MSXmakers support

I bought the linkfor 3rca hdmi device listed below from aliexpress(https://es.aliexpress.com/item/4000102209277.html?spm=a2g0s....), but it does not seem to work. If I connect it to my Omega MSX 2+ (just normally with s-video or rca cables) then i am getting a flashing and rolling screen changing colours all the time.
Do you know what this could be? I have tried different monitors and hdmi cables.

Ludovic Avot sent me this question by email:

Unfortunately there are many things that can be but my first advice is not to rush to solve it, think about what you do and make sure you don't make things worse by trying crazy. This is your opportunity to learn electronics, that's why we built the Omega.
Something you should check is that no component burns, the hottest is always the VDP and although after a while it is really hot, it should not be so hot as to burn your finger.
It's hard to touch every capacitor and resistor in the circuit, but if nothing catches fire nothing will be damaged by testing.
The next thing I would try is to remove the inserted components one by one (from 0), review them and insert them again. Although it may not seem like it, it is possible that the problem comes from a component with a bent pin that has not been a problem until this step.
If that doesn't change the result, I would try to complete all the components on the board and try again.
The reason is I did not use a complete study to determine the parts to place in each step, simple trial and error, but sometimes using a component from a different manufacturer can ruin the result of my smoking tests.
Although perhaps the best thing you can do is keep track of the signs. Check the electrical schematic and check the signals that reach the RAM chip. Power on the computer as it is, with the chips in smoking test 4, press reset, and simply check that /CS of the RAM chip is "0". I think it should be 0 all the time, but you might have to look at it with an oscilloscope to see if it at least pulses low after a reset.
So check the /RAM0_CS signal, on pin 22 of U7, if there is no pulse, this signal comes from U32, then check its pins 1, 2 and 3 which should be (or pulse) 0 too, etc.
When you find one that does act as it should on the input, check the input and output on that same chip and check that it doesn't have a socket or cold solder problem.
Of course this supposes a reverse analysis of the circuit, knowing and understanding what function each chip fulfills.
If the /RAM0_CS signal pulses 0, the problem may be in the slot or sub-slot register.
Do you have any way to verify that the chips are working? What if the RAM chip is simply bad?
Tell me your progress and I'll have more ideas.
Regards.

It looks like you have a problem with /RAM_SL because pins 5, 6 of U32 (not U2) should not stay high, so /RAM_SL is high for you (so U13 pin 15 should not be high).
check that GAL chip, I had several times problems with the three gals and their sockets.
check this: /RAMSL = SLTB * SLTA * /MREQ * RFSH * FFFF * SBSLTB * /SBSLTA
so, pin 15 should be 0 (active) when pins 8, 9, 4, 5 & 7 are H and pins 3 & 6 are L. This happens at any time?

Nice!

humm,
I've heard this before, but I don't remember all the solutions posted.
What I did to solve this was to replace the cheap power supply with a higher wattage one (I actually use a PS 6A) and replaced the input capacitors (I mean 100uF on the motherboard) and the output video capacitors ( 220uF) for ones of type LowESR.
Generally speaking, noise comes from a bad power supply and ends up in the output signals, but with less load the noise usually decreases as well.