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buffi

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What you are describing is exactly how I am using the current version.

Since you are also in sweden, i could hook you up with something prototypey very cheap probably at some point.
 

invzim

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It looks like you use the pots to drive the video signals straight to GND, this is bad(tm), as you're adjusting the level by loading the game - set it up as a voltage divider instead.
 

buffi

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It looks like you use the pots to drive the video signals straight to GND, this is bad(tm), as you're adjusting the level by loading the game - set it up as a voltage divider instead.
I'm a bit confused by this.
I have a 1K trimpot from the video signals acting as a voltage divider into the THS IC.
See schematic: https://i.imgur.com/4mxQ95j.png (old one for non jamma version, but the jamma one is similar)

This should have a constant 1K ohm added in parallel to each Jamma signal, which I think is fine.

What type of circuit do you recommend to use instead?
 

buffi

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Actually, let me just post the new schematic that I'm basing the new one on.

@invzim : I would LOVE feedback on this, since you are a lot more experienced in elecric design compared to me :)

QItK9Bi.png
 

invzim

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Sorry for coming on a bit strong, If you use the pot as a divider and not a variable resistor, I don't think you will damage the board - load should be 1K regardless?

Edit: input on the THS is probably super high impedance, so load would be between 1K and ~0. I would imagine this would make the adjustments a bit jumpy.
 

buffi

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Sorry for coming on a bit strong, If you use the pot as a divider and not a variable resistor, I don't think you will damage the board - load should be 1K regardless?

Edit: input on the THS is probably super high impedance, so load would be between 1K and ~0. I would imagine this would make the adjustments a bit jumpy.
I am using it as a divider, not a variable resistor? :)

Yeah, THS should be high impedance. Load should be 1K regardless right now, since the THS can basically be ignored.

Adjustment works just fine like this on the existing version :)
 

invzim

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Don't forget that the signals need to return, so load is not constant at all. You can probably Imagine the THS being 1MOhm resistor to gnd..
 

buffi

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Don't forget that the signals need to return, so load is not constant at all. You can probably Imagine the THS being 1MOhm resistor to gnd..
I still don't really understand.

The schematic has the trimpot as a voltage divider like:

Code:
SIGNAL -----> R1 ------> R2 ----> GND
                    |
                    |
                  THS(1Mohm)
Where R1+R2=1000 ohm

The THS resistance is high enough that it should not impact the load at all, even if R1 or R2 is zero (and the other one 1000)?
 

invzim

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I think you're right :D Ohms law is deceptively simple.
 

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I'd make the power traces wider and add multiple vias.
 

buffi

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I'd make the power traces wider and add multiple vias.
They are already pretty thicc. More vias is a fair point. Can't hurt, so I'll add that on later revisions (I have a lot of other changes in routing made already).

edit: Think I messed up some things ordering initial prototype... Time to make a second one.
 
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buffi

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Ordered a second prototype PCB. Might get here next week.

Also ordered some parts I'll need since I'm running out of mini din connectors.

Maybe I'll have something end of next week? We'll see.
 

buffi

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Jamma version soldered up and seems to work.
Will try it out in cab tomorrow but not sober enough for that now, and it's getting late.

Here's some pics from trying it out:

OcScDpQ.jpg

q0OSMSd.jpg

Edit: apparently missed some solderpoints on four resistors in that pic. Fixed since
RxKMiDp.jpg
 
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buffi

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Still very happy with the Jamma version pictured above, but added some tweaks for next version. Think this is almost done.

New stuff:
- Volume pot to allow lowering volume a bit more on output. Right now I sometimes get volumes slightly too high on line-in, which can be tuned by the extra trimpot.
- Holes for voltmeter (same spacing as on Minigun). Added +5v and GND pins for it as well (will need a short wire)
- Pin headers for all button + stick inputs (J6 at top). This allows for wiring up autofire or button-capture PCB's to this if that's your thing. Not super useful but I like having it there.

Gonna tweak this a little bit more and then order some new PCBs. If I'm happy with it, I'll post the designs+gerbers on github.

q7XL92z.png
 

lethargyman

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This looks awesome! I have a v0.1 Betsu Betsu (made by evilsim) which I'm using with my Combo AV EX++ control box (which doesn't do RGB attenuation) and OSSC - works great!

One addition that would be really useful for me would be a switch to disable the sync attenuation. If I understand things right, that would allow a Taito F3 to be used with an (unmodded) OSSC via the AV3 input. Is that possible / does it make sense?
 

buffi

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This looks awesome! I have a v0.1 Betsu Betsu (made by evilsim) which I'm using with my Combo AV EX++ control box (which doesn't do RGB attenuation) and OSSC - works great!

One addition that would be really useful for me would be a switch to disable the sync attenuation. If I understand things right, that would allow a Taito F3 to be used with an (unmodded) OSSC via the AV3 input. Is that possible / does it make sense?
Just feeding the raw composite sync signal instead?
I mean, having jumpers for that would be pretty easy, but i have no idea if thats safe or not for the OSSC. Definitely wont be for the scart input.
 
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