B/W vector monitor discharging question

davemcl

Member
Joined
Mar 29, 2010
Messages
128
Reaction score
0
Location
New Jersey
I'm only familiar with discharging color rastar monitors with a screwdriver, wire & alligator clip. I have to discharge a couple 19V2000 vectors & understand I should use 1000K resistance between the screwdriver blade touching the anode & the alligator clip touching the monitor frame. Can I take 10- 100K resistors, solder them togerher end to end, shrink wrap them & then solder a wire with alligator clip to 1 end & a wire attached from the other end to the screwdriver? I'm told if I don't place resistors in the circuit, I'll fry the high voltage diode.
Also, which end of the resistors sould be attached to the screwdriver (end with the last colored band or with no band?)
Thank you
Dave
 
In another thread:


03-22-2010, 02:29 AM

Blades
Senior Member

Join Date: Aug 2008
Location: N. P. Nebraska
Posts: 677

Bob Roberts response....
Quote:
Originally Posted by mhanlen1
After reading the above links, it seems that discharging via the screwdriver method could hurt the diode, if there's ever a pop. For all those experienced with a G05- how do you discharge it? I only have a screwdriver and not the proper tool. Is it necessary? If so where do you buy one, and are they expensive?

You know, I've asked Bob Roberts that same question when I was recapping my GO5. And he told me ... well let me see if I have that email.... yep here it is:


I asked him this:
Also would your Safeback Discharger kit be safe for discharging this
monitor? I read in the B&W Vector FAQ, that it can cause the HV Rectifier
Diode to fail if you don't use Ten 100K-Ohm resistors in series. Is that
necessary? I've discharged raster monitors before(without resistors),
however I don't know if you need to have the recommended resistors in place
for a vector monitor. What do you think? Will your discharge kit work just
as well for this vector monitor?



Bob Roberts responded with this response:

Basic electricity 101 as taught since the days of Edison until now:

"Electricity ALWAYS seeks the easiest path to ground! It does not "care" how
it gets there. If you or your equipment create that path, you will be
placing yourself (and possibly others) in a life threatening situation."

So... if you don't hold onto the ground wire with one hand & touch the metal
frame with the other it will not go through you to get to it's objective nor
will it go through a diode, or any other component, unless you put it in the
path to ground. In the case of discharging a monitor with a Safeback, it's
absurd to think that the electricity with a nice solid path to ground is
going to somehow allow part of it's charge to go in reverse looking for a
much harder path to ground.... yet... the inet stories still grow such as
the one about ketchup containing the HIV virus!

For a common sense view... while the monitor is on there is a constant
17,000 to 22,000 volts applied directly to that HV diode.... not just the
small residual charge left in the CRT.




So there you have it. It makes sense and I've had no problem discharging it with a screwdriver and a wire. Bob knows his sh*t that is for sure.


;
__________________
Ahhhh...Troubleshooting...It's the Game we play for the Games we want to play...
Last edited by Blades; 03-22-2010 at 02:31 AM.
 
Thanks

Thanks, wasn't any voltage present, but better safe than sorry. I tried doig a search before asking, but didn't find that.
Seems I need to replace the insulator/connector from the HV transformer to HV diode. The old one broke apart in my fingers trying to dislodge the diode.
 
I've discharged these monitors hundreds of times with nothing more than a wire, clip and screwdriver and never once lost a diode. These things bleed out pretty quick and you may find nothing at all after about 20 minutes. Bob's statement is right on!
 
Last edited:
There are cases where you do NOT want to discharge directly to the frame but I've never seen that on arcade monitors.

Older Apple Macintosh computers such as the Mac, Mac Plus, SE, and SE/30 had a habit of blowing the single TTL chip on the video board if you discharged to the frame.
 
Thanks!

Big thanks for the advice. Got the HV diode cleaned up, frame transistors replaced, recapped both boards & it's back up & running.
 
I also asked Bob Roberts for a resistor to use to discharge a G05.

This was his message to me:

==============================
Sounds like one of those crazy things you read on the inet. Don't have any
bleeders & never used them. It's a totally unbelievable conception that
discharging a CRT to ground needs to be done with a bleeder. In fact, those
that use HV probes to discharge often find a surprise waiting for them when
they remove the anode :-(
==============================
 
I also asked Bob Roberts for a resistor to use to discharge a G05.

This was his message to me:

==============================
Sounds like one of those crazy things you read on the inet. Don't have any
bleeders & never used them. It's a totally unbelievable conception that
discharging a CRT to ground needs to be done with a bleeder. In fact, those
that use HV probes to discharge often find a surprise waiting for them when
they remove the anode :-(
==============================
I like that writeup. A rather shocking little surprise it is!!

Ive never done more than the screwdriver method. Only change for a older monitor (vector or raster!) is that I repeat the discharge a few times with a good 30min inbetween. Id only use the hv probe to make sure honestly (i dont even own one). Granted, I dont work on monitors much, but i do swap em from time to time.
 
Back
Top Bottom