Trying to Fix a Fried OSSC

[Anonymous]

This OSSC wasn’t a DIY kit, but it seems I’m in DIY territory at this point. Because I didn’t assemble it myself, however, I feel I’m at a slight disadvantage backtracking and knowing where to look for further troubleshooting. So, hoping to get some help here.

Backstory/Symptoms:
Firstly, I damaged this OSSC. This is no reflection on the build quality or the great product that the OSSC is, it was completely self-caused. I have in fact bought a replacement, but am hoping to fix this damaged unit, to have a backup or whatever…and because I always love a challenge.

So, without going into details of my stupidity that lead to the damage, let’s just summarize by saying it was exposed to (either or both) overvoltage and AC voltage where it ought not to have been. At the time of the incident, the OSSC was powered on and when exposed to the harm, it flickered off. Upon re-powering the OSSC normally, it came on, and it would detect the input signal (all inputs and various consoles on all inputs = good). The OSSC would produce no output however.

I contacted VGP, they sent me to their recommended repairers. The repairers troubleshot it and deemed they could not fix it, but offered that replacing the Cyclone FPGA and the IT6613 would fix it.

Where I stand currently:
So, I have swapped out the Cyclone and IT6613. First time dealing with SMD with a pad on the bottom, but eventually got it on, and successfully programmed the firmware (ossc_0.81-aud.jic) to it. And now, it’s doing the exact same thing as before – detects the input, but produces no HDMI output.

I have checked voltage at the Cyclone, IT6613 and 7002 – all good. Checked all pins on Cyclone and IT6613 – no shorts, all solder joints are good. Nothing is obviously (visibly) burnt or fried from the initial incident.

The OSSC comes on with only the green LED light lit up (and LED screen working normally). Cycling through the source options but with no source present, the green light stays lit. If I apply a source, it is detected and displayed on the LED screen, and the red light comes on and stays lit, along with the green light staying lit. At no point does the test pattern screen display.

What to check or replace next?

[marqs]

So you’ve checked output voltages of U15 (1.8V), U16 (1.8V) and U6 (3.3V) regulators? If they are fine, next things to check are F2, and continuity of HSYNC, VSYNC, DE between FPGA and IT6613.

[Anonymous]

Hi Marqs, thank you for the help!

Yes all things you’ve listed check out.

U15 output @ 1.8V
U16 output @ 1.8V
U6 output @ 3.3V
F2 has continuity across it
HS – FPGA pin 103 to 6613 pin 2 – has continuity
VS – FPGA pin 101 to 6613 pin 3 – has continuity
DE – FPGA pin 104 to 6613 pin 1 – has continuity

[marqs]

Do you have a scope for measuring mentioned HS, VS and DE signals (plus PCLK on IT6613 pin 88)? If those signals and voltages are fine, then HDMI output should work assuming no TMDS or HDMI connector pins are floating/shorted.

[Anonymous]

Arrgh, no scope. Haven’t gotten to that level yet. 🙁 I’ll recheck for floating/shorted pins, hopefully find something I’ve missed. Or put it in a box til I take the plunge on a scope.

[Author]

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