RGB amp

[fraggore]

just a bit of info for anyone thinking of doing a RGB mod and needs a amp, the simple transistor amp that mmmonke has up on his site here

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

works a charm and fits nicely into a scart lead done this on a pc engine duo\tg16\and a pc engine duo-r works perfect and its cost about 30p to do and would fit nicely into the console as it so small.

[CGQuarterly]

This is the smallest RGB amp with the fewest # of components that I've seen thus far.  I'd be curious to see how it performs next to the IC-based amp that I use.  If it's just as good, then this is a much easier option.

Chris

[HercTNT]

local techs are aware of this amp. especially thesteve. i would talk with him first before applying such amp as steve knows weather its best for your machine or not. some of mmonkeys mods are not perfect.

[fraggore]

your right some of then are not perfect like the megadrive on tft mod dosent work with all games. i have done this on 3 machines and it works really well it would be interesting to see how it stands up to a IC-based amp, I have only got a iphone but will see if i can take some good pics and post them on here.

[fraggore]

here is a few pics not perfect as it a phone cam taken from my duo-r up close to give you a idea on what it looks like ignore the darker boarders its the camera and 60hrz picture.

To be honest after looking at it again the picture is stunning colours are bright and vibrant its not dark at all plenty of contrast not over the top the picture on all 3 machines is the same.

https://www.box.com/s/03d3c4709737e11fa52e

https://www.box.com/s/2df848381c077b03d46a

https://www.box.com/s/ddc2697f5a88eda2c278

[fraggore]

Here is a small video excuse the outrageous welsh accent.

https://www.box.com/s/e63cdb3ab012b789e76a

[Duo_R]

Cheap and small but not the best

[Drakon]

This amp has been around for ages.  It's probably around 1/2 to 1/3 the power of either an IC amp or a two transistor amp.  The THS7314 is probably the simplest amp you can make.  For the ths amp you need the amp chip, a sop to dip adapter, 1 cap, and 3 resistors, that's all.  I built a couple ths7314 amps then start using the sony cxa series video encoder chips since those encoder chips include a built in rgb amp.  The reason why I switched over is that the cxa chips output amped rgb, s-video, and composite video.

[thesteve]

add 3 4.7K resistors and 3 22uf caps for improved power usage, and less load on the system video chip

[fraggore]

this amp might be putting excess load on the video chip ?.
as for the caps and resistors they will need to go before the transistors yea.

[thesteve]

yes
each transistor gets a resistor and cap in parallel between the transistor and the hudson chip

[fraggore]

ok be better to put it on some strip board then
thanks for the help

[speedlolita]

I followed the guide roughly (result here: http://www.bordersdown.net/showthread.php/115219) and the picture on my LCD TV isn't that solid unfortunately. Looks great on my Commodore 1081 though.

Any links or guides for improving the amp? Thanks. 

EDIT: Would the design in the diagram on this page be a good bet? http://www.gamesx.com/rgbadd/duorgb.php

[fraggore]

you could try swoping the comp sync for comp video that's what i used and seems to work fine connect it to pin 20 on the scart lead i didn't use comp sync wired it just in case but didn't seem to need it.

LCD tv's can has sync problems with old consoles megadrive being the example.

if you switch the comp video for comp sync on the megadrive you can fix a lot of problems but is not perfect and some games at 60hz still don't sync but everything at 50hz does but who wants 50hz right.

[speedlolita]

You know, I was wondering if swapping the sync might work. Would explain (possibly) why it doesn't display on most screens apart from my Commodore.

Do I change how the SCART lead is wired, or which ext port connectors I connect to?

EDIT: Nevermind, found it.

Seems to be working nice, I'll remove the transistor I think.

[fraggore]

no should be fine just swop the comp sync on pin 20 to comp video.
use line A pin 22 on the port as the diagram here.

http://www.gamesx.com/misctech/pcebp.php

[fraggore]

by the look for it your using pin A 22 if so try C 22 that sync comp sync.

[Duo_R]

The 2nd link to the gamesx rgb amp is a better design but also a little dated. I had luck using the design that uses NJM chips. I can link you later or search for it on gamesx. Same one used for N64 with slight modification for PC Engine.

I followed the guide roughly (result here: http://www.bordersdown.net/showthread.php/115219) and the picture on my LCD TV isn't that solid unfortunately. Looks great on my Commodore 1081 though.

Any links or guides for improving the amp? Thanks. 

EDIT: Would the design in the diagram on this page be a good bet? http://www.gamesx.com/rgbadd/duorgb.php

[speedlolita]

Also, is B1 worth grounding or not?

[fraggore]

the only ground i used was pin a 21 and put that on the scart in 4 so you sould be ok.

[speedlolita]

I see, I used 4, 18 and 21 as per mmmonkey guide - doesn't seem to make a huge difference, but whatever. Colour seems very washed out unfortunately. On the 1080p Sony and an old CRT at least. Looks relatively fine on my Commodore monitor (not as good as C-Sync unfortunately) and my Sharp LCD - although the Sharp has image smear which isn't present on the Sony. Irk.

The 2nd link to the gamesx rgb amp is a better design but also a little dated. I had luck using the design that uses NJM chips. I can link you later or search for it on gamesx. Same one used for N64 with slight modification for PC Engine.

Would be much appreciated.

[fraggore]

odd mine displays really nice on my samsung tv and my tft with a upscaller and i am using the comp video to pin 20.

did you use a 75r resistor inked on pins 8 and 16 of the scart lead plus the 5v from the transistors collectors has to be put to pin 8 switching voltage as well

one other thing make shore you have the red,green.and blue wired correct on the scart lead i wired red and blue wrong once was thinking the colours look a bit odd then i realised lol.

[speedlolita]

Yes my colours are correct, it's just the awful scaler in the Sony I believe. Horrible television. I haven't used the resistor no, maybe that might help things. I'll just have to identify one in my packets of resistors that I have. Irk!

EDIT: Adding a resistor doesn't seem to have done anything.   It autoswitched before I guess, thought it might have lowered voltage to level where the TV would detect it at 4:3..

[fraggore]

This may help pic of the pins i used
on the transistors i bent and soldered all of the collectors together then soldered the emiters to pins 15,11,and 7 then soldered the RGB to each base as mmmonkeys guide.

https://web.archive.org/web/20191109000145if_/http://www.mmmonkey.co.uk/console/pce/amp.htm

Then put 5v on the collectors i tock that from the av port.
Then i ran a small wire from the collector to pin 8.
Then soldered a 75r resistor one end onto pin 8 the other onto pin 16.
Tock ground from the av port and soldered that to pin 4.
Added sound left and right to pins 2 and 6.
Then used composite video to pin 20 you could use composite sync but video worked fine for me.



also as thesteve was saying you could add 3 4.7K resistors and 3 22uf cap before the base of all 3 transistors.

I ain't no expert but hope this helps.

[speedlolita]

I think I'll be adding the resistors and caps when I build a new SCART adaptor thing with a new PCB. For now I'm content at least. Completely playable on my Sharp TV - which is my main.

Thanks a lot for suggesting composite video for sync.

[fraggore]

no probs mate

[thesteve]

heres one i just did

the 2 transistor circuit is a sync amp

[fraggore]

interesting have been looking for  good amp you got some values for the components.

i also have this amp i was thinking of making.

[speedlolita]

And how does that need to be modified to work on the PCE?

[thesteve]

that will work on PCE as it sits.
i installed in in a TG16 cd dock.

[speedlolita]

I was referring to the schematic fraggore posted unfortunately!

[HercTNT]

steve is aware of that, he is making sure everyone else is.

[thesteve]

lol
that one works without mod too

[Duo_R]

While the other NJM circuit posted on here would work as is, I have always found each system needed a little "tweaking" when it comes to RGB. The one I use for Duo / PC Engine is a slight variation, however I had better luck removing the 1M ohm resistors on the input line, when I used it the image was too saturated, but again this was using an Atlona box, for some of you it might look fine depending on what converter box you are using.

interesting have been looking for  good amp you got some values for the components.

i also have this amp i was thinking of making.

[Duo_R]

the main difference in this circuit is the 1000pf caps on the output lines, depending on the application 1100 or 1200pf can be used, and this helps filter out things in the signal (and as a result reducing jailbar effect.

[speedlolita]

Didn't see this reply!

I'd actually be using it on a CRT television.

Currently considering the THS7314 method instead of this one, although this one seems to be tried and tested. Hmm.

[Drakon]

The ths one is tried and tested too.  I've built both the ths amp and ths amp.  Both do pretty much the same thing.

[speedlolita]

So either is good? Do you have a preference at all? 

Also I have a Core Grafx 2 - is taking RGB from the expansion port as good as directly from the video chip?

[Drakon]

So either is good? Do you have a preference at all? 

Also I have a Core Grafx 2 - is taking RGB from the expansion port as good as directly from the video chip?

My preference would be the ths one just because there's less parts involved.