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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc. |
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13th Mar 2024, 7:13 pm | #1 |
Dekatron
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 7,444
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B & O MX4000 CTV dead.
Arrived in the workshop yesterday a Bang and Olufsen MX4000 colour TV receiver.
To use the term dead isn't exactly true because an AM radio set nearby is reacting is to one of the power supplies in the B & O. No point any attempt to carry out repairs without service information. Set was made in 1992. Any ideas would be appreciated. DFWB. |
13th Mar 2024, 7:21 pm | #2 |
Octode
Join Date: Jul 2011
Location: Stockport, Greater Manchester
Posts: 1,208
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Re: B & O MX4000 CTV dead.
Quite a complex chassis used in a number of sets using the "45AX" series of tubes. Several densely packed PCB's on a rather fragile plastic frame. Will be a bit "toasted" by now in the small cabinet space. Dry joints and expiring capacitors!
Service data not on here but can be found at https://elektrotanya.com/bang_olufse.../download.html
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Robert |
13th Mar 2024, 7:24 pm | #3 |
Octode
Join Date: Jul 2011
Location: Stockport, Greater Manchester
Posts: 1,208
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Re: B & O MX4000 CTV dead.
If I am not mistaken this chassis does not have an main on-off switch. Just a LED that should either glow red in standby or green when the set is "on"
Page 2-15 for power supply diagram. Need a PDF reader that can rotate, the latest Acrobat one charges for this feature!
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Robert Last edited by bobbyball; 13th Mar 2024 at 7:34 pm. Reason: More informatiom |
13th Mar 2024, 11:00 pm | #4 |
Dekatron
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
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Re: B & O MX4000 CTV dead.
Hi Robert,
many thanks for the link to the Electrotanya.com website. I've successfully downloaded all the contents of the service manual. It certainly is a complex receiver. Time to do reading up before any serious servicing begins. Best regards, David. |
14th Mar 2024, 12:08 am | #5 |
Dekatron
Join Date: Aug 2006
Location: Madrid, Spain / Wirral, UK
Posts: 7,484
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Re: B & O MX4000 CTV dead.
Do you have the remote? If not all bets are off!
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Regards, Ben. |
14th Mar 2024, 9:28 am | #6 |
Octode
Join Date: Jul 2011
Location: Stockport, Greater Manchester
Posts: 1,208
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Re: B & O MX4000 CTV dead.
Ahh the remote, yes you will need that. Beolink 1000. If I recall (all my sets are in storage), when plugged in the "standby "LED should glow red. There is a hidden button which when pressed should bring the set on - LED turns green. As Ben says you need the remote to do anything further! Can't remember where the "hidden button" is on the 4000 but I think it is next to the headphone socket.
A lot of these sets have tired tubes now, made worse by having been run at high brightness due to the "contrast screen" at the front. There is a parallel here with that KB set from the 60's, was it called a "Deep Scene" or something like....
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Robert |
14th Mar 2024, 10:46 am | #7 |
Heptode
Join Date: May 2006
Location: Accrington, Lancashire, UK.
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Re: B & O MX4000 CTV dead.
Yes, off topic, sorry. I had a KB. Rotary UHF and the knob was illuminated red, very reliable.
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14th Mar 2024, 10:54 am | #8 |
Octode
Join Date: Feb 2007
Location: Harrow, London, UK.
Posts: 1,483
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Re: B & O MX4000 CTV dead.
Scart socket Pin 8 high "AV" works on my 4300which will get around which channel was programmed in by the user when first switched on. Otherwise, it's a screen full of noise on my set.
The sets do give a good picture and sound but, the dark filter makes the CRT work hard for its life. Chris |
14th Mar 2024, 7:45 pm | #9 |
Dekatron
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 7,444
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Re: B & O MX4000 CTV dead.
Will ask the owner of the set to bring the remote control handset to the workshop. It's pointless attempting to do any service work without it.
The attachment shows the compact chassis. DFWB. |
14th Mar 2024, 8:16 pm | #10 |
Octode
Join Date: Jul 2011
Location: Stockport, Greater Manchester
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Re: B & O MX4000 CTV dead.
Look at that for a "compact" chassis! Beware as the plastic frames and supports will have gone brittle - ask me how I know that!
Set has on-screen menus (when it is up and working!)
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Robert |
15th Mar 2024, 1:16 am | #11 |
Heptode
Join Date: Jan 2007
Location: Luton, Bedfordshire, UK.
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Re: B & O MX4000 CTV dead.
Check capacitors, especially if this model uses any of those plastic-encased ones, or the gold-coloured Roederstein (ROE) caps. They all had a nasty habit of failing short.
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Regards, John Last edited by John123; 15th Mar 2024 at 1:20 am. Reason: Pictures added for reference |
15th Mar 2024, 8:15 am | #12 | |
Pentode
Join Date: Sep 2018
Location: Devon, UK.
Posts: 151
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Re: B & O MX4000 CTV dead.
Quote:
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15th Mar 2024, 6:55 pm | #13 |
Pentode
Join Date: Oct 2016
Location: Near Coventry, West Midlands, UK.
Posts: 183
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Re: B & O MX4000 CTV dead.
These are indeed sophisticated designs.Still capable of good performance.
The 'tubes (Philips)were generally long lived,except where users insisted on overcoming the factory settings to make the picture brighter,overcoming the purpose of the contrast screen! The screen on these and most B&O tv's is designed to reduce the glare from conventional picture's,and works well.B&O also used a monitoring circuit to auto adjust the levels to compensate for crt wear during the life of the set,again defeated by users tinkering,bah humbug. The power supply runs continually when the set is connected to power,but at a very low level,ramping up with demand,say when switched to Tv mode. The set can also be used in Audio only mode as an amplifier only (with power supply at lower power),as a component of B&O's "link" system concept. Allway's repairable in my experience! Nick Last edited by Max Ripple; 15th Mar 2024 at 6:56 pm. Reason: typo |