NeXT Monitor Problem

[Jerry Weiss]

On 11/8/18 10:08 AM, Ethan via cctalk wrote:
>> The monitor works okay; slight burn in, but otherwise looks okay in 
>> terms
>> of the phosphor. However, something seems to be wonky with the 
>> horizontal
>> scan...the left edge is very wobbly.
>
> Replace all electrolytic caps with new Panasonic of Nichicon 105 
> degree caps from a source like Digikey, Mouser, Newark or AVNet.
>
> So... I've heard a lot of NeXT monitors get dim over time. There is a 
> tool for rejuvinating CRTs. I wondere if it would work rejuvinating 
> NeXT monitor to bring back brightness.
>
My recollection is that the NeXT monitors left their heater (filament) 
on all the time, when the computer was otherwise off. This causes the 
cathode emission to decay over time.  Some of the rejuvenation devices 
work by simply raising the heater voltage. The others work by 
temporarily raising the heater voltage while using a high voltage 
between cathode and CRT to try to reform the cathodes. I don't have any 
experience in using these with the NeXT monitors, but the first method 
is likely to shorten the filament life even further.  If the CRT is 
"gassy", not much can be done.

I would definitely image the drive before it deteriorates any further.  
Be careful about using the 'dd' command with a 'bs' other than the 
sector size of the disk.  Since the drive already has bad sectors, using 
the "conv=noerror,sync" option has some unexpected side-effects when 
bs>sector size.  See http://www.noah.org/wiki/Dd_-_Destroyer_of_Disks 
under "Copy a drive to an image file"

Jerry