60hz mod on a PAL TG-16

[schweaty]

OK, i know this issue has come up before, but i cant verify if anyone has actually accomplished this mod before, so i am bringing up again.  bear with me.

as many of you know, i live in germany so i got an opportunity to buy one of these slick grey units.  it really was sort of a throw in for a larger lot that i bought and i thought it would make a great next project.  these guys say they have done it, but they arent revealing how they do it as far as i can tell:

http://www.otakus-store.net/en/nec-pc-engine-gt-duo/48-turbografx-16-rgb-60hz-region-free-mod.html

could i send my shiny new unit (sts) to them?  sure i could, but that wouldnt be any fun.  so here's what i have been able to discover in a couple hours of research:

1.  first step is to swap out the 17.73448mhz crystal oscillator with a 21.47727mhz oscillator.  i also believe the 21.47727mhz oscillator needs to be a temperature compensated crystal oscillator (TCXO).  if this is the case it would mean going from a 2-pronged crystal to a 4-pronged crystal.  so how would one go about wiring that up?

2.  once you have the oscillator swapped, the system will now be in black and white. so to restore color you need to tap the Hu6260 directly for RGB.  if you can tap the expansion bus for this, please let me know because that is much easier to use for the RGB mod.  im not sure why the color gets stripped out by the PAL mod, but i believe it has something to do with the CXA1145 chip that was added to the PCB

3.  speaking of the CXA1145, i have also read there may be something that needs to be done to one of the pins on it (pin 6 or 7?).  really not sure why this needs to be done exactly.  any info on this is appreciated.

that's all i have so far.  the system is in the mail, so i have a day to 2 before i can even get started.  more importantly, i need to source a 21.47727mhz oscillator.  i believe this one will work, but i dont really want to pay that much so if anyone knows where i can get one for cheaper or has one in a donor console they can sell me, that would be awesome:

http://www.ebay.com/itm/ONE-PIECE-PRECISION-0-3ppm-21-47727MHz-21-47727M-DIP-TCXO-/141476232325?pt=LH_DefaultDomain_0&hash=item20f0a3fc85

any help is appreciated.  i know fidde_se and thesteve have piped in on previous posts about this.  maybe they will on this one too.  any help is appreciated.

[bust3dstr8]

Without a schematic of the PAL TG16 to see exactly what is this is my best guess

Switch to the 21.47727mhz crystal, the two pin should be fine. Look at the datasheet, the load capacitors may need to be tweeked.

Conntect pin 7 of the CXA1145 to Vcc to enable NTSC mode.

Connect Burst on the Hu6260 to clock in on the encoder.
If that doesn't work you may try a separate NTSC crystal or a 1/6 frequency divider from the main crystal.
(this can be made from a couple cheap flip flop and NOR chips)

[schweaty]

Thanks for the response.  I was out of town for the holidays and I just got back.  The Turbob is waiting for me to pick it from the post office tomorrow.

Bust3dstr8, I am going to PM you a few questions for clarification on your post.

[schweaty]

Ok... got it today and opened her up    First thing i noticed is that the AV jack looks the same one in the PCE's that is an easy swap out for an 8-DIN jack.  I will have to test and see which ones are the audio ports, but this should work after the ground pins are swapped. 

Second pic shows the 17.73448MHz crystal oscillator that will have to be replaced (yellow square).  Can someone tell me what the thing is in the red circle?  its clearly related to the crystal, but what do i need to do to it (if anything)

[bust3dstr8]

The TP202 is just a test point to connect a scope or counter.

I did a little research and it seems like there is nothing concrete out there about the this board.
Just a lot of failed attempts in every European language 

Steve and I where kinda curious about this beast and talking about it in chat last night.
It seems that this is a lot more complicated than expected. The extra chips on the PAL board are a
inverter (for clock buffering) and a MCU to adapt the Vsync from 60hz to 50hz.

To get this back to it's former glory it looks like the MCU needs to be bypassed or removed. Then the original clock circuit for the Hu6280 and Hu6260 needs to be restored. Also there are probably some connections between the Hu6270 and Hu6260 that need to be reworked. Vsync is probably the main one. Also the CXA1145 will need to be set to NTSC and have the crystal changed.

I looks like the crystal you circled is actually for the CXA1145 color sub carrier. PAL is 4.43361875Mhz and 4 times that is 17.734475Mhz. Steve was saying RGB encoders often operate at 4X the standard clock...which is pretty much the 21.73448 on that board. So it seems the other crystal is the main clock that would need to be changed to 21.47727Mhz

At this point it might be time to "Take on for the Team" and send it away to be modded.
Then you can share the mod with all us curious peeps here at PCEFX.
If the mod is fairly easy maybe we'll do a group buy to get some sexy gray NOS Turbobs into the USA. I hear there are still plenty of them still unsold in Europe.