Mulja tv repair portal
Equipment Repairs => CRT TV forum => Topic started by: malcolmturnbull on July 30, 2012,18:12:42
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Hi All,
I recently purchased this working Grundig M70 390/90 TV but when I got it home it did not work. I am not sure if there is something broken or if it requires advanced tuning from a service menu (I am not able to find yet).
When switched on the TV displays a black screen with fine scrolling red/green/blue lines that fill the top 3/4 of the screen. When I connect up a source (satellite TV tuner) to the SCART connection it appears as a thin bright white line in the centre of the screen - the TV detects the device as the "PAL" signal is displayed on the front panel when it completely boots up.
When I connect up a coax antenna to the TV I can hear TV stations but get no image. Likewise when I connect a coax to a VHS player I get sound via the VHS TV tuner but no picture. Strangely though I do not get sound from video playback.
I have tried the fine tuning, PAL/NTSC settings and also had a look inside for any manual tuning pots - there were none.
I was fortunate enough to get the original manual in excellent condition. I've followed the tuning guide in the manual with no success. I also have the remote but I am not sure if all buttons are working.
The TV was handled with care from the moment I picked it up to placing it on my bench at home. The first time I turned it on there was some crackling, I thought this was normal when a TV is moved and dust is displaced to other areas. Since that first time it does not crackle when switched on.
Here is a link to the display I am getting and a description of each picture.
http://imageshack.us/g/694/photogcg.jpg/
They are not in the order I wanted. Here is a brief description of each.
1 & 4) Are duplicates of a close up when the AV SCART source is on. (the middle white line)
2) Close up of the red/green/blue lines when the TV is switched on
3) Wide shot of the TV when first switched on
5) Wide shot of TV when the AV SCART source is on (note the white line in the middle and the PAL display)
I can see some image display of when I switch between PAL/NTSC it appears to be looping in the bottom half of the screen.
Any help will be appreciated.
Thanks.
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hello malcolm, does the white line go straight a cross the screen if so, this is a field collapse which may be down to ceramic capacitor that's either got slight bulged or a split underneath i'll try and dig some info for you.
regards
shaun
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Hi Shaun,
Thanks for taking time to reply, I really appreciate it.
Yes it does go right across the screen as shown in this picture:
http://imageshack.us/photo/my-images/221/photo4up.jpg/
When the satellite tuner is switched of it is gone as show in this picture:
http://imageshack.us/photo/my-images/23/photo2fsk.jpg/
Regards,
malcolm.
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yes it's a field collaspe i'll check some notes that's if i've still got them and get back to you
regards
shaun
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right malcolm check these parts C507 100UF IC550 TDA8140 LINE FREQ, if you get stuck get back to me good luck
regards
shaun
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Hi Shaun,
Thanks for the guidance on this. I managed to find a schematic diagram of the CUC3800 chassis online, with this I was able to locate the parts quite easily. Visibly all the parts look fine. The circuit board slides out and I was able to view them from underneath. All looked ok except for TDA8140 which was all brown coloured at all soldered points. I'll get a photo of this after work and post it. I am going to get my hands on a multimeter tomorrow and perform some further testing.
regards,
Malcolm.
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great stuff, i've just been given an bush dvd/tv combi 11ak46 chassis, it's dead just opened the back blown psu so i'll be busy for a couple of days
regards
shaun :sign0098: