K7000 blowing fuses - help a newbie!

ifkz

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I'm far from a seasoned monitor tech, but I've fixed a few things with my 25 inch K7000 chassis. It is blowing fuses. It looks like all of the caps are original save for one newer replacement. The flyback is a replacement.

- IC4 is a replacement with NTE part #1777 073B. Is this a correct replacement for whatever part was here before?
-Same thing for the HOT unmarked but numbers 2SD1398 B06. These usually have a mica or rubber insulator between them and the metal monitor wall. This does not have one. Am I correct? What are my options? Hot tested good using diode (beep) test .529 & .492 black lead on center leg, red lead on right and then left leg.
-Pulled one leg up on C36. Using diode test registered as 1 open, so I think it passed.

Am I doing this right???
 
You need a mica insulator for the HOT. D1398 is fine.

NTE 1777 is a replacement for the STR30130, which is the narrow VR used on some 25" K7000's. The STR3130 is the wide VR used on the other 25" version, but there is no NTE cross that I am aware of.

If you have no insulator, that is probably what is blowing the fuse, although you should check that VR too. Also C36, C38, D18, D13, R89, and R101 can be problematic, and if your flyback has white knobs, you should replace it, too...
 
How do I check this voltage regulator? It has five legs!
I have some unused mica insulators from other HOTs that I can cut to fit. Do I need thermal paste? I have some for computer processors, I guess that would work. Should I apply it to both sides of the mica insulator? One side?
 
Some may say to use thermal paste, but I never do and never have any problems.

As for the VR, test it using diode test. Put the black lead on one leg and the red leas on each of the others. Do that for every combination. If anything reads as a short, pull it and test it again. It also should have an insulator...
 
On the VR the black lead on the center connected to the lead directly on the right gives me a beep. Bad part?
 
Pull and check again. Make sure they're not connected internally normally by checking the datasheet or schematic...
 
Let's see if I can make some art:

__________
|..............|
|...NTE......|
|..............|
------------
.|..|..|..|..|
........b..r

*beep*
 
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NTE pdf says it's the input and output. I guess there is nothing left to do but put it together and sacrifice a fuse to the arcade gods???? Please let me know!
 
if they are the input and output, they shouldn't be shorted. You might be able to buy one at Fry's. I think I have one, too.

And next time you order from Bob, get a circuit breaker fuse jumper so you can test these things without losing fuses...
 
Thanks for the help, I'll make a run to Fry's after work and post results here.
 
-Pulled one leg up on C36. Using diode test registered as 1 open, so I think it passed.

I just repaired one doing the same thing yesterday... check C37 and C38 as well, both of mine were shorted. Test D18 also....
 
Well, I figured $14 would really make a better light show.

IC4 replaced and c37, c38, and d18 tested okay.

Power up and poof!
 
I have no real experience with measuring in Ohms but I set my meter to 200 and 2K ohms to measure the part and I did not get a reading. I disconnected one leg from the board.

I had to do things to the chassis to even get it this far. The power plug was cut so I grafted a new one on from a doner. I didn't think these things had polarity. I matched the black & white wire with the white wire and the pure black wire with the pure black wire.

The bottom of the chassis has some wire hacks that look factory to me. I haven't messed with them and I've always left stuff like that alone on all of my monitors.

This hasn't had a cap kit yet, is that the next step???

I pulled my VR to see if the light show fried it and it is remarkably still alive :)
 
cant hurt. In rare cases some of the smaller caps can short but its pretty rare. Is the hot still good?



I have a 25er now thats gonna be sent to mod the next time i have money to spend- i cant figure it out. went through just about everything and i dunno lol
 
I have a 25er now thats gonna be sent to mod the next time i have money to spend- i cant figure it out. went through just about everything and i dunno lol

Same here. I'm about ready to stab myself in the face with a soldering iron.

And yes, It's getting sent off in a few weeks.
 
Of you give up or need some help, give me a call and bring it over sometime...
 
PM sent to Mod! I guess this is another K7000 stumper for the group? It will be good to have another set of eyes to look this thing over and go over my work.

Yep, the HOT and VR are still good per my tests. The commonly shorted caps are not shorted. I can only assume that something is shorting before it gets to those compenents, something pre-fuse. The bottom of the board is now good, I can't find any more bad solder joints. I bridged the obviously bad broken traces. Nothing is burned or I would have replaced it.
 
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