WG K7500 Help

[DJMOJO]

Thanks guys I am using a Canon Rebel D-SLR 18-55mm lens. Sometimes its hard to get the picture in focus to what you are trying to display since everything is so small and close together but they do come out really good.

I took the C729 off and its still ticking. It didn't seem to have done anything. : ( not sure where to go from here. I checked for any bridged solder joints but i could not see any... ill be going over to Arcaded's house later today to get some fresh eyes on this thing. sometimes its just best to let some one else look at it... i hope we can get this thing figured out soon.

 

[modessitt]

If it's ticking:

a) The first thing to check is the HOT to make sure it's not blown. Set your meter to diode test and put the black lead on the center leg and the red lead on each of the outer legs. A short (zero reading or "beep") means it is bad.

b) Inspect the entire chassis for backwards caps, or pads that separated from traces during the cap kit. This happens more than you'd think.

c) The plastic guide on the back edge of the chassis has been known to through a trace, mess up a solder joint, or cause a leg to break off a transistor. Inspect that area thoroughly.

d) Measure the B+ and report back. You'll probably find it either really high or exactly zero...

 

[DJMOJO]

Ok i looked through this thing with a fine tooth comb. for about an hour and found this solder bridge

I desoldered it and it looks like they are supposed to be bridged...

This is me testing what i THINK is the hot...

This is the other side...

Lastly, i found a pad elevated from the PCB a bit, i desoldered it and sure as shit its not on the PCB anymore, HOWEVER, it is still connected to the tracer... not sure if i can do anything about that.

should i go ahead and put some solder back on the thing?

I definitely know that I dont have any backwards caps. I double checked the plastic guide area and didnt see anything unusual there everything looks normal except for some discoloration from what i think is heat but nothing looks burned or smoked.

The B+ measures 620

 

[DanV]

That's not the HOT.

The HOT (Q704) is on the heat sink next to the flyback (the large one at the left-most position), it's a C3688 transistor.

In your picture you're testing the BDX53A (Q709 or Q710?), which has something to do with the width on the 27" model, but it is not required to be hooked up for the monitor to work. It's not your problem.

 

[DJMOJO]

oh ok thank you for clearing that up for me! Ill find that ASAP

 

[demogo]

Yep, that's not the HOT.

And the experienced chassis fixers here would probably laugh at me but I always start by taking close up pictures of the back of the board with my digital camera before doing any work and I usually end up referring to them -- did I create a solder bridge where there wasn't one before? I can always answer that question easily by checking the pictures.

 

[DJMOJO]

ok the hot is bad im just getting 0s on all legs

 

[DanV]

Desolder it, pull it out and test again to be sure. Sometimes when one thing shorts (especially on the horizontal circuit) lots of things test bad in circuit because there is a short to ground. To be sure you need to remove the part and test again.

 

[DJMOJO]

im one step ahead of you, once i tested it i took it out and retested it. its bad for sure... are these expensive or hard to find?

 

[DanV]

Bob carries them for $8 a piece. I bought a few on eBay a while back for about half that.
You're looking for 2SC3688.

But before you install a new one just to have it blow again, you should go over the chassis and figure out why it died. One may not be that expensive, but no point in throwing money away. If one died, the next one is going to die unless you fix the problem first.

 

[DJMOJO]

GREAT SUCCESS! I got a new hot installed along with a new C734. The monitor now comes on and displays images (poorly) it looks like all the pots need to be readjusted. but its working atleast!

This was what it looked like at first

This is after adjusting the remote board pots.

 

[DJMOJO]

Got it as close as I could, adjusted the fly back and the pots on the neckboard. It looks kind of dim because I have the monitor under a skylight so there is a ton of glare but im sure it'll look awesome when its in the cab in a darker room!

Thanks to everyone who helped me with the repairs! Cheers fellas! : D

 

[ArcadEd]

That a boy! I told you not to give up on it .

Ed

 

[DJMOJO]

Yeah I thought I bit off more than I can chew and in some aspect I did but you guys helped me out so much! : D

 

[DJMOJO]

Put the monitor back in, its lookin really sharp, ill stop spamming pictures now haha sorry guys.

 

[demogo]

What led you to C734?

 

[DJMOJO]

C734 was a cap missing from bobs kit. Modessitt said that it should have been included in the kit so when i went to buy the hot at the local electronics shop i also picked up that single cap just to be sure.

 

[modessitt]

The problem was most likely the HOT (ticking), but replacing the cap was good to do anyway...