CV top of screen shakes

[Charlie_]

I installed a Retrofixes AV mod in my CV. I recently picked up a 32" Toshiba CRT manufactured in 2004.

Using the composite mod, I see a problem with the CV display near the top of the screen. It shakes and is unstable.

When using the RF it does not suffer this problem. I have used this CV with other CRT displays and have not seen this problem.

It only seems to do this when the CV displays certain colors in that area. For example, in the videos linked below, you will see on the castle screen it is stable. When I walk down to the next screen it is unstable. I notice the color grey will make it do that. Particularly when I set the AtariMax cart for grey background it wobbles like crazy. Black and it is stable.

I also linked to the RF. As you can see it doesn't do it at all. All my other game systems work just fine on this same input.

Any ideas as to what might cause this incompatibility with this TV set? This CV did always have a kind of wavy picture on all displays, but nothing like what I am seeing with this display.

 

AV:

https://1drv.ms/v/s!AkqHrw8jl0oZidgKYw-xYeOpkRHclw?e=aoPPjk

RF:

https://1drv.ms/v/s!AkqHrw8jl0oZidgJao-qeK0o8LItvA?e=edF0aL

 

 

[Charlie_]

Here is what I've found about the problem since the first post.

 

I moved the mod to another CV and have the same problem. 

When I try the CV on my flat panel TVs it does not have the problem but the picture has interference and seems way bright or too much contrast. Specifically in the black areas of the screen it looks like they are glowing.

 

So this leads me to think it is the mod board. However when I look on ebay all the composite mod boards look the same.

 

Now I am looking for recommendations for a good composite video mod to put in my CV. Since they all look similar will I see the same results? Or, is that chip on the board programmed differently between the manufacturers? The one I have now is from Retrofixes.

Thanks!

 

 

[Ikrananka]

You're not alone in experiencing this problem : https://atariage.com/forums/topic/270374-retrofixes-cv-mod

 

This mod is a simple amplification circuit and so it may just be that it is being overdriven for the particular TV you have.  I haven't compared this one to other LM318 based mods, but it's likely that the circuits are pretty much identical.  However, you may find that resistor/capacitor values are different and therefore the amount of amplification may well be different.  Others are far better qualified to help than I am but perhaps changing the level of amplification may help.

[+-^CrossBow^-]

I've used the Retrofixes boards several times and haven't encountered anything like that before. Maybe a recent change to the components being used compared to the past? The last composite board I installed uses the same circuit but was designed by Mobius Strip Tech and sold by Console5 for a lower cost vs the Retrofixes boards. It seems to produce the same quality of picture that I've always gotten in the past, but I have been told that this newer board from Mobius includes a solid back ground plane on the bottom of the PCB to act as a shield against interference. Console5 is currently sold out of them but I believe they have been given the gerbers etc to have more made up on their own if they choose to do so.

 

So if you can't it might be worth using some flush cutters to trim everything on the bottom of the Retrofixes board to be as flush with the PCB as possible. Then use some kapton tape to cover the entire bottom of the pcb. Cut out a square of foil tape to attach to the bottom of the PCB. Find a way to ground this foil tape to the pcb and then apply more kapton tape to isolate the foil from anything else. I've not tried this myself but I might have to give it a go as I think I still have 2 of Retrofixes boards on hand that I purchased like a year ago or something?

 

Also, if you notice rainbow color artifacts around bright colors and especially white text. Pretty normal for the CV on composite as EVERY single CV I've seen with composite installed does this. In fact, I can still see it even through RF on my small LCD I use on my work bench so it is just there to begin with in the signal.

 

If you want the best pic possible from the CV then you need to either go with an F18 video upgrade or TMS-RGB. I've not seen the F18 myself, but the TMS-RGB is amazing to me every time I turn on my CV and see it.

 

BTW - if your RF is looking that good through a CRT why add the composite? I have a backup CV that is still stock minus the power switch having been replaced out. I've never wanted to do anything with it because it has a really good RF picture even on my LCD displays compared to the daily driver.

 

 

[Charlie_]

On 1/26/2021 at 9:40 AM, -^CrossBow^- said:

I've used the Retrofixes boards several times and haven't encountered anything like that before. Maybe a recent change to the components being used compared to the past? The last composite board I installed uses the same circuit but was designed by Mobius Strip Tech and sold by Console5 for a lower cost vs the Retrofixes boards. It seems to produce the same quality of picture that I've always gotten in the past, but I have been told that this newer board from Mobius includes a solid back ground plane on the bottom of the PCB to act as a shield against interference. Console5 is currently sold out of them but I believe they have been given the gerbers etc to have more made up on their own if they choose to do so.

 

So if you can't it might be worth using some flush cutters to trim everything on the bottom of the Retrofixes board to be as flush with the PCB as possible. Then use some kapton tape to cover the entire bottom of the pcb. Cut out a square of foil tape to attach to the bottom of the PCB. Find a way to ground this foil tape to the pcb and then apply more kapton tape to isolate the foil from anything else. I've not tried this myself but I might have to give it a go as I think I still have 2 of Retrofixes boards on hand that I purchased like a year ago or something?

 

Also, if you notice rainbow color artifacts around bright colors and especially white text. Pretty normal for the CV on composite as EVERY single CV I've seen with composite installed does this. In fact, I can still see it even through RF on my small LCD I use on my work bench so it is just there to begin with in the signal.

 

If you want the best pic possible from the CV then you need to either go with an F18 video upgrade or TMS-RGB. I've not seen the F18 myself, but the TMS-RGB is amazing to me every time I turn on my CV and see it.

 

BTW - if your RF is looking that good through a CRT why add the composite? I have a backup CV that is still stock minus the power switch having been replaced out. I've never wanted to do anything with it because it has a really good RF picture even on my LCD displays compared to the daily driver.

 

 

I tried another composite board from ebay that is as you describe with the solid back. All I can say is it did the same but a little worse, if that makes sense.. It had the same issue but the wavy was farther down the screen and more often than the retrofixes. Again, these composite "upgrades" do not do this on all TVs. In fact so far it only does it on my 32" Toshiba CRT cira 2004. Oddly I have a 19" Toshiba of the same year (that looks like a mini version of the 32") and it works fine on that display. Being that the 32" is the display I keep setup in my game area, this is a bummer. I also have a stock spare CV so I will use that on RF while I'm using this TV. Perhaps the TMS-RGB is an upgrade I can hire you for in the future? Since the 32" has component inputs I'd love to see the CV in RGB through one of my RGB SCART / RGBs to component devices.