CurtPalme.com Home Theater Forum

jbltecnicspro · Joined: 23 Apr 2016 Posts: 512

Since I still have the two monsters living in the basement, can a G70 power up with just one tube connected? For grins, I would like to rebuild one of the non-working G70's I have.

I was thinking about moving my working G70's PA board and Deflection board (E board?) into the non working set and going from there. I only have one full set of tubes though, so I don't want to be careless. I was hoping that I could hook up my burned blue tube just to see that it fires up like it should before I start moving everything else over. Thoughts?

**Curt Palme** · Posted: Sat May 06, 2017 3:11 am Post subject:

THe main deflection yoke needs to be connected to the set even if you take the tubes out. the rest can stay disconnected.

jbltecnicspro · Joined: 23 Apr 2016 Posts: 512

Thanks Curt!

Another question! The installer manual states that the ventilation holes need to be 12 inches from floor or ceiling. I plan on mounting this beast to my ceiling with the mount more or less flush against the ceiling. Is that enough room, or do I need to lower it?

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

Do what the manual says. If you can't manage 12 inches of spacing, you need to provide for a means to enhance cooling. That usually means to install some fans as part of your mounting system.

jbltecnicspro · Joined: 23 Apr 2016 Posts: 512

**Curt Palme** · Posted: Sat May 20, 2017 3:11 pm Post subject:

Since airflow is front to back on these, I can't see why you can't have it butted right up to the ceiling. Me, I don't read manuals. Very Happy

Seriously though, virtually all CRT projectors in a typical home are flush to the ceiling, with no issues.

AFryia · Posted: Fri May 26, 2017 1:45 am Post subject:

6 years tight to the ceiling and 8+ years inside a box without a problem.

IMO you'll be OK.

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

I know Marquees have a vent on their baseplate. G90s do not have a vented baseplate.

Not sure about the G70. Never looked. But that should tell the tale. If the baseplate is vented, not blocking
that vent is probably a good idea.

AFryia · Posted: Sat May 27, 2017 1:02 am Post subject:

jbltecnicspro · Joined: 23 Apr 2016 Posts: 512

Also, thinking about doing a "chassis swap". I have a newer G70 and an older G70. Currently the older one is functional. But I have more "newer" parts. Like the focus board, for example, is the new style. That kind of thing

I was thinking about moving my PA board and Deflection board into the new chassis, and leaving everything else as-is. That should work, right? Is anything else on the G70 non-interchangeable?

Am I correct in that when the PA board is "calibrated to the set" - it means that the PA board is matched to the Deflection board right? So if I move the PA Board and the Deflection board over, the set should power up just fine right? I won't be moving any of the power boards in the rear-right corner of the projector. The CPU boards won't move either as I want to know how many hours are on the other set.

Any "gotchas" coming my way by doing this? I guess what will happen in practice will be:

1. Remove PA board and Defletion board (I can't remember the name of it for the life of me right now) from "new" set.
2. Place working PA board and Deflection board in the "new" set
3. Move tubes and neckboards over to "new" set
4. Move B board over to new set so that the neckboards and b-board are matching
5. Move DC board over to new set (new set's DC board is shot)

... And is that it?

jbltecnicspro · Joined: 23 Apr 2016 Posts: 512

Just wanted to report that I tried the chassis swap and it didn't work. The other chassis didn't like the new PA board. Oh well.

Now, another question - I know that to minimize electronic correction, sometimes it's necessary to rotate the deflection yokes. What's the secret to that? For the G70, would it be that you adjust the deflection yoke so that the minimum amount of skew adjustment is needed to make the crosshair pattern square with the screen?

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

Zero out convergence and geometry adjustments.

Obtain a laser projector level. Your local big box hardware outlet has them.

Get out your bubble level and make sure the projector is levelled, side to side.

Project the alignment grid pattern and rotate the yoke until the horizontal center line
is parallel with the line from the laser projector level. Tighten down the screw, not too much.

Do this for all three tubes.

Then, check your screen to be sure it's level as well.

AFryia · Posted: Sun Jun 25, 2017 11:23 pm Post subject:

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

By zero out, I mean set them all to the middle of their range. Not quite the same as setting them all to zero.

Just want to clarify that.

jbltecnicspro · Joined: 23 Apr 2016 Posts: 512

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

Primer on CPC magnet adjustments here:

http://www.curtpalme.com/Astig.shtm

jbltecnicspro · Joined: 23 Apr 2016 Posts: 512

I assume it'a a good idea to do both deflection yoke adjustment and CPC while the projector is on the floor and not the ceiling?

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

Actually it's best to align ALL the magnetics, and that includes the CPC rings, when the projector is in its installed position.

The reason for this is earth's magnetic field. Change the orientation of the projector and it can slightly but noticeable affect the
magnetic alignment. You can even see this by facing the projector one way, levelling the deflection yoke with a laser line projector level, then turn it in a different direction, checking it, and finding that level is no longer quite as level.

The difference won't be major but it can be seen.

jbltecnicspro · Joined: 23 Apr 2016 Posts: 512

Yeah, biggest concern I have is that the G70 - when ceiling mounted - is thermally challenged. I'm not a pro and this would be my first time doing the CPC magnets, so it will take me some time. I don't want to have the chassis open all that time while performing these adjustments. Right?

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

I would not worry about it. What you lose in ducted airflow with the case open is likely more than offset by the free-flowing convection currents that you get with the cover off.

My Marquee in my HT room has been running with the covers OFF for quite some time now. It runs cooler with no covers than
buttoned up with airflow being directed through its engineered airflow system.

I've noted the same thing with my G90s. Cover off and hatch lifted, it runs cooler in the tube box than if it's buttoned up and I then open it and check in the tube box.