exxos's Atari, Amiga & retro forum

trixster wrote: 30 Jul 2023 17:20 Fascinating stuff so far!

Thanks, I aim to please :)

So far there are a few options for the cause of the problem.

The HDMI port itself is original They are distinctive in their construction) and a known failure point, so that is up next for replacement. Then there are the diodes around the HDMI port. Having tested them against my other board, I'm not convinced that they are right as the values seem to vary considerably, so I am going to swap them with those on my donor board where values differ.

There is a fuse in the circuit too, but that is ok, and in addition I have checked all the caps for shorts and there are none.

I think the HDMI encoder is probably fine, as are the EMI filters, and I have tested the path back through from the HDMI port to the encoder, via the filters and I believe they are all ok, there are no shorts and continuity is good.

Certainly the readings through the differential pairs are identical, so no cause for concern.

So, if switching the diodes and the HDMI port doesn't fix it, the only option left is likely the Southbridge. I can try a swap with the donor board, though I may well just be better getting a known good pre-balled replacement.

That makes me nervous since I've never installed a BGA IC before, but there's a first time for everything, right?

Can you run the machine out of the box to see if you can read signals using an oscilloscope?

stephen_usher wrote: 30 Jul 2023 20:00 Can you run the machine out of the box to see if you can read signals using an oscilloscope?

Well, I can figure something out for the top of the board, it's the bottom that is difficult. I'd need to rig something up with a heatsink as the APU gets very toasty, vey quickly.

I can probably check the output at the EMI filters though, as they are topside.

I'm going to see if I can find the schematics as supposedly the Southbridge provides 5v for the HDMI circuit, so if I can verify that, then the Southbridge is likely OK.

I am going to replace the HDMI port though, as the pins are known to push back on the original, but you can't tell easily. They are easy enough to replace.

@stephen_usher

Ok, so running the machine 'open top' style is feasible for short periods, though the RAM does get warm due to the lack of heatsink, and it seems I'm getting voltages at the output side of the EMF filters, and they look OK, so I'm now wondering if it really is the HDMI port that is the culprit.

Fingers crossed the replacement will be here soon and I'll find out.

I'm pretty convinced that it is booting properly as I get a white light either when booting normally, or in safe mode. The PSU also make the correct 'click' when reaching the powered on stage.

Just need to figure out the whole HDMI thang.

Well I have been running a old laptop drive in my ps4 to great success. So it appears the factory drive has worn out. Time for a cheap ssd


Tom

Tomswork wrote: 31 Jul 2023 15:35 Well I have been running a old laptop drive in my ps4 to great success. So it appears the factory drive has worn out. Time for a cheap ssd


Tom

Be interesting to see how you get on.

OK, so ZD22, C27, C28 and C61 have now been replaced with new:


Just waiting on the replacement IC, which will hopefully be here today or tomorrow, then I can test and see if repairs have been successful :)

Also arrived is the HDMI port, but before I replace that, I'm taking a look at the area just behind the HDMI port to see if pins 13-19 are good, or if there any shorts or blown components amongst the resistors, caps and diodes. I alreay know the 5v fuse is good at least.

Good luck!

stephen_usher wrote: 03 Aug 2023 13:37 Good luck!

What's the worst that could happen? Another boom, right :)

:lol: