What's New, LabGuy?
Added a new project page today. I got bored yesterday and decided to convert my NBTV Baird 32 line Televisor kit to color operation. What do you know? It worked!
I have completely rewritten the Goldmark 1 project pages. There is a lot more work to go. But, the pages now reflect the completed Goldmark 1 color TV and all the superfluous mucking about has been stripped out. I will add in more details as time permits. For now, enjoy the rebuild.
I have updated the Goldmark 1 project front page. Showing the progress to date. The color servo gets better with each new iteration. The wheel balance issue is going to require a slight rebuild of the wheel and motor mount. I am gong to place the wheel on an axle suspended in ball bearings like I planned to originally. The motor will be on a separate mount. This also allows me to lower the wheel slightl as the new monitor is not as tall as the original Akai monitor. It should be a lot easier to balance the wheel in the new configureation. I plan to attache it to the motor with a flexible coupler to eliminate coupling any vibration back to the motor. Stay tuned!
I took some time this afternoon to dismantle the Goldmark 1 and paint all of the support structure flat black. It came out very well. Also completed bolting down the video monitor so that the vibration doesn't make it walk away. Mounted the power supplies on end to not consume a lot of space. The last thing is to dirll the holes and attach the servo circuit board to the base board. Will need to hit the hardware store for some inch and quarter length number four machine screws. As you can see in the third photo, the Goldmark 1 makes a darn good picture after I tweaked up everything.
There was also some progress toward wheel balance. I have traced the wobble to the color wheel mounting puck. When the set screw are tightend, the mounting flange is not centered on the motor shaft. I put a single layer of scotch tape on the opposite side of the motor shaft, from the set screw faces, and reinstalled the wheel. Run out is now almost zero and the vibration is noticably less. I think it is down to truly balancing the color wheel now. Stay tuned for that.
Earlier that same day....
In the OLDVTRs discussion forum, the subject of color fringing on moving objects came up. The scan converter I use suppresses the effect very well, making it dificult to demonstrate. But, while recording video, the fast movement of the camera produced the effect. You can clearly see the separation of the various scans. But, normally this is not viewable.
Goldmark 1 update. The video monitor achieved first light this week and there are now two YouTube videos showing it in operation.
There are few issues left to resolve. Balancing the color wheel is now number one priority and I will devote some time to this, this coming weekend. Then the monitor must be addressed. The CRT is out of focus and the scan raster is being modulated by the vibration of the near by very large DC motor. This blurs the image even more. At 80% the resolution of NTSC, we have no margins to lose here.
Goldmark 1 works! We made our first color pictures today at 4:45pm PST. There is still a lot to fix. But the basic operation was finally demonstrated. First, the new video monitor is scanning well enough to produce a fine undersized picture. All of my new circuits worked virtually first time. Initially had the video signal inverted. That took only five minutes to fix. Adjusted the pulse width of horizontal drive and got the monitor to operate at its normal voltages. The scans were short in both axis as I expected. Horizontal needs an inductor changed to widen it. Vertical requires a capacitor change. I don't anticipate any problems there. The picture is currently scanning about two inches diagonal and nothing is pulling abnormal current or running hotter than normal.
Then I put it all together for the first time. The video monitor, servo board and color wheel assembly. Turned it all on and proceeded toward success from there. It is making pictures. But, that does not mean it is finished. The servo is very slow to reach speed and it is sloppy when it is locked. It drifts in and out of phase constantly. I will balance the speed vs phase servo summing ratios to resolve this.
The darned thing was hard to photograph clearly because the wheel still needs to be balanced. The whole rig was trying to walk off of the table! Still, this is an excellent milestone. I will update the project article accordingly in a few days.
I fixed the horizontal pulse timing and now have the entire picture on the screen. It was folded over previously. Now I can set the drive pulse width to where the flyback and yoke are working perfectly and also have full image centering control now.
Goldmark 1 project update. Completed the mounting of video monitor number two. It was made by Sony for Tektronix in the mid 1980s. The Akai CRT is on the side lines for now. We will be testing this 3.5" CRT monitor pulled out of an obsolete logic analyzer. It requires plus and minus five volts. So, I added two new voltage regulators and heat sink to the servo board just for this purpose. We will need to add an inverting video amplifier with some unknown amount of gain. I have three spare video op amps on board for just such an emergency. Next step is to measure and make two interconnect cables for between the video monitor and the main servo board. Then add the approriate connectors and new sync and video circuits to the servo board.
I feel some trepidation about getting this new CRT monitor to work at 29.16KHz. It was running at near 15.75KHz in the analyzer. I have the full service manual and monitor schematics. So that helps. But, who knows? It just might work.
Goldmark 1 project update. I have obtained another CRT video monitor to try in this TV. It is an instrument monitor rmoved from a logic analyzer. I fear it will also be a dud in the end because it turns out to be a Sony tummy TV. But the ciruits are stripped to the bare minimum. This might mean that bending the horizontal scan rate won't be as difficult as with the Akai monitor. Fingers crossed there.
I started the day by adding the new plus and minus five volt regulators to the color wheel servo board. The new monitor use this for its primary power supply. Simple enough. Mounted a large solid heat sink for the regulators and had it all wired before lunch time. Have been slowly assembling the monitor support frame. I have created the base platform to fit where the Akai monitor previsouly did. Mounted the CRT bezel to some C channel extrusion and bonded that to the front of the base. Tomorrow, a trip to the harware store for three inch spacers to hold up the circuit board and to completely mount the CRT. Then it will be safe to power up. Please stand by.[Sneak peek 1] [Sneak peek 2]
Happy New Year!
Added an update status report to the bottom of [Goldmark 1, part 7] page. It details the latest progress in designing a horizontal magnetic scan circuit for the three inch field sequential color TV project.
To see years 2007 to 2013 What's New pages, [CLICK HERE]. Scroll to the bottom of each year to find a link to the previous year.
Created: April 6, 2012, Last updated: January 4, 2014