Schematic for a *working* PCE rgb amp with 7314?

Hiya!

as per title I am looking for a working schematic for a PCE rgb amp that uses the THS 7314 amp ... has anyone any info on this with specific parts that are needed before and after the 7314?
Thanks in advance for any info/help!

 

A 7314 schematic for the DUO would be lovely.
But I tried to use the 7314 with the master system, with a nes rgb and it all fails.

I haven't heard of anyone using this piece of crap video amplifier in anything else than the N64.

 

The reason people haven't done it is because it takes some knowhow and equipment to get working. The color components need to be examined with a scope and attenuated to a suitable voltage by a resistor divider, then put into the THS' AC coupled configuration (series cap, 3.5 Mohm pullup IIRC). N64 works completely differently because the signals are TV ready and don't have a significant DC offset so they don't need biasing at all. Amplifiers are basic building blocks but more complicated than you'd think, you can't just throw any signal into them and expect a useful output, there are so many parameters to take into consideration. Basically don't blame them if you don't use them as directed...

 

yes Calpis is right, that's why I made this separate thread from the component one, just in case anyone really found the correct values to make the 7314 work as expected....

 

Well, this makes the THS the first IC I ever used that the manufacture company doesn't know how to use.



This is Texas Instruments schematic, I don't need to say it doesn't work either. And by the way if no one in the whole internet got this working with anything else than the N64 you can only be talking about faith, you have faith that it will work because there's no proof that it would work in anything else than the N64.

 

The design is good *provided* you feed it appropriate signal levels. Once someone measures the PCE signal levels and brings them down to what the 7314 needs then it will work fine. You can't feed the 7314 a signal - for example - 3 or 4 times stronger or weaker and expect from it to work... if you notice that in the input they don't specify values, only a generic "R" for resistors.
At this point I don't know how to measure the pce's output (or any other console for that matter) so whatever design for other device I use it will be wrong.

 

The R isn't labeled in that example because it's intended to match the characteristic impedance of the preceding circuit, but it's implied to be 75 ohms so the circuit functions as a buffer. You wouldn't use that circuit with PCE because its RGB signals are high impedance so you don't want to load down the signals with inappropriate termination. Another reason it won't work is that the PCE requires level shifting, as I've said, accomplished through a capacitor coupled to a pullup bias resistor (the pulldown resistor is built into the THS).

 

This is the normal schematic for PCE RGB amp, if this helps:

 

Ooh, you'll set Calpis off on one.

That's the transistor based one which may be "normal" but apparently not the best. Still interested in the correct values on the THS amp - still haven't modded my Core Graphics II.

 

yeah, I have the transistor-based amp installed in my PCE, it does produce a VERY good image but since it is said that it's not an optimal solution I am still interested on the 7314 amp... but I fear we are stuck on the transistor one for now.

 

There's a French modder that has built a circuit using a THS amp - supposedly works.

www.ebay.co.uk/itm/390449089418

I haven't purchased one as they're expensive but if someone did I'm sure they could jot down some values.

I may just purchase one from this Japanese site: http://homepage3.nifty.com/F-LABO/ProductsList.html - 9th product down. NJM amp as used by Doujindance for his PCE sales, although his are hand assembled.

Would Sony chips be usable at all? Such as a CXA2075.

 

if only we could see the value of the 3 input caps ... the rest is easy, 75ohm resistor at the output and 100nf+22mf at the vcc/gnd...
this amp is tempting me....

edit: I seem to remember that NJM amps are not that great... and here is their schematic

 

Oh? Other than what Calpis has said I've only read good things about them.

 

^ maybe that's what I remember LOL , don't want to discourage you or anything ....

 

I've been using a transistor amp externally at the moment. It does a satisfactory job but I want to explore options before internally modding my own machine.

 

I hear you, internal is what I prefer too so I did this:

 

Nice, looks tidy. I'll be removing the 5 pin DIN on my Core Grafx II and replacing it with an identical 8 pin DIN as per the Doujindance tutorial.

Glad you didn't hack away at the PCE case as per the site's tutorial.

 

nope, that megadrive/genesis2 DIN fits perfectly on the rf hole
but I had to remove some excess pcb on the hucard slot (just empty unused place, I wonder why they left it in the first place) to fit the height of the amp...

 

The reason I hate on the transistor amp so much is because it's not a video amplifier, simple as that. It shouldn't be installed in people's consoles.

The THS amp on eBay doesn't do anything special, it looks like they just have 3 x 10uF caps in series (overkill), without any pullups... I think the level shift, and clamp function inside the chip are what enables it to work at all. Still if it works for them it should work for you. I'd recommend the 3.5M? pullup so it's compatible with most AC-coupled RGB.

 

What is it supposed to be? I've seen plenty of people say how amazing it is and extremely few seem to be capable of doing much more than assembling the circuit and slapping it into a console.