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 Post subject: BVM-A20F1M Sega consoles Sync problems
PostPosted: Fri Jul 29, 2016 1:09 pm 



Joined: 13 Jul 2016
Posts: 48
Hello guys,

Yesterday I setup my 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.

The image quality looks OUTSTANDING on the 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?

Thank you!


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 Post subject: Re: BVM-A20F1M Sega consoles Sync problems
PostPosted: Sat Jul 30, 2016 10:34 pm 



Joined: 13 Jul 2016
Posts: 48
bump


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 Post subject: Re: BVM-A20F1M Sega consoles Sync problems
PostPosted: Sun Jul 31, 2016 2:38 pm 



Joined: 05 Dec 2012
Posts: 335
It's very common to have Genesis / SMS sync issues. There's a few ways to get this working, some more complicated then others. Many people have just added a sync strike to the end of the chain. What is your full setup like?


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 Post subject: Re: BVM-A20F1M Sega consoles Sync problems
PostPosted: Sun Jul 31, 2016 2:49 pm 



Joined: 18 Oct 2015
Posts: 315
I read something somewhere about a VCR mode. Maybe try enabling that if its there in the extended menu


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 Post subject: Re: BVM-A20F1M Sega consoles Sync problems
PostPosted: Sun Jul 31, 2016 2:51 pm 



Joined: 13 Jul 2016
Posts: 48
Thank you for your reply mate, to connect the SCART cables to the BVM I use a Female RGBS SCART to BNC adapter, the specific Sega Megadrive 1 cable that I use is the one from Retrogaming Cables.

https://www.retrogamingcables.co.uk/sega-mega-drive-1-sega-genesis-1-stereo-rgb-av-scart-cable-tv-lead-pro-build?search=megadrive%201

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?


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 Post subject: Re: BVM-A20F1M Sega consoles Sync problems
PostPosted: Tue Aug 02, 2016 2:11 am 



Joined: 13 Jul 2016
Posts: 48
I just bought a Megadrive with another RGB cable that is not from retro consoles UK, same result, image won't sync :cry:


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 Post subject: Re: BVM-A20F1M Sega consoles Sync problems
PostPosted: Tue Aug 02, 2016 9:50 am 



Joined: 18 Oct 2015
Posts: 315
did you try looking through the extended menu for VCR mode?


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 Post subject: Re: BVM-A20F1M Sega consoles Sync problems
PostPosted: Tue Aug 02, 2016 10:29 am 



Joined: 13 Jul 2016
Posts: 48
Yes, sorry, I forgot tonmention, I could not find anything labelled VCR nor AFC on the menus.


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 Post subject: Re: BVM-A20F1M Sega consoles Sync problems
PostPosted: Thu Aug 04, 2016 6:39 pm 



Joined: 13 Jul 2016
Posts: 48
I've done some additional research, I have a french 'Mega Drive RGB label', 1600-09 model no, it appears these type of consoles cause sync problems on some BVM monitors, same for the RGB master system, I've taken appart the Megadrive to try to figure out a better way to wire the csync signal, but need some help figuring out how to do that.

Here's a pic of my board, it has a switchless region free mod.

Image


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 Post subject: Re: BVM-A20F1M Sega consoles Sync problems
PostPosted: Sat Aug 06, 2016 7:11 pm 



Joined: 13 Jul 2016
Posts: 48
Update, I tried to wire the Sync out of CXA1145P chip directly to the Sync of the Scart cable with no results. At this point I'm clueless about what to do please help.


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 Post subject: Re: BVM-A20F1M Sega consoles Sync problems
PostPosted: Sat Aug 06, 2016 9:46 pm 



Joined: 18 Oct 2015
Posts: 315
If you're taking csync directly from pin 10 of the CXA1145P chip, then you need to add a 220uf cap and 75ohm resistor, just the like R G B and Composite lines.


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 Post subject: Re: BVM-A20F1M Sega consoles Sync problems
PostPosted: Sun Aug 07, 2016 1:19 am 



Joined: 13 Jul 2016
Posts: 48
Thank you AndehX, I've google it and as far as I understand this 220uf cap and 75 ohm resistor would be already on the french RGB cable I'm using (see attached link http://www.segakore.fr/index.php/2004/0 ... 6aLxJOLR0t).


What other options do I have? should I try to wire the sync signal from Composite or Luma pinout of the CXA114P chip?


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 Post subject: Re: BVM-A20F1M Sega consoles Sync problems
PostPosted: Sun Aug 07, 2016 1:49 am 



Joined: 18 Oct 2015
Posts: 315
Every RGB cable I've seen only comes with capacitors and resistors for the RG and B signals. Composite video doesn't have the cap or resistor because they're already on the motherboard. I'm not certain but I think csync also has the capacitor and resistor on the motherboard. So if you are taking the signal directly from the chip then you are bypassing the capacitor and resistor on the motherboard. Therefor you need to add them yourself.


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 Post subject: Re: BVM-A20F1M Sega consoles Sync problems
PostPosted: Sun Aug 07, 2016 11:04 am 



Joined: 13 Jul 2016
Posts: 48
This got me thinking, I used my tester and plugged one end at the Csync out of the chip and the other end to the csync megadrive pinout, it measures connectivity! So there isn't anything between those two elements :shock: .


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 Post subject: Re: BVM-A20F1M Sega consoles Sync problems
PostPosted: Sun Aug 07, 2016 11:39 am 


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Joined: 06 Mar 2006
Posts: 10447
Location: Germany
csync on the MD definitely requires the cap. Without it you won't get a picture. Sega didn't include the required components on the board. Resistor is optional though. Still no explanation though why your monitor won't sync to the MD's RGB signal with composite video as sync.


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 Post subject: Re: BVM-A20F1M Sega consoles Sync problems
PostPosted: Sun Aug 07, 2016 5:55 pm 



Joined: 18 Oct 2015
Posts: 315
Yeah, wire pin 11 of the chip manually using the 220uf capacitor, to the csync pin of the multi-out connector and you should be good to go. Theres more info here http://www.mmmonkey.co.uk/console/sega/md-sync.htm

Personally, I have both composite video and csync wired to the composite video pin on the multi-out, with a switch so I can manually switch between composite video and csync when needed, without having to use 2 different SCART cables.


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 Post subject: Re: BVM-A20F1M Sega consoles Sync problems
PostPosted: Sun Aug 07, 2016 6:32 pm 


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Joined: 06 Mar 2006
Posts: 10447
Location: Germany
Quote:
Personally, I have both composite video and csync wired to the composite video pin on the multi-out, with a switch so I can manually switch between composite video and csync when needed, without having to use 2 different SCART cables.

in which scenarios would you ever need to use composite video for sync ?


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 Post subject: Re: BVM-A20F1M Sega consoles Sync problems
PostPosted: Sun Aug 07, 2016 7:46 pm 



Joined: 18 Oct 2015
Posts: 315
Fudoh wrote:
Quote:
Personally, I have both composite video and csync wired to the composite video pin on the multi-out, with a switch so I can manually switch between composite video and csync when needed, without having to use 2 different SCART cables.

in which scenarios would you ever need to use composite video for sync ?

Probably never, but just incase I ever plug it into a TV that doesn't like csync, the option is there to use regular composite video


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 Post subject: Re: BVM-A20F1M Sega consoles Sync problems
PostPosted: Mon Aug 08, 2016 10:02 pm 



Joined: 13 Jul 2016
Posts: 48
I added a 220uF capacitor (rated for 16V) and two sets of resistors in series to make a 72 ohm resistor (my local hardware store did not have a 75 ohm one).

Following the mmonkey procedure (I actually did not cut the track that leads to pin 7 in the din 8 socket, as it is effectively disconnected (the RGB cable csyinc in is directly wired to the 220uF capacitor and 72 ohm resistance and then to leg 11 of the chip).

The setup looks like this:

Image

Image

I still can't get any sync from the monitor, the setup still works with my trinitron CRT though.

After that I tried to wire leg 11 of the chip-> 220uF capacitor-> 72 ohm resistance directly to the csync out of the sega cable. This time both my BVM-A20F1M and Trinitron CRT went out of sync. EDIT: tried adding two capacitors in paralel effectively giving a 440uF capacity, same results.

Guys thanks for the help so far but seems that this is not working either :cry: .


Last edited by PeterWar on Mon Aug 08, 2016 10:25 pm, edited 1 time in total.

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 Post subject: Re: BVM-A20F1M Sega consoles Sync problems
PostPosted: Mon Aug 08, 2016 10:23 pm 



Joined: 18 Oct 2015
Posts: 315
ok just to make sure, I know it might sound silly, but sometimes people miss the simplest of things. You did make sure that the channel sync type was set to external and not sync-on-green right?


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 Post subject: Re: BVM-A20F1M Sega consoles Sync problems
PostPosted: Mon Aug 08, 2016 10:27 pm 



Joined: 13 Jul 2016
Posts: 48
AndehX wrote:
ok just to make sure, I know it might sound silly, but sometimes people miss the simplest of things. You did make sure that the channel sync type was set to external and not sync-on-green right?



Indeed, proof of that is that I don't have any sync troubles with my NES, SNES and N64 on my BVM-A20F1M, they work great.


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 Post subject: Re: BVM-A20F1M Sega consoles Sync problems
PostPosted: Mon Aug 08, 2016 10:32 pm 



Joined: 18 Oct 2015
Posts: 315
so you can get the mega drive to sync properly on your trinitron crt, but not on the BVM, yet other console work fine on the BVM? There doesn't seem to be any logic there as the former would indicate an issue with the BVM, but the latter indicates an issue with the Mega Drive... Im officially stumped im afraid :(


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 Post subject: Re: BVM-A20F1M Sega consoles Sync problems
PostPosted: Thu Aug 11, 2016 12:31 pm 



Joined: 13 Jul 2016
Posts: 48
I've tried now to wire composite cync and luma cync from the chip to Pin 20 of a dedicated scart cable for the mega drive (not the stock sega cable).

Nothing works can't sync with my BVM-A20F1M, for the record, if I add a 220uF capacitor and a 75 ohm resistor to the sync signal I also loose sync on my Trinitron CRT.

Please help, I'm out of ideas now. All I can say is that my BVM works great on the RGB moded N64 and the NES and SNES.


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 Post subject: Re: BVM-A20F1M Sega consoles Sync problems
PostPosted: Thu Aug 11, 2016 2:34 pm 


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Joined: 06 Mar 2006
Posts: 10447
Location: Germany
Is (or was) your MD an genuine NTSC unit or a PAL unit ? What seems to cause problems is when a PAL quartz is running at NTSC speeds or vica versa, so if you MD has a PAL clock you might be able to fix it by exchanging it for a NTSC one.


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 Post subject: Re: BVM-A20F1M Sega consoles Sync problems
PostPosted: Fri Aug 12, 2016 10:21 pm 



Joined: 13 Jul 2016
Posts: 48
Fudoh wrote:
Is (or was) your MD an genuine NTSC unit or a PAL unit ? What seems to cause problems is when a PAL quartz is running at NTSC speeds or vica versa, so if you MD has a PAL clock you might be able to fix it by exchanging it for a NTSC one.


I've tried two different megadrives and two different Master Systems 2, all of them where PAL units, but 1 Megadrive and one Master Sytem had the switchless 50/60hz region free mod.

I can't get any of them to sync.


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 Post subject: Re: BVM-A20F1M Sega consoles Sync problems
PostPosted: Fri Aug 12, 2016 10:54 pm 


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Joined: 06 Mar 2006
Posts: 10447
Location: Germany
Unfortunately I don't an A-series BVM, but some people here do, so it shouldn't be too hard to find confirmation that genuine NTSC machines work fine and if you do a clock change on yours (you just bypass the old one and add a new one), then there's no more difference between your machine and a NTSC one.


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 Post subject: Re: BVM-A20F1M Sega consoles Sync problems
PostPosted: Sat Aug 13, 2016 5:15 pm 



Joined: 04 Jun 2015
Posts: 115
Hey Peter. I pulled my BVM-A20F1 out of storage today and tested it with my PAL Megadrive which has been modded with a 50Hz / 60Hz switch. The Megadrive failed to sync too, regardless of it being set to 50Hz or 60Hz. I then tested it with a NTSC Saturn and that synced perfectly. I tried adding a sync strike into the mix with the PAL Megadrive, but it still didn't sync. I even tried using my NTSC 32X with my PAL Megadrive (switched to NTSC of course) and that failed to sync as well.

A friend is borrowing my Sega Nomad and JAP Megadrive, so I cannot currently test the PAL / NTSC clock theory until I get them back in a few weeks time.

There must be something that the BKM-68X card doesn't like with the PAL Master System and Megadrive clocks.


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 Post subject: Re: BVM-A20F1M Sega consoles Sync problems
PostPosted: Sun Aug 14, 2016 3:22 am 



Joined: 04 Jun 2015
Posts: 115
Follow up :

Just tried my A20F1 with a PAL Megadrive II (no region switch) and it also would not sync. :cry:

I then tried a PAL Playstation with a sync-on-luma RGB SCART cable and that worked fine without any sync issues at all.

I really want to get my NTSC Megadrive and Nomad back now so that I can test them with the A20F1.


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 Post subject: Re: BVM-A20F1M Sega consoles Sync problems
PostPosted: Sun Aug 14, 2016 2:57 pm 



Joined: 13 Jul 2016
Posts: 48
xga, thank you so very much for your feedback, I'm so glad that someone is also troubleshooting this issue ;)

I have an RGB SCART cable for the Neo Geo on its way, expected delivery tomorrow to test the Neo Geo on the BVM-A20F1M as well.

Also, my local modder has suggested to cut leg 6 of the CXA1145p chip (the oscilator, XO in) to surpress a source from interference. Another possible "solution" could be to use an RGB bypass kit like this one:

http://store.retrofixes.com/collections ... 2152111687.


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 Post subject: Re: BVM-A20F1M Sega consoles Sync problems
PostPosted: Sun Aug 14, 2016 3:24 pm 



Joined: 04 Jun 2015
Posts: 115
No worries, mate. I'm sure that we'll get to the bottom of the issue soon.

I actually have one of those RGB bypass boards for a Megadrive minus the components. I never got around to ordering the parts for it. Instead I'm waiting for when these become available for sale - https://vmod.wordpress.com/megamod-v3-0/.


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