Can someone help me on a simple schematic question?

jonathan1138

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Can someone help me on a simple schematic question?

I have a Tron with a WG42 monitor, which *i think* is equivalent to the WG4900 series.

Game plays blind, but get neck glow. Can be anything at this point. First plan of action is to check all solder joints, as some were suspect when i capped the monitor.

One area that needs attention - C702 when i capped, a trace lifted up immediately upon applying solder - this was a concern. I pushed it down / soldered on the leg of the cap (to the bottom of course). I followed up by checking continuity to other points by following the trace. Unfortunately, i couldnt tell what should have continuity and what shouldnt - i dont want to guess.

So from the manual - page 14 - is it safe to say that anything having a line drawn to C702 should have continuity to it (i should get a buzz?).

Again i want to make sure the trace is back in / doing its job.

http://arcarc.xmission.com/PDF_Monitors/Wells Gardner 19k4901 19k4906 19k4951 19k4956.pdf
 
Also, it would be ideal if someone can look at page 14, tell me what C702 should buzz with - this will help to understand better.

Thanks.
 
I assume by "buzz" you are referring to a continuity test. Check for continuity from all legs of the damaged trace. I just fixed a K7000 yesterday that someone had jumpered the trace in one direction but not the other.

Depending on which leg of C702 you lifted you should get continuity either to J402 Pin 1 and the cathode (side with the line) of D702 or pin 9 on the flyback and one side of R372, R389, R311 and R313 (as well as others).


If you are asking what you should see when you test C702, you can't really test it with a multimeter. You can look for continuty across the legs, you should get a fairly high reading that climbs. If you get continuity (a buzz) then the cap is shorted.
 
Thanks Oryk - thats what i needed - i want to make sure the cap is connected to what it should be in the circuit, (the other resistors / points as you noted).

I cant wait to check tonight. When the trace lifted - and i pushed it back down / soldered the legs - i was getting continuity to points to the left of the C702 cap (by following the traced outline on the board) but not to points right of the cap (again by following the traced outline on the board). Visually everything looked ok, but that can be misleading.

I guess it could be the bad trace is stopping me from getting to where it needs to be (jumper it in that case). Will try it tonight.
 
Just looking at it again - and to help understand - should i be getting continuity to R368 / R369?

Also, C701 was suspect - (lower right corner on the schematic) - should he only ping with R701?

I will read up more on schematic deciphering but this will help for the near term. Thanks.
 
Just looking at it again - and to help understand - should i be getting continuity to R368 / R369?

Also, C701 was suspect - (lower right corner on the schematic) - should he only ping with R701?

I will read up more on schematic deciphering but this will help for the near term. Thanks.

You should not have continuity to either of those resistors. When you look at schematics there are lines running everywhere. Often times these lines cross on the schematic, but they only touch on the board if the intersection point of the lines has a large black circle on it. This circle is referred to as a tie point. If there is not tie point then there should not be continuity.



C701 should show continuity to C703 and D701 on one leg and continuity to ground on the other leg.
 
Perfect! This really helps.

Now that i think about it, 701 was the suspect trace, and he had limited continuity - this is in line with the diagrams. Knowing this info know i can probe through the board and see if i can find any connection issues (after i reflow).

Thanks again.
 
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