Pay someone to service my B&O MX7000

whats wrong with it?

Monstermug wrote: whats wrong with it?

Well picture and sound seem unaffected which almost lull me into contining to use it, but I've decided to repatch all my systems into the LCD after the issue with the B&O appears to have worsened.

At the first the issue was a low level intermittent tick sound which was accompanied by a small flicker in a random line of the picture whenever the tick happened. Almost like a small power surge. This behaviour would occur when the set was first turned on but would die down after 5 mins or so when the set warmed up. However I noticed this fault appeared to be getting worse ie more ticks when powered on, as time went by.

A week or so later now the ticks have stopped completely but instead there is a worrying sound coming from inside the chassis. Sort of a buzzing 'Schrrrrrr' sound, again this is most apparent when the set is powered on and does subside after awhile but since, as before it appears to be getting worse, I've made the decision to simply not use it anymore incase something is about to blow. I'd imagine there could be quite some damage if one of the big caps goes and that could make repair perhaps impossible.

robotech wrote: The b&o tvs that i have had come apart nicely all small boards that are clipped together cleverly around the bottom of the tube Was easy enough to take apart and recap if you have soldered and recapped anything before Just take photos of where the interconnecting wires/plugs go between boards A lot of caps though from what i can remember Theres got to be some old tv repair shops around still that can do Crt,s if you dont want to have a go yourself

Thanks this is good to know. Perhaps I could post pics of the inside and you might like to see if you think anything is obviously amiss. My soldering is not the best but I can handle an iron. My fear would be with the increased power cycling through a CRT, a bad solder join could be a potential fire hazard? If all else fails I guess I'll have to take on the job myself but I would prefer a pro for my own piece of mind. Even if it meant a me removing the board/boards and sending somewhere

Edited by Lastmarine - 30 Nov 2019 at 8:05am

no fans in the 7000, I took one apart recently.

Hi. So I have opened up the set, you were right it is very easy. After some head scratching I worked out how to pull out the innards and open them into the servicing position. I also removed the AV board and couldn't find any faults there with caps or joints.

From the way the fault appears, I get the impression that the issue will most likely be found on the main motherboard where the power supply is located. looking over the caps that I can see it appears to my untrained eye, that the caps look okay. However to truly inspect the board properly I will need to remove it completely from the chassis. To do this I believe I need to remove the all the high voltage wires which concerns me some. is there a preferred method for removing this board and dealing with high voltage areas of these sets. I've left the set unplugged for over 24hrs. Is that sufficient to decharge any leftover volts?

here's some pics.

https://www.dropbox.com/s/gkimxjygz0anc4d/20191201_142006.jpg?dl=0
https://www.dropbox.com/s/q8aqcoxunsqoe5u/20191201_141735.jpg?dl=0
https://www.dropbox.com/s/lc7gpq0k5d3q2an/20191201_141910.jpg?dl=0
https://www.dropbox.com/s/lc7gpq0k5d3q2an/20191201_141910.jpg?dl=0
https://www.dropbox.com/s/bs3ncag1q1pn2z8/20191201_141950.jpg?dl=0
https://www.dropbox.com/s/9uf5ubbcuq6neil/20191201_142106.jpg?dl=0

Ah yes good advice. I have done so and despite it being rather a scary experience I have documented the issue on video.

Definitely seems to be coming from the main motherboard. Particularly the large red thing. I am going to assume that's a large TMR? As you can hear if you watch to the end, a worrying sparking sound suddenly starts up out what appears to be the large black power supply to the right of the TMR which I assume feeds power to the tube. I think perhaps eiher one of those might be the culprit but it could of course be something else. Perhaps you could have a watch and see if anything clicks for you?
I should add thankfully there is no smell of burning or electrical damage coming from the set but I didnt leave it on long as you can see when I panic and switch it to standby.
https://youtu.be/VQpVFonfg2k

Thanks alot Lix. I did worry that if the issue was related to the transformer there would likely be little I could do to fix it. I will certainly try and clean the area once its had some time to discharge. I found this excellent thread on the B&O forums from a while ago which talks through replacing the most likely failed components. No mentioned of the transformer though. Also shame imageshack has removed all the photos. Good idea on the lights off recording. Will try and have a go

https://archivedforum.beoworld.org/forums/t/24571.aspx

Inside the transformer is thousands of turns of hair-thin insulated copper wire, to get rectified mains voltage up to 30kV.
Over time the insulation breaks down, so I’d imagine there’s a fair possibility of arcing internally.

Edit: sadly it’s the sort of reason why folk are mad to pay lots of money for old broadcast monitors and TVs sets as they’re full of obsolete components. At least there’s a fair amount of spares around for some arcade monitors.

Edited by John Bennett - 02 Dec 2019 at 9:29am

I'm sending some Commodore branded monitors to Jan Mlotkiewicz in Coventry.

It's almost certainly arcing from the lopt as said above. If you've got an air compressor, that's probably better to use that to blow the dust out rather than a brush. Is the room damp in any way? If so then there's the possibility of HV trying to escape from a possibly slightly deteriorated anode cup on the back of the tube. Also, do you notice any problem with the focus of the picture (sharpness of the image) when you've first turned on the TV? If so then you may have a problem with the neck socket (easily replaced). That lopt appears to be of the type that doesn't have the focus or screen voltage controls on it, as such these would be elsewhere (sometimes lopts can start to crack around the focus and screen controls).

Oh my that is amazing thanks so much eggplant. I'd have never found that on my own. That could well be a life saver. Even if the issue wasnt related to that it's worth getting the part while its available still. I'll wait to see if it's the correct one.

Edited by Lastmarine - 02 Dec 2019 at 10:03pm