Jaguar Rgb issues

[MissDeLaRocha]

Hi just wondered if anyone could help.. Recently upgraded to rgb cables to my Jag on RF the colours are spot on but wanted better sound and video so got a set of RGB cables from retrogamingcables and when I boot it what should be White is Yellow and there's a muddy yellowing over screen in the games too. I've also tried an rgb cable from retro computer shack and I'm having the same issue.

[Zerosquare]

Try cleaning the video port with alcohol, and checking that the cable is firmly inserted on both ends.

[MissDeLaRocha]

Already cleaned the edge connector and I can assure you it's not an issue with the rgb scart lead not being inserted correctly. But thanks for the reply. Any more help would be appreciated.

[+madman]

Are you going into a PVM or similar RGB monitor? Are you using an upscaler? Presumably all other RGB cables/systems you have work fine on the same setup?

[MissDeLaRocha]

Going into a crt tv. I've tried the jag on my other crt tvs and get the same results. My other consoles work fine via rgb on these tvs. No upscalers

.

[Zerosquare]

It's unlikely that both cables are defective in the same way, so the issue must be with the console. But it's the first time I've heard of a Jaguar with this problem.

Are you comfortable using a soldering iron?

[MissDeLaRocha]

I'm not a soldering wiz but I own a soldering iron or two, what is your suggestion?

[Zerosquare]

There are not many components that may cause the problem you're seeing. They are highlighted in yellow on the picture:

 

Checking and replacing them if necessary should solve the problem. It may also be a broken track, which can be found with a multimeter.

[+Stephen Moss]

It is an interesting issue, do you have another RGB source you can try to see if it is the inputs to the display are at fault?

 

I may be wrong but the fact that the colours are correct via RF suggests that the Jaguar is generating the correct colours otherwise they would be off there as well. Zerosquare has already indicated the area to investigate, personally I would be looking at the 75R resistors, ferrite beads & as Zerosquare suggested a broken track in that area because if anything prior to that was off I would expect the colours in RF should be off as well.

 

White should be 100% R, G & B either therefore either all the colour voltage levels are off and everything looks a darker/grubby shade of what it should or one colour is off, does either R, G or B look off more than the others? Personally I would suspect Red if it is looking slightly yellow.

[Zerosquare]

I had missed the part about colors being fine on RF. This narrows the problem down further more, to resistor R43 and ferrite L14 (and the tracks that are connected to them).

Edited February 27, 2019 by Zerosquare

[The_Son_of_Farore]

On 2/27/2019 at 1:00 PM, Zerosquare said:

I had missed the part about colors being fine on RF. This narrows the problem down further more, to resistor R43 and ferrite L14 (and the tracks that are connected to them).

I have a similar problem where I'm getting only the green signal from the av port but everything works perfectly fine with RF, would these parts be the likely culprits for me too?

[Zerosquare]

What kind of video cable are you using?

[The_Son_of_Farore]

1 hour ago, Zerosquare said:

What kind of video cable are you using?

Retro access RGBs cable. I checked continuity and it seemed right (at least for the red line). I'm assuming the issue is the same for all the lines (RBs) if they all suffer the same thing. 

[Zerosquare]

For red, the parts to check are resistor R29 and ferrite L15.

 

If you can, also check that your TV/monitor/converter works correctly with another RGB source.

[The_Son_of_Farore]

7 minutes ago, Zerosquare said:

For red, the parts to check are resistor R29 and ferrite L15.

 

If you can, also check that your TV/monitor/converter works correctly with another RGB source.

I checked continuity from u7 to the end of the red line and it seemed to check out, would continuity not help in this situation? I know for a fact the monitor work because I use it for all rgb consoles I have. It's a direct connection. I'm quite certain the issue is internal. 

[The_Son_of_Farore]

Can anybody give me the part information on R29, R43, R48, R38, Q2, Q3, Q4, L15, honestly just the whole color circuit in terms of resistors and ferrites? I accidentally fried something small trying to get this to work and now rf starts normal then white turns to yellow. 

[Zerosquare]

Here it is:

 

[The_Son_of_Farore]

1 hour ago, Zerosquare said:

Here it is:

 

Hey thanks man, this helps out a lot. Hopefully just replacing all the suspected parts will fix it. I'm not so good with the specifics of ordering replacement parts. Please let me know if anything on this cart seems amiss. 

 

[+Stephen Moss]

Make sure you are selecting to correct package size for the resistors, you appear to have a listed a mix of 0603, 0805 & 1206. I do not know if those are the correct sizes for the parts you are replacing or not.

 

If mouser does not give the dimensions of each resistor you should be able to find the package sizes on line then compare them to those on the PCB, the difference between 1206 & 805 is quiet marked but between 805 & 603 is much harder to tell and you may need to measure them with a micrometer to correctly identify which size they are. 

[Zerosquare]

Resistors are 0805 size.

 

The ferrite beads are 1206 size. The original part number is Murata BLM31A02, but it appears not to be manufactured anymore. You can use a Fair-Rite 2512067007Y3 instead.

[The_Son_of_Farore]

Managed to fix whatever it was I broke. Doesn't seem like replacing those components had any effect to the original problem though. I'm at a loss here. What else could it possibly be? There is a resistor before the transistor that I intended to replace but somehow I didn't get the resistors in my order. Could those be the culprets? (R30, R37, and R46)

[Zerosquare]

Are you sure the monitor is actually set up for RGB mode, not YPbPr mode?

Also check that your cables are connected properly.

[The_Son_of_Farore]

20 minutes ago, Zerosquare said:

Are you sure the monitor is actually set up for RGB mode, not YPbPr mode?

Also check that your cables are connected properly.

Quite sure it's set to rgb, that was the first thing I checked. Been fidgeting with the cable all the while over here. It's the same issue, completely unchanged. Turning off ext sync seems to make the pvm reconstruct a sync from just the green signal, but it's a very broken sync. 
 

 

[3dfx]

Is there anything special to note with Atari Jaguar RGB is there a by pass or something ?

[+Stephen Moss]

Not sure what you mean by a bypass but the colours come out of Tom as 8 bit RGB, go strait into the RDAC which converts to analogue RGB, which is then amplified by a Darlington transistor (see schematic in post 8 above).

From there, unless there is something missing from the schematic, it goes to both the AV port on the rear of the Jag (Via an indictor) and U3 where it is converted to composite and S-video.