Where to get a logic level c-sync signal on the PCE?

[keropi]

Hello!

is there a place to get c-sync at logic level from the PCE? I want to pass it through the amp discussed here so I can use it with RGB:



I have already tried with the expansion port point and pin #44 of Hu6260 but unfortunately none worked with the amp.
Anyone knows of another point to try?
TIA! 

[viletim]

I bought a PC Engine only a week ago! I'll just pull out the CRO and have a look...

There is indeed a composite sync signal available from the expansion connector. It's not a TTL signal so the 74 series logic won't help here. As a quick solution I suggest using an LM1881 in the usual configuration (a 100n cap in series with the input) to make this non-standard c-sync into a TTL signal then feed this to your 74HC04 logic chip.

Note that pin 13 of your 74HC04 is an input and must be connected somewhere (ground will do) else strange things might happen. You can leave out R2 as well if you like... save a few milliwatts for the next generation.

... Now back to Galaga '88.

[RGB32E]

I bought a PC Engine only a week ago! I'll just pull out the CRO and have a look...

There is indeed a composite sync signal available from the expansion connector. It's not a TTL signal so the 74 series logic won't help here. As a quick solution I suggest using an LM1881 in the usual configuration (a 100n cap in series with the input) to make this non-standard c-sync into a TTL signal then feed this to your 74HC04 logic chip.

Did you measure the CSYNC signal?  I tried feeding CSYNC through one of the channels of a THS7374 (AC coupled) and didn't observe any issues when connecting the AC coupled output (75 ohm + 220uF cap) to my PVM-2030 or XRGB-mini.

[viletim]

Did you measure the CSYNC signal?

I did. I measured it to be 800mV peak to peak. The R/G/B/V signals all measure 800mV p-p too. This is without any load. The signal is referenced to the 5V supply so actually varies between 5.00 and 4.20 (ie. there's a large DC offset). While I was at it I measured the audio too which is approximately 300mV p-p on the loudest part of the Street Fighter II title screen/demo.

My PC Engine is the little white one (original model, I think).

  I tried feeding CSYNC through one of the channels of a THS7374 (AC coupled) and didn't observe any issues when connecting the AC coupled output (75 ohm + 220uF cap) to my PVM-2030 or XRGB-mini.

That works well... considering some sort of video driver is required for the video signals, the same again for the sync (or the composite video, both have sync information) will do the job.

[keropi]

since you brought this back to life I might as well update on what *I* did 
I have tested with the 7314 and various configurations on input pullups etc based on the info I got from helpful forum members. For C-SYNC I used the old transistor based amp since I could not make anything better. My findings were that no configuration with the 7314 gave better results than the old transistor-based RGB amp. The picture was fine BUT the colors seemed either washed out or with wrong tones - again compared with the old amp.
So I abandoned this for the time being, replaced the 7805 on my console and just used again the old amp. If someone finds the correct pullup values then the 73x4 amps might shine.