Help me with RF interference - Videokarma.org TV - Video

TinCanAlley · #1 03-08-2015, 06:17 PM

Okay, this one is driving me crazy (as most things I can figure out do).

My Avante is having some RF issues. It covers most of the screen with dots and other static. When I move the antenna lead around it goes from better to worse and sometimes I can get it to go away. It seems if I get the lead in just the right angle, it goes away, but it won't stay like that for long as the slightest change in angle will bring it back.

This is definitely being introduced at the connections on the TV. If I touch either one of the screws with my finger, the interference gets really bad. If I touch one and then the other, it goes from bad to not so bad. I've looked inside the set for any issues with the routing of the twin lead and don't see any. It only at the connections. I did notice that one of the connections is not original. Looks like it must have been pulled out and they put in a similar one, but soldered the lead to it instead of it being a removable connection.

I really wish I knew what it was as I doesn't look like the normal interference I'm used to seeing with vacuums, compressors, etc. The static doesn't roll up or to the side. Each piece of it changes, but not location, just intensity.

Hope this makes sense.

Electronic M · #2 03-08-2015, 08:15 PM

Look for arcing in the HV (including the connection to the CRT), focus and yoke sections. Since the noise is synched to the screen I'd guess the source is internal, and probably due to arcing.

TinCanAlley · #3 03-08-2015, 09:01 PM

I have checked and found no arcing.

If it is internal, how does moving around the leads on the external connections clear it up or make it worse?

Would providing a picture of the best/worst of the interference help diagnose?

Thanks

old_coot88 · #4 03-08-2015, 09:13 PM

Look for any coaxial cable having a broken/intermittent ground at one end.
E.g., a coax RF input cable, or the IF cable from tuner to chassis.
I've seen it happen with a pickup mic cable (in a remote set).

TinCanAlley · #5 03-08-2015, 09:16 PM

I have check every external cable. I have also checked the two twin lead connections inside the TV. I will check all the cables inside connected to the tuners ( I believe there are three and one jumper).

I am attaching a couple of pics of the static at its worse. I can adjust the external connection orientation to almost eliminate it, but it doesn't completely go away (but pretty close).

***Eric H*** · #6 03-09-2015, 12:56 AM

Could be a device inside your house, CFL light, Wall Wart, Computer, Router, etc.

I'd try unplugging everything you can, one at a time to see if it goes away.

Dude111 · #7 03-09-2015, 03:16 AM

This happend to us in the 80s and it turns out it was our nieghbour on his ham radio

zeno · #8 03-09-2015, 08:57 AM

If it were arcing the focus pin of the CRT socket was common
on these especially if it had open S-caps or divider.
Test by pulling all ground straps & check them for HV.

But this looks external. Try using an AM radio to track it.
It can be almost anything. I live out in the woods & the QRM
kills AM radio. During blackouts it comes alive with Philly
at high noon ( apx 300mi).

We used to have an FCC that worried about interference but now
they are just a rubber stamp for bad ideas.

73 Zeno

Username1 · #9 03-09-2015, 08:59 AM

Is it only on this tv.....? Put a similar tv in it's spot in the house, does it
have the noise too....?

.

Electronic M · #10 03-09-2015, 09:30 AM

Zeno, what is QRM?

Dangler · #11 03-09-2015, 09:35 AM

Google it.

Zenith26kc20 · #12 03-09-2015, 10:01 AM

QRM = NOISE!
The owner of the business next to mine has a laptop that drives the analog TVs nuts with that kind of interference. I can tell when he turns it in and when he turns it off!
Also, check your focus divider for a small crack in it's housing. This will allow a slight discharge which can cause that kind of interference.
If the focus pin is green (corrosion) on the CRT it could be leakage on the socket. Usually this causes focus troubles too.

Electronic M · #13 03-09-2015, 12:13 PM

Quote:

Originally Posted by Dangler

Google it.

I did before asking, but I got a bunch of non-electronic related crap that was clearly not the same acronym being used here....

jr_tech · #14 03-09-2015, 12:45 PM

Quote:

Originally Posted by Electronic M

I did before asking, but I got a bunch of non-electronic related crap that was clearly not the same acronym being used here....

"Q codes"
http://www.qsl.net/w5www/qcode.html

jr

TinCanAlley · #15 03-09-2015, 01:28 PM

Well I found it. I checked everything I could think of. Turns out it was the only piece of equipment I needed. It turned out to be the RCA RF modulator introducing the noise. I got my hands on an older RS modulator and the problem is gone.

Thank you for all your input. It's so nice watching it without all those annoying dots!