Main > Monitor/Video Forum
Recapping a Billabs BL27CB0P
the_77x42:
The B+ filter was super easy to install. I reassembled everything, triple checking all my pictures and...... a pure white screen. Panic. Then the realization that I must have bumped the screen pot on the flyback, so I adjusted it down and things are perfect. Well, the edge squeezing is gone, but the corners of the monitor are still very blurry.
At lower Screen pot settings, making the picture darker, the focus is much better, but adjusting the top two pots on the flyback can't perfect anything other than the very center of the monitor. Leaving the screen pot darker isn't viable because the brightness/contrast settings don't go high enough to compensate. It's been like this since I bought it, however. Hopefully I'll find an adjustment at some point.
On the board I have:
* B+ adjustment
* HV adjustment
* H center adjustment
the_77x42:
I wound up fixing my focus issue by doing the following:
* Adjusted the convergence rings to perfect convergence
* Adjusted the three pots on the board above the yoke to align the corners better
* Increased the Screen/G2 pot on the flyback and lowered the brightness and contrast on the OSD
* Adjusted the focus pots on the flybackThe result is the best the picture has ever looked. There is maybe a one-inch square blurry patch in each of the corners, but it is still readable and not noticeable in game. I'd say this whole project has been a complete success. :)
the_77x42:
Well, I had hoped my recapping would last ten years and it didn't even last eight. The horizontal linearity problem at 15kHz is back and worse than ever. I actually have a bit more experience with board rework now, so I'm hoping to fix this issue once and for all.
After some digging, I'm fairly certain this chassis is a Wei-Ya C2929D-6 (rev 6. that is). That should be the 15-50kHz model. I can't find any schematics for it though. With a similar chassis and problem, changing a capacitor value was able to fix the issue for these folks. Unfortunately, that caused other problems at other resolutions/frequencies.
Since I replaced the board with all Nichicon caps, I'm fairly certain they're still good. Thinking back, I'm not sure the cap kit fixed the right-side compression fully, just made it a lot better. I'm thinking now that it's possible it's the poly caps that are suspect.
I should note I was able to get into the advanced operator's menu by holding UP on the MENU button while the monitor powered on. That had an HL adjustment, which didn't do all that much, but the menu also wasn't available in 15KHz mode. Strange, just the standard menu was available. There's actually no way to H-POS the monitor all the way to the right. There's always about a 2-3" black bar and the image will wrap around itself.
the_77x42:
I finally had some time to look at this.
R74A was measuring at 61Ohms and it should be 68 Ohms. I also noticed it had heat damage, so its replacement will be 5W instead of 2W. I also noticed a couple of the Nichicons that went in previously were a tad leaky, so they'll be replaced. I'm also replacing all the film caps with high quality Panasonic parts.
The main culprit looks to be a fried MOSFET Q31 in the horizontal section. All three pins were shorted and there was some heat damage. I tested all components in the region and they were fine, but I'm putting in some better ceramic caps (C73) and a higher quality MOSFET.
Fingers crossed!
the_77x42:
Unfortunately, replacing the obviously bad MOSFET, the 61 Ohm with a 68 Ohm, most of the film caps, a few leaky electrolytics, and a couple bypass caps in the horizontal section didn't do much. I'm leaning towards a full recap. Again. I've tested the diode in circuit and the resistors close by the MOSFET. The only thing in the horizontal secion I can't test are the small transformers. They have a unique part number that I haven't been able to find:
LL-224-023-00
and
LK-228-050-00
Does anyone know what these are?
EDIT:
I did a bunch of more testing. This monitor is a strange beast. At any resolution other than 400x254, even 15KHz, I can get the pro menu (hold MENU UP when powering on the monitor) and those resolutions do not have any horizontal linearity issues. The screen compresses slightly in all four corners but it's not that noticeable. However, in 400x254, I can't get the pro menu, just the standard menu. I thought maybe the pro menu would be helpful here because it does have a horizontal linearity adjustment, but it never adjusts the right side of the screen, only the left (again though, this menu isn't available in 400x254). Also, in either menu, I can't seem to RECALL my settings. I think I was able to before.
Since I replaced those film caps and MOSFETs, I notice the picture no longer can wrap around itself when I do the horizontal positioning. I also actually think the linearity is slightly better.
Unfortunately, that MOSFET was tied into the proprietary IC on the board. If the MOSFET fried, I wonder if it took out the IC as well. That particular pin on the IC must have been for something like this 15KHz mode, because it's not used on the 30KHz variants that I have a schematic for. I almost get the feeling it has to do with turning on those S-correction caps.
I might give this thing one more go and replace the rest of the caps I found that were slightly leaking. I'll check the diodes and transistors as well. Maybe I'll try and identify the IC. Unfortunately, this is all close to exceeding my skillset. I don't have an oscilloscope and don't feel comfortable enough working on monitors while they're powered on.
EDIT 2 (FINAL, SUCCESS):
- I gave it another go and replaced 2/3 of the high voltage film caps (DigiKey didn't have stock).
- I also reflowed the solder on the small transformers and large coils.
- I also tested and replaced a bunch of the aluminum electrolytic caps, with a few in the horizontal section. I replaced them all with Panasonic FR caps, which are extremely low ESR.
Many of the caps I tested were approaching or above 1 Ohm. They were all Nichicon caps from my first cap kit.
- I replaced C91 (2000uF, 35V). Despite it testing OK, it gave off the classic leaky fishy smell when I desoldered it.
- I tested all resistors, transistors, and diodes in the horizontal section. As far as I can tell, the blown MOSFET didn't affect anything else.
I wasn't too optimistic after doing all this work. And despite the Recall feature working again and the picture being absolutely amazing, at that one screen size, there is still significant right-side compression. I think this monitor might have been this way from the factory. One last ditch effort was to change my MAME configuration. Low and behold...
First I tried adjusting as much as I could in ArcadeOSD, but nothing seemed to help.
I'm running GroovyMAME 0.178. I do this because it has the best support for the old ATI card I am using. I turned off modeline_generation in mame.ini so GroovyMAME would use the modelines generated by VMMaker instead of generating them on the fly. Despite the two pieces of software having the same monitor configuration, the generated modelines for the Midway games were different... 400x256p @ 16.7KHz instead of 15ishKHz. I couldn't believe it too when the geometry at that modeline was ABSOLUTELY PERFECT. I mean, it's bang on now! I tried a bunch of different games and they all had perfect geometry as well.
So:
1. I have no idea what that MOSFET was doing.
2. All the components I replaced probably did nothing more than extend the life of my chassis.
3. My geometry issues appear to have been fixed in software.
In short: success?
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version