RGB -> Scart -> HDMI Horizontal snow / Yes, sorry, another scart thread

[arjorge1987]

Hi!
I have spent the whole day searching for "scart" keywords in this forum, and reading threads going back to 2017, but I didn't fund anything like my issue.

Context:
* Amiga 500 Rev 6A.
* Composite image is terrible with the A520, so I decided to go Scart/HDMI.
* Got an RGB Scart cable from Ebay: The cable on eBay
* Got the Scart -> HDMI converter that almost everyone else has.
* I'm in Canada, so no Tvs with Scart input around to test "just the cable"

Issue:
I have a heavy horizontal snow. Only present when using Scart->hdmi, not when using Composite with the A520.

Pictures time:

Image using Scart->hdmi:


Full size: Link

Image using Composite:


Full size image: Link

The Scart cable:


The Scart to HDMI:


So, from my understanding this could be related to something on the RGB Scart cable, right?

Aside from the horizontal snow, the image looks good, and I have sound.

I don't know, I don't have anyone else to talk about this stuff, so maybe someone had any idea or have seen this before.

Thanks!

PS: Sorry about my english.

[Leon Besson]

I don’t think the cable or the Chinesium box you have is the problem. There is a YouTuber in the USA who uses something similar. But he uses a Dell Monitor and can use PAL or NTSC modes without issue.

The problem could be on your Motherboard or the Television/Monitor you are using perhaps?

I use that same setup on A1200 and A600 systems on a PAL setup using a Dell monitor without issue.

[arjorge1987]

Originally Posted by Leon Besson

The problem could be on your Motherboard or the Television/Monitor you are using perhaps?

I just tested the output in 3 different places and see the exact same horizontal snow.

* Insignia TV.
* LG QHD monitor.
* HDMI USB video capture.

In the three of them the image has the exact same problem, so I think we can rule out the TV, it didn't change a bit.

Now, on the motherboard, that is something can be on the table. You mean a problem with Denise? I recently recapped the board, so all capacitors are shiny new.

[jbenam]

I suspect that these el-cheapo SCART-to-HDMI boxes are of *very* varying quality. Heck, quality with the GBS-8200s was all over the place. These should be slightly better, but I suspect that the company (companies?) producing them would not have a single problem in slapping in whatever cheapest compatible component they can get in order to increase margins.

Do you have another SCART-based console/computer to test it with?

[Stedy]

Hi,

Inside the 23/25 way backshell for the Amiga, are there any resistors?
On pins 10, 22 & 23 of the Amiga end there should be some resistors, to set the correct sync level and RGB mode. They may be hiding on the SCART cable backshell, if there are no resistors, that is the root cause.

[Lord Aga]

Well... with the OCS/ECS Amigas, there's really no excuse not to go down the RGB2HDMI route.

[arjorge1987]

Originally Posted by jbenam

I suspect that these el-cheapo SCART-to-HDMI boxes are of *very* varying quality. Heck, quality with the GBS-8200s was all over the place. These should be slightly better, but I suspect that the company (companies?) producing them would not have a single problem in slapping in whatever cheapest compatible component they can get in order to increase margins.

I wound't be surprised by that... You can find this product by many names and with very different "made by".

Originally Posted by jbenam

Do you have another SCART-based console/computer to test it with?

No, nothing. :/ The other PAL stuff that I have is mainly Composite (Commodore 64, TI 99/4A, etc..)

[arjorge1987]

Originally Posted by Lord Aga

Well... with the OCS/ECS Amigas, there's really no excuse not to go down the RGB2HDMI route.

I will think about it.

In my defense my original plan was to try to have as few modern mods as possible. For me the Gotek was kind of like "Ok, but just because I don't want to buy 5000 diskettes".

[arjorge1987]

Originally Posted by Stedy

Hi,

Inside the 23/25 way backshell for the Amiga, are there any resistors?
On pins 10, 22 & 23 of the Amiga end there should be some resistors, to set the correct sync level and RGB mode. They may be hiding on the SCART cable backshell, if there are no resistors, that is the root cause.

Well this is something that I was not expecting at all. When I was reasearching about the topic, I saw a bunch of posts here were you guys were discussing about the resistors in these cables. But... Since the ebay publication from the cable says "tested before shipping", I didn;t wanted to force opening the glued db25/23.

My hands hurt a little but I think it was worthy, let me know your opinions, it looks like there is some resistors.

Scart end (Edit: I think there are some resistors on the long black sleeves):


DB25/23 end (hard to see, I was not able to separate the other side yet, but I see most of the cables going directly to the pinout)



Later I will try to unglue the other side to confirm.

After some review, I think that they might be there on the scart side. I will try to check that in detail later. (I'm writing this while I work, haha)

Thanks!

[arjorge1987]

Ok... So this is something interesting.

I was using this schematic to follow the cable connections, and found the following.



DB23 16 -> Scart 17 (In the schematic goes to 5)
DB23 10 -> resistor -> Scart 20 (is present just like in the diagram)
DB23 22 -> scart 8 -> resistor -> scart 16. (So the resistor is acting between 22->16, but I'm not sure what is the purpose of the bridge between 8 and 16. )

And I don't have the DB23 23 -> Resistor -> Scart 8.

From what I understand depending on if you want to use RGB or AV, you choose to connect:

23 -> 16 RGB
22 -> 8 AV

In my case I have little bit of both?

22 sending 12 V directly to 8. And then bridged with a resistor to 16.

Maybe adding a resistor between 22 and 8 could help? But the problem is that if I do that I will mess the value that 16 is getting from 22 with the resistor from 8. (Or I could split 22 in two, and have a resistor to 16, and another 22 with the resistor that already has to 8)

What do you think?

[arjorge1987]

FIXED.

Thank everyone, and sorry for wasting your time, it was my fault for trusting the cable that I got from eBay.

So I end up splitting DB23 22 in two.

One cable with the resistor that already had to Scart 16.
The second cable with a 1K resistor to Scart 8.

Now it looks awesome!!

I still have some guru meditation from now and then, and 3 keys that don't work on the keyboard... BUt at least looks great!!

Thanks everyone.

[arjorge1987]

So...

Fun story...

I dissasembled the Amiga to try to see if I can fix the keyboard.

Fixed 2 of the 3 keys that don't work sticking a little piece of aluminium foil below the key.

BUT, I have assembled it again, and now I have the horizontal snow AGAIN...

The perfect picture lasted only 1 day for me. I don't know what to think...

[Kin Hell]

Canada

[arjorge1987]

Originally Posted by Kin Hell

Canada

It does look great, for sure.

But at this point I wonder if something changed after I disconnected and connected the keyboard. Like some soldering around Denise or something, because the problem is back but nothing changed on the cable.

[arjorge1987]

In case this is useful to someone.

I spent the afternoon dissasembling and resoldering almost anything related to Denise. I hate everything.

This was the issue:



The Scart/HDMI converter uses a 5v PSU. I disconnected it accidentally and voila!!!

Perfect image.

Now I hope I didn't mess anything while resoldering everything.

Thanks everyone, and I hope this helps someone googling about this in the future.