Hi. My how time flies.

Almost a year ago I posted asking for some help with my Marquee, and only now have I been able to actually try some of the thing suggested. I've been soooo busy.

My 8500LC has a strange focus problem. When you first turn it on, the focus has to be set very low (~8) for the PJ to focus. (After a full projector reset so everything in service focus menu is set to 50.) As time goes buy (a couple of hours, say, sometimes more, sometimes less), it drifts further and further out until it is no longer possible to focus the PJ.

The focus problem effects all 3 tubes equally, so I've been trying to find a source of the problem that would be common to all three tubes at the same time. (i.e., it's unlikely the output op-amps of all 3 tubes failed in exactly the same way that they all drift equally -- it's far more likely that something upstream that effects all three tubes at the same time is the problem.)

Curt said to check the HVPS, that HV drift can cause this problem. He also said to clean the contacts on the various boards; I did that too. I haven't seen in HV drift yet (not to say it's not there), but when I turn on the PJ i have this problem right away and the HVPS voltage seems a tad high, but within the spec'ed 1% tolerance. (The HV was tested with an 80K-40 HV probe from the input line... i.e., I removed the input line from the voltage splitter block, isolated it up very high from the rest of the electronics, turned on the set, and measured the voltage with the probe. I hope turning on the set with the HV line disconnected won't harm anything -- I can't think of a reason why it would, but if this is bad please let me know.)

The results of my tests are as follows:

HVPS: 35.18KV < (34.9 * 1.01 = 35.25)
+12v rail: 12.5V
-14v rail: -15.2V
+14v rail: 15V
RCOMP: 6.79 volts
RTEMP: 5.83 volts

All of the focus coil voltages look "reasonable" in that when I raise and lower the focus, the static waveform rises and falls, and the dynamic waveform exhibits the characteristic parabolic waveform one would expect.

I do suspect the static focus waveforms somewhat: The troubleshooting guide says, rather cryptically, that "A +15 Vdc to -15Vdc level should be observed at these points depending upon the setting of the Focus paramter (PIC 4)." The waveforms are not DC: they have a parabola built into them for vertical comp. The waveforms I've scoped do take excursions to +/-15 Vdc, but the actual parabola parts don't ever get past -13V to 9.8V, which is a good 5 volts less that +/- 15V. But maybe this is normal?

If anyone is familiar with the marquee's FM, can you look over these voltages and see if they seem reasonable? I've placed cursors on the top and bottom of the parabolas of each pattern.

The dynamic focus coil voltage (R-DYN-H) looks like this:

http://www.avsforum.com/avs-vb/attachment.php?attachmentid=94743&stc=1&d=1195438188


The static focus coil voltage (R-STAT-H) looks like this at focus = 100 (very unfocused)

http://www.avsforum.com/avs-vb/attachment.php?attachmentid=94744&stc=1&d=1195438188

The static focus coil voltage (R-STAT-H) looks like this at focus = 50 (unfocused)

http://www.avsforum.com/avs-vb/attachment.php?attachmentid=94745&stc=1&d=1195438188

The static focus coil voltage (R-STAT-H) looks like this at focus = 0 (mostly in focus):

http://www.avsforum.com/avs-vb/attachment.php?attachmentid=94746&stc=1&d=1195438200

I´m not expert, but i was thinking what happens if/when those 100uf bipolar caps goes bad on FCM:confused: That drift issue what you have might be related to bad caps. Maybe TSE or someone else knows better.

Wow, now that's what I'm talking 'bout..:) I love it when request for help and questions are asked with this level of support.

I have the manufacturers waveforms on a CD at the shop. I'll get them later and post back.

For now, I think the best thing to know is does those waveforms change over time, and can you also measure the filament.

Dang, just looked back over the waveforms and noticed that you are showing both in and out of focus.

I think you'll need to look at the pulse from the CLM that feeds the focus module and see if those changes are coming from the CLM.

I suspect the CLM.

Hey Chiem, I was wondering what happened to you..:)

I still maintain that it's the HVPS that's bad. I've never had a drifting EM focusing issue on any Marquee, I'll defer to Mike or Tim though, maybe they have. All my drifting focus issues (and I've only had two of those) were due to drifting HVPS.

As strange as the horizontal waveform looks it is right. The dynamic focus winding is connected in series with a resonant capacitor that serves to reduce the voltage needed to get the parabolic current waveform.

The static waveform looks about right, too.

Out of focus condition would be caused by anode voltage wrong, current in the windings having a DC offset, or the focus magnets having the wrong gauss.

You could try running the projector with the focus magnet unplugged from the FGM. If it drifts then it would be the HV drifting or you are near some strong external magnetic fields.

Scott

You guys are amazing. I woke up this morning and had a plethora of new things to go check. I haven't even had a chance to check these things yet, but still I wanted to say THANK YOU.

<edit again...>

Ok, I'll go ahead and leave whats below up for those that are curious, but I've finally decided to stop pulling my hair and send the FCM and HVPS off to Curt. I really like to work on my PJ, but I just don't have enough information to isolate this problem without some boards to swap with. So thank you all for the help that you've given me so far!

<edit...>

Could someone do me a favor? According to the troubleshooting guide, the static waveform on pin 3 of the various focus coil plugs should range from -15V to +15V. I'm not seeing that on my PJ, but what I do see doesn't seem that unreasonable.

Could someone just hook up either a scope or a meter to pin 3 of one of the tubes and run the focus from 0 to 100 and let me know what the voltages read as, as well as how you took the readings? (i.e., DC, AC, AC true RMS, Scope top of parabola?) Please set the center focus on the tube you are going to test to 50, otherwise the adjusting pic/focus won't actually swing over the full range. (option 9, code 0901, RGB focus; only the center focus needs to be adjusted to 50).

This will greatly increase how much I know -- so far my biggest clue is that the static focus waveform parabola never rises above 9.8v, even though the op amp rail goes to 14v, but I still don't know if a 9.8v max is normal or abnormal. (The PJ is in focus at 9.8V, so it seems that if it could go higher that would solve the problem.)

I am, right now, running the projector non stop trying to get the focus to drift with one tube unplugged from the FCM and the scope monitoring the static coil, dynamic coil, RTEMP and RCOMP. Now that I have my scope hooked up and test wires soldered to several points on the FCM, the board wants to be stable, although the focus is still way off to one rail. <GRR...> I'll leave it on all day to see if I can get it to drift. I keep thinking if I can get it to drift then I can see what parameter changed, but things never do what you want them to. Maybe taking the cover off made the stability better because of less heat...

I'll be sure to watch the HVPS output voltage per Curt. I know it's within spec right now at 35.18KV. If the focus drifts for me, I'll recheck it.

In the mean time, I think the answer to this question might be helpful:

Here's a photo of how unplugging the FCM from the green tube affects the green image. Does the level of focus this seem consistent with what you would expect under these conditions, or is it much more unfocused than it should be? (The room had some sunlight in it.)

If the focus is much worse than you'd expect, then perhaps the FCM is struggling to refocus the image and the HVPS/gauss of permanent magnets is the bad guy.

If the focus is pretty much what you'd expect, then perhaps the HVPS/magnets are fine and the FCM is the bad guy.

http://www.avsforum.com/avs-vb/attachment.php?attachmentid=94766&stc=1&d=1195497382

Here are measurements at fcm module (green tube, black wire, pin 3 at focus connector) Scope "Hot" pin at pin 3 and ground at chassis ground

http://img99.imageshack.us/img99/6150/fcmparabolafocusmaxuf5.th.jpg (http://img99.imageshack.us/my.php?image=fcmparabolafocusmaxuf5.jpg)

http://img155.imageshack.us/img155/4707/fcmparabolafocusmidvn8.th.jpg (http://img155.imageshack.us/my.php?image=fcmparabolafocusmidvn8.jpg)

http://img99.imageshack.us/img99/3577/fcmparabolafocusminlv5.th.jpg (http://img99.imageshack.us/my.php?image=fcmparabolafocusminlv5.jpg)

I hope that those pics helps you to troubleshoot that error.

Actually, that tells me a lot. Thank you very much. I assume that was taken at 5V/division vertically? (It says 5V in the upper left corner). That means at 0 the voltage peaks at about 12.5V, which is higher than mine peaks out out. If I had that extra few volts, I'd be good.

Thanks for taking the time to do that.

You guys don't play nice. You have newer scopes than I do.

Not fair!

Actually, that tells me a lot. Thank you very much. I assume that was taken at 5V/division vertically? (It says 5V in the upper left corner). That means at 0 the voltage peaks at about 12.5V, which is higher than mine peaks out out. If I had that extra few volts, I'd be good.

Thanks for taking the time to do that.

Because the static winding is 60 some ohms and the amplifier runs from +/- 15V the current is max a little more than +/- 200mA. The magnet should not need either extreme of current to focus. Static focus should happen between 30 and 70 on the slider bar (service menu) . That is with focus in the Picture menu at 50.

Scott

I'm no tech or anything, but he says it goes out of focus over time(warmup). do you think it might be something wrong with the themosistor circuit in the foucus board? I think i read something about that in the service manual.

Athanasios

You guys don't play nice. You have newer scopes than I do.

Not fair!

:) I have allways liked that HP 546500b Scope. It is digital scope with analog display. very suitable for ctr-projector repairing/troublesooting :D

Actually, that tells me a lot. Thank you very much. I assume that was taken at 5V/division vertically? (It says 5V in the upper left corner)

Yes, that was 5v/division