PCE Turbo Duo RGB - No jailbars - working solution

[leonk]

New method:

quoting viletim from a few messages down "I've made a page about this. It's part of the AV-Driver docs.

http://etim.net.au/av-driver/pcebars/

Basically, it's just noise on the power supply rail getting into the video DAC. You can fix it by putting a large ceramic cap across both the analog and digital power rails of the DAC (HuC6260).

It's better to use the existing decoupling capacitor positions than attaching caps to the pins DAC directly (which probably works, but is a bit odd). Only ceramic capacitors are suitable for decoupling high frequency noise like this. Electrolytic caps wouldn't perform well."


Old method:


Of all the RGB modded systems I've done over the past few years, none are as prone to vertical jailbars as the Turbo Duo / TG16. I've tried many different RGB amps and they all exhibit the exact same output. The jailbars are introduced into the video stream before the RGB amp. I would like to thank thesteve from pcenginefx forum for figuring most of this stuff out. He knows his obey stuff like no one else. Thanks dude.

Now onto the guide. There's actually multiple modifications you need to do to your Turbo Duo to get absolutely jailbar free RGB output.

1. HU6260 modification



As per http://pcengine.freeforums.org/jailbar-fix-t233.html you will need to add 2 capacitors to pin 41/42 and pin 43. (ignore the 3 wires - they're there for the RGB mod)

I used the following capacitors: http://www.digikey.com/product-search/e ... -3300-1-ND - 22uF SMD ceramic capacitors. Rated at 16V.

2. C961 Capacitor

The original capacitor at this location is rated 10uF 16V. Replace it with a 220uF 16V capacitor

Digikey link: http://www.digikey.com/product-search/e ... -5357-1-ND

3. Better grounding on 8 pin DIN port



If you replaced the stock 5 pin DIN port with an 8 pin DIN port, you need to improve the grounding. As is, the GND pin goes though a choke. You need to bypass the choke. Because the ground is shared by all the other pins, the choke causes inverted crosstalk.

The results: (please ignore the horizontal lines - it's hard to capture a good picture off a CRT / Sony PVM).

Before: (note the vertical jail bars in the sky)



After: (all clean!!)

[Guspaz]

Is it just the camera, or does the post-fix version have less saturation?

[leonk]

Is it just the camera, or does the post-fix version have less saturation?

It's just the camera. Different angle and different lights on in my workbench. Exact same RGB amp was used on same system. These smart phones suck at taking pictures of CRT. Heck, even my Canon 5D is not that much better.

[CkRtech]

Hey leonk,

Thanks for adding this write-up. I took some notes from various places about various repairs from various people...I did make note of thesteve's comments from pcenginefx a long time ago, but I never ordered the caps.

Although I have Duo, I use a Duo-R for my main Turbo Duo. Have you done a similar modification to the Duo-R? I assume the HuC6260 change might be the same, but the board layout difference would most likely negate the C961 modification. Any thoughts?

[Pasky]

I can verify this fix works, fixed my Turbo Duo and my TG-16. Credit goes to TheSteve on PC Engine forums.

[leonk]

For TG16, I believe the fix is to replace C142 with 220uF elect. cap (16V minimum) instead of C961. I believe it won't hurt to do Step 1 as well. Step 3 is not required as the TG16 originally does not have a 5 pin DIN, it has an RF only adapter which gets replaced by an 8 pin mini-DIN (same as Sega genesis port). Given it's a whole new port, GND should be good there already.

For TG16 I strongly recommend also using Tim's AV-Driver as it will have the required audio Amplifier.

For Turbo DUO-R, the 2 I've examined did NOT require a cap kit! NEC went back to using through hole caps rather than SMD ones! And they all tested good. I do believe though that all 3 mods still apply for DUO-R/RX. I never did an RGB mod on a DUO-R (it already had it) I just tested both of them to make sure they didn't need a new cap kit.

The only system I'm impressed with when it comes to clean RGB is the original white PCE. I did an RGB mod on an IFU-30 suite case, and the stock PCE RGB was clean.

[Fudoh]

The only system I'm impressed with when it comes to clean RGB is the original white PCE. I did an RGB mod on an IFU-30 suite case, and the stock PCE RGB was clean.

wasn't for me. Same IFU30 setup with a Core II instead was considerably cleaner. Still not perfect though, so I'd love to have this fix for all three PCE variants (White/Core1/2).

[Voultar]

The Core Grafx syatems typically yield the worst jailbars out of all the hardware. Followed by the PC-Duo/Turbo, and OG PC-E. That TG16 typically produce the least RGB jailbars, though they're still present.

The Duo R/RX DIN connector doesnt have a choke inductor. All that's necessary to clear up the jailbars on those systems are a power to ground and sync to ground caps on the 6260 to take the edge off.

I have a pretty decent writeup about the Duo R/RX @ Retromods if you want to check it out.

The Duo on the other hand, does have a ground choke on the DIN.

Good post. This information tends to get lost through the theads.

[CkRtech]

All that's necessary to clear up the jailbars on those systems are a power to ground and sync to ground caps on the 6260 to take the edge off. I have a pretty decent writeup about the Duo R/RX @ Retromods if you want to check it out.

This one? http://www.retromods.net/viewtopic.php? ... uo+R#p5566

[kamiboy]

A long while back I tested all three of these on my Coregrafx without luck. They did diminish, but did not remove the bars. I may need to redo the 6260 fix with better caps, low ripple low profile perhaps. During my testing I used regular sized caps and after seeing little improvement I removed them as they were too large to fit.

The GND mod I came up with independently it seems as a way to guarantee good GND on the new AV port since I had issues with that in the past.

It bears mentioning that the colour blue is not the best litmus test for the presence of jailbars. The best test I found was the sky of the desert level in Dragon's Curse, or Adventure Island as it is called in Japan.

[mickcris]

thanks for documenting leonk. Has anyone tried these other places that Otaku store has for larger caps?:
http://www.otakus-store.net/en/content/6-guide-nec-rgb

wondering if those help

[leonk]

thanks for documenting leonk. Has anyone tried these other places that Otaku store has for larger caps?:
http://www.otakus-store.net/en/content/6-guide-nec-rgb

wondering if those help

I tried this mod on a different PCE Duo. It made the bars fainter but they were still visible.

[Voultar]

Here's a DUO-R with Vcc to ground and sync to ground caps on the 6260.

Taken on my 35" RGB modded KV Trinitron.

Excuse the blurriness and moire pattern, but the jail-bars are non-existent.

I've found that Keith Courage and Twin Bee are some of the best games to benchmark PC-E jailbars.



The Framemeister can also act as a fairly competent tool for testing image noise and cross-talk when you disable a lot of the post processing image filtering. Clean as a whistle.

[mvsfan]

How did you RGB mod the Trinitron? i have a kv32fs120 id like to do that on.

someone really needs to do a thread on this since its one of the most popular retro gaming tv and the info just isnt out there.

[Corredor X]

The only system I'm impressed with when it comes to clean RGB is the original white PCE. I did an RGB mod on an IFU-30 suite case, and the stock PCE RGB was clean.

wasn't for me. Same IFU30 setup with a Core II instead was considerably cleaner. Still not perfect though, so I'd love to have this fix for all three PCE variants (White/Core1/2).

Same here, in my case I have a RGB modded white PCE in a standard IFU30 and the picture looks like the first Keith Courage one. Maybe if I put a better mod on the IFU (the one on the PCE is that ancient one from a japanese magazine or something, bought the console with it already installed) I can get a cleaner picture?

[Voultar]

How did you RGB mod the Trinitron? i have a kv32fs120 id like to do that on.

someone really needs to do a thread on this since its one of the most popular retro gaming tv and the info just isnt out there.

Spoiler

The info is out there. Grab the service manual for your set and look at the specs. How does the Jungle I/C look? Does it have .7vPP RGB inputs? Are the RGB inputs clamped by the Jungle I/C? If so, great! Terminate each RGB input with a 75ohm resistor to ground to match impedance for all of your 75ohm load hardware. Add coupling caps to each of your RGB inputs for black level resto so the screen doesn't volt up. Follow the RGB input signal path in the diagram and pay mind to the value of the coupling caps going into the RGB inputs. Just look at the block diagrams and schematics in your service manual, and build accordingly. Television sets have sophisticated sync separation circuits. Just hijack a composite input and feed your sync source into that. For this particular set (look at the datasheet screens) holding the blanking pin high (with a low voltage source) will enable the RGB inputs. In this case, you can simply wire the 5V coming off your consoles to switch this on. Or, you can install a simple switch to handle it, manually. I built a little circuit of NPN's/PNP's that are biased on by the 5V source that will keep OSD operational. I isolated the OSD inputs from my own RGB source all together. Typically, the OSD is what utilizes the RGB inputs on most NTSC Jungle I/C's.

I made the content a spoiler because there are too many pictures that'll just spam up the thread.

The problem with doing a thread on the process is that the circumstances are different for whatever chassis you'll be modifying for RGB input. There is no "standardized" way of doing something like this. If you have a decent understanding of how video signals work, it shouldn't be very difficult. You should be able to take my info and put together what needs to happen. It all starts with the service manual. If you can take advantage of the Jungle I/C, that's fantastic. If you can't, you're going to have to drive the guns with a video circuit. Mmm, AC-Coupled video...

I don't own one, but I wonder if the Turbo Everdrive exacerbates the jailbars. As the logic powering the board adds to the load on the 5v rail there.

[leonk]

I only have a TD everdrive. The above pictures were taken using 1. So issues.

[RGB32E]

I assume the HuC6260 change might be the same, but the board layout difference would most likely negate the C961 modification. Any thoughts?

IIRC C961 connects to Hu6260 pins 43 & 46, which is the same as C142 on the TG16. Console 5 has a schematic of the Hu6260 circuit for TG16 that can be referenced for NEC HW.

[leonk]

I did this mod to my USA TG16. It uses Tim Worthington's AV Driver as the RGB amp. I added the 2 ceramic caps to pins 41/42 and pin 43. I also replaced C142 with a 220uF cap.

The jailbars went from very visible (same as on Turbo Duo) down to 2-5% visible. You need to look for them hard, but you'll find them. Regular players will never see them during normal game play. On Turbo Duo I simply can't find them in the same spots.

[mvsfan]

Is there any difference between SuperGs board and the A/v driver with regards to picture quality, after the fix mentioned in this thread is applied?

just looking at it it looks like the SuperG one has less wires and would allow for a neater installation.

I just bought my first turbografx (never owned one all these years) and could use rgb since my other consoles already have it.

[viletim]

I've made a page about this. It's part of the AV-Driver docs.

http://etim.net.au/av-driver/pcebars/

Basically, it's just noise on the power supply rail getting into the video DAC. You can fix it by putting a large ceramic cap across both the analog and digital power rails of the DAC (HuC6260).

It's better to use the existing decoupling capacitor positions than attaching caps to the pins DAC directly (which probably works, but is a bit odd). Only ceramic capacitors are suitable for decoupling high frequency noise like this. Electrolytic caps wouldn't perform well.

[kamiboy]

Holy cheezus on crackers, great work Tim! Now this is a proper fix if I ever saw one. Going to do this on all my PC Engines post haste. I'll prolly be buying one or two of your drivers in the future as well.

[leonk]

I've made a page about this. It's part of the AV-Driver docs.

http://etim.net.au/av-driver/pcebars/

Basically, it's just noise on the power supply rail getting into the video DAC. You can fix it by putting a large ceramic cap across both the analog and digital power rails of the DAC (HuC6260).

It's better to use the existing decoupling capacitor positions than attaching caps to the pins DAC directly (which probably works, but is a bit odd). Only ceramic capacitors are suitable for decoupling high frequency noise like this. Electrolytic caps wouldn't perform well.

On digikey .. ordering caps .. amazing work as always!

[CkRtech]

Oh man. My 22uf caps from leonk's post just arrived yesterday....

[leonk]

Oh man. My 22uf caps from leonk's post just arrived yesterday....

You can still do that on Turbo Duo. It works great! It's the other consoles that it's so-so with.

[RGB32E]

Basically, it's just noise on the power supply rail getting into the video DAC. You can fix it by putting a large ceramic cap across both the analog and digital power rails of the DAC (HuC6260).

Most excellent job! Extremely pleased you root caused the actual issue and provided clear and simple steps to resolve! I'll have to give this a try in the near future on my TG16 and Duos!

Oh man. My 22uf caps from leonk's post just arrived yesterday....

I'd imagine they didn't cost too much, and could be useful for a different project down the road.

[CkRtech]

Oh man. My 22uf caps from leonk's post just arrived yesterday....

I'd imagine they didn't cost too much, and could be useful for a different project down the road.

Yeah. It ended up being just an instance of funny timing. Ordered some of the caps Tim mentioned.

Going to do this on my Duo-R first. Will probably also perform it on the Duo.

I'll try to snap some cap location photos on the Duo-R and add them here for reference unless someone beats me to it.

[Tarma]

I've recently installed the RGB amp that mickris supplied me to my PCE Duo and I've got zero jail bars from the mod.

I have had all the caps replaced though, so whether that's made the difference I don't know. Overall, I see no need to add any additional modifications for the picture to improve to be honest!

[mickcris]

I've recently installed the RGB amp that mickris supplied me to my PCE Duo and I've got zero jail bars from the mod.

I have had all the caps replaced though, so whether that's made the difference I don't know. Overall, I see no need to add any additional modifications for the picture to improve to be honest!

it seems to be somewhat console dependent and also what scaler or monitor you are using. i have trouble seeing them on my BVM and xrgb-mini.

[kamiboy]

BVM's do significantly reduce the artefact, I can confirm this myself.