Can anyone improve the rgb output on my duo?

[gtsamour]

Will these suffice? http://www.ebay.co.uk/itm/100UF-16V-SURFACE-MOUNT-TANTALUM-CAPACITORS-x10-blb173-/400267121772?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item5d31c7946c

[thesteve]

thats what i use

[gtsamour]

Thank you... I went to a local store but they only had the non electrolytic tantalum type (without polarity) so I'll get some from ebay.

[gtsamour]

I replaced the C961 electrolytic SMD capacitor (up side of the board, below the card slot and to the right) with a tantalum 100uF but I saw absolutely no improvement, not the slightest...

[thesteve]

then you may have a different issue

[gtsamour]

Oh it is the jailbar issue allright... I have it on all my PCE type consoles. Its just that on the DUO it is more intense.

Just a question.... does the Sync signal (that Im getting straight from the chip) need amplification or not? Because right now I am amplifying it... I'm using the good amplifier that I made myself using the popular schematics https://www.pcengine-fx.com/forums/index.php?topic=9299.0. I also used it on a bunch of other PCE consoles with good results but its the first time (the DUO) im using it taking all signals from the chip, i took the signals from the expansion port on all the others...

[gtsamour]

No reply?

[Frank_fjs]

I don't 'think' that it needs amplifying, and I don't think this would cause jailbars either way. I'm not 100% sure though as I've never used the amp that you're using, I've always been fine with the 3 x transistor method.

[gtsamour]

Well the schematics also include an amplifier for the Sync (just sync and not composite sync) thats why I asked. I tried with and without sync amplification and the difference that I could notice was that WITH Sync amplification the colors were more "normal" and without the colors were more intense...
Jailbars were present in both cases in the same intensity but thats not the reason why I'm asking, its the colours Im worried about.

[thesteve]

sync is composite sync.
yes it will need amplification for most monitors as its only 0.3V not 5V (TTL)
its also not the jailbar issue.
2 things cause jailbars (power filtering) and (crosstalk)
some have had issues with region mod installs causing crosstalk.
the capacitor fix is for power filtering.

[gtsamour]

Yes right, I got confused because in many mod schematics on the internet a lot of people show mixed up info. Some get composite (which i know does not need amlification) and indicate it as composite sync (which obviously does).

Could a weak sync signal cause incorrect colours or is it just my imagination?

As I said before, the 100uF tantalum cap did nothing for me that I could see. Maybe because my DUO is totally recapped recently and a difference is seen with old caps boards? Who knows...
I also have replaced the 7805 power regulator with a fresh one.

[thesteve]

a weak sync can cause color issues with composite.
PCE RGB does not match the colors PCE composite uses, due to the component blending not being even in the system stock

[gtsamour]

I would like to ask your opinion about the most popular amp at this time I believe...


https://gamesx.com/rgbadd/rgbturbo.htm
https://gamesx.com/rgbadd/duorgb.php

Is it a good amp from a technical point of view or is it flawed? Does it draw a lot of current or it's power consumption is negligible?
Well the results it produces according to my experience are excellent but just out of curiosity...
Im asking because on another forum someone was presenting this amp as an amateur cirquit drawing more power than the Hucard itself... ofcourse he could be just another a-hole...

[Frank_fjs]

I'd like to know the answer to the above questions as well.

Would also like to know what the experts thought about the simpler 3 x transistor 1 x resistor method, as shown on mmmonkey.

wayback://mmmonkey.co.uk/console/pce/amp.htm
https://mmmonkey.co.uk/pc-engine-rgb-mod/

[thesteve]

that mmmonkey amp is seriously flawed, but closer to ideal in 1 way
the amp gtsamour showed is a good amp, just could be better

[Frank_fjs]

How is the mmmonkey amp flawed Steve? I ask as I know of a lot of people using it (built into the SCART plug) and have never heard of any problems.

Also, Steve, don't you have a pre-made PCB amp available for sale, or is it bluebmw I'm thinking of? Either way, is a pre-made amp available from somewhere? I swear I recall reading something about it and seeing some pics of a prototype, just not sure if it ever eventuated into anything.

More importantly, what do you guys use for an amp?

[gtsamour]

that mmmonkey amp is seriously flawed, but closer to ideal in 1 way
the amp gtsamour showed is a good amp, just could be better

There was this hypochondriac guy on another forum going crazy saying that its not a good amp, it doesn't have termination, it doesn't output the correct currents, it has high power consumption etc so it got me thinking.... is it true its not a good amp or is he stupid or something?
And if its not a good amp how could it have been published in a japanese book in 1988 and how come so many people still use it...

[Drakon]

the pc engine 1988 2sc1815 amp is a simple amp I certainly wouldn't call it a good amp.  I've had issues with that amp in the past where other amps were fine.

[gtsamour]

What kind of issues did you have?
Speaking for myself, I used this amp on 6 different (different kinds) PCEngines already and I got perfect results evereytime on more than one tv sets.

[thesteve]

the mmmonkey amp needs coupling caps on the outputs or voltage offsets on the inputs.

the 1988 amp is a basic video amp (not flawed in its basic design) it could just be mode more specific for the PCE signals.

[gtsamour]

I thought it was made specificly for the PCEngine signals because the generic amp has 100 Ohm where the book's amp has 75 Ohm. Also the Sync part of the amp has 300 Ohm resistor. I hope I'm not forgeting something but maybe I am...

edit: Here's the generic amp schematics


https://tronixstuff.files.wordpress.com/2010/07/1txamp.jpg

[incrediblehark]

sync is composite sync.
yes it will need amplification for most monitors as its only 0.3V not 5V (TTL)
its also not the jailbar issue.
2 things cause jailbars (power filtering) and (crosstalk)
some have had issues with region mod installs causing crosstalk.
the capacitor fix is for power filtering.

I forgot to say my US Duo is region modded, any effective way to reduce crosstalk you mentioned? (if it is even an issue with my system) Although my system hasnt had a full cap swap yet, and could also be an issue, but I'm very close to being jailbar free, or virtually free

[thesteve]

caps are a big part.
you want the IC region mod
wires short as possible

[incrediblehark]

ok thanks for the info, shouldn't be the problem then. not looking forward to the cap replacement...

[HercTNT]

My duo-r has problems with its region mod and jailbars on the rgb. i'm pretty sure its because the wires are way to long on the region mod. eventually when everything else i have being modded or fixed gets done, i will have steve straighten my duo out.

[thesteve]

I thought it was made specificly for the PCEngine signals because the generic amp has 100 Ohm where the book's amp has 75 Ohm. Also the Sync part of the amp has 300 Ohm resistor. I hope I'm not forgeting something but maybe I am...

edit:
Here's the generic amp schematics http://tronixstuff.files.wordpress.com/2010/07/1txamp.jpg

this amp is slightly better, but 100uf is too small for video

[Todd Gill]

solved


to solve jail-bar issue on rgb modded system replace capacitor C961 10uf with 100uf tant or 220uf aluminum.
the cap is from hu6260 pin43 to ground.
C142 on the TG16

Bumping this back up as I have a relevant question.

Anyone know if there is a corresponding cap to this in the Supergrafx?


I have installed the two tant caps from pins 41 and 43 to ground from the 6260, but curious if there is a similar cap to C961/C142 in the Supergrafx.


It looks like it might be C107 as it sits directly above the 6260 and is also a 10uF cap.

Thoughts?

[thesteve]

the 6260 does require a filter cap for each output circuit, so it must
couldnt tell you what cap without one in front of me

[Ravij]

Another quick question - where is the best place to tap 5 volts to power my NJM based amp? I'm going to stick the amp PCB over the HU card slot, as there is plenty of space there, and no heat sources.

Since you'll be sticking it over the HuCard slot, pin 38 on the slot would be an ideal place to grab 5V.

Thought I'd post a pic of the completed RGB mod:

PC Engine DUO with RGB Mod by ravij1, on Flickr

[ApolloBoy]

Holy shit those are some thick wires.

[Ravij]

Holy shit those are some thick wires.

Used an old VGA monitor lead, the RGB leads are individually shielded. Overkill I'm sure