B+ Question

nerdygrrl

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I am just starting to learn how to repair my monitors. I know very little about the ins and outs of these guys and have been hesitant to work on them.

I have a couple of monitors with waves in the screen. I just assumed throwing a cap kit in there would do the trick, but someone mentioned adjusting my B+.

Can somebody please explain to me what this is and how to go about testing/adjusting it. I tried tracking down a thread here, but the search term is too common.

Thanks
 
B+ is the final voltage to the flyback that is then stepped up and used for the voltage to create your picture. It is adjustable on most monitor chassis, and it usually varies from 108vdc to 130vdc depending on chassis. What monitor chassis are you working on?
 
I have a couple of WG K7500's with waves. I am just now getting into monitor repair and didn't know much about the B+. I have heard the term thrown around a lot, but had no idea what it was referring to.

I am guessing that since it adjustable I should just look for a pot on the chassis or schematic. Can I damage the chassis if I crank it up too high? How do I know what the ideal volts are supposed to be?
 
B+ is a DC voltage, usually around 130 volts or so (this value varies from monitor to monitor) that is used to power various components on the monitor. The flyback transformer, which generates the high voltage used for the electron beam in the cathode ray tube, is probably the most important component powered by the B+.

Testing for B+ varies on different monitors, so you will have to look at specific monitor guides to find where the test point is, etc. Usually you clip one lead of your meter to the metal frame of the monitor and the other to the B+ test point. Sometimes B+ can be adjusted by a pot. Sometimes in order to get it back to the correct voltage you have to replace blown components that regulate the B+.
 
88 MPH and Oryk Zinyo, thanks for the info. I have been reluctant to work on my monitors and now as a result I have about a dozen that need this or that. I think the two with the waves should be easiest to diagnose/fix. After that I'll deal with the cap kits and flybacks.
 
I have a couple of WG K7500's with waves. I am just now getting into monitor repair and didn't know much about the B+. I have heard the term thrown around a lot, but had no idea what it was referring to.

I am guessing that since it adjustable I should just look for a pot on the chassis or schematic. Can I damage the chassis if I crank it up too high? How do I know what the ideal volts are supposed to be?

Here's a doc that might help...

http://www.wellsgardner.com/pdf/repair/K7500.pdf
 
smalltown guy, thanks for the trouble shooting sheet! I am going to head out to the store now and buy some clips and get to diagnosing these beasts. I am guessing that adjusting the B+ is only a temporary fix and I will still need to replace the caps.
 
You're welcome. I actually have to thank YOU, because I've got a K7400 that's been kicking my ass for about a year now, and I just realized that the troubleshooting sheet I just posted here also covers that model too. It lists a faulty U701 as a cause of jittery video, which is what I have.

U701 lists in the service manual as a LA7850, which also crosses to NTE7086. Now I just gotta find someone who sells this chip so I can see if that fixes my issue.
 
Is it me or do the 25 inch monitor fail a lot more often than the old 19 inch monitors. I have about 18 19 inch monitors in games that work pretty damn good and have had little work done to them. The 8 or so 25 inch monitors that I have are all shit. Bad caps, bad flybacks, missing colors, etc. What's the deal?
 
I think it's more of a correlation than anything. 25" monitors got popular later in the game - and that's when parts started to get cheaper and cheaper.

I've yet to see a reliable 25" monitor either.
 
I doubt your waves are caused by the B+, which probably will be hard to adjust since they glued the pot.

I'd like to see pics of the waves, so I can diagnose it properly (hula, interference, hum bar, etc)...
 
Here is a photo of one of the monitors. I was going to do a new cap kit and flyback to essentially tune it up, but was told that some times a faulty B+ could cause a wave.

I just pulled the monitor out so I can bring the cab upstairs. I am hoping that maybe tuning in while it's out will reduce the distortion.

IMG_2612.jpg


The other monitor has a similar "wave" to it and my paperboy has and actual vertical moving wave . I'll try and take photos of the others later.

Thank again everyone for all of your help. Hopefully I can get this monitor stuff down.
 
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I can see the distortion in the Battletoads logo, but does the same distortion occur through the entire image on the screen? Or is it localized to just the top half?
 
It is just localized to this portion. The Neo-Geo is the same way. The Paperboy actually has a wave that cycles vertically.

Did I miss diagnose the toads? Is this distortion and not a wave?
 
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