OSSC Repair help/suggestions

[buffi]

So.... ground your cabs people.

I managed to fry the blue channel on my OSSC when disconnecing my capture gear connected to a OSSC from the board it was connected to, while also touching my cab frame. Looks like OSSC was properly grounded and my cab was not (now fixed), which gave my right arm a small zap, and killed all the blue from my OSSC.

That was real dumb, I know.

Now... what is the most likely thing to be dead here? (luckily not me!)
I'm looking at the OSSC schematic at https://github.com/marqs85/ossc
...and the ADC is a TVP7002PZP, which is just connected through some AC coupling caps.

Should just be to replace that right? Anything else that I should think of?

 

[Raph_friend]

Don't replace tvp yet, first try all the inputs (mainly vga) and check if the problem persists. Get the PDF schematics and follow the blue signal, so measure all components on the line.

 

[buffi]

I'll try to find something to hook up to VGA to see if that works.

I guess if it does, then it should be the TVP that's busted. If it does not, it is likely something else?

 

[Raph_friend]

Like I said, there's some components before the signal in, check the schematics.

https://www.niksula.hut.fi/~mhiienka/ossc/diy-v1.5/ossc_v1.5-diy_schematic.pdf

 

[buffi]

Ahhh, I see.
VGA is connected through RGB3_B directly to TVP through a decoupling cap.

SCART is connected through RGB1_B through THS7353, which becomes RGB_12_B which is then connected to the TVP through a cap...

So might be the THS7353 buffer.

I'll try to find some VGA output to debug this a bit more.

I really hope it's the THS7353, since that would be a lot easier to replace

 

[Raph_friend]

Check the resistors around it too.

 

[buffi]

Check the resistors around it too.

Sounds smart. Just did and R6-R8 all meassure 75ohm on the multimeter, so it's unfortunately not that easy at least

 

[buffi]

Alright, found a VGA box for my dreamcast.

VGA looks fine, so maybe I'm lucky and it's just the THS7353

 

[Raph_friend]

Need to determine where the signal is lost.

You can buy the tvp and ths, both are easy to swap if you already work with smd IC.

 

[Raph_friend]

Alright, found a VGA box for my dreamcast.

VGA looks fine, so maybe I'm lucky and it's just the THS7353

There's a good chance.

 

[buffi]

Need to determine where the signal is lost.

You can buy the tvp and ths, both are easy to swap if you already work with smd IC.

Yeah, I'll buy one of each.

I'm ok with SMD parts, and have a hot air station, so the THS7353 I could probably do in like 10 minutes.

The TVP is a TQFP-100 which are fucking awful to solder though...
I have done it before, and can do it, but then we're talking like an hour including inspection.

I'll just try swapping the THS first and hope for the best.

Thanks for the help though, really appreciate it!

 

[Raph_friend]

Do It. I have assembled some OSSC, the FPGA is the worst part hehe

 

[invzim]

Need to determine where the signal is lost.

You can buy the tvp and ths, both are easy to swap if you already work with smd IC.

Yeah, I'll buy one of each.
I'm ok with SMD parts, and have a hot air station, so the THS7353 I could probably do in like 10 minutes.

The TVP is a TQFP-100 which are fucking awful to solder though...
I have done it before, and can do it, but then we're talking like an hour including inspection.

I'll just try swapping the THS first and hope for the best.

Thanks for the help though, really appreciate it!

The tvp also has a pad underneath that I'm pretty sure you need to 'solder' too.

 

[Raph_friend]

Need to determine where the signal is lost.

You can buy the tvp and ths, both are easy to swap if you already work with smd IC.

Yeah, I'll buy one of each.I'm ok with SMD parts, and have a hot air station, so the THS7353 I could probably do in like 10 minutes.

The TVP is a TQFP-100 which are fucking awful to solder though...
I have done it before, and can do it, but then we're talking like an hour including inspection.

I'll just try swapping the THS first and hope for the best.

Thanks for the help though, really appreciate it!

The tvp also has a pad underneath that I'm pretty sure you need to 'solder' too.

It's a big GND.

 

[buffi]

Got the parts and replaced the THS7353, and everything started working right away.
(colors on pic below are real dark since I didn't feel like messing with the color pots of the betsubetsu right now, and I've been using other digitizing gear (XRGB-mini) which seems to have more gain)

Thanks for the help

 

[Raph_friend]

Nice, try to adjust Pre-ADC Gain.