CurtPalme.com Home Theater Forum

**Curt Palme** · Posted: Thu Jun 23, 2011 2:59 am Post subject:

OK, fixed it. It was.....

2 bad tubes.

Now, it could be bad yokes, but I put the set on the bench, and changed the 3 main boards AGAIN from another set, just to make sure I didn't miss anything. Nope, still shaking.

I noticed that the green shook more than the R and B, so I decided to pull the complete tube assembly out of one of my sets, and dropped it into the bad set.

That seemed to cause less shaking on the green, in fact I thought I'd fixed it, but then saw the R and B tubes shake a bit. So the blue seemed worse than the red, so I swapped that too. Solid as a rock.

Tomorrow I'll throw the 'bad' tubes into the test chassis, and then I'll swap the yokes. It did seem before I swapped the green tube that tapping the green neck caused the instability. Not quite sure though.

Anyways, it's one for the books as being an oddball. What if elements were loose in the tube, and they vibrated and caused the magnetic field in the yokes to change? That's about all I can think of,

Back to the customer tomorrow.

VideoGrabber · Joined: 09 Apr 2006 Posts: 933 Location: Michigan

VideoGrabber · Joined: 09 Apr 2006 Posts: 933 Location: Michigan

**Curt Palme** · Posted: Thu Jun 23, 2011 12:58 pm Post subject:

Would you believe all three tubes are causing this? I ran the set overnight, came down this morning and saw that the red had shifted left about 1/2" on the screen and was shaking. The G and B images were solid. I'll swap that this morning, but I now believe it to be a yoke issue, and I think I know what's wrong with the yokes, but I'll prove that later this morning and will post.

draganm · Joined: 08 Mar 2006 Posts: 8990 Location: Colorado

**Curt Palme** · Posted: Thu Jun 23, 2011 3:54 pm Post subject:

I did on site, but only one yoke at a time. I've been running the 3 new tubes/yokes for an hour now, rock solid.

I'm actually suspecting internal arcing in a tiny resistor embedded in the yoke, I'll prove that to myself later today.

holdenkicks · Joined: 29 May 2011 Posts: 56

CasetheCorvetteman · Joined: 09 Nov 2008 Posts: 6326 Location: Australia

It is worth it, cause its a good projector.

A CRT projector can almost always be reasonbly easily repaired, where as the only alternative being a digital, which quite often cant be repaired, and isnt worth buying in the first place let alone fixing.

Jeremy112 · Joined: 28 Sep 2006 Posts: 2649 Location: Fond du Lac, WI

Theres one of these on ebay you can pick up for $230 or so bucks, for that price id risk buying it and if it worked, easy repair Razz

At least with Curt dealing with this issue may help out some DWIN owners in the future so I really don't think it was a waste of time anyway.

WTG Curt! Thumbs Up

**Curt Palme** · Posted: Sun Jun 26, 2011 2:45 pm Post subject:

I quoted the guy a flat rate of $500 incl the 'one' service call that turned into 4 trips. THey weren't new tubes, he more or less got another whole DWIN put into his set. Mild wear on his tubes, I'll rebuild my test set next weekend. At the end of the second trip, it turned into more of a 'WTF is wrong with this set' than trying to make money, or to convince the customer he had to pay me more.

Had I walked away from it, it would have been hard to collect the $200 service call charge. Instead I had a happy customer that's going to get a few more years out of his CRT, and me with the knowledge of WTF was wrong with the DWIN. Smile

**Curt Palme** · Posted: Tue Jul 26, 2011 11:21 pm Post subject:

OK, I am back working on this DWIN chassis, and I FINALLY figured it out! A bit more light in the customer's basement, and this wouldn't have taken 4 trips...

All three yoke connectors had bad connections on the H windings. I've seen this before, but not on all three yokes at the same time! Funny that a new motherboard with good pins didn't solve this. These three yokes are TOAST!

BTW, it's good preventative maintenance to check your DWIN 700 yoke connectors for this corrosion//melting once a year. I've had a yoke connector flame out about 3 times, resulting in phosphor burn.

macgyver655 · Joined: 22 Aug 2007 Posts: 8508

**Curt Palme** · Posted: Wed Jul 27, 2011 12:06 am Post subject:

I did change one yoke at a time, but there was enough tarnishing on all three to affect them. Of course I could barely duplicate it at the shop with a different motherboard..

macgyver655 · Joined: 22 Aug 2007 Posts: 8508

Yeah, it was a very odd display problem.

How did you make out with that NEC?

**Curt Palme** · Posted: Wed Jul 27, 2011 1:29 am Post subject:

Next on the list of stuff to work on tomorrow. Repairs and parts sales are almost up to date.

draganm · Joined: 08 Mar 2006 Posts: 8990 Location: Colorado

**Curt Palme** · Posted: Wed Jul 27, 2011 5:18 pm Post subject:

oh yeah? Ever seen a BArco or Ampro do it? Very Happy

I have seen two Marquees do it, but I think that the DWIN Molex current rating is lower than anyone else's, thus the problem.

**AnalogRocks** · Posted: Thu Jul 28, 2011 1:48 am Post subject:

Gannon · Posted: Thu Jul 28, 2011 3:34 pm Post subject:

You mentioned Caig contact cleaner for our guy NW of Detroit that I'll be seeing tonight.

I have Cramolin, but that is more of a tweak (or so I think)...and I was going to use that.

It worked GREAT on the silver contacts of the Dual turntable I traded out from the same guy.

If Caig is better, I hope I can find a local source for it today...

Cheers,
John

**Curt Palme** · Posted: Thu Jul 28, 2011 3:36 pm Post subject:

Cramolin is the same thing.. I think. That should work fine.