Pay someone to service my BO MX7000

[Lastmarine]

Hi. I have spray duster if that's the same thing? The tv is situated in a garden cabin. The room is built with 50mm thick siberian larch and a further 40mm of insulated plasterboard. However there is obviously no central heating so I have electric heaters inside. While they are set to come on at 5 degrees to avoid antifreeze obviously it's not as good as inside the house. I haven't noticed any moisture however it may well be coincidence but obviously the issue has only occured since it's been in the cabin?

My plan going forward was to completely remove the main board and do a proper check over of caps and joints. Especially if this LOPT mentioned by Eggplant turns out to be a fit. I'd like to recap the set anyway.
I wanted to ask you guys advice on removal of the LOPT. I've never removed one. To discharge should I use a decharging rod that's sent to earth somewhere? I dont own one but can buy one. I was gonna check first but I wasnt sure if leaving the set unplugged for 24hrs plus, would do that job sufficiently? Also how do you even remove the wires? I've seen a guide on removal from the tube but there is a second feed going into the gun which looks a fiddle to remove. Can I just unplug the two wires direct from the transformer?

Oh and to answer your other question. No haven't seen any issue with focus. As I said originally, the image and sound seem unaffected and as good as ever. Apart from that slight picture flicker that accompanied the tick sound on random lines of picture when this fault first began. Like a small power surge.

 

[Lastmarine]

Hi Barry. Not sure on pins in the neck. If theres any way the tube can be salvage I'd definitely be up for it. I hate to see these old CRTs especially quality ones like the B&O go in landfill. Such a shame no one wants to repair them anymore cos of cost. We all know how great CRTs are. I wish the general public could look beyond size and weight of the things.

 

[Lastmarine]

Also thanks so much for all your help everyone really appreciate it.

 

[eggplantUK]

Hi. I have spray duster if that's the same thing?

Compressed air is effectively the same, usually not as high pressure and you have to be a bit more cautious about it freezing and blasting liquid over electronics. Don't use long blasts and keep it upright.

To discharge should I use a decharging rod that's sent to earth somewhere?

God, no! The TV should be unplugged, not earthed. Use a HT probe (or the TV tech's old trick, two screwdrivers) clipped to metal on the chassis and shove it under the anode cap. Just be very careful not to touch anything as you're doing it. Leave one hand outside the set if you're unsure. A probe is insanely expensive.

I was gonna check first but I wasnt sure if leaving the set unplugged for 24hrs plus, would do that job sufficiently?

Absolutely not. It's a huge capacitor with the ability to recharge. It's possible it has a self-discharge and nothing will happen - but it's also possible it isn't functioning.

Also how do you even remove the wires?

Unclip the anode cap then pull the neck board off. Unclip the focus wire on the CRT socket and desolder.

https://www.youtube.com/watch?v=3vBBteGF0Nk

 

[Lastmarine]

Cheers for all the info. Replacing that LOPT does look like a job for someone with more experience than me. I'd give it a go but I'd worry a bad solder join on any of those many connections could be a real hazard. Soldering on the Gun board looks a little skillful too which isnt me.
Im sure I can at least get it off the board though

 

[Lastmarine]

Hi Guys.

Just wanted to say that I haven't electricuted myself removing the LOPT

.
I'm still here, Just awaiting some tools before i take on the work.
Haven't heard anything back from the various people I contacted
regarding service the B&O. Even tried the Instagram Guy RetroRestorationUK as you suggested RIchard May, but alas no response. I guess he is overcome with work. However after some diliberation I have decided to take on the work myself. After totting up the cost of recapping the boards and the new LOP, it really would have been just to dear to make it worthwhile paying an engineer to service the set also, especially considering postage costs.

I found this excellent post over at the B&O forums which indicates how to service and more imporantly which caps need replacing on the the MX range of sets to illiminate 98% of issues. I've put together a shopping list of parts via Donberg. However I have a couple of questions I was hoping someone with some better knowledge of circuitry might be able to help me with.

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

Firstly I am unable to find a couple of the exact caps listed on that thread on donberg. Namely C31: 1x 47uF 63V. Could I use a higher voltage or uF as a substitute if the exact same cap cannot be located ie in place of the above 47uf 63v could a 50uf 63v, or 47uf 70v for example be used?

Also can someone help me understand the difference in labelling on caps? for example if I search for a 50uF 50v cap, I am presented with 50V, 50VR, 50VA, 50VH, 50VRHT, 50VARHT. I gather that VA and VR refer to either Axial or Radial ie the alignment of the pins, and obivously V refers to the voltage, but what is VH, VRHT, VARHT etc.

Much thanks for explaing what is probably the most basic of engineering theory. I am really a novice with this.

 

[John Bennett]

A higher voltage rating is fine, just watch for the dimensions (although always check that as caps are often smaller than they used to be).

Capacitance... close and never smaller is a fair rule-of-thumb. So 50uF is fine for 47uF. These are supply buffer capacitors rather than part of something like a precision RC oscillator.

The letters will be manufacturer specific. I'd say anything goes for a TV - it'll be things like extended temperature ranges, which you won't need, but do no harm.

 

[Lastmarine]

Thanks loads that's very helpful.

 

[Monstermug]

Doesn't grant fix commercial tv sets?

 

[thegreathopper]

I don’t think so, there is a B&O dealer down in Hove who repairs new TV,s the avant and horizon, he has worked on B&O for 20 years or more and used to fix the MX tv’s... may be worth a try.