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help,Marquee Convergnce board problems

644 Views 17 Replies 8 Participants Last post by  cmjohnson
well after 2 years of faithful service I lost part of the red channel on my conv. board a few weeks ago. PJ shut itself off at 1:00 AM halfway through I Robot followed shortly by that burnt transistor smell.:( Machine powered back up but no control of RED convergence on left and right of screen (center still works) . Found a bad power transistor on RED channel (the flat ones that clip to the heatsink) and a couple of blown resistors in front of it. Well I had the bad parts replaced by a friend (electronics engineer) but still no CONV. control in red channel periphery. I would appreciate some suggestions, bad CONV. yoke, something else wrong on the CLM maybe? I am getting dperessed without my HT, :(
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Say Dragan

Try an ohmmeter across the windings of a convergence yoke that is working, and compare readings to the red yoke for starters.
A reall smart aleck would just tell you to converge blue and green to match red and call it a day! :D

Give Curt a call and get a replacement convergence board and yoke from him.

That's the simplest way to go, and the easiest.

I'd check my setup if I were you, too. Raster centering, etc... because the

less work you give the convergence circuit to do, the cooler it will run and the

longer it'll last. When you go to the convergence screen and hit 0,0,0 on

the remote, that'll reset convergence to default. At that point, the centers

of the rasters should still be perfectly converged, and the height and width

of all three rasters should be matched, too.

I'm sure you know this already, but it never hurts to repeat it for the benefit

of any newbies who may be reading. The better the mechanical alignments,

the easier the electrical alignments become, and the less work they have to do, resulting in a longer service life.

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Make sure the convergence yoke didn't get pinched. It's very unusual for the convergence board to fail out of the blue like that. It's possibe that an arc inside the red tube took out the transistor, but again, it's rare.
Sorry to hear the news! Draganm :(

P.S. I tried leaving feedback for you on Videogon but was getting an error.

I will try again tonight!

Originally posted by tim
Say Dragan

Try an ohmmeter across the windings of a convergence yoke that is working, and compare readings to the red yoke for starters.
thanks Tim, I did try that and it measures the same as the good channels with the Conv. board unplugged. I will compare measurements on red to G+B tonight with the board plugged in.

CJ, ,my set-up skils have been honed pretty well over the last 2 years. Everything was pretty well set-up except for raster widths, they were close but not perfect. Finally dialed those in last night spot-on but maybe a little too late.

Curt what do mean by the Conv. yoke getting pinched? It's been up for a couple of years, can something have changed in yoke location over that time?
Hah. This is really funny. I went to do a full setup on an 8110 that I just got

a commitment to sell. I have spent several hours on it today and I'm not done yet.

I start by almost taking the machine apart, doing the thorough inspection thing.

I discovered that the convergence board is not where it should be on the rear

heatsink, the horizontal deflection processor board has been snapped off of

the conv/HDP board assembly, and, most significantly, one of the heat sink

clips is nowhere to be found!

I salvaged one off of my "spare" projector and tagged it so as to remember

not to run it without a clip installed on the heat sink.

I get the projector together (the one I'm prepping for delivery) and....

Would you care to guess what's not working? :D

Yep...the RED convergence!

Crisis time. I don't have an EXTRA convergence board, so it's going to get

the convergence board off my experiment-in-progress machine.

I have already secured a replacement convergence board off of ebay. If you

need one for yourself, there's another one there with a buy it now price of 95 bucks. I suggest you snag it in a hurry!

Odd, that I should end up with the same problem as you on the same day,

and there are two such boards available immediately on ebay.

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why red, on all the machines I've seen the width slugs are always maxed out on red while B+G are turned in? Tonight, I checked the resistance values with the board wires unplugged, got .3 ohms or open depending on how I plugged in the meter. With the board wires hooked to the board, meter showed .3 to 4 ohms on the good channel and .3 to 1.5Kohms on the bad channel. Obviously, the red channel repair is not complete. I guess I should be grateful, pulling the Conv. yoke with the PJ on the cieling is not what I wanted to do, not to mention complete redo of Yokes, stig, flare, a-ya-yay:(
I just found another oddity.

I transferred over the convergence board from one machine to another, as I

mentioned before, and it works, but it wasn't long before I noticed that on

this machine, an 8110 with version 4.0 software, I can't move the red or blue

convergence grids all at once like I can with my 8000 with version 2.0.

On that machine, I can move the entire grid at once from the central

convergence zone. On this 8110, I don't have that ability. I can move the

blue and red grids VERTICALLY there, but NOT horizontally.

In every other zone I have full freedom of movement.

Is this a version issue or a board issue? I'd really like to have the version

or board that gives FULL control in the center zone as even the centers can

drift slighly with time and I'd rather use the remote than have to realign the

tube toe-in to get convergence dead on.

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My experience with the convergence board was a short (a lead on the back of the board got bent over and shorted) that quickly fried a resistor. After hours trying to find which components were damaged, I finally gave up and just replaced all of the transistors in the circuit. It has been working great ever since. As I recall, I spent less than $20 for all of the transistors.
Originally posted by Curt Palme
Make sure the convergence yoke didn't get pinched.
Yep, that's more likely your problem. And it's more likely that your yoke wire had been pinched all the while, with a final break in the cable later happening. Convergence boards will very rarely fail on their own, and if that happens, the failure would not cause one of the power transistors to fail, the self failure is more likely stabilty (drifting).

Repair is not as easy as it seems. The actual circuits are very similar to complimentary push pull audio circuits. And these circuits must have correct bias and off-set levels before the circuit will ever operate correctly. When one of the finals (mounted on heatsink) fails it'll usually take out the bias circuit. Therefore the best way to repair them would involve a variable +/- power supply and sine wave generator. Very difficult board to repair correctly, you'll need to see a good sine wave driving a 2 ohm test load (the coils are .6 ohms)... replace the board!


CJ, check your connections. Make sure you have your red and blue yoke connectors on the right plug on the HDM.
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I checked that very, very carefully. The first convergence board is definitely

out to lunch on the red channel. No movement.

The second one seems to work fine but I get no movement in red and blue

when in the center zone. All other zones move normally.

Software, maybe?

As long as I'm at it, I might as well ask about the focus magnets.

This 8110 has six pole magnets. I've found four pole magnets (well,

actually they do seem to be six pole magnets but they don't have

the rotating adjuster on them) and I was wondering if there's any

reason not to install six pole magnets in place of the four pole magnets,

and if there's any real benefit to doing so anyway.

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Originally posted by cmjohnson
I get no movement in red and blue

when in the center zone. All other zones move normally.

Software, maybe?

If your reference to center (left to right) is the same as the static (global) convergence, it's not controlled by the convergence board, it's controlled thru the HDM.

The convergence function/control is not effected by software version.
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So if I can't move the entire red and blue grids from the central zone, it's an HDM issue?

Another piece of the puzzle: I can move the grids VERTICALLY from the center

zone, now that I think about it, but not horizontally.

Does this point to an HDM problem?

I guess my next step is to see if the whole image shifts if I use the phase

control, just for test.

I do remember specifically that the green grid can be moved in any direction.

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Even if all three plugs were removed from the convergence board, the global convergence should still move top/bottom - left/right on all three colors.

HDM - left/right

VDM - top/bottom
I guess I need to break out the service manual and start poking and prodding.

That particular HDM went a bit flaky and was having a case of the horizontal

shakes when it was in my 8000. I retired it for a spare board, but I just

resoldered a bunch of connections on it that were questionable. Now the

shake is gone, but I've noticed this issue only since resoldering. Maybe I

bridged something?

I guess I need to take a good look at it.

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have a close look at the connectors on the hdm.

maybe you mismatched red & blue.

exactly the same happend to me and it took several hours to find out.

i was absolutly sure that the hdm was right connected.

if you go into the guided setup menu, all 3 rasters will lit up during raster alignment. this was how i found it out.

the optics were taken off and in the angle of my eye i saw the blue moving while i tried adjusting red.

maybe this helps,

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Double, triple, and quadruple checked. Plugs swapped just for drill though

I physically traced them from blue to the socket labelled BLUE and red to red.

Nope, this convergence board has issues in both red and blue.

That's OK, I have a spare or two and the machine is running perfectly with

a spare installed.

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