k7000 ic3

ssnow

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I have a k7000 that I replaced the filter cap after I put it back together it ran for a few seconds then made a loud pop and went into vert colapse I dont see anything wrong with the new cap and it is in the right way but I also reflowed some joints but I dont see any bridges.I pulled the board and ic3 popped a large chunk material off it between pins 2 and 3, so before I replaced it i was checking the voltages, pin 2 seems to be off at 26.15 and pin 7 may also be off at 25.5. also this chassis has been recapped and has new fly.Just wondering if this could be somthing common or am I just missing somthing dumb.
 
sounds like a solder bridge. you should not have that much voltage running threw that chip.

check your work very carefully even unsolder things to check if you have to.

you can pull the manual and check the circuit to see if any resisters have drifted out of speck and if any diodes have shorted causing to much current top flow to the IC.

Peace
Buffett
 
well I've been looking today in the mag light checking most of componets that come to pin 2 havn't found anything out of spec yet, testing tp5 which is pretty close on the schematic i'm getting 15.5 alot closing to the 12.2 thats on the dc voltage page of the manual so somewhere between the two the voltage is rising. Thanks
 
ok still checking components but i've come across r82 now has a 390 ohm resistor as marked on the outside of the resistor the manual lists a 820 ohm not sure why they dont match unless it was factory, also seems that q4 was clipped off, i'll have to find a 820 and see if brings pin 2 down to where it should be.
 
just wondering if before I change R82 to the 820ohm if anyone can confirm I only ask because this also has a different ic3 then listed in the manual this is a la7831 and not the upc7823 perhaps thats why R82 was changed. Thanks
 
what are the bands on the original resister look them up and see what it was rated for then measure it out of circuit to see if it is in tolerance or not.

you could always hook the chassis up leave the resister leg out of circuit and see what voltage you measure across it wile the chassis is rubbing.

it should not mater if there is a load on it or not.

that would tell you if your problem is that resister or something else before it is out of tolerance.
this way you dont smoke another IC if it is possibly the wrong part.

i usually put what is in the schismatics back in unless i have seen a service update or a recommendation from several trusted sources telling you that, that is an acceptable mod to do.

Peace
Buffett
 
it says 390 on it correct?? it is kinda blurry in the pic
if it does then 387 means it is good.

also post a pic of the chassis if you have a med res chassis then some parts will be different.

Peace
Buffett
 
Sorry yeah I know the pictures are pretty low rez, I think it is standard rez k7000.
 

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