SOLD OUT: PCE/Turbografx RGB THS7374 amps and cables

mickcris · 04/27/2016, 05:47 PM

I'm not a video engineer so not sure if i will explain it correctly but i will try. But yes, this applies to all PC Engine and TurboGrafx systems.

The standard RGB signal is 0.7 volts. After amplification on the THS7314 or NJM2267 (both are 6dB amps), this is what the output of the console should be sending to the monitor as it is what it is expecting.
http://www.syncblaster.com/RGBfaq.html

When you amplify the SNES or N64 with one of these amps it produces 0.7v, but when amplifying the signal from the pc engine it is 0.8v. So the voltage being too high will make the picture too bright. I have not actually measured it myself, but the output of the PC Engine RGB lines should measure around 0.4v before amplification and on an N64 measure around 0.35v.
http://www.sengpielaudio.com/calculator-amplification.htm
The reason the output resistance was changed from 75 ohms to 100 ohms was to compensate for this. Doing it with the 91 ohm (with 470 ohm parallel to ground) makes it appear to be around 75 ohms to the monitor. Before this amp was not taking into account that the monitor is also expecting 75 ohms along with 0.7v. This new design corrects that. Although the 100 ohm resistors on the output were not going to damage anything.

thesteve · 04/28/2016, 01:00 AM

it gets a bit more complicated then that
the 6260 uses a Vref-lo and Vref-hi to set the top and bottom of the RGB output, so it can differ between systems, but generally doesnt
also the output rigidity of the 6260 is quite low making its output differ depending on what amp its driving

mickcris · 05/08/2016, 05:07 AM

I got a sample batch of the new pcbs in the other day. Have sent a couple out to get some feedback before I make an order for more boards.

they are the same overall size as the old boards

MNKyDeth · 05/10/2016, 12:21 PM

I made a video installing the new RGB amp. it is a bit long for just an amp. I even cut out a lot of crap because I found out I ramble and apparently I very much like to ramble a lot.

So... Here is the link of me installing the new RGB amp from Mickcris.

Btw, its a bit fuzzy, blurry, but hopefully it is good enough. Let me know your thoughts on youtube and I will try to do more hardware stuff and hopefully, eventually get better cameras and stuff to make it better.

wildfruit · 05/10/2016, 01:03 PM

You sound different to what I imagined. I don't know why.

mickcris · 05/15/2016, 04:48 PM

OP updated. There are a few new boards available and have the old ones discounted if you dont care about the resistors being soldered to the back (its the same circuit).

MNKyDeth · 05/17/2016, 09:08 AM

Quote from: wildfruit on 05/10/2016, 01:03 PMYou sound different to what I imagined. I don't know why.

Not sure if good or bad...

mickcris · 05/26/2016, 08:09 PM

got my shipment of pcbs in. should have enough that i will never have to order anymore. just need to start on building up some more. I have 5 ready to go. still also have about 10 "fixed" versions available also.

mickcris · 06/08/2016, 07:52 PM

switched to tantalum caps on the output to lower the height of the board

mickcris · 07/03/2016, 07:16 PM

Bump

mickcris · 07/24/2016, 05:45 PM

bump. still have a few "fixed" boards left and some new style ready to ship.

shugs81 · 08/04/2016, 01:18 AM

Hi bud... Do you ship to the UK and if so how much???

Thanks!

mickcris · 08/04/2016, 01:21 AM

Quote from: shugs81 on 08/04/2016, 01:18 AMHi bud... Do you ship to the UK and if so how much???

Thanks!

I do. Depends on how much it weighs. I just charge whatever it costs to ship.

mickcris · 08/25/2016, 01:29 PM

bump

mickcris · 10/14/2016, 11:15 PM

I tied out a new install location on the duo now that the amps are pretty low profile. Replaced a different amp with mine:

https://imgur.com/a/gXniJ

Ignore that hole the wires are going through. The previous modder drilled that and I just used it cause it was there. You can just bring the wires up on the back of the PCB, directly behind that hole. I also put some kapton tape on the shield below the amp just in case it would ever fall (which isnt very likely). There is still plenty of clearance between the caps on the amp pcb and shielding.

I will probably take some more pics when I do another one that doesn't have extra holes in it.

blueraven · 10/15/2016, 12:42 AM

Looks awesome! Those last install photos were incredibly clean.

...and that is one huge bag of chips

mickcris · 10/15/2016, 12:45 AM

Quote from: blueraven on 10/15/2016, 12:42 AM Looks awesome! Those last install photos were incredibly clean.

...and that is one huge bag of chips

Thanks. Would be nice if all those pcbs already had the components soldered to them.

mickcris · 10/20/2016, 08:54 PM

Did another one, but this one was from scratch so no extra holes all over the place.

https://imgur.com/a/DazFG

everything fits nicely

mickcris · 11/03/2016, 10:56 AM

turbografx system added

mickcris · 01/12/2017, 09:05 AM

bump. amp has been updated and now uses a THS734 instead of a THS7314.

xcrement5x · 01/21/2017, 10:17 PM

Ever put one of these in a Laseractive? Just wondering how the output from there will look.

mickcris · 01/22/2017, 01:28 AM

Quote from: guest on 01/21/2017, 10:17 PMEver put one of these in a Laseractive? Just wondering how the output from there will look.

I have not. I'm sure it can be done though. I think I've seen somewhere about doing it, but it only works in the pce/tg16 module and not laser active specific games iirc

xcrement5x · 01/24/2017, 03:43 PM

Quote from: mickcris on 01/22/2017, 01:28 AM
Quote from: guest on 01/21/2017, 10:17 PMEver put one of these in a Laseractive? Just wondering how the output from there will look.
I have not. I'm sure it can be done though. I think I've seen somewhere about doing it, but it only works in the pce/tg16 module and not laser active specific games iirc

Oh yeah, I know about the limitations of the RGB, basically it can only take the RGB from the PAC not the LD since the video is natively in composite. Other implementations I've seen for RGB on the LA make it so that you basically have RGB for both the Genesis and PCE PACs.

I guess I'm basically just wondering if the tweaks that have been done for this chip to make it optimal for the PCE would impact the stronger RGB signal that is sent by default from the Genesis PAC.

mickcris · 01/24/2017, 05:52 PM

i never really looked into how it was done before. but yes, it should make the output for the gensis a little darker, but it would make the output for the tg16 look right. if you use an amp that has the 75 ohm resistors, the opposite would happen. this is assuming that the PAC is just a tg16 consoles shoved inside of it as i have never really looked into this before.
you could maybe rig up some sort of switch for the output resistors to swap between different ones.

mickcris · 02/09/2017, 10:23 AM

bump. have lots of amps ready to ship

mickcris · 02/11/2017, 05:49 AM

~~I have 4 of the previous rev amp with the ths7314 for a discounted price is anyone is interested.~~

~~price is $12 a piece shipped if you are in the USA. if you are outside of the USA, there might be a small shipping charge also.~~

all gone

MobiusStripTech · 02/26/2017, 08:19 PM

Installed one of mickcris boards in my personal Duo R this weekend. Can't recommend it enough. That and I hear he is a rather handsome fellow as well as a gentleman.

mickcris · 02/27/2017, 09:20 AM

Quote from: MobiusStripTech on 02/26/2017, 08:19 PMInstalled one of mickcris boards in my personal Duo R this weekend. Can't recommend it enough. That and I hear he is a rather handsome fellow as well as a gentleman.

haha. thanks.

mickcris · 03/02/2017, 12:01 PM

have replaced the sync strip scart cable with a small add on board to be installed in the console. It could also be installed in the scart head if you really wanted to, but better to do it inside the console. Board outputs 75 ohm sync, but could be easily modified to output TTL sync if one required it.

com4 · 04/20/2017, 11:51 PM

Works great, thanks!

mickcris · 05/28/2017, 07:18 AM

regular sized 8 pin din euro scart cables now have a pcb

I was thinking this would make building them quicker but that's not really the case. Still, they look a bit nicer than my previous cables with the all the ground jumpers.

mario64 · 07/24/2017, 09:23 PM

Quote from: mickcris on 05/28/2017, 07:18 AMregular sized 8 pin din euro scart cables now have a pcb

I was thinking this would make building them quicker but that's not really the case. Still, they look a bit nicer than my previous cables with the all the ground jumpers.

How can I go about ordering one of these? I'm hoping it will address the audio hum from my Duo R

mickcris · 07/25/2017, 01:09 AM

Quote from: mario64 on 07/24/2017, 09:23 PM
Quote from: mickcris on 05/28/2017, 07:18 AMregular sized 8 pin din euro scart cables now have a pcb

I was thinking this would make building them quicker but that's not really the case. Still, they look a bit nicer than my previous cables with the all the ground jumpers.
How can I go about ordering one of these? I'm hoping it will address the audio hum from my Duo R

Sent you a pm

mickcris · 10/14/2017, 06:12 PM

bump

mickcris · 12/07/2017, 10:18 AM

bump

mickcris · 01/06/2018, 03:18 AM

I have updated the amp with output resistor values closer to the ideal values of 86 ohm with a 586 ohm to ground. The ideal values can only be done with 4 resistors so have changed to the closest I could get it with 2. Now using an 86.6 ohm resistor with a 604 ohm resistor to ground. Both resistors are 0.1% tolerance. See the math below:

https://i.imgur.com/M22k3bg.jpeg

mickcris · 05/25/2018, 09:40 AM

since im no longer selling these, i shared the files if anyone wants to build there own
https://oshpark.com/profiles/mickcris

NightWolve · 05/25/2018, 09:49 AM

Nice looking amp, so how did it compare to turbokon's (http://www.tg16pcemods.com/) ? Just curious, even with discontinuing it.

mickcris · 05/25/2018, 09:56 AM

see the 1st post. that amp uses 75 ohm resistors which make the output too bright.

xcrement5x · 05/25/2018, 01:41 PM

Are you going to make more eventually? I think they are great amps and used them in my laseractive.

mickcris · 05/25/2018, 02:45 PM

Quote from: guest on 05/25/2018, 01:41 PMAre you going to make more eventually? I think they are great amps and used them in my laseractive.

I dont plan on it. I got sick of soldering them. I was doing every one by hand so not the most efficient method.

console5 still has some kits if you are interested in soldering one together
https://console5.com/store/ths7374-rgb-pcb-kit-for-nec-turbo-grafx-turbo-duo-pc-engine.html

or if someone on here wants to get some boards made from the link above and sell them pre built that's fine too. I just got tired of doing it.

also, mobiusstriptech informed me of this earlier today

they should be selling what is the same thing soon (not that im really supporting these guys, but that might be the only option to get on pre-soldered since i'm no longer selling them).

the v1.0 circuit was an update to micro's original with viletim's brightness fix added. then the newest version just swapped out the ths7314 for the ths7374 and made the parts smaller. Its still basically the same circuit from the data sheet.
https://nfggames.com/forum2/index.php?topic=4822.msg34061#msg34061

xcrement5x · 05/29/2018, 10:19 PM

Man, that assembly line makes me appreciate even more what you were doing.

I'm glad they are doing a bit of QA on them at the end but still, that video has some interesting comments going on.

mickcris · 11/29/2018, 11:55 AM

It has come to my attention that there is a mistake on the 7374 PCB. The 4th output is unused and is tied to ground while it should be floating. This is causing the IC to run hotter than normal. I would think the risk is fairly low as some of these have been in use for almost 2 years now. My guess would be that it running a bit hotter will cause the amp to wear out faster. Its also a possibility that the 4th channel could just go out and the chip return to normal temps. The temp its running at is still below the continuous operation long term reliability max temp. Having said that, I have not had any reports of any of them failing yet but you may want to either modify the board or discontinue using it.

I tested one and after running for an hour, I measured it with my Fluke 87 meter and its running at 65 °C. With the 4th output floating the temp is 30°C. Per the data sheet:
Maximum junction temperature, continuous operation, long-term reliability is +125 °C

You can fix this by lifting that leg. Here is pic with an arrow pointing to the pin that needs lifted
https://imgur.com/a/cMeWI3l

I found it easiest to just de-solder that side of the IC, lift/break off the leg, then re solder that side down.

If you purchased one of these and would like me to lift the pin for you or give you a refund, send me a message and I will get back to you. I may need proof that you purchased it from me. I will only refund ones that I sold that I had soldered. If you bought one from console5 though i will lift the pin on it.

If you want me to lift the pin, send me the pcb(s) along with a piece of paper with a return address and you email. I will lift the pin and then send it back.

If you want a refund, send me the pcb(s) along with a piece of paper with your paypal email address. I will then send $20 to your paypal account per amp.

Ergot_Cholera · 12/03/2018, 06:38 PM

I am the one who noticed this

. Maybe I should have contacted you directly but I wanted to make sure that I was correct in my findings. I didn't post here because its mostly dead

mickcris · 12/03/2018, 06:59 PM

Quote from: guest on 12/03/2018, 06:38 PMI am the one who noticed this . Maybe I should have contacted you directly but I wanted to make sure that I was correct in my findings.

thanks for pointing it out and figuring out what was causing it. Someone pointed me to your post. i did put the same post on all other forums i was selling these on.

someone had mentioned earlier this year (i think) that they thought it was running hot, but i didnt think too much of it at the time as they were the 1st to mention it. thinking back i should have looked into it at the time.

NightWolve · 12/03/2018, 07:36 PM

Quote from: mickcris on 11/29/2018, 11:55 AMYou can fix this by lifting that leg. Here is pic with an arrow pointing to the pin that needs lifted

I found it easiest to just de-solder that side of the IC, lift/break off the leg, then re solder that side down.

That's too bad, one little mistake on what looks like an otherwise professionally-designed/built board.