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buffi

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Right now I have a really bad method of capturing audio+video from my cab (pictured here: https://imgur.com/a/l6exCFL ), which basically consists of one of those cheap jamma - -> SCART splitters that just use series resistors (that I bumped in size a bit to be safer). This then feeds into OSSC and then the computer. Audio capture relies on external stereo ports (like in this case the MVS2).

I'd like to replace this with something more proper. One approach would be to wait on something like the Splitfire, which I'm sure would work quite wonderfully!

... but I'd also prefer to just have something hooked up into my cab all the time and not have to worry about big adapters on the jamma cable.

This lead me to the idea of making a small PCB which solves my problem by providing:
- Small footprint! (layout I threw together quickly in kicad is 76x37mm right now).
- Proper audio adaption with galvanic isolation (see: http://hacks.slashdirt.org/hw/supergun/ )
- Buffering and unbiasing of Video and Sync signals to safe levels
- Mini DIN 8 port to easily hook up to OSSC or XRGB Mini
- Audio Jack to hook up audio to computer directly
- Trimpots for video signals
- Cheap! The most expensive parts on the board are the MINI DIN connector and the TY-145P transformer, and both of them together ~10$. Total board parts cost should be less than $20 or so maybe?

Things I'm NOT trying to solve
- No JAMMA connector (big, I don't like Jamma adapters)
- No handling of inputs (this is not a supergun)
- No support for Stereo right now (only really relevant for MVS? and that often has an audio jack anyways...). Handling that edge case would increase the size a lot, by adding another transformer.

I'd love some input on the schematic and board layout before I go ahead and print the first PCB version and order stuff from digikey.

Nothing on here should really be revolutionary or anything. It's about the same circuit as any THS7374 RGB amp, and the exact audio circuit as the supergun linked above (but mono only).

Schematic:
8RFPc2n.png

Board:
wuqXSqt.png

Known issues:
- Need screw-holes on the board.
- Should have a power led.
- Trim pots should be labeled by their color
 
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buffi

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Some modifications to the board + wired up.
Want to iterate on it a bit more, then send it off to printer for a Version 0.
lVJxPBF.png

75x40mm right now. Seems like a good size.
 

buffi

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... and sent off the design to Aisler for printing, and ordered parts off digikey. Should have the PCB in 1-2 weeks.

Looks like BOM will be a bit more than I expected, so <20$ might not be realistic after all. We'll see where it ends up...

Once I have something working with my cab, I'll close this thread and move it to the Project Showcase I guess :)
 

buffi

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Board rendering sent for manufacturing. Not perfect but good enough for a prototype.

M1FgVqi.png
 

digitron

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Very cool! I'd love to solder one of these up and test once/if you release/sell it. 8)
 

buffi

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PCB arrived.
T1E7BIqr.jpg


Unfortunately my cab has busted sync, and needs a recap so cant test it for a bit.
 

buffi

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Took me almost an hour to solder this thing.
Now I just need to fix (recap) my cab monitor as well, before trying this thing out... Currently busted sync on my astro.

Z7q06ab.jpg
 

biggestsonicfan

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Great stuff so far! I've been looking into things like this but nothing on the market quite suits my needs. I'll be watching this closely!
 

buffi

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Great stuff so far! I've been looking into things like this but nothing on the market quite suits my needs. I'll be watching this closely!
Thanks. Current status of this is that I hope to have time to recap my monitor on Saturday and see if I get it working. Then I can try this thing out quickly afterwards.
 

evilsim

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Great idea im really keen to hear how it goes.

The owner of 1989 retro/gaming bar in Newtown, Sydney would love to get this going for his cabs so he can record their output for competitions/events etc. me too!


Just on your soldering, have you done a continuity test on all of the legs of the THS video amp to make sure none are touching ? To clean up those legs you can use a hot iron with a clean tip and no solder on it ; just drag the tip from the IC end of the leg to the outside of the leg. This will clean those solders up and remove any excess solder which may be creating an unintended bridge. using flux if you have any will make the solders clean themselves up and be nice and shiny too. Shiny solder = good. Always clean you tip a lot, using copper wire is the best. ALl your SMD solders look fine, maybe its just the pic which makes me think there may be a bridge.
 

buffi

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Just on your soldering, have you done a continuity test on all of the legs of the THS video amp to make sure none are touching ? To clean up those legs you can use a hot iron with a clean tip and no solder on it ; just drag the tip from the IC end of the leg to the outside of the leg. This will clean those solders up and remove any excess solder which may be creating an unintended bridge. using flux if you have any will make the solders clean themselves up and be nice and shiny too. Shiny solder = good. Always clean you tip a lot, using copper wire is the best. ALl your SMD solders look fine, maybe its just the pic which makes me think there may be a bridge.
If anything, I just used too much flux, and ive been lazy about cleaning it up.

Here's a pic through the scope. Continuity is absolutely fine.
AOLjLZy.jpg


... also, I got my monitor working after fucking with it a bit and I have a cool video coming up soon...
 

buffi

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You know how sometimes, things don't work on the first attempt?

Well this was not one of those times. Works great!

Put this thing on a fingerboard to try it out:
LS1MhA0.jpg


And works right away!
2CfhtHu.jpg


Video of it running:
https://www.youtube.com/watch?v=0Q3_mlm3J2k

Audio sounds good, and levels look great (https://i.imgur.com/I1q8QJy.jpg) !

Will play around a bit with this design and do some improvements, but seems extremely solid!
 

evilsim

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Excellent ! Yes it was the pic which tricked me in to thinking the soldering was bridged. Your soldering is great, plz ignore my comments heh.

Nice work on the 1st try win!

Whenever these will be available for general consumption I'll be interested. Thanks
 

Derick2k

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Awesome work! 8o Glad it worked out in the first try. Are you able to test it out to make sure it’s outputting proper levels,etc. Also, you thinking of using the better audio transformer?
 

buffi

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Excellent ! Yes it was the pic which tricked me in to thinking the soldering was bridged. Your soldering is great, plz ignore my comments heh.

Nice work on the 1st try win!

Whenever these will be available for general consumption I'll be interested. Thanks
Current idea is to fix some things in the design, and then I’m going to release the gerbers and so on.

Will build some amount of boards for selling as well, but need to figure out how to handle that.
 

buffi

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Awesome work! 8o Glad it worked out in the first try. Are you able to test it out to make sure it’s outputting proper levels,etc. Also, you thinking of using the better audio transformer?
I have a scope, so I’m going to make sure things seem fine with that some time later this week. Output circuit is a direct copy from the AC coupled example in the THS7374 datasheet though (same as on Minigun).

Yes, I want to try out the other transformer as well. No idea on the typical frequency ranges output by jamma amplifiers, but should be better in theory at least :)

Since this is less of an idea, and more of an actual project now, I’ll make a thread in the projects section instead some time soon as well.
 

buffi

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Current thinking is that DC coupled output should be fine, which removes the need for 8 capacitors.
The input capacitors and the output resistors can be put in an array package since this board already requires soldering a TSSOP with similar pitch.
This makes it easy to get a board size of below 40x60 millis with plenty of space for holes and stuff.

Want to try out the ty-250p transformer as well, so the next iteration currently looks like this (WIP)

kOxroeE.png

EtvAvZH.png


Current BOM cost is around 15$, a bit less maybe.

Next steps:
1. Try out DC coupled outputs on existing board (just short the output cap instead of placing something there)
2. Try out TY-250p (already ordered)
3. Assuming both of those things work, order new PCB, then wait ~2 weeks for it to arrive :|
 

buffi

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Just to make sure the design above worked, I did a quick and dirty hack and just shorted the output caps to get the DC coupling of the output.

Works fine, and quality seems ok to me!

Here's a capture of it hooked up to a OSSC and a USB3HDCAP.
After the intro sequence (during the fight), I'm messing around with the video pots a bit to try to tune the colors better which is why the colors jump around a bit :)
I'm horrible at color adjustment.



Pic of current prototype board:
-LYkcm8T_eKoXaF1yaXd4TQMO7nRDxIarXog8ejp4bs3I1P6gNQd1WWmG9TLK0kfK8BEAFcyq9SdZBxhB2O9QoM-D5wiJQ9R44fQipCf7GhMuxsqwBhYOmzVeuKVNI7PaF5MgUdVMPt5U4EycfclCzqnCorLylz2H30C783uU57F-LY5UR5xLOcCwUxIf930WqE7tWlPXJiLqsp14jzE-LmS_O6adJZdbFNMADA1Xu5uKHgBxwhpExqv1VWg8mYCHOLWL1HU8C_lT42pt9r0i2qGY2tJW8ndojTm2SP4-tHonjIsXqlNmsg1oB5U-OFXUQPcrA3ok5gNC5tPkv2wX6A8eqmyUag4kbg2TrbaY3tnmBS6EYcuqC2gWWtM7JvKhk1h1VS1azqTRS98dSGBTUB09eHEckMUQXZZElsPW7shsht2YvxqgSHXJvBI46bgECmaBEgiWXxnTJeSj2ksHbGUBxfnDaaNvvYE96Y3SxkZMT7b_-nxrrjbMhRr_1-89BcGCINzLY4I-JDFcxBGumZYW-po1-ltG2CMXTuxbgMGdb5PlobpdcKjYJ42aF7UuwquyjB7aBU6udKA8c4oYyoyTn6BNoDLD6ZHdXZE3suZuppzo4Jm7d0O6UEnA0cpLtlEDCM4Nju_UwWt2Yf74Bi7l9kckPZZtkrVc_7bG_7XO0Bd_K92AIrj=w924-h1231-no


I should get a TY-250P transformer some time soonish off ebay, so I can try that out as well while I wait for the new PCB.
 
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