CurtPalme.com Home Theater Forum

nombz · Joined: 09 Mar 2006 Posts: 119 Location: Stockholm, Sweden

Hi

I have a BG1208s/2 (bought from Curt some years ago). Lately it has started to arc both "small" ones that makes the picture move just a litte (looks like just a couple of lines moves really), but also bigger one (one per movie approx) that sounds like a bang and makes the whole picture move quite a lot. After each bang everyting is back to normal.
I have used compressed air to blow all dust out, and have tried to inspect the HV lines (have not looked close to the tubes since that requires more disassembly) and cannot find any problem.

Today I tried troubleshooting a bit more. and it looks like it only affects the green tube. If I use "color select" in the adjustment menus and use only read and blue, I looked for a long time without any problem at all. I switched to only green and it didnt take long before the "small" arcs started followed by a big one. Is this even possible or is it only imagination?
I guess that all the HV lines carries the same voltage regardless of which colors I activate/deactivate? Does the option in the adjustment menus only affect the actual signal?

Any other idea on what I could look for?

/Anders

stefuel · Posted: Wed Dec 26, 2007 1:33 am Post subject:

open it up and watch it while it's running to see where the arc is coming from. A big snap should not be that hard to spot. Inspect the HV line from the supply to the splitter, the splitter it's self and the cables going from the splitter to the tubes.

Tom.W · Joined: 09 Mar 2006 Posts: 6635

Should look something like this ... Wink

http://www.youtube.com/watch?v=FY-AS13fl30&NR=1

nombz · Joined: 09 Mar 2006 Posts: 119 Location: Stockholm, Sweden

Hi, thanks for your answers.

I still would like to know if it possible that it is only when the green is used. What is switched off when I choose to only use read and blue in the adjust menu? Is the hv splitter a passive device always sending the same static HV to all tubes?

nombz · Joined: 09 Mar 2006 Posts: 119 Location: Stockholm, Sweden

A bit of an update.

I received a PM explaining that selecting colors in the menus only meant that I stop the video signal but the HV is still present on all tubes (kind of logical, but I was not sure). Thanks for that!

But, after watching moves for a long time (or at least 40 min which is much more than it should take before the first arc) with only red and blue I get no arc at all. Running only the green tube and it only takes max 10 min before the arc.

Next step is to use a borrowed camcorder to try to record if there is an arc to be seen.

I have also inspected the HV lines pretty throughly, and I must say that I cannot see any problem with them. The only strange thing is that the HV line to the blue tube has two transparent tubes (the other lines only one) around it. I dont know the reason for this, does anyone have a clue?

/Anders

nombz · Joined: 09 Mar 2006 Posts: 119 Location: Stockholm, Sweden

Okey, so now I recorded the arc.

It is seen within the green tube so it is not a HV lines issue.

In the attached picture, I have marked with a red circle where the arc can be seen.
The url is a small video where the arc can be seen (its only max 3 sec long). You can hear the pop and if you look closely where the red circle marked the spot, you can clearly see something happening.

URL to the videowww.bredbild.se/arc.wmv

Any ideas what might cause this?

Also, on the neckboard there is a green led for each. I THINK that they have something to do with AKB (or what it is called), is this correct? I notice that when I start the projector, only the green tubes green led is lit up all the time. The red and blue are sort of blinking a bit in the beginning, but the green tubes is lit up all the time. Is that a problem?

I am very grateful for any ideas and thoughts on this!

/Anders

Tom.W · Joined: 09 Mar 2006 Posts: 6635

Could be a bad neckboard or tube socket. Did you try swapping the neckboards yet ? There all the same. See if the trouble follows to another tube.

nombz · Joined: 09 Mar 2006 Posts: 119 Location: Stockholm, Sweden

No, I havent tested swapping neckboards yet.

If I swap them just to try, do I have to do any adjustments on the boards? (I know there is a couple of pots there, I think for black level etc). Or can I just swap them and see?

I got the answer from Curt on avsforum that I probably have a problem with the tube. I hope not, but I guess the only way to know is to swap the boards. Also I got the tip to clean the neckboardsocket to make sure that there is no problem there, since that is the simplest to do I will try that first.

If there is a problem with the tube, what could cause that? it is only <1000h on it (lots more on the chassis).

Tom.W · Joined: 09 Mar 2006 Posts: 6635

Here's a link...

http://www.thegleam.com/ke5fx/crt/sencrt.pdf

**Curt Palme** · Posted: Sun Dec 30, 2007 1:07 am Post subject:

Swap the neckboards, there's nothing to adjust. Make sure you don't bend a pin when putting the sockets on.

Contamination like this in a tube is indeed rare, but possible. If it is the tube, there's nothing to do but change it. you can try putting the set lenses down, and gently tapping on the neck while the set is on to see if the contamination will loosen and fall into the bottom/front of the tube, but it's unlikely that will work.

I've seen a couple of new tubes and a couple of VDC rebuilds do this, and standard CRT 20" sets used to do it once in a while when I worked at the TV shop in the 80s.

nombz · Joined: 09 Mar 2006 Posts: 119 Location: Stockholm, Sweden

Hi,

Thanks for all your input and ideas.

I started by cleaning the pins on the green tube (they were pretty oxidized actually), but that didnt help.

I tried today to swap the neckboards, and the arc stays on the same tube, so I guess I am now looking for a new tube or a Sencore device(or a new 9", but dont tell my girlfriend) Wink

Thanks!

/Anders

nombz · Joined: 09 Mar 2006 Posts: 119 Location: Stockholm, Sweden

Just wanted to report if someone else ran into this problem.

I read on another small forum that using the run-in-cycle feature that is used for new tubes might fix the problem. I ran it for 24h and the problem was still there. Ran it again for another 24 hours, and it now seems to have dissappeared. I have ran the pj for a total of maybe 10hours after the last run-in-cycle and no arc. Before this "treatment" there was an arc about 2 times during one movie (so I guess one each 45-60minutes).

Before I got the tip about this, I did pull the trigger and are now a happy owner of a 1209s (and of course the existing 1208s/2). Will keep running the 1208s to make sure that the arc problem is really gone.

Heywood Jablome · Joined: 12 Mar 2006 Posts: 1548

I've successfully saved three 9" tubes with a Sencore CR-70... a red had a G1 short (contamination) that was successfully blasted by the Sencore. (This was a red tube Chip picked up somewhere and was not run before or since, so I can't speak to whether it had a comparable failure mode.)
The other two tubes were low emission... a blue P19 from one of Chips Ampros' and a green P19 from my newish Marquee 9500.

Where are you? I'm in SE Massachusetts and would be willing to give it a try. (Need a pinout first.)

Ile · Posted: Thu May 08, 2008 7:15 pm Post subject:

I probably have similar problem in my new green p16lnn tube. It works fine few hours and then zap and convergence goes little off or pj turns off.

Newer happened when looked inside projector so I thought it is bad HV cable. Chanced it yesterday and if it doesn't help I try run in cycles...