Atari 720 H-Width Coil - Glow Plug?! ACK!

Mikebetz42

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So, I bought a 720 that had a "Strange issue" with the monitor. Wells Gardner K5515

The guy said he capped the monitor, but it made it worse.

When I asked about the "Made it worse" he said that the monitor worked, but was really dim.

I pulled the chassis to look for any issues with the cap kit, but it looked fine. All the caps were in there correctly. but the horizontal width coil plug was allmost all the way unscrewed out the top.

So I screwed it back down into the coil a bit, about half way. Plugged in the chassis and fired up the game. it was dark out when I did this and was looking at the chassis when I plugged it in (to check for a spark/smoke).

So I see a red light/glow, then noticed it was the bottom of the Horizontal Width coil. Pulled the plug imediately.... WHAT happened? Can you make a width coil do this if you screw it down too far?

Anyways I am perplexed.... I wonder if it's the coil or something on the board causing the coil to do this.

The monitor did fire up, I could hear it click on, and the HV static. I did not run to see if it had a picture as the width coil was red in about a second.

HELP!

Thanks,

-Mike
 
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Bad solder

Most likely the coil has a bad solder connection to the board and is arcing.
If you pull the chassis and inspect the connection you should be able to fix it up a bit with some solid copper wire. If the board is burned badly you can use the wire to construct a new trace in most cases.

PS... the dim problem is likely an aged CRT.
 
It looked like the solder jounts were ok when I had it out, but I will take another look. I took a quick look at it, as the plug/core was up sticking out of it about 1/4 of an inch. Not to say I may of broken something loose when I messed with it....

Anything else would make this happen? There was no metal that I could see in it or under it. It was a great glow, like it was an LED.

I have a chassis that may work as a test in my Papperboy.... I will see if it's the same..

Thanks,

-Mike
 
glow

I assumed the glow was coming from under the coil... but if the actual coil windings themselves are glowing then you have obviously got an over current issue. Something is causing excessive current to flow through the coil. I would start by checking components directly connected to the coil for lower than rated resistance or shorts.
Whatever it is can't be blowing the fuse... unless a higher than recommended fuse is being used, which is not a good idea.
Check c723 for a short.
 
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coil adjustment

The position of the slug in the coil shouldn't cause it to glow red, and the design of the coil would make it unlikely that tightening the slug down too far would cause any damage.
Usually the ferrite slug will simply start to 'skip' on the plastic threads of the slug housing when turned in too far.
I would suspect a pre-existing condition... it IS possible that disturbing the chassis may have caused this condition to show itself.

If the coil is glowing red, as I understand, this is VERY unusual and most 'normal' troubleshooting procedures one would use are not applicable in this case. This condition IS however indicative of excessive current flowing through the coil.... the next step is obviously to determine why.... and what components could theoretically cause this to happen.
Some monitor problems are real head-scratchers, but all are correctable if you have patience and perseverance...not to mention a large supply of parts.
 
were you using an allan key to adjust it?

Only to screw it back down, before I put it back in it's cab... I did not leave it in there. There were no fragments left inside the core.

I have heard about the metal tools in the coil causing them to heat up and do some dammage!

-Mike
 
The position of the slug in the coil shouldn't cause it to glow red, and the design of the coil would make it unlikely that tightening the slug down too far would cause any damage.
Usually the ferrite slug will simply start to 'skip' on the plastic threads of the slug housing when turned in too far.
I would suspect a pre-existing condition... it IS possible that disturbing the chassis may have caused this condition to show itself.

If the coil is glowing red, as I understand, this is VERY unusual and most 'normal' troubleshooting procedures one would use are not applicable in this case. This condition IS however indicative of excessive current flowing through the coil.... the next step is obviously to determine why.... and what components could theoretically cause this to happen.
Some monitor problems are real head-scratchers, but all are correctable if you have patience and perseverance...not to mention a large supply of parts.

It was definately under or behind the coil, I am sure there is going to be a burn mark. There was no smoke, but you could smell it charing the PCB... :(

I will pull it tomarrow and post some pics, maybe pull the coil and take a good look at it... anyone sell a new one for this chassis? Did not see it on Bob's site...

-Mike
 
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coil

Lots of coils around, but I would check it closer before assuming the coil itself is bad.
I've repaired monitors for over 20 years now and I have only changed width coils because they were physically broken, not burned up.
I would still suspect an open connection under the coil somewhere.
It would be a stretch to say that 'perhaps' if you tightened the slug down too far and it didn't skip in the sleeve that you 'may' have caused the coil to 'lift' due to the 'jacking' action of the slug and you may now have a break either where the coil wire connects to the mounting pin, or the pin itself may be loose in the circuit board. If the wire is broken off the pin, simply unwind a winding and resolder.... you won't have an issue you can't adjust out with the slug. If it's simply a loose lead, resolder.
 
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