- CRT question - 9 Updates
| etpm@whidbey.com: Aug 22 10:31AM -0700 On Thu, 22 Aug 2019 09:02:25 -0700, Jeff Liebermann <jeffl@cruzio.com> wrote: >>Eric >Well, there might be a component failure, but let's play with the >knobs a bit more first to see if things improve. I'll need to see if I can get thing to make just a straight line. If not I can lock the display to just showing digits. Then I can adjust the astigmatism and see if the digits on the right hand side of the display get sharper. I can also swap the X axis wires, which mirror images the display. I know because I already did this accidently. If the focus problem mirrors too then I wonder what that would mean. I'll try the astig. adjustment first later today. Thanks, Eric |
| Jon Elson <elson@pico-systems.com>: Aug 22 01:38PM -0500 On Wed, 21 Aug 2019 16:47:10 -0700, etpm wrote: > So I built a kit that uses an electrostatic deflection CRT for the > display. It all turned out very well except the display is much more in > focus on one side of the screen. Do they use true differential deflection signals, or unipolar (ie one plate of each deflection pair is held at a constant voltage)? If unipolar, it can cause this type of trouble. Jon |
| etpm@whidbey.com: Aug 22 12:11PM -0700 On Thu, 22 Aug 2019 13:38:15 -0500, Jon Elson <elson@pico-systems.com> wrote: >plate of each deflection pair is held at a constant voltage)? If >unipolar, it can cause this type of trouble. >Jon I dunno Jon. How would I tell? Measure voltage to ground and see if one or both changes? Eric |
| Paul Drahn <pdrahn@jodeco.com>: Aug 22 12:48PM -0700 > I dunno Jon. How would I tell? Measure voltage to ground and see if > one or both changes? > Eric If you physically rotate the whole device 90 degrees, does anything change? Possible magnetic flux from your shop! Paul |
| etpm@whidbey.com: Aug 22 01:59PM -0700 On Thu, 22 Aug 2019 12:48:31 -0700, Paul Drahn <pdrahn@jodeco.com> wrote: >If you physically rotate the whole device 90 degrees, does anything >change? Possible magnetic flux from your shop! >Paul Greetings Paul, Yeah, the CRT is especially sensitive to magnetic flux. But the thing has the out of focus problem no matter the rotation or where I stand in my shop. It is always less focused on one side. But thanks anyway. I know almost nothing about tubes in general and CRTs in particular. Eric |
| stratus46@yahoo.com: Aug 23 02:12AM -0700 > even? > Anyway, thanks for any help. > Eric High Voltage on CRTs tends to use very high resistance. An 11 meg meter could load down the test points and give faulty readings. A high Voltage probe is often around a gigohm load and cause much less disruption in the readings. G² |
| John-Del <ohger1s@gmail.com>: Aug 23 05:01AM -0700 > even? > Anyway, thanks for any help. > Eric In theory, voltages shouldn't have any affect on the focus across the face of the CRT, but in practice, all sorts of variables happen. It's indeed possible that your problem will go away if you get the CRT close to it's designed operating voltages. At least, that's what I would do before condemning the CRT as defective. Is there a schematic of what you built on line? |
| etpm@whidbey.com: Aug 23 08:44AM -0700 On Fri, 23 Aug 2019 05:01:33 -0700 (PDT), John-Del <ohger1s@gmail.com> wrote: >In theory, voltages shouldn't have any affect on the focus across the face of the CRT, but in practice, all sorts of variables happen. >It's indeed possible that your problem will go away if you get the CRT close to it's designed operating voltages. At least, that's what I would do before condemning the CRT as defective. >Is there a schematic of what you built on line? No, there is no schematic. Paul Drahn suggested to me that the CRT may need to be degaussed. I have a demagnetizer designed for demagnetizing tools. I'm sure it would work to degauss a CRT. Eric |
| John Robertson <spam@flippers.com>: Aug 23 09:16AM -0700 > need to be degaussed. I have a demagnetizer designed for demagnetizing > tools. I'm sure it would work to degauss a CRT. > Eric A Weller heavy duty soldering gun is also useful as a small degaussing tool if you don't have a proper open coil one handy. John :-#)# -- (Please post followups or tech inquiries to the USENET newsgroup) John's Jukes Ltd. MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3 (604)872-5757 (Pinballs, Jukes, Video Games) www.flippers.com "Old pinballers never die, they just flip out." |
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