"Wiebe Cazemier" wrote in message
b.home.nl...
On Saturday 26 April 2008 19:40, bz wrote:

So, what is different about 'just turned on'?
Components are cool.
High transient currents occur.

Look for places that those can make a difference.

(snip)

From the symptoms, I would start by looking at the PSU outputs.
Troubleshoot by 'divide and conquer'.

Divide the device logically into two halves, and localize the problem to
one of the two.

Continue until you reach the bad part.

I've been reading the repair faq at
http://www.repairfaq.org/sam/crtfaq.htm. At
some point it says this:

Occasionally, small conductive flakes or whiskers present since the day of
manufacture manage to make their way into a location where they short out
adjacent elements in the CRT electron guns. Symptoms may be intermittent
or
only show up when the TV or monitor is cold or warm or in-between. Some
possible locations are listed below:

One of them is: Heater to cathode (H-K). The cathode for the affected gun
will
be pulled to the heater (filament) bias voltage - most often 0 V (signal
ground). In this case, one color will be full on with retrace lines. Where
the
heater is biased at some other voltage, other symptoms are possible like
reduced brightness and/or contrast for that color. This is probably the
most
common location for a short to occur.

That appears to be exactly what's happening. The blue gun is turned on
completely, also showing the retrace lines. Also, remember that I have
been
able to reproduce the fault a couple of times by tapping the cathode
assembly.

I will try the "put the monitor on it's face and try tapping it to
dislodge the
short" method first. If it works, it would be a very low tech, but
effective
solution

The "blow out the short with a capacitor" method also seems fun, but also
a
little risky

Don't be so quick to condemn the CRT, sure it could be at fault, but
eliminate the external stuff first! A bad connection on the neck board can
just as easily cause the same symptom.