K7000 medium res (paperboy) dead

shardian

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I recently rebuilt a std res K7900 that was DOA, but the fuse was good.

Last night, after being on for 2-3 hours, my paperboy monitor was dead. It gets power at the connector, but has absolutely zero life - including degauss. The fuse is still goodjust like the other K7000. I plan on going ahead and doing a full rebuild, because I see the typical cracks near the focus pot on the flyback.

My question is with the medium res aspect. I know the cap kit, hot, and flyback is the same. There is a bunch of extra 'stuff' on the left side of the chassis I assume is for the medium res part. Is there anything in that area I need to watch out for or pay special attention?
 
I recently rebuilt a std res K7900 that was DOA, but the fuse was good.

Last night, after being on for 2-3 hours, my paperboy monitor was dead. It gets power at the connector, but has absolutely zero life - including degauss. The fuse is still goodjust like the other K7000. I plan on going ahead and doing a full rebuild, because I see the typical cracks near the focus pot on the flyback.

My question is with the medium res aspect. I know the cap kit, hot, and flyback is the same. There is a bunch of extra 'stuff' on the left side of the chassis I assume is for the medium res part. Is there anything in that area I need to watch out for or pay special attention?

Too bad you didn't have a replacement monitor to just stick in there.
 
I recently rebuilt a std res K7900 that was DOA, but the fuse was good.

Last night, after being on for 2-3 hours, my paperboy monitor was dead. It gets power at the connector, but has absolutely zero life - including degauss. The fuse is still goodjust like the other K7000. I plan on going ahead and doing a full rebuild, because I see the typical cracks near the focus pot on the flyback.

My question is with the medium res aspect. I know the cap kit, hot, and flyback is the same. There is a bunch of extra 'stuff' on the left side of the chassis I assume is for the medium res part. Is there anything in that area I need to watch out for or pay special attention?

Treat it like a run of the mill K7000. Same bad caps, same cold solder locations...

Matt
 
I found nothing unusual about the one I rebuilt - until lightning shot out the side of the flyback while I was testing it....
 
Got my Bob Roberts order Wednesday, so I pulled the monitor for a cleaning last night. I was greeted by my first tube with the black stuff that washes off. Luckily I noticed immediately and went to a light rinse off. I only knocked off about 2 quarters worth of black stuff on one side.

The medium res chassis definitely has alot of add-ons over the standard res I did a few weeks ago. Nothing new on any of the caps though, so no biggie. The solder joints on R101 look kind of crappy, along with the other giant resistor on the board. I'll go ahead and clean them up just to be safe. Everything else looks pretty fine. No bulged caps, only minor cracks in the flyback.

I am hoping this is a cut and dry rebuild.
 
The medium res versions really heat up the chassis. I'm sure you've noticed there are some pretty crispy sections of the board. Make sure to check each and every component for bad solder joints. This chassis is known for bad solder joints and lifted pads due to heat. Especially in the middle front and toward the back somewhat left of the chassis (while facing it as if you were looking at it from behind the monitor).

Worst case - I have a rebuilt chassis sitting on the shelf waiting for you to buy it. The problem is that I was never able to verify it worked because my tube was bad. Chris rebuilt it so I am semi-confident it will work. It also has a brand new flyback on it. I sort of was keeping it for the day my Paperboy does what yours did, but in an emergency situation I am sure we could work out a deal.

That said... take your time and inspect inspect inspect. From my recollection the blue/purple ceramic caps (or whatever they are) that sit pretty high off the board tend to loosen up. Look especially at the crispy areas...and re-flow all headers.
 
Eh, there isn't much really crispy. The day the monitor died, I noticed the fan had come unplugged somehow. Heat may or may not have been the culprit. When I finish rebuilding, I will be adding a 12 volt fan to blow across the chassis like Chris did in his outrageously awesome restoration.
 
The fan was a great idea and it keeps the monitor around 10-15 degrees cooler. As others mentioned, the rebuild is pretty much the same. Don't know if you metered the B+ at all but there's a real good chance that the regulator is bad. Do a full cap, throw in a new hot and flyback and make sure the r89/101 traces are solid and try it a again. If you get a little static on start-up and nothing else, your regulator is the problem. You can verify this before you do anything else by pulling a leg on the D10 diode and try firing it up again. Get a working/wavy pic? Replace the regulator as part of your rebuild. Short answer, have a fresh regulator handy.
 
I'm pretty sure the regulator was the issue on the other one and this one. I got the deluxe rebuild kit, and a regulator. Might as well do it all if I have it out.
 
Finished the rebuild today, put it all back together and fired her up.

Nothing on the monitor still. Wow...that sucks.

At this point, I'm not even sure where to go. What is that white thing that is bolted to the frame, off to the side of the chassis? Seems power runs through it.

Any recommendations? I repaced all caps, flyback, HOT, regulator, desoldered/cleaned/resoldered suspect connections, including the 2 large resistors.
 
Finished the rebuild today, put it all back together and fired her up.

Nothing on the monitor still. Wow...that sucks.

At this point, I'm not even sure where to go. What is that white thing that is bolted to the frame, off to the side of the chassis? Seems power runs through it.

Any recommendations? I repaced all caps, flyback, HOT, regulator, desoldered/cleaned/resoldered suspect connections, including the 2 large resistors.


Recheck all caps are in properly. What's your B+ running at?
 
P.S. the flyback looked almost fine from what you can normally see. After taking it off, the whole adjustment face was about to break off! It was very, very badly busted up.

As for B+, is there a tried and true method for checking/adjusting it? I swear I read somewhere that you can't adjust it on a K7000.
 
Worst case - I have a rebuilt chassis sitting on the shelf waiting for you to buy it. The problem is that I was never able to verify it worked because my tube was bad. Chris rebuilt it so I am semi-confident it will work. It also has a brand new flyback on it. I sort of was keeping it for the day my Paperboy does what yours did, but in an emergency situation I am sure we could work out a deal.

I need your Secret Service pin to die, that way you are desperate for the CPU board I have here. Then we can make a trade.:D
 
Could this chassis be any more difficult to access when installed?
I haven't had spare time to test the B+ yet, because I need to pull the monitor and remove a side panel to get access.

I did measure the AC input again though - 122 volts at the plug. Power is getting there, but is not making it into the chassis. I replaced the fuse with a brand new one as standard practice when doing the cap kit. The old fuse was fine of course, so that is not the issue.

I suppose it is a possibilty that the Vreg that bob gave me is bad, but I have my doubts.
 
Chris recommended I check some resistors, so I went to town this evening.

Resistor Expected Actual
R89 3.9k 3.73k
R96 1.0k 2.5 ohms (shorted) - Also has a white wire to R91
R97 270 270
R101 6.8k 4.19k - Problem here?
R103 2.7 ohm 3.0 ohm


Traces look a little black here and there- should I scrap the sealant off all the way?

Input please!
 
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