Thanks Dave, all good advice. Sorry for the lack of response. Did some investigation but didn't have time to write up.
A brief history
So this MTX-500 I got last year from an Ebay seller (untested, without power supply) and other than a quick 'power up and bash the keys a bit' test, I haven't touched it. It has it's composite output pinned to monochrome and I wanted to fix that. Now when I tested it, I tested it on a small 7" LCD that I have and that told me the input was 60hz, which I thought was odd at the time as it has a TMS9929 in there, so can't be a US machine.
I gave it a good clean - think it had had a cup of tea spilt in it some time ago as there was a brown sticky residue on the underside of the keyboard PCB that was a little hard to shift.
And so...
I decided to change the link on the video daughterboard from b to a and I must say, it's quite a densely packed little board and my de-soldering skills are somewhat behind my paltry soldering skills.
However, got it done and tested continuity with my Multimeter and it looked good. Placed it back inside the MTX500 and as it was evening I used one of my work-from-home screens to test. So this probably was a bad idea, as it is a Sony Playstation 3D display and the only analogue inputs are the Y/Pr/Cr inputs. So, by utilising the Y input, I can get an MTX to display a ropey b/w image, which is good enough for testing. But no dice in this case, nada. To make matters worse, this display also powers down after a few seconds if there is no video signal, so I couldn't even do the CTRL-G bell test.
Thus I posted an SOS here (why do i do these things at night?
)
The next morning
I had another MTX512 that was also a 4000-05 board and that outputs a monochrome image too. So I tested that again on my Sony display and yes, I get a b/w image . So I took the daughterboard out and put it into the MTX500 - no image. At this point I thought the MTX500 was generally faulty.
So, I took the daughterboard from the MTX500 and put it into the MTX512... no image. Ok, so now I'm thinking I have a dodgy MTX500 and I've ruined it's daughterboard. I put the original daughterboard of the MTX512 into the MTX512 and tested again, got a b/w image.
Some time later, as commitments allowed, I hooked up the MTX500 to the TV in my bedroom (which is 32-inch Bush/Argos job with a side-av in). I get a colour image!! So both the MTX500 and daughterboard work!
- MTX500_colour.jpg (230.77 KiB) Viewed 28119 times
I take it back to the Sony display and no, same thing -"No signal detected" and it goes to standby.
I start thinking it's the presence colour in the signal that is making it not work, perhaps the colour carrier is affecting the monitors ability to sync or similar.... ? Then I remember that my Danish MTX512 outputs colour and that used to show a b/w image if I fed it through the Y input of the component-in on the Sony display. Only one thing left to do: hook up my Danish MTX to the Sony display and the answer is, yes it does show an image.
Conclusion, TL;DR
Something with the MTX500 machine outputs a somewhat out of spec signal (compared to my other two MTX machines) that the Sony display can't handle. Given that I'm abusing the component-in to do this, I guess that's reasonable.
Anyway, I have a Retrotink Mini in the post so this kind of funny business will be a thing of the past. Sorry for sending up the Bat signal unnecessarily!!
, no beep or black screen, just no signal. FYI: Keyboard is detached.
