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tse
Joined: 03 May 2006
Posts: 1014
Location: Sweatbucket, Fl.
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| Posted: Tue Jun 24, 2008 12:00 am Post subject: |
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The G-2 voltage stays constant. It is set so that when the cathode and G-1 voltages are at a certain voltage difference the tube begins to conduct. Projection tubes are usually at 180V difference at this point or what is known as "cut-off".
Scott
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km987654
Joined: 25 Jul 2007
Posts: 2874
Location: Australia
TV/Projector: Barco BG809s
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| Posted: Tue Jun 24, 2008 12:38 am Post subject: |
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Would it be possible to reduce the G2 voltage applied to the Barco tubes to 6KV or 7KV similar to the Ampro.
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tse
Joined: 03 May 2006
Posts: 1014
Location: Sweatbucket, Fl.
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| Posted: Tue Jun 24, 2008 12:55 am Post subject: |
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The G-2 voltage is determined by the tube characteristics and the difference between cathode and G-1 with "black" input. It is about +500 to +900V. The focus voltage is determined by the tube characteristics and the final anode voltage. With the final anode voltage at +34kv the focus voltage will be about +6kv to +10kv. It can't really be anything else.
Scott
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km987654
Joined: 25 Jul 2007
Posts: 2874
Location: Australia
TV/Projector: Barco BG809s
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| Posted: Tue Jun 24, 2008 2:31 am Post subject: |
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In this case the tubes in both PJs are SD146A so if 7KV G2 value works in the Ampro I should be able to drop the Barco G2 value from 10.9KV to 7KV via the EHT. Curt seems to think this might cause focus problems though.
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km987654
Joined: 25 Jul 2007
Posts: 2874
Location: Australia
TV/Projector: Barco BG809s
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| Posted: Tue Sep 02, 2008 10:49 pm Post subject: |
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I am leaning towards the fact that EHT is not the issue with SD146A tubes. I have had a number of these fail and on close observation the problem is always associated with the way the lense is glued to the tube bell. It really looks like glycol finds its way through the silicon sealant to the glue and the glue is affected by the glycol which eventually allows air into the tube causing the tube to fail.
Ampro 4000 uses the same tube without destroying anywhere near as many. All EHT voltages on the Ampro appear to be the same as those that Barco uses so it seems this is not likely the problem. Ampro Tanks are not as deep as Barco tanks so it would be more difficult for Glycol to finds its way to the glue and I believe this explains why tubes fail less in Ampros.
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Z-Photo
Joined: 07 Mar 2006
Posts: 2749
Location: Huntsville - Alabama
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| Posted: Wed Sep 03, 2008 5:51 pm Post subject: |
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| AnalogRocks wrote: | | km987654 wrote: | | That makes plenty of sense. Has anyone tried or am I a pioneer. Also Analog Rocks how is your Ampro 4000g does it throw a good image? Does it chew tubes? |
The tubes in my Ampro are minty white. I can never keep a HVPS in their long enuff to put any wear on them. 
No the Ampro 4000 doesn't power up like that. It brings up the fans, then the CPU, does an onboard diagnostic then brings up the HV about 10 seconds later.
It throws an amazing image. I had 1080i dialed in from the HDFury, through the Extron running Chronicles of Riddic. It looked great! Then 2 hours latter the HV PS blew again. |
Typical Ampro
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The Only GOOD AMPRO - is a Dead AMPRO.
wait - are they not all DEAD already?
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stefuel
Joined: 07 Mar 2006
Posts: 3353
Location: Green Harbor MA USA
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| Posted: Thu Sep 04, 2008 10:49 am Post subject: |
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| Z-Photo wrote: | | AnalogRocks wrote: | | km987654 wrote: | | That makes plenty of sense. Has anyone tried or am I a pioneer. Also Analog Rocks how is your Ampro 4000g does it throw a good image? Does it chew tubes? |
The tubes in my Ampro are minty white. I can never keep a HVPS in their long enuff to put any wear on them.
No the Ampro 4000 doesn't power up like that. It brings up the fans, then the CPU, does an onboard diagnostic then brings up the HV about 10 seconds later.
It throws an amazing image. I had 1080i dialed in from the HDFury, through the Extron running Chronicles of Riddic. It looked great! Then 2 hours latter the HV PS blew again. |
Typical Ampro |
It's Alive. Just when you thought it was safe to go back into the water
I knew if I busted your balls it would smoke you out. Something about "pushing a Barco out a second story window onto a un-suspecting passer by" 
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Chip
A Barco is only a AmPro with training wheels
Card carrying member of the AVS chain gang.
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Z-Photo
Joined: 07 Mar 2006
Posts: 2749
Location: Huntsville - Alabama
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| Posted: Thu Sep 04, 2008 1:32 pm Post subject: |
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Since I have not had any issues with my Barcos (for the last 2 years) I have not had to post much lately..
The retro is even kid proof- my 6 year old can use it. I have never heard of any Ampro being that user friendly (unlesss electrocuting the owner counts).
Pete
Card carrying member of the HE-MAN AMPRO HATERS CLUB
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The Only GOOD AMPRO - is a Dead AMPRO.
wait - are they not all DEAD already?
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AnalogRocks
Forum Moderator
Joined: 08 Mar 2006
Posts: 26706
Location: Toronto, Ontario, Canada
TV/Projector: Sony 1252Q, AMPRO 4000G
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| Posted: Fri Sep 05, 2008 12:41 am Post subject: |
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| Z-Photo wrote: | | AnalogRocks wrote: | | km987654 wrote: | | That makes plenty of sense. Has anyone tried or am I a pioneer. Also Analog Rocks how is your Ampro 4000g does it throw a good image? Does it chew tubes? |
The tubes in my Ampro are minty white. I can never keep a HVPS in their long enuff to put any wear on them.
No the Ampro 4000 doesn't power up like that. It brings up the fans, then the CPU, does an onboard diagnostic then brings up the HV about 10 seconds later.
It throws an amazing image. I had 1080i dialed in from the HDFury, through the Extron running Chronicles of Riddic. It looked great! Then 2 hours latter the HV PS blew again. |
Typical Ampro |
That I do agree with 
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km987654
Joined: 25 Jul 2007
Posts: 2874
Location: Australia
TV/Projector: Barco BG809s
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| Posted: Fri Sep 05, 2008 6:40 am Post subject: |
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You guys get side tracked easily. This was not really about Barco or Ampro but rather the tubes. While we are on this though of all tubes I have and I have quite a few almost all that were from Barco have failed and almost all from Ampro have not. I am a Barco owner not and Ampro owner. So Ampro may have many problems but chewing tubes doesn't seem to be one of them.
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AnalogRocks
Forum Moderator
Joined: 08 Mar 2006
Posts: 26706
Location: Toronto, Ontario, Canada
TV/Projector: Sony 1252Q, AMPRO 4000G
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| Posted: Fri Sep 05, 2008 6:42 am Post subject: |
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| km987654 wrote: | | You guys get side tracked easily. This was not really about Barco or Ampro but rather the tubes. While we are on this though of all tubes I have and I have quite a few almost all that were from Barco have failed and almost all from Ampro have not. I am a Barco owner not and Ampro owner. So Ampro may have many problems but chewing tubes doesn't seem to be one of them. |
Side tracked? Us?! Puhh-leeezeee.
Yeah it's strange how the old Barco's eat tubes. I was going to buy a couple of the old 1100's for fun but then one of the tubes cracked. Too bad. These SD146 tubes put out a decent picture on a 9-10 foot wide screen.
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km987654
Joined: 25 Jul 2007
Posts: 2874
Location: Australia
TV/Projector: Barco BG809s
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| Posted: Fri Sep 05, 2008 8:39 am Post subject: |
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Side tracked definitely and your speeding down a road that is a dead end!!!!
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Tom.W
Joined: 09 Mar 2006
Posts: 6635
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| Posted: Fri Sep 05, 2008 11:49 am Post subject: |
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| km987654 wrote: | | Side tracked definitely and your speeding down a road that is a dead end!!!! |
So were back to talking about Ampros...
They don't live long enough to go through a nice set of tubes.
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garylm
Joined: 28 Feb 2009
Posts: 7
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| Posted: Mon Mar 30, 2009 5:21 am Post subject: |
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| km987654 wrote: | | I am leaning towards the fact that EHT is not the issue with SD146A tubes. I have had a number of these fail and on close observation the problem is always associated with the way the lens is glued to the tube bell. It really looks like glycol finds its way through the silicon sealant to the glue and the glue is affected by the glycol which eventually allows air into the tube causing the tube to fail. |
I just did an autopsy on my blown red tube and it appears that the implosion occurred through the glue that joins the tube to the face.
I cut through the silicone and separated the glycol coupler jacket from the tube. Then I scraped the silicone clean from the tube. I was surprised at how thin the silicone bead was in places. In some places the glue layer was wet with glycol. The glue that had come in contact with the glycol had a pasty consistency, and I could put a dent in it with my fingernail. The caulking around the face of the tube actually covered the glue layer, so that you could not tell whether the glue was in contact with glycol.
The replacement red tube that I received last week had a glycol leak, and feeling brave, I cut into the silicone on the new tube. The bead was thin on this tube as well, and it covered the glue layer. As I peeled the silicone away, I discovered several places where the glue was wet and pasty with glycol.
I decided that I would prefer to know that there was a glycol leak before the glycol spent any time in contact with the glue. It doesn't make sense to seal the tube in a manner that the glue layer cannot be inspected. So I re-caulked the new tube so that the caulking does not cover the glue layer. The seal seems to be holding fine so far.
Now it looks like I've got fungus starting in the glycol jacket on my green tube. I'm looking forward to re-caulking that one as well. Maybe these tubes will last forever if I can just keep glycol and glue apart.
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km987654
Joined: 25 Jul 2007
Posts: 2874
Location: Australia
TV/Projector: Barco BG809s
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| Posted: Mon Mar 30, 2009 7:00 am Post subject: |
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What I ended up doing was to place a spacer between the face of the tube and the LC tank. The spacer is a plastic washer cut into 4 this leaves a gap that allows silicon to set in, it also causes the glue layer to be raised out of the glycol. This came from Ampro.
Barco mounted the tube with almost no silicon between the face of the tube and the LC tank which is a leak just waiting to happen.
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