Trying to repair CRT TV Philips 14GR1220 - Page 1
Forum section: electronics / repair

author: crt_cowboy
author_rank: Regular Contributor
timestamp: July 26, 2022, 10:46:27 am
content: Hello,I have a Philips 14GR1220 (also known as Discoverer) a TV that shows a dark bar in the center of the screen.See attached picture. I never seen similar issue.Any advice on where to start for troubleshooting ?Service manual can be foundhttps://elektrotanya.com/philips_14gr1221.zip/download.htmlMany thanks in advance !!

author: inse
author_rank: Super Contributor
timestamp: July 26, 2022, 10:56:49 am
content: Is a signal source connected?Try to make a photo showing a picture where one can imagine what it should look like.A test pattern in best case.

author: Uunoctium
author_rank: Frequent Contributor
timestamp: July 26, 2022, 11:49:59 am
content: An slow moving vertical bar (asynchoneous) is mostly associated with huge hum from PSU. Check ripple on voltages, check also electrolytic capacitors in PSU, bridge rectifier...

author: AndyBeez
author_rank: Frequent Contributor
timestamp: July 26, 2022, 02:06:34 pm
content: Is that a static of crawling bar? Are you driving the screen with a clean signal source or is it just floating static? For clarity, PAL, NTSC or SECAM?One visual observation, the width of the dark bar is about the same width as the sync pulse or back porch. Has the horizontal deflection drifted?I would certainly check all capacitors for ageing and the pcb for dry joints > when unplugged and grounded.

author: PKTKS
author_rank: Super Contributor
timestamp: July 26, 2022, 02:12:19 pm
content: Quote from: crt_cowboy on July 26, 2022, 10:46:27 am1) Service Manual - ok2) a clean CRT signal generator.3) possible source of signal.... with a decent scope probe 2 channelYou need a reasonable clean source signal with options to switch each gun and also RGB at all to have a simple BW and synch signals..Injecting this signal in TDA3xxx family will show you a reasonable guess from where the spurious signal came in..Got mine on the very early 80s.. used way so much paid for itself in the first year....Paul

author: crt_cowboy
author_rank: Regular Contributor
timestamp: July 27, 2022, 04:50:54 am
content: Thanks for all the replies. I found a damaged trace near the FBT, fixing it removed the bar that was visible on the picture. I take note for next time to display a test signal on the screen.Quote from: PKTKS on July 26, 2022, 02:12:19 pmJust for my education, you would directly inject the signal in the TDA IC ? I guess on the signal input pin ?Is the idea to rule out the tuner part of the TV ?

author: PKTKS
author_rank: Super Contributor
timestamp: July 27, 2022, 11:07:37 am
content: Quote from: crt_cowboy on July 27, 2022, 04:50:54 amYes. The proper CRT signal generator is designed for that.All TDA3xxx accepts plain luminance CHROMA or just composite on the proper pins.Provided that you also put the synch (sand castle) it will function - maximum Vpp is on datasheet.Usually you put the composite on the direct RCA jack at first and in turns switch the generator to see the outputs.Provided the proper setup you also use this to trim the DELAY LINE ( 1L or 2L cf the chip)Still have some... very hard to find these daysPaul

author: shakalnokturn
author_rank: Super Contributor
timestamp: July 29, 2022, 06:16:33 pm
content: You haven't answered some of the questions asked that would be useful to better understanding the problem.One thing that strikes me on the photo is the blue / red skirting. Is convergencethatbad? Any chance TV has been dropped?