NES/Famicom Rainbow Banding Issue

[atheistgod1999]

There's this weird rainbow effect towards the left edge of the screen, but it abruptly stops before it reaches the edge of the screen. I've experienced this on both an NES Toaster and AV Famicom via composite. Here's some pictures of it on the AV Famicom:

[BazookaBen]

That may be reflection from inside the tube of some video material that is supposed to be overscanned. Lots of NES games have extraneous color or patterns on the edges of their image.

[atheistgod1999]

I fixed the issue by shrinking the screen by 25%.

[FBX]

I fixed the issue by shrinking the screen by 25%.

Then that would be your TV's fault. I've seen this before on arcade CRTs, where the gun beam starts to fold in back onto the tube after hitting the edge. This is usually caused by the various caps going bad on the TV's circuit board.

[Skips]

Its not a cap problem with a PVM (although you are right about that on arcade monitors). If you have the H-Size Set too high they will do this with the NES. I have still seen this even after doing a full recap on a 20L5. The BVM-20F1U and PVM-20L5 seem to show it the worst but its visibility just depends on the monitor being used. Even monitors like the NEC-XM29 show it albiet you have to get really really close to notice it because its so faint.

P.S. The deflection block on that PVM looks like its in need of a recapping. That would most likely clear up your other geometry issues.

[BazookaBen]

even after doing a full recap on a 20L5.

20L5's aren't even that old, right? Did you actually notice a difference in anything after the recap?

[Skips]

They might not be very old but when they get tons of hours they may still need to be recapped. Caps can wear out/dry out from heavy use and show no signs visually that they have gone bad. In fact out of the 40 something PVM's I have owned I have yet to see any capacitor that visually shows it has gone bad. Nearly every PVM I have recapped the deflection circuit in came out with damn near perfect geometry when I was done. This includes PVM's where there geometry looked pretty fucked up. A lot of the times bad capacitors are the cause of geometry issues so it is always a good place to start even if it is a royal pain in the ass to do. In the 20L5's case it ironed out the geometry back to perfection once I went back and adjusted it after the recap.

[BazookaBen]

Yeah, my 20M2's geometry does bother me sometimes, in scrolling scenes especially. How many capacitors did you need to replace and how long did it take you?

[kel]

Yeah, my 20M2's geometry does bother me sometimes, in scrolling scenes especially. How many capacitors did you need to replace and how long did it take you?

Ditto Although mine's a 20L2.

I've been thinking about recapping the deflection circuit but without a service manual it's hard for me to tell which caps are on the deflection circuit and which are not and I don't fancy replacing every cap in the set just to make sure that I get the right ones.

[atheistgod1999]

My monitor only has about 5.5k hours; could it really be the capacitors?

[Skips]

How you could possibly know it only has 5.5k hours on it boggles me since the 20L5 does not have a way of looking at hours on it. There is no way of telling how many hours of use a 20L5 or 14L5 has on it, Sony did not put counters on that sort of stuff until the BVM line.

And YES for the last time it could still be the capacitors. That monitor is at least 10 years old now, that is enough time for capacitors to dry out and go bad.

[atheistgod1999]

How you could possibly know it only has 5.5k hours on it boggles me since the 20L5 does not have a way of looking at hours on it. There is no way of telling how many hours of use a 20L5 or 14L5 has on it, Sony did not put counters on that sort of stuff until the BVM line.

And YES for the last time it could still be the capacitors. That monitor is at least 10 years old now, that is enough time for capacitors to dry out and go bad.

When did I say I own a 20L5? I own a BVM-20F1U.

[Skips]

Yeah, my 20M2's geometry does bother me sometimes, in scrolling scenes especially. How many capacitors did you need to replace and how long did it take you?

Ditto Although mine's a 20L2.

I've been thinking about recapping the deflection circuit but without a service manual it's hard for me to tell which caps are on the deflection circuit and which are not and I don't fancy replacing every cap in the set just to make sure that I get the right ones.

Typically with PVM's the deflection circuit is somewhere around the side of the PCB where the flyback transformer sits. Even in models where the flyback has its own little PCB the deflection circuitry tends to still be on the side of the main bottom PCB that is near the flyback. Its not always the case but its a good place to start. Sadly its been awhile since I opened an L2 so I can't remember if its the same case with that monitor.

[Skips]

How you could possibly know it only has 5.5k hours on it boggles me since the 20L5 does not have a way of looking at hours on it. There is no way of telling how many hours of use a 20L5 or 14L5 has on it, Sony did not put counters on that sort of stuff until the BVM line.

And YES for the last time it could still be the capacitors. That monitor is at least 10 years old now, that is enough time for capacitors to dry out and go bad.

When did I say I owned a 20L5? I own a BVM-20F1U.

My bad, I think I got you mixed up with another person with the same problem. Either way it still could be. That deflection block is removable and it could have many more hours on it than the monitor itself. People that rebuild these things for resale will usually pull parts from other BVM's in order to get a single working unit. The monitor itself might only have 5.5k but the card itself could have more.

Also being a BVM-20F1U it is most likely older than a 20L5 so the point on capacitors and age still stands.

**Edit** and if you don't want to recap it you can also try buying another deflection card for it and see if that clears it up.

[kel]

Typically with PVM's the deflection circuit is somewhere around the side of the PCB where the flyback transformer sits. Even in models where the flyback has its own little PCB the deflection circuitry tends to still be on the side of the main bottom PCB that is near the flyback. Its not always the case but its a good place to start. Sadly its been awhile since I opened an L2 so I can't remember if its the same case with that monitor.

Yeah, it seems to be the case for the L2 also as that is the area where the wires from the deflection coils go to. I suppose I will just have to trace the circuit around that area to minimize the amount of caps that I can get away with replacing to fix the problem. Thanks for the tip though.

[atheistgod1999]

What kind of capacitors are on the deflection card?