Barco data 808s static hv arcing

dkhudson · 26-07-2009, 10:17 AM

I have a Barco 808s that runs well, despite a bit of tube burn on the green.

Recently it has developed a worrying fault. After running for at least 30mins there is a 'crack' noise and a flash of light from within the casing.

At first I though I'd imagined it, as I only saw the flash from the rear of the machine in my peripheral vision as I was watching the screen. Since then it has done it a couple more times, with the flash visible from the front opening around the CRTs.

Otherwise and despite this the machine runs perfectly.

I have opened the casing and can see no scarring or evidence of HV discharge. That said, with the area of earthed aluminium shell, to take up any lightning strike, I'm not sure there would be a mark.

Given that the HV/UHT feed is clipped to the side shell, I image that this is the beginning of insulation break down, or some other HV/UHT drive fault.

Any suggestions?
Anybody had anything similar?
Any ideas on repairs?

It is normal to hear a little bit of static on any CRT device, but this is a bit extreme...

I have switched it off for now, which is anoying as I recently re-did the convergence/colour balance and it was looking superb!

Barco Data 808s IRIS2
year 1998
R 9002032
s/n 1119215

David

Durham - United Kingdom

Roland @ B4 · 26-07-2009, 3:27 PM

It always sounds and looks more scary than it really is.
First thing I would do is disconnect the HT cable for one tube at a time to isolate which one it is.
I've tried cleaning some of the dust off in the past with doubtfull effects.
Some people have success by sliding heat shink up to the base of the tube. Others have used extra silcon (Make sure you leave week to dry because there is a lot of fluid to come out of most silicons)

Tom.W · 28-07-2009, 8:48 AM

Quote:

Originally Posted by Roland @ B4

It always sounds and looks more scary than it really is.
First thing I would do is disconnect the HT cable for one tube at a time to isolate which one it is.
I've tried cleaning some of the dust off in the past with doubtfull effects.
Some people have success by sliding heat shink up to the base of the tube. Others have used extra silcon (Make sure you leave week to dry because there is a lot of fluid to come out of most silicons)

Disconnect one tube at a time from the HV splitter not from the tube.

Can you open the CRT compartment and see any high voltage arcs ?

dkhudson · 28-07-2009, 6:36 PM

Quote:

Originally Posted by Tom.W

Disconnect one tube at a time from the HV splitter not from the tube.

Can you open the CRT compartment and see any high voltage arcs ?

Thank you Tom and Roland.

The arcing is very occasional (maybe once per hour), so I will have to run and watch the machine for a long time... I haven't run it with the cover open yet.

But your logic has given me a clue, one of the arc flashes definitely was seen through the rear ventilation grille and another from the front aperture. The only HV cable in both front CRT and rear compartments is the feed cable from the HV source to the HV splitter. So I'd guess that is the culprit.

The cable in question appears to be bonded/potted into to the HV source, so is this a case of over coating it with shrink wrap, or do I go on a parts search for a new HV supply?

Yours,

David

Tom.W · 28-07-2009, 7:17 PM

Sounds like a bad quadrupler or EHT module or splitter but if you saw the arc from the rear I would say it is most likely the quad. Start looking for a spare before a complete failure occurs.

The quad cannot be repaired but if you have arcing from the high voltage cable to chassis try some RTV silicone on the location of the arc but let it dry for several days as Roland pointed out.