Overvolted OSSC 1.6 has no input nor output [updated]

[Arnopesto]

Hi ! I bought a secondhand vgp.com’s OSSC 1.6 recently, it has been plugged to a 9v power supply (of course) and I thought I could repair it (I already repaired one with a blown F1 fuse). But this time things are more difficult.

The LCD screen lights up but is blank, green LED is solid, no output. IR receiver seems to register remote signals because the LED reacts.
I saw an “Init Error -2” message only once (???), otherwise LCD is blank as I said

I changed d5 first just in case
F1 fuse is OK

The problem seems to be on A33VDD line ?
U6’s VOut is shorted to ground. Tried to remove it but the issue persists. Tried to remove C95 too, still the same. I think C18 has a short too but I forgor
Others Ux seem to work fine (I didn’t check voltages though)

If there wasn’t these shorts I would’ve tried to reflash the firmware but I’m doubting it because I suspect U1 is actually the culprit
And changing a chip with more than 6 legs is beyond my capacities, patience, and tools 😀

Do you have any idea ? Should I send it to repair ? (I don’t have the order number but maybe I can ask the vendor for it)

Thanks, have a nice day !

• This topic was modified 2 months ago by Arnopesto. Reason: Update title

[Arnopesto]

Hi again !

Unless someone has an idea/advice in the next days I guess I will send it to the repair service soon

I got the order number now, is it enough for sending it to repair ? I don’t have the bill as I bought it secondhand

It’s a 5-digit number, is that correct ?

Thank you ! <3

• This reply was modified 2 months, 1 week ago by Arnopesto. Reason: added a question about order number

[Arnopesto]

So, Update !
I found the 1.6 pcb schematics, it helped me follow the 3.3V line.
So I sat down a little more and by testing, I thought the C18 capacitor was shorted
After removing it and feeding (temporarly) U5 into U6 (which was previously removed) I can get the OSSC to boot and display the usual menu on the LCD.

BUT, I get no HDMI output (not even the test pattern), and even if I plug any cable, SCART RGB or Component, the OSCC still displays “NO SYNC”

So maybe U1 and/or U3 is definitively fried, or maybe there is another faulty capacitor / voltage regulator ? Or maybe somehow the whole board is cooked ? x)

Other regulators seems to output the right voltage.
Could it be a shorted clock or sync line, something like that ? It may explain the sync problem for the input and output ? How could I debug this ?

Stay tuned

• This reply was modified 2 months ago by Arnopesto. Reason: More infos and questions lul

[Morpheus_79]

Since C18 is a decoupling capacitor for the (by U6 delivered) 3.3V supply of the analog part of U1, it may be possible that U1 is at least partially broken. There would be a “Init error -3” message on the LCD if U1 does not respond at all – but since there is no message, a partially damaged TVP7002 is still possible.

A partially broken U1 would explain the “NO SYNC” message. But it does not explain the missing test pattern, since the FPGA outputs the test pattern istself, without needing the video ADC for it. A shorted clock line may be possible – but there was a pretty new thread in here, where someone had a broken oscillator… which resulted in no LCD output at all. So i would assume: the (main) clock signal is pretty much needed for everything to work properly. A missing/shorted clock would result in the OSSC not doing anything at all. But if you have an oscilloscope, you could check if the oscillator outputs a stable clock.

The same 3.3V line that drives the analog part of U1 drives the analog part of U8 too. U8 delivers the digitized audio to the HDMI transmitter (U3). So it may be possible, that (because of a short in that line or from an overvoltage) U8 was damaged too and sends some I2S-data-garbage to U3, that confuses it… resulting in U3 not working properly.
That’s just an educated guess… but you can test it by removing U8. If this does not give you the test pattern, U3 may be damaged. It is driven by a different 3.3V line (from U5) – but it’s hard to tell what voltage U5 delivered after powering it with the out-of-specs 9V…

Btw… the shorted C18 is kind of strange, since common 0603 ceramic capacitors are rated for 16V or even more (the official BOM uses a 16V rated capacitor) – 9V would not do them any harm (there are 6.5V ceramic caps available, but because of the DC bias effect it makes no sense to use them in 5V systems). So there could be another reason than just “i accidentally powered it with 9V” behind the damage of this broken OSSC…

[Arnopesto]

Hi ! Thanks for your answer !

Sadly I don’t have an oscilloscope, but I think my multimeter can measure Hz (I don’t know to which extent, and if it can help)

About the C18 capacitor… The more I think about it, the more I’m convinced it was fine.
I guess this is a low resistance line so my multimeter was beeping as a false positive. When I measure the actual resistance of the line, I get about 6 ohms IIRC (whereas I get about 0.05 ohms on ground).
Initially I thought it was faulty because it was heating, but I realize now that the heat probably comes from U1 (which is really hot). I was impatient, I should have tested to feed 3.3V to the line before removing it.
So, let’s consider it wasn’t shorted for now. (And I can’t test it because I have no idea where I put it, it vaporized lol)

Anyway, removing U8 may be the next step you’re right. And if it doesn’t work I guess I will send it to repair. Do you have an idea how much it will cost ? 40$ is the initial price and I’m fine with it but if the bill increases it may not be worth it

Thanks again for the advises. I think I will test this next week !

Stay tuned 😛

• This reply was modified 2 months ago by Arnopesto. Reason: Add info about C18

[Morpheus_79]

I think my multimeter can measure Hz (I don’t know to which extent, and if it can help)

It’s an 27Mhz oscillator. While your multimeter may have some oscilloscope features, such additional functionalities are mostly rudimentary and limited to a kHz range.

 

Do you have an idea how much it will cost ?

Sadly i don’t know. The repair may be cheap in replacement parts… but the final cost highly depends on the invested time and complexity for the fault finding and repairing.

[Arnopesto]

Well, I finally removed the U8 chip and… nothing changed. And I ripped some U8’s pads in the process 🙄
I think I can now consider this unit as dead.

On the bright side, it did not cost me much, and I learned about electronics troubleshooting so, yay (I guess ?)

Thanks for the help anyway, have a nice day everyone !

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