Millions of CRT PC monitors are being disposed of and substituted with flat LCD
monitors.

Those old boatanchor monitors contain A LOT of hard-to-find components:

- high voltage transistors and FETs (e.g. 1500V, 15 A)
- high-power fast-recovery and Shottky diodes
- high voltage electrolytics and capacitors
- high power resistors
- large ferrite beads and toroids
- inductors of all possible kinds
- beautiful heat sinks
- line filters
- integrated circuits
- etc. etc.

Typically, you will find two boards, a main board and a smaller board which is
directly connected to the CRT socket. Both are valuable.

You may get CRT monitors for a few bucks or even for free (e.g. my company is
getting rid of all CRT monitors and the boards can be easily removed before
disposal).

For quick components extraction you will need a powerful soldering iron, at
least 100W.

I wonder whether anyone would could help me understanding the rationale behind a
strange inductor I found in many of those boards. It is wound on an (apparently)
ferrite core, say one inch long and half inch diameter. The strange thing is
that the core is magnetized, so it attracts any piece of iron close to it. What
can the reason be to use a magnetized core?

73

Tony I0JX

Antonio Vernucci wrote:
- high voltage transistors and FETs (e.g. 1500V, 15 A)
- high-power fast-recovery and Shottky diodes
- high voltage electrolytics and capacitors
- high power resistors
- large ferrite beads and toroids
- inductors of all possible kinds
- beautiful heat sinks
- line filters
- integrated circuits
- etc. etc.

I would be unwilling to trust electrolytics pulled out of monitors,
but they usually have a lot of nice film capacitors in there too.

Typically, you will find two boards, a main board and a smaller board which is
directly connected to the CRT socket. Both are valuable.

You may get CRT monitors for a few bucks or even for free (e.g. my company is
getting rid of all CRT monitors and the boards can be easily removed before
disposal).

Agreed. They are great parts goldmines for anyone building homebrew radio
gear.

I wonder whether anyone would could help me understanding the rationale behind a
strange inductor I found in many of those boards. It is wound on an (apparently)
ferrite core, say one inch long and half inch diameter. The strange thing is
that the core is magnetized, so it attracts any piece of iron close to it. What
can the reason be to use a magnetized core?

I can think of two reasons: first of all the core could be deliberately
magnetized because it has an asymmetric waveform going through it and needs
to handle big pulses in one direction without saturating, but doesn't need
to be able to handle them in the other. The other possibility is that it
had excessive asymmetry on it and magnetized the core inadvertently.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."