Recapped my k4900, and something seems completely wrong.

Mimatt

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Recapped my k4900, and something seems completely wrong.

I just got finished recapping my k4900 on my Robotron and yes, I double checked to make sure everything was installed properly.

This is my first 4900 I've ever recapped, but I've capped plenty of other monitors before. I got the two pinchy wires on the anode back into the tube, but I couldn't get the round, flat part to go in the tube. Does that part need to go in as well?

The picture on the screen is coming up fine, but you can hear a small, constant crackling noise, and viewing from the back of the tube, it looks like one of those plasma balls you see in spencers - the little ball with the purple lightning inside. And there is a terrible ozone smell coming from the monitor.

This can't be normal... The picture looks great, but I'm now scared to turn on my Robotron. None of the caps blew during the time the monitor was turned on.
 
You should be fine. You need to get a better connection at the anode hole.

No, the disc does not go inside the tube. The 'teeth' both go inside, but the disc sits on top.

Turn off the monitor, discharge it, pull the anode cup and make sure the anode wire is tucked fully inside the rubber boot at the top of the suction cup. Sometimes the end of the wire can pop out or 'ride up' inside the suction cup. Make sure everything is tucked in well.

Then, clean the area around the anode hole. Make sure there's no dust/debris. Try not to get any water in the hole.

Once everything is nice and clean. Reattach the anode lead and once you've made sure everything is secure, plug her back in. As long as everything is clean and dry, the arcing should not come back.

Is it humid where you are today? High humidity can cause the anode to spark too.
 
The anode prongs are in the tube - not the disc.

The arcing is coming from inside the tube, itself - not the anode leads. And the ozone smell is really strong. It wasn't doing this before I replaced the capacitors.

But the picture on the screen is prefectly fine. I'm just worried that if I leave the monitor on for more than 20 seconds, the tube will explode.
 
The arcing is coming from inside the tube, itself - not the anode leads.

Wha.....?????

Are you seeing the purple plasma glowing inside the tube itself? If so, the tube is bad - it's gassy either from a crack or a slow leak somewhere.
 
You forgot to answer my question about humidity.

Humidity has been high, but the machine and my workspace are inside, with air conditioning and a dehumidifier

Wha.....?????

Are you seeing the purple plasma glowing inside the tube itself? If so, the tube is bad - it's gassy either from a crack or a slow leak somewhere.

Yes. If you look at the tube from the rear, it's coming from the inside of the tube.

Another thing is, when I discharge the anode, I'm not getting the cracking noise you usually hear.

Before I capped it, the monitor worked, but sometimes came up really dim, and if you tapped the side of the chassis, or slapped the side of the cabinet, the monitor would come back at normal brightness. I resoldered all the cold solder joints as I recapped the monitor. But when I plugged it back in, this started.
 
post a pic or video of this....

you did remember to reconnect the tube ground to the neckboard correct?

i would not expect the tube to work at all if it has lost vacuum or been cracked.
 
post a pic or video of this....

you did remember to reconnect the tube ground to the neckboard correct?

i would not expect the tube to work at all if it has lost vacuum or been cracked.

Yes, I screwed the tube ground back to the chassis.

mon2.jpg

mon1.jpg


I couldn't get a good picture or movie, so I marked the spot where it's arcing.
 
FIXED IT! Turns out when I resoldered the cold solder joints on the main PCB, I forgot to do the ones on the neckboard!

One of the pins on the neckboard had a really bad cold solder joint. So I resoldered much of the neckboard, and VOILA!! No more arcing/crackling noise and ozone smell!
 
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