Re: Computer Monitor

Hi Alan,

Comments interspersed below.

> Original Poster: ARSONIST01-at-aol-dot-com
>Tonight my neighbor threw out a computer monitor because he said
> it was old and not compatible w/ his new computer. I happened to be
>the lucky one to pick it up(w/ the intentions of taking the thing apart
>for parts).  I have a few questions though:

> 1) What kind of Transformer does it have?(i know its probably nice
>since when I  busted it open, i saw a "Danger" sign with 25000v
>under that little lighting bolt)

This (all monitors, TVīs, CRT devices) is a flyback transformer. It is a
ferrit cored, high frequency, transformer. Output current usually around
2-3mA, maybe even less. It provides the "excitation" voltage for the
CRT (cathode ray tube) to operate properly (really: at all).

>     2) Now i've opened it up, but does anyone know what the xfmer is?
>i can tell the screen tube and this piece that the tube plugs into, but
>i'm not sure what the  xfmer looks like.

Look at the CRT. In the upper center you will find a rubber "cup" and a
very well insulated wire (usually in "HV" red). Follow this wire back to
the PCB. The funny looking "tower" is the flyback (HV) xformer.
BEWARE, when you disconnect the HV line at the CRT, you might well
receive a shock (CRT acts as a cap). To prevent this from happening,
take a wire and tie it to the CRT ground, which is the bare (!) wire
(NOT the insulated dual wire, this is a degaussing coil) running all
around the crt frame and carefully slip the other end underneath the
cup. If you hear a crackling sound, you have discharged the CRT and
it is safe to remove the cup. Donīt wait too long, because the CRT
WILL regain charge pretty quickly. Be careful when handling the
flyback. The ferrit core is easily chipped or broken, if you drop it
(as ferrit material is very hard and brittle).

>     3) The most important is if this xfmer could be used on Tesla Coil
> applications,   or even jacobs ladders?

I would say ho-hum. You CAN make a small coil with it, but you would
need to build a HF generator (555 and 2x 2N3055) and donīt expect
mega sparks from it. A powerful flyback will give you maybe an inchs
or two worth of sparks (at the flyback), due to the minute current
that the flyback can supply.

Coiler greets from Germany,

P.S.: If you plan on using some of the other parts inside, beware of
the big electrolytic cap used in the SMPSU (real danger!) and if you
use any caps or resistors that were in the horizontal output stage,
check them to make sure they are still okay (= measure them on a
(like Fa. Tomīs) C-meter). Electrolytic caps tend to dry up and die
in monitors and TVs. Esp. those subject to high heat or around
(circuitwise) the HOT (horizontal output transistor) and which are
constantly subjected to "radical" pulses (hard on the caps, due to
their ESR=heat=higher ESR=more heat=death). Whenever I fix
TVs or monitors, I will replace ALL these caps (only a few cents
worth anyway), otherwise Iīll have to open up the da#~-at-~#! thing
again soon .....;o((. So donīt expect much (in the form of e-caps).
The film-foil or ceramic disk types donīt experience this problem,
which means you CAN save these.