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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc. |
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5th Dec 2013, 10:30 pm | #21 |
Dekatron
Join Date: Aug 2013
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Re: Crackling Inside Beovision 7802
Yes outside but I was meaning the DAG coating on the inside of the glass where it connects with the Final anode socket. The thought was that too much current there could damage the joint where the anode connector and DAG meet. It was only painted over and would be a thin film.
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5th Dec 2013, 11:02 pm | #22 |
Dekatron
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Re: Crackling Inside Beovision 7802
I was replying to Okto, but I suppose a large CRT could hold quite a bit of energy. I've also discharged them with a short, but it has never caused any damage.
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5th Dec 2013, 11:18 pm | #23 |
Dekatron
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Re: Crackling Inside Beovision 7802
Sorry, I thought you were replying to me.
It is one of those things that may never happen, it was just classed as best practice where I was. |
5th Dec 2013, 11:30 pm | #24 |
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Re: Crackling Inside Beovision 7802
I think you're right, using abrasive polish on the screen is likely to make it worse. So it will just have to stay.
As for the switches, both my sets (Beovision 9000 and 7802) are now permanently stuck in the on position. Maybe I'll try to replace them some time (although difficult to change doesn't sound so good). I'm currently not sure if I can get a new switch anywhere anyway, and it isn't essential. The only remaining problem with this set is a puzzling buzzing from the speakers/headphones. With the speakers it's there, but subtle enough I don't mind it. With the headphones, it's very annoying and seems louder. I've tried it with nothing attached to the aerial and scart socket, I've tried unplugging everything else on the circuit, and nothing has changed it. Adjusting the volume doesn't affect it either. I can only guess it's something the TV is doing itself, but it shouldn't be. Anyway, thank you to everyone for your advice. |
6th Dec 2013, 2:13 am | #25 |
Dekatron
Join Date: Dec 2007
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Re: Crackling Inside Beovision 7802
It is indeed best practice to use a resistor, but as long as you don't discharge the tube tens of times the damage to the inner conductive layer is probably minimal to none.
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6th Dec 2013, 11:25 am | #26 |
Dekatron
Join Date: Apr 2005
Location: North Wales, UK.
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Re: Crackling Inside Beovision 7802
Hi
I hold my hand up to using the 'two screwdriver' method of discharge - at least you know it can't bite any more! There shouldn't be a buzzing - check the internal wiring hasn't been disturbed, especially the scan coil leads. It could be a capacitor but somehow I doubt it. Ideally the mains switch should be replaced, but ulike the Philips ones which used to arc and cause a hazard, in my experience these suffered from mechanical failure which resulted in them being permanently 'on'. Perhaps a B&O expert (hi Tim) could comment? Glyn |
6th Dec 2013, 11:43 am | #27 |
Nonode
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Location: Surbiton, SW London, UK.
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Re: Crackling Inside Beovision 7802
B&O's reputation was seriously harmed when the insulating material used (srbp) for the line scan coils on the tube actually caught fire causing a number of fires and a death.
The solution was to remove a pin and its wire and sleeve it. If the material had been glassfibre (for a few more pence) this would not have happened. |
6th Dec 2013, 12:53 pm | #28 |
Heptode
Join Date: Mar 2011
Location: Dorset, UK.
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Re: Crackling Inside Beovision 7802
Seen a few charred scan coil PCB's but luckily no major fires. The field service guys, as part of company policy, would either resolder the connections if board not showing signs of heat or we would just simply fit a new set of coils and bill back to B&O. But more often or not, the Mullard/Philips scan coil assemblies on these sets would hum badly due to a detached ferrite yoke. Many of these were replaced under warranty with a different scan coil assembly (I think probably ITT). At its peak we were typically changing five to ten scan coils a week.
Mains switches were a regular PITA, even the correct B&O replacements did not last long and this must have cost B&O dear since the majority were replaced under warranty. Two main problems were; broken latch mechanism and contacts welding in the on position. This points to the wrong contact material being used or excessive turn on surge current. On my own B&O, knowing the problems, the mains switch was never turned off. Instead it was switched to standby and turned off at the wall socket, reasoning being it was cheaper to replace the wall socket! Well this method worked fine for over 25 years until the tube failed, but the socket is still working fine. Cheers Rich
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6th Dec 2013, 9:55 pm | #29 | |
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Re: Crackling Inside Beovision 7802
Quote:
As for capacitors, I'm wondering why not suspect them as they should be pretty old by now? |
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8th Dec 2013, 12:45 pm | #30 | |
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Re: Crackling Inside Beovision 7802
Quote:
I'm not sure how to solve this, so it might be the end of the TV. I'll have to investigate more, but not a lot has turned up so far. Any advice would be very welcome? |
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8th Dec 2013, 1:51 pm | #31 |
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Re: Crackling Inside Beovision 7802
Ok, after a bit of googling, puzzling at some Danish, and a cup of coffee later I have found a new EHT cable that I believe is the correct replacement part:
http://www.donberg.ie/catalogue/line...s/hr_1689.html I don't want to use silicone tape as some sites suggest, that just doesn't sound safe. However, I'm not too sure where to start with the process of replacing it. I can do the anode cap, but the rest (the destination of the other two cables) is a mystery for now. I should have a good clear idea what I'm doing before starting. |
8th Dec 2013, 2:14 pm | #32 |
Dekatron
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Re: Crackling Inside Beovision 7802
Hello,
Here are some pictures from a very similar Beovision 8800 (type 3312) 26" set. Is your TV like this? Regards, Dazzlevision |
8th Dec 2013, 2:19 pm | #33 |
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Re: Crackling Inside Beovision 7802
Hi, thank you. These pictures are very similar. The notable parts appear identical, which are the anode cap, the resistor box and the two cables coming out of it. I believe one is for focus and the other I assume is the high voltage supply. My technical problem is not knowing quite where they go and how they're attached.
Last edited by AC/HL; 8th Dec 2013 at 2:25 pm. Reason: Unnecessary quote of the entire previous post removed |
8th Dec 2013, 2:42 pm | #34 |
Dekatron
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Re: Crackling Inside Beovision 7802
If it arcs, the TV set is obviously working, if it wouldn't work at all there wouldn't be any arcing. What are the symptoms?
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8th Dec 2013, 3:21 pm | #35 |
Octode
Join Date: Jul 2011
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Re: Crackling Inside Beovision 7802
The EHT cable assembly goes back to the high voltage transformer where it is "held" by turning a sort of locking collar on the transformer itself. The focus feed goes to the focus control. Whether the part you have found from Donberg includes the correct connectors at the ends of the wires is not made clear but they could be removed from the old one.
This problem, apart from the well known dry joints in the IF can, is probaby this series of chassis' worst vice.
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8th Dec 2013, 3:26 pm | #36 |
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Re: Crackling Inside Beovision 7802
Ok, to be clear I mean there's no picture or sound. When I plug it in the set is in standby mode and this seems normal, but when I wake it up with the remote there's an arc from the resistor box to the coating on the back of the tube, then it pauses and does it again. I turned it off pretty fast and tried again a while later, but the same happened again.
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8th Dec 2013, 3:38 pm | #37 |
Octode
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Re: Crackling Inside Beovision 7802
Sounds like the EHT cable/resistor assembly has finally broken down then. As a test, you could always try the cable assembly from the other set if you wanted, as far as I recall they are identical unless they did longer or shorter ones for different tube sizes, though electrically they would be identical.
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Robert |
8th Dec 2013, 3:42 pm | #38 | |
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Re: Crackling Inside Beovision 7802
Quote:
Also, thank you to you and everyone for the advice. It's helping me form a better idea what is going on here. |
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8th Dec 2013, 3:54 pm | #39 |
Octode
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Re: Crackling Inside Beovision 7802
No special tools needed, just common sense about working with high voltages.
The cable(s) push down tube(s) in the high voltage transformer and there is a locking assembly at the mouth of the tube which can be turned about 90 degrees to clamp the cable in place.
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Robert |
8th Dec 2013, 5:48 pm | #40 |
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Re: Crackling Inside Beovision 7802
Thank you, this sounds manageable enough so far. I've sent an order for the EHT cable and will see what happens when it gets here.
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