GX4000 RGB out

[opossum]

Hi, my GX4000 looks pretty awful in RGB - at least on a 29'' Trinitron. The image is kinda washed out, there's definitely a grill and and a greenish tone overall. I'm using a good SCART cable...Do you think anything inside has to be replaced? (caps etc..) If not, is there a way to improve the RGB out?

Thanks for attention.
A.

[gerald]

Hi, my GX4000 looks pretty awful in RGB - at least on a 29'' Trinitron. The image is kinda washed out, there's definitely a grill and and a greenish tone overall. I'm using a good SCART cable...Do you think anything inside has to be replaced? (caps etc..) If not, is there a way to improve the RGB out?

Thanks for attention.
A.

Are you using the SCART ouput or the DIN one ? 11V supply or 5V ?

[opossum]

Are you using the SCART ouput or the DIN one ? 11V supply or 5V ?

Hi gerald, I'm using a quality male to male scart cable connected to Trinitron RGB IN, your C4CPC, and the alternative power supply you recommended in 11V port... I tried with original power supply and Burning Rubber cart, i obtained a little improvement but the image is still blurred...

If i use a CPC+ RGB cable in DIN out is it going to work? And above all, is it going to improve the quality of the image on a trinitron? i've read the monitor DIN  port is driven directly from the DAC while the SCART out is driven by a CX1145...

[gerald]

Hi gerald, I'm using a quality male to male scart cable connected to Trinitron RGB IN, your C4CPC, and the alternative power supply you recommended in 11V port... I tried with original power supply and Burning Rubber cart, i obtained a little improvement but the image is still blurred...

Do you have a picture ?

If i use a CPC+ RGB cable in DIN out is it going to work? And above all, is it going to improve the quality of the image on a trinitron? i've read the monitor DIN  port is driven directly from the DAC while the SCART out is driven by a CX1145...

The DIN ouput is direct from the DAC. Regarding the SCART, the french GX4000 (without the modulator) only has transistor buffer.

[opossum]

Do you have a picture ?
The DIN ouput is direct from the DAC. Regarding the SCART, the french GX4000 (without the modulator) only has transistor buffer.

I actually tried to take some pictures, but actually in the pictures of crt you can't see the defects...

If I buy an RGB cable built according to these instructions:


TV SCART cable - CPCWiki


and a 5V regulated power supply, can I use it with C4CPC without problems?


Above all, is this kind of connection going to improve the image quality (less blur etc.)?


Please let me know.
Thanks.
Andre

[gerald]

I actually tried to take some pictures, but actually in the pictures of crt you can't see the defects...

If I buy an RGB cable built according to these instructions:


TV SCART cable - CPCWiki


and a 5V regulated power supply, can I use it with C4CPC without problems?

C4CPC will work without any problem with the 5V supply

Above all, is this kind of connection going to improve the image quality (less blur etc.)?

The DIN may give you a brighter display.

[Velktron]

I hope I'm not stating the obvious, but have you tried your TV with other sources/in other modes? Old Sony CRTs are prone to develop greenish displays and all sorts of color stability problems, and those will be there regardless of what you're watching with it. Sadly, they only get worse with time, and a repair is not always worth it unless you have the correct part and can do it yourself, and then again it's often temporary (some tech once told me that it's the internal circuits trying to protect/compensate for wear on the CRT). Other symptoms may be  a delayed turning on, excessive brightness, color "blooming" etc.


Is that TV also used as a daily "beater" in order to watch OTA TV programs (with a set-top box for receiving digital TV) or you only use it for retrocomputing/console gaming?

[opossum]

The Trinitron is just used for gaming...

I've tried on Panasonic Plasma 50 with Framemeister...same thing, upscaled.

[Velktron]

At this point, I wonder if there's some crucial difference between the wiring of the various DIY CPC -> SCART adapters and the one used "officially" on the GX4000. What always puzzled me is how most CPC -> SCART wiring diagrams seem to use the Luma/Sync pins interchangeably, or even short them together. 

[Bryce]

Define "official"? If you mean how it's done inside the GX4000, then it's completely different, it uses a proper driver IC to create the SCART signals. For the DIN to SCART cable there's lots of ways to wire it, here's a whole page of alternatives: TV SCART cable - CPCWiki

The reason why LUM and Sync can be used to essentially do the same thing is because the LUM signal contains a Sync pulse too. The other information within the LUM signal is at a voltage level that doesn't (usually) effect the TV Sync.

Bryce.

[Velktron]

Define "official"? If you mean how it's done inside the GX4000, then it's completely different, it uses a proper driver IC to create the SCART signals.

Yes, that's what I meant. I wondered if good old Amstrad simply wired the SCART the same way those DIY adapters did, or if they were somewhat more refined about it.

The reason why LUM and Sync can be used to essentially do the same thing is because the LUM signal contains a Sync pulse too. The other information within the LUM signal is at a voltage level that doesn't (usually) effect the TV Sync.

So, in effect, the LUM signal on the CPC could be viewed as a complete composite video implementation (minus the color), while the SYNC signal alone is useful only in special cases. This means that most CPC -> SCART adapters practically use "sync on composite". Hmm....

[Bryce]

Yes, the GX4000 used a Sony CXA1145 IC to create the RGB that goes to the SCART socket. I believe the French version is slightly different and uses addition transistors to make it Peritel compatible.

As for LUM: LUM is the weighted sum of the Red, Green, Blue and Sync signal. If you take a look at that section of the schematics (below), you can see R,G and B being mixed together through Resistors R131, R132 and R133. The Sync signal is then added through R135.

Bryce.

[CanonMan]

Old Sony CRTs are prone to develop greenish displays and all sorts of color stability problems, and those will be there regardless of what you're watching with it.

Really?


I've repaired plenty of Sony Trinitron TV's in my time and I've never experienced the 'greenish display' thing!

[Velktron]

I've repaired plenty of Sony Trinitron TV's in my time and I've never experienced the 'greenish display' thing!

Sadly, I've had two going AWOL on me. One was a relatively recent (90s) model. Excellent TV by all aspects, but in 2011 or so it started acting up, with the CRT brightness/blooming problems I mentioned. A couple of techs I talked to said that this was a known problem with some ICs trying to protect what they thought was a failing CRT. When turning on, the TV would at first just show a too "bloomed" picture for a while, then go back to normal, then as time went by colors became increasingly blurred, until at some point turning it on would leave the TV with audio only (!) for up to half an hour until the CRT turned on, with severely reduced brightness. That TV was sadly tossed because repair would be uneconomical. I miss its sound, most of all. None of the new flat panel TVs has a decent pair of speakers, it seems.


Another case is an 80s Trinitron Sony TV I still have, which was actually a garbage find. It's functional, but the display has had a greenish hue ever since I found it, as well as visible trailing whenever there are horizontal dark/bright transitions. I kept it around because it also had excellent sound (4 speakers!) and was multi-system, even though it lacked a SCART input. Probably that one is salvageable with a recapping, but I doubt I'll ever bother with it.


Finally, in the 90s I had my first PC's SVGA 14" monitor "green up" before my eyes while playing Doom (!) 


It was usable, but extremely annoying. Luckily, it was repairable (turned out it was a blown cap) and hadn't a problem since. I kept and used that monitor until 2008, when I donated it to the Army, if I recall.

[opossum]

In the end what's the best way to connect a GB/Spain GX4000 to a PAL Trinitron? RGB cable through DIN 8 port and 5V power supply?

[arnoldemu]

Hi, my GX4000 looks pretty awful in RGB - at least on a 29'' Trinitron. The image is kinda washed out, there's definitely a grill and and a greenish tone overall. I'm using a good SCART cable...Do you think anything inside has to be replaced? (caps etc..) If not, is there a way to improve the RGB out?

Thanks for attention.
A.

Same thing?

Dirty video on 6128 Plus RGB Scart

[Bryce]

The capacitors mentioned in the other thread won't help against a "washed out" picture. I'd first of all clean the contacts on the DIN socket and see if that helps. Things that will cause a washed out picture: SCART cable too long. Bad connections. Wrong settings on the TV.

Bryce.

[opossum]

The capacitors mentioned in the other thread won't help against a "washed out" picture. I'd first of all clean the contacts on the DIN socket and see if that helps. Things that will cause a washed out picture: SCART cable too long. Bad connections. Wrong settings on the TV.

Bryce.

Well I'm connecting tge GX4000 through a simple 1,50 m male to male scart cable

[Bryce]

Then try a DIN to SCART cable instead.

Bryce.

[Velktron]

Well I'm connecting tge GX4000 through a simple 1,50 m male to male scart cable

Try a better SCART cable then  

Seriously, not all are created equal. I recently hacked a cheap SCART cable open in order to make a 6-pin DIN to SCART adapter for my CPC, and was appalled by what I saw: a mass of all-identical, black, thin cables, crimped at the SCART's terminals. The entire SCART cable thickness was not over 6-7 mm, including the external rubber sheath. Needless to say, I set not to reuse any of those cables or worse, trying to figure out which of the 21 (identical) black micro-cables went to which pin on the other end, but rather, uncrimped them from the SCART male plug's pins, and crimped the cables from the 6-pin DIN cable directly on the now free contacts, without even soldering them, and it worked like a charm. At least the SCART plug's terminal could be disassembled and pins could be accessed and removed/added individually, so I left only the pins I needed inserted.

[Bryce]

Back in a minute, need to find my magnifying glass....

Bryce.

Edit: Ok, you got the font size right now.

[opossum]

Try a better SCART cable then  

Seriously, not all are created equal. I recently hacked a cheap SCART cable open in order to make a 6-pin DIN to SCART adapter for my CPC, and was appalled by what I saw: a mass of all-identical, black, thin cables, crimped at the SCART's terminals. The entire SCART cable thickness was not over 6-7 mm, including the external rubber sheath. Needless to say, I set not to reuse any of those cables or worse, trying to figure out which of the 21 (identical) black micro-cables went to which pin on the other end, but rather, uncrimped them from the SCART male plug's pins, and crimped the cables from the 6-pin DIN cable directly on the now free contacts, without even soldering them, and it worked like a charm. At least the SCART plug's terminal could be disassembled and pins could be accessed and removed/added individually, so I left only the pins I needed inserted.

I'm just using top quality RGB scart cables for all my consoles, included Packapunch line. With Framemeister you need such quality cables.

[opossum]

Then try a DIN to SCART cable instead.

Bryce.

That's what I'm going to do.   Is this power supply ok? -> Alimentatore a spina tensione fissa Dehner Elektronik SYS 1381-1005-W2E EURO 5


Thanks
Andre

[Velktron]

That's what I'm going to do.   Is this power supply ok? -> Alimentatore a spina tensione fissa Dehner Elektronik SYS 1381-1005-W2E EURO 5

The voltage and current seems OK, but the end connector looks like the one used by some Sony devices -well, you can always solder a big round one, if the GX4000 uses the same one as the classic CPC models.

FWIW, my CPC 6128 powered on with a 1200 mAh, 5.2V adapter which just happened to have the right shape of plug, but that was with no peripherals attached.

[gerald]

That's what I'm going to do.   Is this power supply ok? -> Alimentatore a spina tensione fissa Dehner Elektronik SYS 1381-1005-W2E EURO 5

The plug is a 5.5 x 2.1, you won't be able to plug it on the 5V port.
You need a5.5x2.5