HP Ultra VGA 1280 / D2807A monitor degaussing coil

[rvdbijl]

Hi All,

I've had this nice old CRT monitor for a while, but it's always had a funny color gradient and slight bending of the image on the top right corner of the screen. I'm pretty sure someone has had some fun with magnets with this thing in the past. It has a degaussing function on the menu, however, when I select it, nothing happens (besides a slight click), but nothing like what I'm used to seeing on other monitors (like a buzz, shaking image, etc). So I suspect something in the degaussing circuit or coil is broken.

Does anyone have any hints on how to begin to diagnose / fix this? Or is it a total loss?

Thanks!

 

[modem7]

Or is it a total loss?

Assuming a 'lack of degaussing' cause, in the worst case, you could always just periodically use a cheap CRT degaussing wand, such as eBay item 183543449913.

 

[rvdbijl]

Assuming a 'lack of degaussing' cause, in the worst case, you could always just periodically use a cheap CRT degaussing wand, such as eBay item 183543449913.

Good point.. Going to try that first instead of trying to open up this monitor. Maybe I'm a bit on a fix-it kick since I just fixed an old IBM 5151 monochrome monitor. But that was way easier than one of these I'm sure!

Thanks!

 

[modem7]

Good point.. Going to try that first instead of trying to open up this monitor.

What you could do is get the cheap CRT degaussing wand to prove that the problem cause is a 'lack of degaussing', then attempt to hunt down the fault in the inbuilt degaussing circuitry. I guess you could also (with appropriate use) use the degaussing wand for floppies/diskettes.

Maybe I'm a bit on a fix-it kick since I just fixed an old IBM 5151 monochrome monitor. But that was way easier than one of these I'm sure!

Not necessarily. On the older CRT's, the circuit was as simple as the ones shown at [here]. Your CRT will have extra components so that degaussing can also be done on demand. You could discover something as simple as a bad solder joint on the thermistor.

 

[Hugo Holden]

A degaussing wand would be likely to fix it. Often, the internal degaussing is not powerful enough to demagnetize a well magnetized shadow mask and just won't do it, even if the degaussing system is normal....but be aware of this:

The radiated fields from degaussing wands extend a long way from the wand, the field 3 feet away is still very significant. It is important do deploy it well away from any electronics devices, wrist watches, floppy disks and drives. To avoid disaster, I take the TV or monitor out of the workshop to a place like the living room table, where there are no devices and degauss it there. The wand can be held near the CRT front screen (don't put it near the gun) then once activated move it in circular motions slowly away from the screen to at least 4 feet before switching it off, that way there is minimal residual field in the CRT's shadow mask. Most wands heat up quite quickly so don't hold the button down for too long, 5 seconds or less is plenty.