CurtPalme.com Home Theater Forum

**Curt Palme** · Posted: Mon Aug 23, 2010 10:32 pm Post subject:

NO question that the V board has still be a failure issue in these sets. Maybe I did something wrong, it was just bad when I'm 1/2 way across town with a set that I put a good 24 hours of testing on, only to have to pull it down again.

The whole day today is a writeoff, from driving in the wrong direction to forgetting stuff. I'm taking a nap, let me know when it's tomorrow. Smile

Jesse S · Joined: 12 May 2007 Posts: 209 Location: Etobicoke

Today while watching a movie my image started to shake up and down a bit, then it rolled over vertically like the vertical hold on an old tv being tweaked a bit. I looked into the tubes and didn't see any bright beams at the edges.

Sign of another issue or this issue?

HD-DAVE · Joined: 16 Feb 2007 Posts: 225 Location: Delta, BC

After 6 great years of service after buying it from Curt in 2007, my XG 135LC appears to have suffered the V board failure referenced in this thread Sad

. Was missing the green image on a power up the other day, checked to make sure it wasn't an input issue, then noticed there was an extremely bright flare running off the tube edge on the bottom when I looked into the lens. Didn't run it very long lest I crack the tube.

My main reason for posting is,

Can the V board issues (blown STK's,etc) be repaired without taking the damn thing down from the ceiling ?

Will I need to do much re-calibration once its repaired ( I would think mainly convergence / linearity ? ) ?

Thanks,

...Dave

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

Youll only need to pull apart the case and remove the board to send into Curt, you may need minor touch ups when its all back together, but wont be much unless you f*** up the astig rings getting boards out...

**Curt Palme** · Posted: Mon Apr 08, 2013 3:10 am Post subject:

http://curtpalme.com/NECXG_Layout2.shtm

It can be done, but it's a PITA. Don't use the set, you risk nuking the tube.

HD-DAVE · Joined: 16 Feb 2007 Posts: 225 Location: Delta, BC

Thanks for the advice, Curt and Corvettman... yeah I really dont want to toast the green - particularly since it was a brand new one you put in the set b4 selling it to me, curt ! I'll round up some neighbours and take it down. I'm an electronics tech so I usually take care of all my own repairs but we'll see. I'll be in Main Electronics today so will inquire as to whether they can get the STK's.
Dave

**Curt Palme** · Posted: Mon Apr 08, 2013 5:17 pm Post subject:

DO NOT buy ANYTHING from Main!

Counterfeit semiconductors are their name of the game, and I stopped using them years ago. Get a chip from there, and you're guaranteed to nuke the tubes. I've got stock of good tested chips and parts.

HD-DAVE · Joined: 16 Feb 2007 Posts: 225 Location: Delta, BC

Wow - this is the first I've heard of Main Electronics being suspect - I've always trusted their stuff going back 20 odd years... are you sure you aren't referring to Lee's electronics a few doors down ?

HD-DAVE · Joined: 16 Feb 2007 Posts: 225 Location: Delta, BC

If not local store like these two, where are you or other folks getting guaranteed non-counterfeit Sanken (STK) stock ?
Digikey ? Jameco perhaps ?

**Curt Palme** · Posted: Mon Apr 08, 2013 5:42 pm Post subject:

I REPEAT, DO NOT BUY FROM MAIN!

Good guys, but they've taken zero responsibility for their shite transistors that have cost me countless hours of head scratching, dating right back to the early 90s. Life was much better since I stopped buying anything but NTE from them, worst case scenario. I buy my chips in bulk from China, from trusted suppliers.

HD-DAVE · Joined: 16 Feb 2007 Posts: 225 Location: Delta, BC

Hi again

...well today I finally rounded up some neighbour muscle and took my XG down. Opened up the set, raised the cage, removed the main lens off the Green crt so I could see the tube face. Spent the last couple of hours trying things, and was perplexed as my testing results do not exactly match the 'classic' set of symptoms for the "V-board failure" described by Curt and others this thread:

- first off its not hard failure which one would expect if one of the STK chips are blown/toasted but rather the problem is intermittent, sometimes the raster is perfect and the set will run til warm and beyond.

- most of the time it fails to show a perfect raster....out of the dozen times i've power cycled the set today only twice did it come up perfectly.

- if it powers up ok it usually goes bad the second l power cycle the set. Whether I leave it off for awhile does not change how likely to show a perfect raster on power up.

- Sometimes the degree of "badness" changes!!! The two different flavours of bad i have observed:

A - when its "slightly bad" there is initially no raster at all, then as the set initializes with an input source (using S-video), there is brief low brightness spot/orb of light at the top of the face of the green tube, which is quickly extinguished. Maybe 5 or 6 seconds later the spot shows up again , a bit brighter than before at the top of the tube (its bleeding off the top slightly), and again its extinguished after 1/2 a second, as though a protective circuit is activating. After that it just sits there - no tube face activity if i leave it...

B - when its "very bad" its the same as above except the initial spot at the top of the tube , and beyond is very bright and DOES NOT get extinguished...its then that I am leaping for the power button after a few seconds of that.

- i pulled the V-Drive board and did some measurements on the STK chips ...none of the basic "diode" (forward/reverse) readings the STK's measured any different, IE comparisons between the three stages for one or the other of the two modules. (which are basically high power Op Amps....one stage each for R / G / B). If the green drive portion of these chips was bad I would have expected to see odd readings for it but i don't. Neither of the two STK's show any physical blemishes nor do they smell cooked. Didn't notice any bad caps (all test ok ESR wise, not swelled), no toasted looking resistors (measured all the higher power non-surface mount ones - all ok). No toasted looking surface mount IC's, no cold solder joints, etc.

- i've went thru the circuit boards and connectors around the tube area, reseating every one of the four boards sitting between the crts as well as re-seating all the ribbon connectors. I also pulled the neck board off the green tube and reseated it to the tube. That didn't change anything, its still intermittant as above.

- there are no fault codes showing the rear panel LED. I was hoping for codes given the "slightly bad" symptoms looked like a protective reaction was happening.

Thoughts, Curt, or anyone ?

gjaky · Joined: 05 Jun 2010 Posts: 2802 Location: Budapest, Hungary

You should observe the signal at the deflection yoke with an oscilloscope and with the service manual one could track down where is the problem coming from. If this is too much for you, then leave this to Curt.

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

Swap all the yoke connections at the yokes with the red tube. If no change, swap the board ends of the yoke connections between green and red.

HD-DAVE · Joined: 16 Feb 2007 Posts: 225 Location: Delta, BC

THanks for the tips corvetteman and gjaky. I had thought of swapping the yoke connections but without a service manual & schematics/parts list to see if the drive circuits are identical and the yoke part specs are identical I couldn't ascertain whether that may be a safe option. I would dearly love to get a service manual - will have to be more aggressive looking for one given this issue and the fact that my XG is over 10 years old now and is showing its age.

I will try the G/R yoke swap but I am going to go ahead and replace the STKs on the V-DRIVE board anyways as even if still good they are a risk and thus I may kill two birds.

HD-DAVE · Joined: 16 Feb 2007 Posts: 225 Location: Delta, BC

Dave, I've got no issues with you servicing your own boards, but please don't bring other sites onto this one where there are schematics. That cuts right into my business (my opinion only, we've discussed the pros and cons of this before), which is why I don't post anything but really old schematics for download here.

That's why I deleted your contents of this post. Smile

Curt

Larry K · Joined: 08 May 2013 Posts: 16

Hi guys, Curt thanks for bringing this to our attention.
I've got some symptoms on my XG85 that may have something to do with this problem. When I boot it up, the blue tube started projecting soft uneven cloud looking images on screen, when I look at the raster, it seems to have a brighter noisier raster on the tube. After a bit of time the picture would come up and although it is not perfect, it settled down and improved as it warmed up. I got the same blue images on the screen upon shutdown.
Over time, it has been getting worse and now it appears the red raster is a bit more noisy as well but I also have other problems. When I boot up, sometimes it will shut off and come back on again a number of times while showing an FC failure, then it's recovering and once warmed up it works ok. I have a feeling that there's more than one issue here, what do you think?

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

FC relates to the power supply i think, im not sure.

**Curt Palme** · Posted: Thu May 09, 2013 5:02 am Post subject:

Larry- if you have a full raster but no video, then the V board is fine. NECs actually have more video issues than V board issues, but it's always a good idea to get the V board repaired, as these boards are now 13+ years old...

A bad V board can implode a tube neck before you realize the V board is bad. I've done it.. twice.

Larry K · Joined: 08 May 2013 Posts: 16

I reseated some boards and plugs, and just finished watching a movie. It seemed to work a bit better but I still have the blue spots during startup and shutdown but no rapid self restarting or error codes. I will try it again tomorrow night.

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

Can you show us a pic?