SNES-Mini RGB Measurements

Is there any signal and/or components to ground left on this trace after you've removed C18?
If you want to test safely first, then you can add a common coax cable to your signal and route that into your scart connector pin 20.

 

according to the schematic posted in the previous page there are some grounded components... it seems I need to isolate the pin via other means to be sure: lifting or cutting trace...

 

c18 + c50

 

Is this C-Sync circuit even suitable for the PAL SNES? Being as though the PAL scart cable has a 75ohm resistor in parallel with the TV's 75ohm resistor making the load impedance only 37.5ohms.

On a side note it seems that the N64 has the same C-Sync circuit as the SNES except the 1.8kohm resistor is 1kohm, the 3.3kohm resitor is 10kohm and the 100ohm resistor is 75ohms.

 

You mean if you cut composite and replaced it with the discrete c-sync? Yeah it wouldn't be compatible, you'd have to remove the resistor. (Or you could leave off the 100 ohm series output R, but then the transistor will be burning a lot of current to drive the 37.5 // 300 ohm load instead of 175 // 300 ohm. That wouldn't be advisable unless you had a very low DC offset.)

 

^ that's exactly what I want to do, add c-sync to a PAL console using the driver in question. What resistor do I need to remove from the schematic to make it PAL-compatible? It is unclear to me...

 

Yeah that's what I meant. Thanks for the explanation Calpis.

@keropi You will need to remove the 75ohm resistor connected to GND in the scart cable on the composite video line.

 

^ thanks!

 

Hey Ultron, Have you had a free moment to accomplish this? I've been eagerly awaiting for your results and checking this thread every so often to see all the progress that's been made.

 

I updated my SNES guides (that use a THS7314 amp) to use Ultron's method. I haven't tried this method using the stock RGB amp on the Mini yet:

SNES Mini: http://www.retrorgb.com/snesminirgbmod.html#brightness

SNES 1-CHIP: http://www.retrorgb.com/snes1chip.html#brightness

 

Oops, sorry! I'll work on it this weekend. You can check out RetroRGB's site, as he said he updated it.

 

retrorgb,

Do you have plans to make new PCBs to replace the old method? Or are you still waiting on Ultron's results as well? It would be great to have an updated solution on a slick PCB.

If not, I may take it upon myself to update borti4938's board design once I see what Ultron had in mind.

 

vvv, your posts were auto-moderated, hence they didn't show up. You should have received a message telling you they would need approval. If it happens again when you post the next few times, just hang tight - one of us will get round to approving your post

 

I was still thinking about the PCB design as well, but haven't done it yet. The only thing I did so far is to replace the not needed plated vias at the MultiAV port with simple holes.

Best

 

Don't forget, you also added a pad connecting to composite sync. A thoughtful addition.

I was fiddling with your board layout and routing over the weekend in an attempt to make it single layer, thinking that by keeping the bottom of the PCB bare, perhaps an accidental short could be prevented. I did it, but am not completely satisfied with the results. Besides - It will probably change if some type of voltage divider is necessary per Ultrons updates, so I'll wait before trying again.

 

I still have such a design

A friend of mine has such a design. Although to my point of view the hight of the MultiAV pins is quite large such that the risk of an accidently short is quite low - never happend to me

 

There's some interesting info on the sync signal on the shrimps forum posted by RGB32E.

http://shmups.system11.org/viewtopic.php?f=6&t=33450&start=630

The post is halfway down the page. From reading other spots on the internet, I think the TTL CSYNC signal coming out of the S-RGB chip should be good enough to use for sync unless you are using a really old monitor that can't handle TTL Level for SYNC. You can wire a 75 ohm and 220uF cap if the TV has 75 ohm termination and it would still be a TTL level signal.

It it would be interesting to measure the sync output on a 1-CHIP or even a regular old SNES of SFC since they seem to use the same csync amp.

 

It would be great if we can find out how to pull sync from the via on the board that connects directly to the video chip (SNES Mini location shown below). It would make the installation easier and possibly clean up the sync signal. I might be wrong, but it should just need to be amplified, then have a resistor and capacitor added.



I have a few different SNES systems on hand...would I need a scope to test the output?

 

Speaking of scopes what would be a good scope to use for these retro consoles within reasonable price range? Recommendations please.

 

I have a Rigol 1052, same as Ultron.

However, I believe they have released a replacement now. check out eevblog really for suggestions and reviews.