K7000 r103-104

srarcade80

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I have 2 k7000s, both were shorted at A/C causing cabinet fuse to blow. After inspecting all the power supply and having everything check out, I pulled R103 and R104 since that is where the shorts seemed to be coming from and sure enough that was it. Oh and the HOT was bad on both of these as well, plus the fuses were blown.

So my question is- how did these big suckers get opened in the first place? These are big resisters, I just am wondering how a component like this can go wrong. I don't know any history on these, I have never run these chassis before, I got them in some trade or they magically appeared in my stockpile somehow.

EDIT - I am a moron- these are 2.7ohm and 15ohm respectively. On my DMM, these will always measure open on a continuity check because of their low resistance. On an ohm check, they are measuring 3.3ohm and 15.6ohm. So these are not likely the culprit in my problem. (good because i don't have replacements anyway!)
 
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If you're blowing fuses on a K7000 - possibly from it being plugged in without an isolation transformer - in addition to the bad HOTs, you should check for shorted VR (IC4), shorted D20/D21, shorted C36, and shorted C38...
 
Fixed fuse blowing, replaced VR with a new one (even though old one tested good). Monitor still in shut down, need to measure B+ at R301 but ran out of time and had to run. Pulled leg on all diodes, all are good, replaced HOT, re-flowed most of the power supply components. Checked crit cap out of circuit as well, its good. Should be able to solve this one with a little more time.
 
have you done a complete cap out on them.
this can keep them in shutdown if a cap is shorted.

have you reflowed the chassis and checked for broke traces.

check the C23 and R101 area this area is nortourious for shutdown problems.

Peace
Buffett
 
Have not done a complete cap on this, looks like someone did a cap kit on this chassis not long ago, they are pretty clean compared to the other components. R301 is getting 0 VDC on either side, thats about all i had time to check last night. I will check the traces around the C23 and R101 stuff next and reflow the power area completely.
 
I pulled R103 actually ahead of time and replaced it with another one. They both looked good anyway, measures good resistance, only off by .3 ohms.

I pulled the filter cap, it did not measure open so i put it back.

Still scratching my head on this one...everything looks really good at this point. If i had a spare cap kit around i'd install it for the heck of it.
 
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