G07 Rebuild
The G07 monitor and chassis have been sitting on the shelf mocking me since this project began. The new cap kit arrived. Time to clean up and rebuild the monitor.
I had already done a quick pre-clean on the chassis, but it was still too dirty and still had a harsh chemical smell to it. I did 2 more thorough scrubs before doing any soldering.
https://drive.google.com/file/d/1K94IGaIJSJGHnReLja_CSGxjlSysmfDZ/view?usp=sharing
My plan was to do a standard G07 cap kit, replace the crusty old potentiometers, check the transistors, apply new heat sink compound as needed, and reflow all the big pin headers.
Capacitors to replace:
Component: Value/Rated Voltage
C905: 10µF, 250V
C523: 1µF, 160V
C408: 4.7µF, 50V
C504: 1µF, 50V
C411: 100µF, 160V
C521: 2200µF, 25V
C511: 47µF, 160V
C107: 10µF, 250V
C403: 100µF, 16V
C412: 3.3µF, 160V
C302: 220µF, 16V
C518: 220µF, 16V
C517: 100µF, 16V
C701: 100µF, 6.3V
C407: 4.7µF, 63V
C506: 33µF, 16V
The cap kit included replacements for all of these. It also included a new R908 (47k, 1/2W).
The G07 chassis is a single-sided board so its easy to work on. Even my cheap bulb-type desoldering tool made quick work of the capacitor removal. I made sure to take pictures of every cap before taking them out.
Although it wasn't going to be replaced, I removed the big C904 cap to make (even more) board scrubbing easier. While it was out, I measured it to be sure it was still good. It was.
Along with the cap kit, I splurged and bought $5 worth of pots to replace the Hfreq (5k), Vhold (10k), Vlin (200), and Vheight (200) potentiometers. The old ones looked long overdue for retirement:
https://drive.google.com/file/d/1sKclKu31hY3URyXL8cemjO61247pKkXl/view?usp=sharing
With all these caps removed, it was obvious some of them had leaked:
https://drive.google.com/file/d/1_gaJPPauZzKucsTlHkZQ-jYipeGopF5u/view?usp=sharing
I know some people just put their chassis in the dishwasher to clean them. I suppose this would work. But, I don't like the idea of this electrolyte residue splashing around the same space as my dishes.
I did one last cleaning with Simple Green and a toothbrush. I'm finally feeling like this board is clean enough. Most of the white residue is gone.
Next, I unsoldered the C1106 regulator transistor from the circuit to test. Its not shorted, but the gain (22) seems a little low. It may just be my tester. This is a high voltage, high wattage transistor and this little tester isn't really pushing it. Since its not shorted, I'm betting its fine:
https://drive.google.com/file/d/1krO94DNmQMXy0GKlix-RXSWaJ8bb6bfU/view?usp=sharing
The horizontal output transistor was next to test. This one showed up as a common cathode diode network (i.e. a transistor with no gain). Again, not shorted so probably OK. The gain of this transistor isn't that high anyway (like 8).
Pretty sure this little tester isn't testing with high enough voltage/current to accurately gauge the performance of these TV transistors. Back in it goes.
https://drive.google.com/file/d/1s2o6LKqHy5i1Y8yea3PjOCVNoj_SUJak/view?usp=sharing
More Repair Notes:
1- The plastic inside horizontal width coil was broken. This means I cannot make adjustments if necessary. Its not deformed, so I'm going to leave it. If the picture width is OK it won't matter.
The flyback is visually good. I think these blow out pretty bad when they fail. I'm not gonna mess with this right now either.
2- I made sure to put new thermal paste on the heat-sinked transistors in the center of the board.
https://drive.google.com/file/d/1U2omJOJAh7Lmo7ZvLIN4uQ9vDIgfUmfP/view?usp=sharing
R908 tested good, so I left the old one installed.
There's a Mod for G07's to fix curling problems. I didn't do this mod.
All the fuses were good.
The polarity of C302 shown on the solder side is wrong. The polarity shown on the parts side is correct. My advice is to take pictures of all caps before removal to ensure no polarity errors with the new ones.
I reflowed all the pin headers to avoid cold solder joint issues.
All done with the chassis!
https://drive.google.com/file/d/1rAziCLNFg_mAuVVyu4B8DJtHOv_WI9R3/view?usp=sharing
On to the tube cleaning...
While I was content to spray/scrub the front of the screen and the frame, I just dry brushed the back and used a little compressed air. The aquadag looked good, and I DID NOT want to screw it up by cleaning too much. I also just gently brushed the yoke and neck. I'm OK with some grime here if I can prevent a cleaning related catastrophe.
https://drive.google.com/file/d/12LapCq1_BwgVyureFGA1CGl4U24J2AJ-/view?usp=sharing
Attaching the chassis completed the monitor. While it certainly LOOKS way better, I have no idea if it works. I don't have a monitor test rig (isolation transformer and test pattern generator), So I'm just going to wait until the cabinet is done and test it then.