schematics said they should.
I will go and check the connection between the modules. Also I will check the grounds as this TV has had bunch of cold solder joints I had to fix.

[old_tv_nut]

Pins 4 and 14 are far out of spec. Have you checked all the power supply voltages?

[liammc00]

Originally Posted by old_tv_nut

Pins 4 and 14 are far out of spec. Have you checked all the power supply voltages?

On the schmatics pin 4( 4.5 -11volts ) RF AGC range and
Pin 14 ( 6.7- 11volts ) IF AGC range. So it is in range and its like it's trying to drive the gain as hard as it can like a weak signal.

[liammc00]

Originally Posted by old_tv_nut

Pins 4 and 14 are far out of spec. Have you checked all the power supply voltages?

I did check the vcc pin on the chip 11.4v and all other voltages seem to be fine. which what the schematic says. However I found problem I created in the tuner I forgot to resolder a capacitor lead while I was testing the caps. The replacement chip was a defective as picture had a lot of noise but it worked otherwise. That's how it behaved in set I pulled it of before I scrapped that TV. So I put the original chip back and much better still has the same problem as it did in video one but at least the picture is clear and the AGC set at the factory gives the best picture.

[liammc00]

I know for a fact that the replacement chip was a defective part I'm going to try with another chip I had SK7635 but I'm going to use an NTE1413 chip as I got 5 of them for $4 a peace with free shipping in there original bag.

[liammc00]

Digging around in parts I have i found a genuine OEM chip for the TV made no difference. I rechecked the RF/AGC with signal and have 8.1 should be at 4.7 but can range as high as 11volts. On the IF/AGC I get 6.9 which is close enough to 7volts. The RF AGC with no signal goes to 9volts. The RF/AGC goes through a few passive components which I have checked and are good. After that it leaves to TS-9 module on connector J8. On that module it's has only part a 22uf cap which is good. Then it goes to connector J22 back to U/V tuner module 3402910001. I have resolder all the connection so it looking like its the tuner module. The TV works fine on AUX inputs (composite in) the only part in If haven't tested because I don't now how is SAW filter the IF goes in to it and then it splits off the video and audio.

PS I have added some pictures of in side the the set please click on first link that will take you to the Google drive where the files are keeped.