Picked up a donor 19 inch and it's blowing fuses.

Jaak

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Donor 2024-2025
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So I managed to find a 19 Inch commercial tv with a promising yoke reading to swap into the 19k7000 I've been trying to match up to a CRT. It's an Orion tube from a Sansui branded TV. I hooked it all up and it lit up the fuse for a moment and then burned it open. It's the strangest thing. I checked at the usual culprits on the board and everything checked out good. Put another fuse in and it did the same. I put in a third fuse and plugged the chassis into a know good tube with an incompatible yoke and everything works fine.

Can anyone explain how a tube can fail in such a way that it will blow a fuse on a k7000.

Another thing I noticed is that the model number had the number 19 tacked on at the end instead of ending in a letter. The model in this case is A48LGS30X19. Of all of the tubes I've seen so far in the past year have all had model numbers 9 characters long ending in a letter (usually in an X).

Maybe the pin out on the tube is custom? But it did fit the cr31 socket like a glove.

Anyone have any insight on this?
 
According to Tubular.Atomized.org, it is a CR-31 socket. Test the yoke and post the readings here. Some of the monitor gurus here may be of help.
 
According to Tubular.Atomized.org, it is a CR-31 socket. Test the yoke and post the readings here. Some of the monitor gurus here may be of help.
The yoke checks out and the tube does not exist in Tubular, only the shortened version of the model number without the 19.
 
The yoke checks out and the tube does not exist in Tubular, only the shortened version of the model number without the 19.
Basic questions:

"what does yoke checks out" mean? The values are within K7000 range? The yoke isn't shorted?

Are you using isolated power?

I assume this is a known working chassis; blowing fuses is a power supply issue. I would go though the power section and check every component.

I assume you are hooking it up properly, but post up a pic.
 
You are describing a dead short condition.

You'll need to figure out the new tubes wiring, and make sure the connector wiring is the same. It sounds like something got shorted to ground in your hookup. Stop and meter every thing to the chassis before you let the magic smoke out and do damage.
 
Basic questions:

"what does yoke checks out" mean? The values are within K7000 range? The yoke isn't shorted?

Are you using isolated power?

I assume this is a known working chassis; blowing fuses is a power supply issue. I would go though the power section and check every component.

I assume you are hooking it up properly, but post up a pic.
Yoke checks out as in it is reading as expected inductance ranges for a 19 inch tube. 3.3mH on the horizontal coil and 26mH on the vertical coil.

I am issuing an isolation transformer.

I did check the power supply section of the board and everything is measuring as expected. No damage done.

I am certain everything was hooked up properly. Like I said, I also hooked it up to another tube that I rejected but still had around and it worked. No fuses blowing. I hooked it up to my CR70 using the standards cr31 pin out and I'm unable to set the cutoff level nor test for emission. Needle won't move at all for those tests.

It's the strangest thing.
 
You are describing a dead short condition.

You'll need to figure out the new tubes wiring, and make sure the connector wiring is the same. It sounds like something got shorted to ground in your hookup. Stop and meter every thing to the chassis before you let the magic smoke out and do damage.

I confident the problem is internal to the tube. I posted to see if anyone had ever come across something similar.
 

Looks like you're not the only one. I once ran into a CR-23 25" tube that was similar in that there was no emissions or unable to set the cut offs, no neck glow, nothing. I just tossed it.
 

Looks like you're not the only one. I once ran into a CR-23 25" tube that was similar in that there was no emissions or unable to set the cut offs, no neck glow, nothing. I just tossed it.

Yha, it's in my recycling pile now.
 
I confident the problem is internal to the tube. I posted to see if anyone had ever come across something similar.
If you can find the pinout for the tube, you can check this. Look for shorts on the guns. It sounds like a non-compatible tube to me.
 
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