[OSSC BITFUNX] – Dark display with scart input

[Michael1260]

Hello,

To manage my retro consoles (mostly using SCART), I have two OSSC units (v1.8) BITFUNX

Suddenly, one of the OSSCs started producing a very “dark” output (this happens when using the SCART input; I tested with VGA input and it works fine, though I couldn’t test RCA RGB as I don’t have a compatible console). So, I likely have an issue with the SCART input stage.

I should mention that when I swap the faulty OSSC for the second one in my setup, everything works perfectly (using the same cables).

I reset the configuration to factory defaults, but that didn’t help (and I hadn’t changed any settings prior to the failure anyway).

Upon opening the OSSC, I noticed the SCART port was loose. I replaced it (the new one fits perfectly on the PCB), but that didn’t fix the issue.

I suspect a faulty component in the SCART processing stage, given that the other inputs work fine.

Could someone help me troubleshoot this board?

I have the necessary testing and repair equipment (oscilloscope, soldering iron, etc.).

It’s not very visible (my phone enhances the image), but I’m attaching a photo (from a Matra Alice, a French 8-bit computer from the 80s):

With the other OSSC (same cables) – Very good picture

 

 

Thank you

 

ps: I have the V1.8 schematic and the bill of materials to guide me on what needs checking.

• This topic was modified 1 month, 2 weeks ago by Michael1260.
• This topic was modified 1 month, 2 weeks ago by Michael1260.
• This topic was modified 1 month, 2 weeks ago by Michael1260.
• This topic was modified 1 month, 2 weeks ago by Michael1260.
• This topic was modified 1 month, 2 weeks ago by Michael1260.

[BuckoA51]

Can you try a screen with multiple colours on, e.g 240p test suite perhaps?

[Michael1260]

First, thank you for your reply 🙂

 

Can it help ?

Faulty OSSC (green problem ?)

 

Good OSSC :

 

[marqs]

Are you able to test a AV2 (component video) source? Both that and AV1 are routed via a LPF+mux chip so knowing if both have similar issue would better indicate where the fault is.

[Michael1260]

Unfortunately, no. I can’t test AV2; I don’t have a source for it. As I said, I was only able to test via VGA (which works).

[Michael1260]

Is it possible to use a function generator on the AV2 inputs to simulate the signal? If so, what voltage and frequency?

[Michael1260]

I should have the cables to test AV2 on Saturday (for a PS2 and a compatible PSP). I’ll post the results in this thread.

[Michael1260]

LPF is THS7353 (U17A) ? Am I right ?

AV1 and AV2 are the inputs (on PIN 2 – 7) then the outputs (RGB_12_x) are going to U1 ?

I hope it’s not a problem with U17A (Difficult to replace)

We’ll see on saturday with the cables

• This reply was modified 1 month, 1 week ago by Michael1260.

[marqs]

If the green channel on AV2 is completely dead, then you don’t even get sync from component. You could also try connecting a CVBS source into Y-jack to check if you get B/W picture via AV2.

[Michael1260]

My cables are scheduled for delivery tomorrow. I’ll run the tests and post a message with the results.

[Michael1260]

With PS2 on AV2 :

Good OSSC

 

 

Swap OSSC with bad one :

 

 

So, there is also something wrong with AV2 🙁

 

Can it help ?

[marqs]

Since you mentioned you have a scope, can you scope output on U17A pin 19 (or from C11 pin facing it) with PS2 source? You should see same periodic sync / Y as from U17A input (pin 2). That should reveal whether the issue is with U17A or U1.

[marqs]

Actually if you get sync via AV2, then it already indicates the fault is with U1, or C103. If you have good luck, then it’s the latter or just a weak solder joint on U1 pin 2.

[Michael1260]

Yes, I believe the first thing to do is to look with scope and reflow U1 and / or C103. Probably this week end (I hope it’s not a faulty U1, impossible to find / buy and replace).

I have also C103 (SMD 603) if I need.

I just need some time 🙂

• This reply was modified 1 month ago by Michael1260.

[Michael1260]

Which pin  to check for output of U1 ? (Input looks like it’s good). Thank you

[Author]

Posts