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Swap RGB encoder?
http://forums.nesdev.com/viewtopic.php?f=12&t=16052
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Author:  juanmiglesias [ Wed Jun 07, 2017 11:29 am ]
Post subject:  Swap RGB encoder?

hi there, I have a bunch of broken snes and snes jr. I was wondering if anyone, if possible, has swapped the Video encoder between a regular non 1chip snes (like S-enc or BA6595F) with an encoder from a jr S-RGB to get the best rgb output. This assuming the S-enc is the one actually adding the horizontal blurring on the output.

this is the best info I have found on each video encoder
http://nfggames.com/forum2/index.php?topic=3525.0

Author:  lidnariq [ Wed Jun 07, 2017 11:31 am ]
Post subject:  Re: Swap RGB encoder?

To the best of my knowledge, the blurriness of the pre-1chip SNESes is actually due to the DACs inside PPU2, not the RGB-to-NTSC encoder.

Author:  juanmiglesias [ Wed Jun 07, 2017 11:39 am ]
Post subject:  Re: Swap RGB encoder?

lidnariq wrote:
To the best of my knowledge, the blurriness of the pre-1chip SNESes is actually due to the DACs inside PPU2, not the RGB-to-NTSC encoder.


that makes more sense.. well back to figuring out what the snes jr have broken lol..

I have two that are bugging me, the power is good in the fuse, switch, ac port, etc.. but when I switch it on id drops to 8.5v, the LM7805 only gets 8.5 and the output is 4.0v, I ordered a couple of LM7805 to test these two and a non 1chip snes that does the same. the power brick is good as it is the one I use on my rgb modded regular snes, which gets 9.04v on the LM7805 and output 5.0v
but I was wondering if any other component can be broken on the power schematic.

Author:  lidnariq [ Wed Jun 07, 2017 11:55 am ]
Post subject:  Re: Swap RGB encoder?

juanmiglesias wrote:
when I switch it on id drops to 8.5v, the LM7805 only gets 8.5 and the output is 4.0v
Uh. The 7805 should never both have a 4V drop and undervolt the output. I'd assume something's drawing way too much power, but then the fuse should blow... I'd think?

Put an ammeter in series with the power switch?

Author:  juanmiglesias [ Wed Jun 07, 2017 1:23 pm ]
Post subject:  Re: Swap RGB encoder?

lidnariq wrote:
juanmiglesias wrote:
when I switch it on id drops to 8.5v, the LM7805 only gets 8.5 and the output is 4.0v
Uh. The 7805 should never both have a 4V drop and undervolt the output. I'd assume something's drawing way too much power, but then the fuse should blow... I'd think?

Put an ammeter in series with the power switch?


I did a test as you said on the switch and I only see 0.861A avg.. nothing out of ordinary and the fuse won't blow.. could it be the LM7805?

Author:  lidnariq [ Wed Jun 07, 2017 1:42 pm ]
Post subject:  Re: Swap RGB encoder?

0.86A sounds really high to me? The canonical power supply (SNS-002) is only good for 850mA.

Is anything other than the 7805 getting conspicuously warm?

Author:  TmEE [ Wed Jun 07, 2017 3:06 pm ]
Post subject:  Re: Swap RGB encoder?

RGB from PPU output has fast rise times but really slow fall times, leading to blurry output.

Author:  ccovell [ Wed Jun 07, 2017 5:10 pm ]
Post subject:  Re: Swap RGB encoder?

Related to that, I did some measurements and made this page: http://www.chrismcovell.com/gotRGB/snesblur.html

Rise and fall times are both quick... enough. It's any transition to a mid-tone that takes forever. I don't know the electronic theory involved...

ImageImage

Author:  mikejmoffitt [ Wed Jun 07, 2017 9:55 pm ]
Post subject:  Re: Swap RGB encoder?

ccovell wrote:
Related to that, I did some measurements and made this page: http://www.chrismcovell.com/gotRGB/snesblur.html

Rise and fall times are both quick... enough. It's any transition to a mid-tone that takes forever. I don't know the electronic theory involved...

ImageImage


I don't know, that's a pretty bad rise time too. Even the bright one is fuzzy on both sides. Seems like a boost of high frequency content would do a lot for it.

Author:  juanmiglesias [ Thu Jun 08, 2017 1:06 am ]
Post subject:  Re: Swap RGB encoder?

Got to love this page!.. great page chris! I saw it for the first time a couple of days ago.

about other parts getting warm, I didn't find anything relative warm to touch at least, I kind of new into full blown electronic, so I have experience on the soldering side, reflow, eprom use, basic pcb design, and right now self learning a bit into the function of every component.

I measure the V on the power before turn it on at 13v, but once is switch it on goes to 8.65, what components can be responsible? the mini don't seem to have the diode, could the filter be responsible? I ordered some LM7805 just to keep some stock and replace to test, but if you recommend any other component swap let me know, I have 2 snes jr, one snes and one sfc (non-1chip), and all 3 do the same drop :/ but my working snes gets 9V and 5V... unfortunately I have only one power block at hand for now.


And chris unrelated question, I'm fairly new to oscilloscopes, and I wanted to be sure I'm outputting 0.7Vpp to the rgb lines, I have a nec xm29plus, and I follow the console to scart diagrams using custom cables and VGA ports on my consoles, everything works ok, no prob with brightness or contrast, only issue I had is sync, which from what I see the nec takes TTL and 75ohm, all consoles work ok in both settings, but the genesis only works on "high" (switch on the back to turn off the 75 ohm termination). If I followed the recommended caps/resistors added to the sync line (as seen on retrorgb) I wouldn't get an image/sync (on any console), so I guess is something related to SCART inputs only?

but well my question about the Oscilloscope, I have a tenma 72-720, analog, and I got to trigger the signal of a RGB line, used the tv filter, and got a dotted curved shaped like this /l/l/l and range seems to be inside the 1V.. hard to tell as this is analog.

do you know any step by step guide to measure Vpp on rgb? from where to connect the ground/probe to the shapes?

Author:  ccovell [ Thu Jun 08, 2017 6:55 am ]
Post subject:  Re: Swap RGB encoder?

I'm probably the wrong person to ask about oscilloscopes and voltage testing for video. Perhaps others here have detailed advice?

Author:  lidnariq [ Thu Jun 08, 2017 11:20 am ]
Post subject:  Re: Swap RGB encoder?

juanmiglesias wrote:
I measure the V on the power before turn it on at 13v, but once is switch it on goes to 8.65
That's mostly expected. Older external power supplies are often "unregulated", and the no-load voltage is often quite higher than the loaded voltage.

For the SNES, specifically, I'd still expect it to drop to 10V when the SNES is on instead of 8.65V, though. I guess I should actually test on my SNES...

Ok, so:
No-load voltage on my SNES, measuring ground plane to +ve side of the power switch: 13.69V
Load voltage on my SNES, same measurement points: 10.67V
Voltage out of regulator, when on: 5V

.... and now my SNES has stopped booting. Lovely. I was going to measure current next, but any result will be suspect.

Quote:
but well my question about the Oscilloscope, I have a tenma 72-720, analog, and I got to trigger the signal of a RGB line, used the tv filter, and got a dotted curved shaped like this /l/l/l and range seems to be inside the 1V.. hard to tell as this is analog.
A picture would be much more useful.

In general, component video should look something like this for composite, s-video/component luma, or sync-on-green. For Y-B, Y-R, R, B component, it should look similar, just without the square notches that go down.

Author:  psycopathicteen [ Thu Jun 08, 2017 1:27 pm ]
Post subject:  Re: Swap RGB encoder?

If RGB was that bad, how bad was composite and RF for older SNES systems?

Author:  juanmiglesias [ Thu Jun 08, 2017 1:49 pm ]
Post subject:  Re: Swap RGB encoder?

lidnariq wrote:
Ok, so:
No-load voltage on my SNES, measuring ground plane to +ve side of the power switch: 13.69V
Load voltage on my SNES, same measurement points: 10.67V
Voltage out of regulator, when on: 5V

same measurement I get on my working SNES :/, I will wait for the regulator to test if there is any changes.

I do the oscilloscope test again this weekend

Author:  mikejmoffitt [ Thu Jun 08, 2017 3:11 pm ]
Post subject:  Re: Swap RGB encoder?

psycopathicteen wrote:
If RGB was that bad, how bad was composite and RF for older SNES systems?

Not much of a difference, because the low bandwidth of composite produces a similar effect anyway.

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