REPAIR ADVICES AND HELP FOR BROKEN OSSC 1.6

[kadird]

[sorry for duplicated message but i think posted my first message to wrong place.]

Hi,

I broke my OSSC when trying new RGB to SCART cable for Amiga 500 by build myself. Connected the scart socket came from Amiga to OSSC’s AV1 SCART in and something goes wrong and test pattern in HDMI out is gone. I think i applied 12v from Amiga to one of the OSSC’s AV1 SCART pins and this is fried the U1 chip. Also a periodic click sound started in audio out. This sound is permanent now.

But OSSC’s LCD screen works normally and i can acces the menus. I tried fw update first but nothing changes. Video out of OSSC complete blank now. No test pattern, no anything.

Where should i check for repair? I think U1 is gone, but why sound out became parasitic?

Thanks.

[marqs]

Is the sound from digital AV out or from passthru 3.5mm connector? If menu and character display work but there is no image, then perhaps U3 needs replacement. I’d also check regulator output voltages first and whether any of them becomes hot (which could indicate a short on that rail).

[kadird]

hi marqs,

sound comes from digital av, not 3.5mm jack.

requlators and pcb is cold. i will check regulators and will try to change u3 myself or in local cellular phone service.

thanks.

[kadird]

Hello again everyone,

It’s a bit late, but in the meantime, I was only able to take care of the ossc repair today.

I have now replaced the u3 chip with a new one but the situation is the same. The problem is not solved. What do you suggest furthermore?

edit: btw, i just noticed that, u8 will become very hot when power on the ossc and sometimes lcd screen shows init error -2. but not every boot, randomly gave that error.

I wonder if I remove this overheating U18, so that the excessive current it draws will be cut off and will the circuit get better even if it is silent? I’m thinking of trying it, but I don’t want to expose the pcb to a hot air gun for too long.

• This reply was modified 2 years, 8 months ago by kadird.
• This reply was modified 2 years, 8 months ago by kadird.

[kadird]

also when i turn on the source (ps1 and ps2 for now) the following happens on the lcd screen:

[marqs]

U8 should never get very hot in normal operation so most likely it’s damaged and should be removed.

[kadird]

hi marqs, thanks for answer. I removed the u8 and that way nothing on the lcd screen. menus and characters gone. only led lights work. Since I don’t have a new adc chip, I couldn’t solder it and now u8’s place is empty in pcb. I’ll buy one and try it. any other suggestions can you have?

[marqs]

Removing the audio ADC chip should not break other functionality. Make sure excess solder is removed around the chip, perhaps I2C pads got shorted while removing the chip.

[kadird]

hi marqs,

I didn’t clean the pads completely for convenience when soldering the new one of the adc chip. I checked whether there is a short circuit on the pins visually and with a magnifying glass app. the best thing to do is to clean it and try again. I’ll post the progress, thanks.

edit: i just cleaned the pads of u8, ossc started normally. everything run for short period of time, even pattern at hdmi out came back but then gone again in seconds. i think i have to improve my smd soldering skills, should buy a microscope and try resolder ite chip again, not only adc.

• This reply was modified 2 years, 8 months ago by kadird.
• This reply was modified 2 years, 8 months ago by kadird.

[kadird]

Hello everyone, marqs I hope you are still around 🙂

After a long time, I had the opportunity to deal with my broken ossc again. This time I also have a microscope and a hot air gun. I also replaced the it6613 with a new one once again to ensure the integrity of the chip. This time the soldering work was better, I removed the old chip with a hot air gun and soldered the pins of the new chip one by one with a soldering iron. Now, when I run ossc, the LCD screen looks normal, the menus work as they should, it writes the sync info of the signal at the inputs without any problems, but there is no image at the HDMI output. There is no pattern on the TV screen, no OSD menu, no source image, nothing. In this case, I think I should test the components between it6613 and hdmi output. I haven’t had the opportunity to do this yet. By the way, I wanted to write here in case anyone comments on this issue. Thanks 🙂

 

notes: 3v at the f2’s output goes to hdmi out pin 18, instead of 5v. input side is 5v. should i replace it?

• This reply was modified 1 year, 10 months ago by kadird.
• This reply was modified 1 year, 10 months ago by kadird.

[marqs]

Yes, the fuse should be replaced if you’re not getting 5V on HDMI DDC5V pin.

[kadird]

Since it is difficult to access this part quickly where I live, I tried to short-circuit it temporarily, still no image…

 

edit: when i do this short, u3 becomes very hot. That’s why I think that u3 may have burned out on the first try because excessive current was drawn from the 5v line. That’s probably why f2 is getting fried. In this case, how can I tell if the U3 I have soldered is defective? Does the fact that the menus are working and communicating indicate that the chip is completely healthy? Or could the hdmi out tmds output stage be defective, although the side of the u3 encoder facing the FPGA is intact? I have another brand new it6613, but I don’t want to ruin it like this. What should I check in the circuit for this? What could be the source of this problem of overheating u3 and burning F2 by drawing high current?

• This reply was modified 1 year, 10 months ago by kadird.
• This reply was modified 1 year, 10 months ago by kadird.
• This reply was modified 1 year, 10 months ago by kadird.

[kadird]

Hello again,

After I broke my OSSC’s U3 chip and replaced it with a new one, it worked fine for a short while. However, since I had removed a few pads while installing the new chip, I connected the pins to the PCB with wire. Since it would be very sensitive this way, I wanted to cover those parts with UV PCB resin. I applied resin to the relevant areas and dried it with a UV lamp for about 5 minutes. But after this process OSSC is completely broken, there is nothing on the LCD screen anymore. I thought I needed to flash with JTAG and bought a clone usb blaster. I installed the necessary drivers and three different versions of Quartus programmer. First, I tried it on a Windows 11 machine with the current latest version of Quartus, 23.1. When I got the “Can’t access JTAG chain” error, I tried it with 17.1 and Quartus II 13.1 versions respectively. I got the same error with these too. I switched to the Windows 10 desktop machine I have. I got the same error there too. Finally, I tried the same things on an old laptop with Windows XP installed, and I got the same error again. This time I disassembled the u3 and repeated the same things from the beginning. I failed again, the Can’t access JTAG chain error still persists. Now, since the FPGA chip may be broken, should I replace it or should I buy the original instead of the clone USB blaster? Since the original blaster was about 10 times more expensive than the clone one in my country, I couldn’t order it immediately without being sure. What do you think, what should I do in this situation? Thank you.

[marqs]

I’d measure all supply voltages before making any conclusion on the FPGA. If they are within spec and there is no sign of life from FPGA, then it has likely been damaged (firmware is stored on a flash chip and should not corrupt that easily).

[kadird]

I measured correct VDDs on the relevant legs of the FPGA, but now the status LED of the OSC has turned red. I think this device is beyond saving now, I’m tired of trying desperately. thanks.

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