CurtPalme.com Home Theater Forum

Ohmess · Joined: 11 Sep 2008 Posts: 242 Location: Vienna, VA

So, I am having a problem with my convergence board, have it out of the projector and am checking it out. I found a couple of problem resistors and am in the process of replacing them when I discover that all of the .47 ohm resistors I put in my board following Nashou's thread do not measure .47 ohms!!! They all measure 0.7 ohms! I've made dozens of measurements with my meter; I'm pretty sure my meter is not the problem.

I checked the ones I have left over. Brand new in the packaging they all measure 0.7 ohms. WTF?!

I made three different purchases of these babies; all from Mouser and all Vishay/BC components. They all look precisely like the resistors pictured in PaulB's post in the middle of this page:

https://www.curtpalme.com/forum_archived/viewtopic.php@t=9608.html

Don't they QC this stuff before offering it for sale? Do you guys test the new stuff you purchase prior to installation? This sucks.

Heywood Jablome · Joined: 12 Mar 2006 Posts: 1548

Really Dumb Question, but it has to be asked: Did you check the probe resistance tip-to-tip? My cheap Rat Shack meter has three tenths of an ohm unless I scrub the tips together.

Ohmess · Joined: 11 Sep 2008 Posts: 242 Location: Vienna, VA

Actually, this may not be a really dumb question. How exactly is that done?

Say, perhaps, if I touch the tips together and the meter reads 000.2? ok, I'm feeling stupid.

Nashou66 · Joined: 12 Jan 2007 Posts: 16171 Location: West Seneca NY

Even that small of a resistance difference wont matter to much I'd assume .
Heywood is correct some meters have a slight resistance. Also remember you cant always measure components
in the board as other parts of the circuit might affect it. So what is the issue your having with the board?

Athanasios

Ohmess · Joined: 11 Sep 2008 Posts: 242 Location: Vienna, VA

Hi Nashou --

It is precisely this problem again:

https://www.curtpalme.com/forum_archived/viewtopic.php@t=12991.html

In looking at the board, R329 was toasted. Not only was it black, but the pcb underneath it was burnt as well. I've replaced it, along with both Q312 and Q313. Tried it in the projector again, no joy and the same LVPS error light on the back with the third light on the LVPS blinking. (one of the 24 v rails; I forget which one).

So, I was checking the green circuit further. I've found several other problems: R417, R418, R317, R310 and R305 all need replacing. So, I'm about to heat up the soldering iron again.

Heywood Jablome · Joined: 12 Mar 2006 Posts: 1548

Ohmess · Joined: 11 Sep 2008 Posts: 242 Location: Vienna, VA

I now have something new going on. There are fine horizontal lines on both my red and blue tube, which appear when no signal is present, or when I run one of the internal test patterns. My pictures such, but here's a picture of the red tube with a cross hatch. You can just make out the lines in the grid behind the cross hatch pattern.

For comparison, here's the green tube cross hatch. I do not see the fine horizontal lines in this image, nor do I see it when there is nothing on the tube face.

I'm thinking I might switch around my neck boards and see if anything changes.