Sync problems with my Sony BVM

PeterWar

New Challenger
Hello guys,

First post on these forums ;)

I'll be buying my first Neo Geo AES tomorrow, I'm excited!. In preparation of the big event, this week I've been setting up my Sony BVM-A20F1M with the following consoles:

-Moded RGB french Nintendo 64.
-SNES with RGB SCART cable Sync on Luma.
-RGB french NES with stock SCART cable.
-RGB french Master System II wiith stock SCART cable.
-Megadrive model 1 with RGB SCART cable.

To connect the SCART cables to the BVM I use a Female RGBS SCART to BNC adapter and plug everything in my X68 analog board.

This setup works very well on my NES, SNES and N64 but can't get the Master System II and the Megadrive to sync, both consoles work just fine with the same scart cables on two other CRT.

Any idea on what is going on? It appears to be SYNC issue, can't find any VRC or AFC setting in the menu, the monitor is settup to accept external sync and I've been playing with any sync setting I can think off without results.

Would you recommend mending the cable to sync on composite? I can solder but need more information to do this. Also, does a sync strike introduce a latency?

Thank you!
 

Jibbajaba

Giga Shock!!
Is it a first generation Megadrive? If you're using a csync cable with it and having issues, then it's possible that it's one of the console revisions that has the csync hooked up incorrectly. You'd have to mod the system to fix it, or switch to composite video for sync (but that may give you jailbars).
 

MtothaJ

Host for Orochi
Is it a first generation Megadrive? If you're using a csync cable with it and having issues, then it's possible that it's one of the console revisions that has the csync hooked up incorrectly. You'd have to mod the system to fix it, or switch to composite video for sync (but that may give you jailbars).

I am 99% sure that that is exactly the case.
I have a VA4 MD1 and to get it working with the official Sega cable I had to run a wire from pin 11 of the CXA1145 video encoder to the av out din connector. Also afair for this to work there may be a resistor or something attached to that csync leg of the din connector on the bottom of the board which needs to be removed (or the din connector leg cut so that its not making contact).
 
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PeterWar

New Challenger
I am 99% sure that that is exactly the case.
I have a VA4 MD1 and to get it working with the official Sega cable I had to run a wire from pin 11 of the CXA1145 video encoder to the av out din connector. Also afair for this to work there may be a resistor or something attached to that csync leg of the din connector on the bottom of the board which needs to be removed (or the din connector leg cut so that its not making contact).

Yes it's an European model 1 with high definition graphics labelling and what looks to be a VGA port in the back (but just isn't).

But howcome the console works just fine when connected on a Panasonic and a Sony Trinitron TV trough the supied RGB scart cable and not with the monitor?
 

MtothaJ

Host for Orochi
Yes it's an European model 1 with high definition graphics labelling and what looks to be a VGA port in the back (but just isn't).

But howcome the console works just fine when connected on a Panasonic and a Sony Trinitron TV trough the supied RGB scart cable and not with the monitor?

Is this a France market machine ('Mega Drive RGB label', 1600-09 model no)?
 
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MtothaJ

Host for Orochi
It is indeed, just checked.

AFAIR these models are a bit of a special case since they don't have a RF modulator onboard nor do they have composite hooked up to the AV out. It may be the case that the cysync signal from the encoder is slightly modified / goes through some additional circuit before it goes to the AV out in these variants which is fine for TV's but is causing problems for the BVM to sync to.

As I mentioned, I am ok with using this cable on a PAL MD1 with a BVM-14M4DE after I had wired the csync straight from the encoder to the AV out. On this basis you could give the following a try:
- open up the Megadrive and connect a wire to the sync out of the encoder in the console
- open up the Sega Adapteur RVB box, and on the IN side desolder the csync line going from the AV out and solder in the wire you just connected from the encoder.
It the above works for you then reatach the original csync wire in the Adapteur RVB and on the Megadrive end isolate the csync leg of the AV out din and wire the csync straight through from the encoder.
Other than the above there is really not a whole lot you can do to troubleshoot further.
 

PeterWar

New Challenger
AFAIR these models are a bit of a special case since they don't have a RF modulator onboard nor do they have composite hooked up to the AV out. It may be the case that the cysync signal from the encoder is slightly modified / goes through some additional circuit before it goes to the AV out in these variants which is fine for TV's but is causing problems for the BVM to sync to.

As I mentioned, I am ok with using this cable on a PAL MD1 with a BVM-14M4DE after I had wired the csync straight from the encoder to the AV out. On this basis you could give the following a try:
- open up the Megadrive and connect a wire to the sync out of the encoder in the console
- open up the Sega Adapteur RVB box, and on the IN side desolder the csync line going from the AV out and solder in the wire you just connected from the encoder.
It the above works for you then reatach the original csync wire in the Adapteur RVB and on the Megadrive end isolate the csync leg of the AV out din and wire the csync straight through from the encoder.
Other than the above there is really not a whole lot you can do to troubleshoot further.

Thank you for your input, I've taken appart my Megadrive with switchless region free mod, here's the image of the main board, it's a VA4.

28735586146_8858400d87_z.jpg


If you may clarify where is the sync out of the encoder and where do I have to connect it to that would be of great help.

Also, I have the same problem with a french master system 2.
 
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MtothaJ

Host for Orochi
Thank you for your input, I've taken appart my Megadrive with switchless region free mod, here's the image of the main board, it's a VA4.

28735586146_8858400d87_z.jpg


If you may clarify where is the sync out of the encoder and where do I have to connect it to that would be of great help.

Also, I have the same problem with a french master system 2.

To get to the video encoder you have to remove the heat sink of the voltage regulators, it is more or less here:

cxa1145.jpg

Check that the chip in question is a Sony CXA1145. The pins on this chip are numbered and you should attach the wire to pin 11 (Cync out). Have a look at the below diagram for clarification where the pin is:

CXA1145-pinout.png

You have nothing to worry about doing the soldering, compared to other consoles then pins here are big and easy to solder to.
 

MtothaJ

Host for Orochi
I'm logged in, perhaps a moderator could help?

Dont really know why you cant see the pictures, but they are not really needed.
The video encoder is under the metal heat sink thing- on the chip it should say Sony CXA1145.
You need pin 11, if you google 'Cxa1145 pinout' you will get plenty of diagrama showing which one it is. There should be somr numbering on the Megadrive pcb also.
 

Jibbajaba

Giga Shock!!
The reason I had a quick answer for OP in this thread is that I had been researching the subject this week. While I didn't have problems with my Genesis syncing up with anything, it had horrible jailbars, and from what I was reading, I needed to be using csync instead of composite video. Both of my Genesis systems are model 1, so it wasn't as simple as re-wiring the scart cable. This morning I wired pin 11 of the video encoder chip directly to the AV out of my Genesis, putting a 75 ohm resistor and 220uF cap in-line (I used the composite video pin on the AV out jack, as I will never again need composite video out of this unit). Jailbars gone.
 

MtothaJ

Host for Orochi
If you have a French Mega Drive and are using the Sega 3085 RGB cable you have to modify it to make it work on non-SECAM displays.

It's easy as pie.

It's in french, but you get the picture:
http://www.segakore.fr/index.php/20...votre-cable-rgb-fr-vers-pal-ntsc#.V6TJ2NfRb-s

This is basically to switch between cvideo and csync for sync. In any case you have to have the appropriate connections wired to your din connector.
The whole Secam thing is a misconception - with RGB the TV system doesn't matter, and this is precisely the reason the French Megadrive was made RGB only - because nobody wanted to deal with shitty Secam.
 

Atro

Who?,
This is basically to switch between cvideo and csync for sync. In any case you have to have the appropriate connections wired to your din connector.
The whole Secam thing is a misconception - with RGB the TV system doesn't matter, and this is precisely the reason the French Megadrive was made RGB only - because nobody wanted to deal with shitty Secam.

IF you have a Secam Mega Drive.

That cable has to be modified in order to play on other PAL/NTSC machines.
I have two of these cables. Before the mod, they both only outputted sound. The Sync/Comp switch is just a plus.

This is what I meant:
mod_cable_rgb_fr_md_04.jpg

A simple cut and solder job. Otherwise, only audio will come out of that cable.
 
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