Finlux 9670 with waves in picture

Guest · Posted: Sun Dec 16, 2007 5:55 pm Post subject: Finlux 9670 with waves in picture

The problem is a Finlux 9670 (very old thing).

The picture is bulging a little according to the the signal. Vertical lines in the picture gets a wave-like shape.
It looks a bit like the 50 Hz ripple that you might get if the main supply capacitor in the PSU is faulty, but I have tried to replace this one, without any result.

Any ideas ?

torbjorn · Joined: 07 Jun 2007 Posts: 370 Location: Sweden

One possibility could be a 50 Hz interference introduced via some fault in an antenna amplifier, cable tv network etc. Try feeding a signal from another source (for example, a DVD player) to the tv and see if the interference disappears. It can also be interesting to try the RF input as well as the SCART connector to see if there is any difference.

In seldom cases, the voltage control circuitry of a SMPS might begin oscillating for some reason. If i remember correctly, old Finlux sets often have a TDA4601 or similar SMPS controller, there is a number of small electrolytics (say, 47 uF or 100 uF) around it that might be suspect.

Pilsener · Joined: 18 Dec 2007 Posts: 8

Have tried with another PSU - No result.
Different signal sources (tuner/dvd) - Same result.

I am, however, pretty sure I have experienced this fault somewhere before...many years ago...and I have a distant memory about some faulty capacitor. Too bad all my notes about these tv's are gone.

Here's a pic to show how it looks like. You can see the vertical lines in the menu are being "bent". This bulges are moving according to the video signal.

torbjorn · Joined: 07 Jun 2007 Posts: 370 Location: Sweden

Do the contrast and brightness settings influence the bulges?

Pilsener · Joined: 18 Dec 2007 Posts: 8

No. Contrast and brightness does not influence it.

hirollcenter · Joined: 19 Dec 2007 Posts: 5 Location: bluegrass

Looks like the vertical deflection has trouble,vert.output,power supply noisey,or the pin cushion, maybe in those areas somewhere...

torbjorn · Joined: 07 Jun 2007 Posts: 370 Location: Sweden

Then it seems like that the video signal contents influence the horizontal oscillator in some manner.
I remember that some old Finlux chassis had a double-side PCB without plated-through holes in the video area, the feedthroughs were made by soldering some component pins on both sides. Those solder joints often crack, and this can cause very strange faults.

Another possibility is if video contents should be carried on a supply line, +12V or something like that, that also feeds the horizontal oscillator. Then the problem might be a bad decoupling cap for this supply.