CurtPalme.com Home Theater Forum

Mark_A_W · Posted: Mon Jun 09, 2008 6:03 am Post subject:

Well you could have saved me the trouble!

All other issues aside, 600-900 watts will cost A LOT of money over a year...if it lasted that long.

**AnalogRocks** · Posted: Mon Jun 09, 2008 3:06 pm Post subject:

I didn't want to deny you, your do.

matze584 · Joined: 29 Oct 2007 Posts: 7 Location: Germany / Westerwald

Hi all!

As far as i know, the 1100 doesn't eat tubes because of the fast rising HV-Supply.
Most electron tubes (including CRT's) have a much higher peak anode voltage rating with the
heater cold, than with the heater on.
Basing on the knowledge and researches of a frind of mine, it's because barco drives
the SD146a quite hard to get the brightest CRT at the time the 1100 got to market.
So the tube face may get overheated by a too high beam current. This in turn results in cracked front glass.
Then, the tube sucks in the cooling fluid (whereby glycol is a more or less reasonable conductor for that high voltages)
and blows up the controlling circuits.
If you hold the contrast / brightness levels low, nothing would happen at all.

Greetings!
Matthias

secstate · Joined: 20 Mar 2006 Posts: 720

David_Web · Joined: 02 May 2007 Posts: 418 Location: Sweden

My M8000 clocks in at 290W running 1080i@96
24W in standby. Heater at around 4V IIRC and fans running at low speed.

km987654 · Posted: Sun Jun 15, 2008 10:00 am Post subject:

Sorry to take so long to respond to all your help I have been in The US for the last week and didn't check any emails.

Curt

Yes I did buy all the Ampro tubes and also the rest of the projectors. I might have a go at getting one or two of those going as they don't eat tubes. Yeah I can hear all the Ampro dooms day people now but destroyng tubes in this Barco is a real downer. As I have mentioned it's killed two tubes and looks like a third is on the way and it has only run for a few hours. By the way two of the tubes died at start up both went with a BANG!!. The latest tube problem runs for a minute or two then SNAPS and resets the PJ to the Barco start up screen.

I believ that I am using the latest EHT board but I will check that.

km987654 · Posted: Sun Jun 15, 2008 10:42 am Post subject:

km987654 · Posted: Sun Jun 22, 2008 6:16 am Post subject:

OK I have spent some time reading the specs for EHT on both the Ampro 4000g (2000) and the Barco 1100 (800-801). The result is that both the Ampro and Barco produce about the same EHT of 34KV (barco 34.7KV) the barco EHT board has a slow power up of EHT also.
So too much EHT on the barco doesn't seem to be the reason it chews tubes, unless the 700volt difference is cause and it should not be that EHT is instant on either since the barco employs a slow start up.

So why would the Ampro not destroy tubes when EHT specs are similar to the Barco that does??

**AnalogRocks** · Posted: Sun Jun 22, 2008 2:16 pm Post subject:

Interesting research. Does the barco hit you with full on voltage when the HV does kick in and does the AMpro ramp it up slower? I'm just guessing here...

TbX · Joined: 06 May 2006 Posts: 94 Location: Sweden

I think the problem is the way the LC housing is siliconed to the tube

SONY tubes have glued frontglas the glue absorbs the glycol when it is sufficient amount of glycol in the glue it will conduct the HV to find a new way to ground BLAM hole in glue vacuum in tube sucks in glycol end of tube......

//TbX

km987654 · Posted: Sun Jun 22, 2008 9:22 pm Post subject:

Tbx

Ampro holds the tube in with silicon and we don't get the same problem. You are right about glycol though I have seen this effect.

AnalogRocks

According to the barco technical data the EHT employs a slow start up but no time is given. I suppose the point here is it is not full on right away so this should not be the problem.

matze584 · Joined: 29 Oct 2007 Posts: 7 Location: Germany / Westerwald

Hi all!

Interresting, that my post is ignored in every way Wink

but never mind *g*

But nevertheless, maybe it could be better to strip
the problem down, part by part?
When does the problem occour? Directly after powering the mashine on?
Or while it is powered on allready for an undefined time?
Wich time goes by until another tube dies, after replacing it?
And may it be possible, that the strength of the beam isn't a factor too?
It could be interesting to compare the voltages betweend ampro's G1 / G2 and
Kathode-potentials against barcos values.

Greetings!!
Matthias

tse · Joined: 03 May 2006 Posts: 1014 Location: Sweatbucket, Fl.

The Ampro projector has CRT cut-off at 180V so G-2 is controlled by that. The HVPS does have a slow turn on but is less than one second. Average beam current is limited to less than or equal to 1ma. That means the tube face doesn't have to dissipate more than 34W of power (34kv x 1ma). Tube failures after prolonged running might indicate high screen power dissipation (high temperature).

Scott

km987654 · Posted: Sun Jun 22, 2008 11:44 pm Post subject:

Matthias

I hate being ignored too. I had read your post and its my lack of understanding as I thought driving the tube hard was directed at the HT value and from what I can see that is not the case its more to do with G2 values and that is something I need to research.

Tse

Most tube failures happen at start up and they go with quite a bang. Having said that the last one would give a loud SNap after running for a few minutes. That tube will not run at all now it just produces a colored light in the neck of the tube (now disconnected).

tse · Joined: 03 May 2006 Posts: 1014 Location: Sweatbucket, Fl.

Going at start-up is kinda strange. Focus voltage on these tubes is 1/4 to 1/3 the final anode voltage. Usually the focus voltage is had by dividing down the HV with resistive voltage dividers. That way the focus electrode voltage "follows" the HV as it goes up or down. How is the focus voltage made in the projectors with the tube failure problems? HV type pots or something else?

Scott

km987654 · Posted: Mon Jun 23, 2008 12:57 am Post subject:

I believe they are driven by pots on the EHT board but this is probably a good question for curt.

km987654 · Posted: Mon Jun 23, 2008 9:51 am Post subject:

Well the Barco G2 voltage is 10.9KV. I don't know the Ampro 4000 G2 Voltage. Perhaps someone else does then we can compare. On the surface though I am finding it really difficult to understand why the Barco destroys tubes.

**AnalogRocks** · Posted: Mon Jun 23, 2008 10:06 am Post subject:

I think Curt said the G2 on the ampro is only 6K volts

tse · Joined: 03 May 2006 Posts: 1014 Location: Sweatbucket, Fl.

The focus voltage is in the 6-10kV range. G-2 is less than 1000V. Those can't be changed too much. They are what they are to make the tube work correctly.

Scott

km987654 · Posted: Mon Jun 23, 2008 9:32 pm Post subject:

Is the maximum G2 voltage applied all the time no matter how G2 is adjusted or is it varyable?