RE: Atari B&W: no HV

> As for shorting the HV diode to the chassis, that sounds really
> dangerous...I would never even consider it. In fact, I'm going to test
> everything _else_ first. Thanks for the warning, though.

Just to make sure that you understand:

This discussion relating to 'shorting' has to do with discharging the CRT
(unit powered off and unplugged). As you are probably aware, a CRT will
hold a residual charge and needs to be dissipated prior to working on the
monitor (this applies to both raster and vector monitors). Some monitors
automatically dissipate the CRT charge over time, some don't -- and the CRT
can hold the charge for a LONG time.

The proper method to discharge the monitor is to short the second anode
(place where suction cup attaches to the CRT) to the DAG (spring or metal
strap on back/bottom of CRT). You *don't* want to short the second anode to
the chassis ground, etc. because then the discharge has the potential to
travel through circuitry (this case speaks of the HV diode) and cause
incidental damage.

There are numerous topics on proper methods for discharging, some of which
are mentioned in subsequent messages.

Finally, you *NEVER* want to short/discharge the CRT when power is applied
to the unit.

> -----Original Message-----
> From: owner-vectorlist@synthcom.com
> [mailto:owner-vectorlist@synthcom.com]On Behalf Of Anthony Ramos
> Sent: Thursday, December 6, 2001 7:09 PM
> To: vectorlist@synthcom.com
> Subject: Re: VECTOR: Atari B&W: no HV
>
>
> Thank you for the suggestion. I will check the other incoming/outgoing
> voltages and report what I find.
>
> As for shorting the HV diode to the chassis, that sounds really
> dangerous...I would never even consider it. In fact, I'm going to test
> everything _else_ first. Thanks for the warning, though.
>
> on 06 12 01 10.20, John Robertson at jrr@flippers.com wrote:
>
> > Easy test. Check the other voltages for the HV transformer
> circuit. If you
> > get the other HV's but no 12KV, then your HV diode is shot. If
> you do NOT
> > get the 90VDC and 400VDC (? I can't remember, something like
> that...), then
> > you have a problem somewhere else.
> >
> > ---->>>Remember: NEVER, EVER EVER SHORT A B&W HV ANODE TO THE
> > CHASSIS!!!!!!!!!!!<<<----
> >
> > You must use a HV meter or a series of 1 meg resistors (total 10Meg
> > insulate the suckers!) to discharge the HV anode on the side of
> the tube.
> > This is what is killing the HV diodes, getting the anode shorted by a
> > jumper wire to the chassis common...
> >
> > John :-#)#
> >
> > At 10:41 PM 12/05/01, you wrote:
> >> Hi again everyone,
> >>
> >> Awhile back I asked for help diagnosing my Battlezone
> cabaret's monitor. It
> >> has yoke chatter and neck glow, but gone no picture, charge on the tube
> >> face, or hissing/whistling sound that used to come from the HV cage.
> >>
> >> A couple of people suspected the HV diode. I'd order a
> replacement, but at
> >> $15 each, I'd like make sure I need one.
> >>
> >> Is there any way for me to test this diode? I don't have any
> known-good HV
> >> cages to put it in.
> >>
> >> Besides, I thought that a bad diode caused screen *bloom*, not
> total picture
> >> loss. Shouldn't the transformer still be hissing/whistling?
> >>
> >> I'd appreciate any suggestions. Thank you...
> >>
> >> -Anthony R.
> >>
> >> --
> >> Anthony Ramos________
> >> 600 SE 39th Ave., # 3 \__ aramos@ele-mental.org ..
> aramos@hyperreal.org
> >> Portland, OR 97214 \___ information design .. multimedia
> production
> >> (503) 236-6303 \____________interactive art .. image
> synthesis
> >>
> >>
> >>
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> >
>
> --
> Anthony Ramos________
> 600 SE 39th Ave., # 3 \__ aramos@ele-mental.org .. aramos@hyperreal.org
> Portland, OR 97214 \___ information design .. multimedia production
> (503) 236-6303 \____________interactive art .. image synthesis
>
>
> ------------------------------------------------------------------
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> "UNSUBSCRIBE" in the
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> ** questions, comments, or problems to neil@synthcom.com.
>

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Received on Fri Dec 7 11:39:14 2001