Atari 130XE and SAVO wiring?

[macsonny]

Hi All,

 

I've decided to try and improve my Atari 130XE video output with a VBXE and SAVO. I have already installed a VBXE in my unit but not 100% satisfied with the quality and have a few ideas to fix based on suggestions from this group. In the mean time I'm also going to install a SAVO unit to try and reduce issues from the cable.

 

I've read the wiring diagrams for the VBXE and SAVO and want to make sure I've got things right as follows:

 

1. R, G, B, GND and RGB CTRL signals will come from the J4 connector on the VBXE and then connect to SAVO.

2. Composite signal will come from DIN connector on Atari and then connect to SAVO.

3. Audio (mono) will come from DIN connector on Atari and then connect to SAVO.

 

SYNC, LUMINANCE and CHROMINANCE on the SAVO will not be connected to anything. Is that correct?

 

Also, the installation instructions for SAVO says "s-video is provided by the Atari XL/XE". Where do I take the s-video signal from on the Atari and which pin does it connect to on the SAVO as none of the SAVO pins are labeled "s-video"?

 

Have attached relevant installation manual pages for VBXE and SAVO for reference.

 

Thanks

 

Sonny

Edited July 31, 2023 by macsonny
Fixed mistakes.

[Rybags]

The diagram mentions Sophia 2 - it does scan-doubling to be compatible with modern monitors.  Chances are old SCART TVs probably won't like the 31 KHz signal.

[Beeblebrox]

There won't be a single labelled svideo connection. Svideo is from the luma, chroma and composite signals. On an XE these can be taken from the tops of the l9(luma), l7(composite) , and l31(chroma) ferrite beads. 

 

As such hook the savo's points for these 3 to those points. That way as I understand it you'll get your non rgb signal on the savo's cable, but also rgb for the VBXE with connections for rgb ctrl, etc wired up. 

 

I have a savo xl board myself but never got around to using it on any of my machines. 

 

See here for the above hookups for svideo I just mentioned:

 

 

 

 

 

Edited July 31, 2023 by Beeblebrox

[woj]

I am away from my computer, my docs, and my machines, and my memory is now hazy, but from what I remember on the VBXE diagram the composite signal serves the sync purposes on the SCART end and it was suggested in other places to use the actual sync off the 4050 chip (or Spectre) instead. Because of the sync signal on the SAVO not to be used and also marked as alternative 9V I am totally thrown off to be honest.

[Peri Noid]

Why don't you ask the author? @Piotr D. Kaczorowski

[flashjazzcat]

7 hours ago, macsonny said:

R, G, B, GND and RGB CTRL signals will come from the J4 connector on the VBXE and then connect to SAVO.

Take RGB CTRL from 5V on the motherboard, not from RGB CTRL on VBXE (which won't work, because there's a current-limiting resistor in the Saturn cable).

7 hours ago, macsonny said:

2. Composite signal will come from DIN connector on Atari and then connect to SAVO.

3. Audio (mono) will come from DIN connector on Atari and then connect to SAVO.

 

SYNC, LUMINANCE and CHROMINANCE on the SAVO will not be connected to anything. Is that correct?

All correct, unless you also purchase a Saturn s-video/composite cable, in case for some reason you wanted to get the legacy video signal from the same Saturn connector instead of the DIN5 connector already on the motherboard (in which case, tap chroma and luma from the DIN5 as well).

 

Other than that, make sure the Saturn cable pushes home fully into the connector. I found this impossible without drilling out the RF modulator hole a little anyway (on two separate machines), although others suggest (further) trimming down the plastic shroud on the cable connector.

Edited July 31, 2023 by flashjazzcat

[BillC]

On 7/30/2023 at 11:22 PM, Beeblebrox said:

There won't be a single labelled svideo connection. Svideo is from the luma, chroma and composite signals.

S-video is just the CHROMA and LUMA signals on a mini-DIN4 connector, before s-video became a standard and was introduced for video tape recorders in the 1980's some companies had the CHROMA/LUMA signals on separate RCA jacks(the Commodore 1702 monitor has this feature).

[Peri Noid]

Actually, S-Video means chroma+luma with standardised voltage levels. Chroma and luma that we have in Atari have different levels than standard.

[Piotr D. Kaczorowski]

Hi @macsonny!

 

Q: R, G, B, GND and RGB CTRL signals will come from the J4 connector on the VBXE and then connect to SAVO.

 

R, G, B, GND are provided from VBXE.

SAVO 'RGB CTRL, +5V' should be connected to a +5V power source. This can be sourced from the +5V points on the old RF Modulator soldering points. Alternatively, you can use the +5V from the VBXE RGB Ctrl, but you'll need to remove the 150R SMD resistor from VBXE (this requires experience and/or a microscope). It's important to note that the first point is labeled as '+5C' and the second point is labeled as '+5A' - these are different power routes (and different levels of noise) located on the Atari motherboard.

 

Q: Composite signal will come from DIN connector on Atari and then connect to SAVO.

 

After removing the RF Modulator, the Composite/CVBS signal is no longer available on the regular Atari XE board. However, it can be sourced from UAV/Spectre AV or other CVBS signal generating boards. In Poland, some people produce RF Modulator CVBS replacement PCBs.

 

Q: Audio (mono) will come from DIN connector on Atari and then connect to SAVO.

 

 

This is the best source of mono sound in the Atari XE. It is the center of a voltage divider (with a 1k pull-down resistor). This point is also the source for the DIN5 audio pin.

 

Q: SYNC, LUMINANCE and CHROMINANCE on the SAVO will not be connected to anything. Is that correct?

 

SYNC - is only used when you have the NTSC version of Sega Saturn with a Euro SCART cable, and synchronization is provided independently, not via the Composite/CVBS signal.

 

The standard Sega Saturn to Euro SCART cable added to the SAVO is PAL region compatible, and synchronization is provided through the SAVO Composite (Sega Saturn Composite pin).

 

If you want to connect the optional cable "Sega Saturn to RCA, S-video," you can connect the luminance (mono) and chrominance (color) signals from the Atari board to those pins.

 

The pair of those signals, "luminance and chrominance," is colloquially called s-video. In fact, s-video standard includes not only this pair of signals but also specifications for their voltage levels. Some Atari video mods correct the levels of these signals and convert them to s-video levels, but that goes beyond the point.

 

Q: In the meantime, I'm also going to install a SAVO unit to try and reduce issues from the cable.

 

Noise is a very broad topic. It may come from the Atari, or it may be back-noise generated from the cable, which in some circumstances can act as an antenna. It can also come from the TV set (I have one that introduces interference).

 

On the Atari side, it is possible to eliminate noise using various methods. It can involve replacing capacitors or adding electrolytic capacitors with original Atari chips. You could also change dynamic memories to static ones or remove Freddie (if you have VBXE and SRAM).

 

I am currently working on rev. 2 of the SAVO board (aka SAVO Classic), which will include Atari noise filtering and back noise reduction by galvanically isolating the sync signals. It's all in testing right now.

 

This topic will also be relevant for the new SAVO+ boards, SAVO MAX, and HAVO. SAVO+ will have true s-video and CVBS generated from RGB in addition to RGB output. SAVO MAX is an enhanced version of SAVO+ with an additional Component Video output. These boards will undergo testing next week. There are plans to include stereo sound mixers as well. The HAVO boards (HDMI Atari Video Output) are the next stage, but their release is likely to be around Christmas.

 

 

 

 

 

 

 

 

 

 

 

[macsonny]

Thank you for taking the time to provide great clarity. It will help alot.

 

I'm waiting on a SAVO to arrive here in Australia that also comes with the video cable. I assume the instructions you gave above are all correct for the cable that comes with the SAVO right?

[Piotr D. Kaczorowski]

@macsonny,

 

That's correct.

[macsonny]

On 8/5/2023 at 1:19 AM, Piotr D. Kaczorowski said:

Hi @macsonny!

 

Q: R, G, B, GND and RGB CTRL signals will come from the J4 connector on the VBXE and then connect to SAVO.

 

R, G, B, GND are provided from VBXE.

SAVO 'RGB CTRL, +5V' should be connected to a +5V power source. This can be sourced from the +5V points on the old RF Modulator soldering points. Alternatively, you can use the +5V from the VBXE RGB Ctrl, but you'll need to remove the 150R SMD resistor from VBXE (this requires experience and/or a microscope). It's important to note that the first point is labeled as '+5C' and the second point is labeled as '+5A' - these are different power routes (and different levels of noise) located on the Atari motherboard.

 

Q: Composite signal will come from DIN connector on Atari and then connect to SAVO.

 

After removing the RF Modulator, the Composite/CVBS signal is no longer available on the regular Atari XE board. However, it can be sourced from UAV/Spectre AV or other CVBS signal generating boards. In Poland, some people produce RF Modulator CVBS replacement PCBs.

 

Q: Audio (mono) will come from DIN connector on Atari and then connect to SAVO.

 

 

This is the best source of mono sound in the Atari XE. It is the center of a voltage divider (with a 1k pull-down resistor). This point is also the source for the DIN5 audio pin.

 

Q: SYNC, LUMINANCE and CHROMINANCE on the SAVO will not be connected to anything. Is that correct?

 

SYNC - is only used when you have the NTSC version of Sega Saturn with a Euro SCART cable, and synchronization is provided independently, not via the Composite/CVBS signal.

 

The standard Sega Saturn to Euro SCART cable added to the SAVO is PAL region compatible, and synchronization is provided through the SAVO Composite (Sega Saturn Composite pin).

 

If you want to connect the optional cable "Sega Saturn to RCA, S-video," you can connect the luminance (mono) and chrominance (color) signals from the Atari board to those pins.

 

The pair of those signals, "luminance and chrominance," is colloquially called s-video. In fact, s-video standard includes not only this pair of signals but also specifications for their voltage levels. Some Atari video mods correct the levels of these signals and convert them to s-video levels, but that goes beyond the point.

 

Q: In the meantime, I'm also going to install a SAVO unit to try and reduce issues from the cable.

 

Noise is a very broad topic. It may come from the Atari, or it may be back-noise generated from the cable, which in some circumstances can act as an antenna. It can also come from the TV set (I have one that introduces interference).

 

On the Atari side, it is possible to eliminate noise using various methods. It can involve replacing capacitors or adding electrolytic capacitors with original Atari chips. You could also change dynamic memories to static ones or remove Freddie (if you have VBXE and SRAM).

 

I am currently working on rev. 2 of the SAVO board (aka SAVO Classic), which will include Atari noise filtering and back noise reduction by galvanically isolating the sync signals. It's all in testing right now.

 

This topic will also be relevant for the new SAVO+ boards, SAVO MAX, and HAVO. SAVO+ will have true s-video and CVBS generated from RGB in addition to RGB output. SAVO MAX is an enhanced version of SAVO+ with an additional Component Video output. These boards will undergo testing next week. There are plans to include stereo sound mixers as well. The HAVO boards (HDMI Atari Video Output) are the next stage, but their release is likely to be around Christmas.

 

 

 

 

 

 

 

 

 

 

 

So good news is that SAVO arrived today with cable. Installed great per your instructions above. Only wire I didn't connect on SAVO is the 9V SYNC line.

 

My audio issues have gone. Really nice sound now but I am getting a lot of jailers. More than before I installed SAVO.

 

Any tips on removing jailers for Atari 130XE?

 

Thanks

[Beeblebrox]

6 minutes ago, macsonny said:

So good news is that SAVO arrived today with cable. Installed great per your instructions above. Only wire I didn't connect on SAVO is the 9V SYNC line.

 

My audio issues have gone. Really nice sound now but I am getting a lot of jailers. More than before I installed SAVO.

 

Any tips on removing jailers for Atari 130XE?

 

Thanks

can you upload a pic of the screen as well as the savo installed?

Edited August 8, 2023 by Beeblebrox

[macsonny]

27 minutes ago, Beeblebrox said:

can you upload a pic of the screen as well as the savo installed?

See attached.

 

[Beeblebrox]

do you have an image of the SAVO installed and also it's wiring? Worth double checking where you are hooking up from on the A8's PCB, (as per Piotr's advice), and also where the wires pass over on the PCB.

 

 

Edited August 8, 2023 by Beeblebrox

[macsonny]

22 hours ago, Beeblebrox said:

do you have an image of the SAVO installed and also it's wiring? Worth double checking where you are hooking up from on the A8's PCB, (as per Piotr's advice), and also where the wires pass over on the PCB.

 

 

Ok - so slightly annoyed now. Just shortened a few wires in the installation and now I get a really odd colour on the screen per attached photos. Checked and doubled checked my wiring and can't see anything obvious. Can any one see my mistake?

 

[Beeblebrox]

Have you double checked the crimping on the dupont connections/continuity? Could be in reworking the wiring something isn't connecting 100%

 

Also (and I can't recall 100% if this is the case), but I don't think you need the 4050 in place if you are no longer using stock video and are just using VBXE's RGB via the SAVO.

 

I seem to recall I had a similar display issue on stock video on my 800 which was down to a bad 4050 chip/bad socket.

Edited August 9, 2023 by Beeblebrox

[flashjazzcat]

23 minutes ago, Beeblebrox said:

I don't think you need the 4050 in place if you are no longer using stock video and are just using VBXE's RGB via the SAVO

CSYNC is required for VBXE output to work, so he had better leave it be. In addition, stock video will be useful to have if VBXE output fails for any reason and the user has to run the FC.COM core flasher to recover the FX core (not to mention for viewing APAC and other modes which aren't properly emulated by VBXE unless the GTIA emulation core is used).

 

Looks to me like one of the RGB lines is broken, anyway (perhaps the green).

 

I noticed alloy solder having been used on the SAVO header pins as well, so it would be well worth checking every contact point.

Edited August 9, 2023 by flashjazzcat

[macsonny]

Noticed I had the wiring to the 74LS138 wrong and I have now fixed it. Now getting a horrible dark red screen. Any ideas?

 

[macsonny]

58 minutes ago, Beeblebrox said:

Have you double checked the crimping on the dupont connections/continuity? Could be in reworking the wiring something isn't connecting 100%

 

Also (and I can't recall 100% if this is the case), but I don't think you need the 4050 in place if you are no longer using stock video and are just using VBXE's RGB via the SAVO.

 

I seem to recall I had a similar display issue on stock video on my 800 which was down to a bad 4050 chip/bad socket.

Found the header PIN 2 on J3 was not connected. Had to put in my own bodge wire from that PIN to PIN 3 on Freddie. Full continuity now. Still getting horrible red screen though?

[macsonny]

44 minutes ago, flashjazzcat said:

CSYNC is required for VBXE output to work, so he had better leave it be. In addition, stock video will be useful to have if VBXE output fails for any reason and the user has to run the FC.COM core flasher to recover the FX core (not to mention for viewing APAC and other modes which aren't properly emulated by VBXE unless the GTIA emulation core is used).

 

Looks to me like one of the RGB lines is broken, anyway (perhaps the green).

 

I noticed alloy solder having been used on the SAVO header pins as well, so it would be well worth checking every contact point.

Reflowed each of the header pins just to be sure. Didn't solve issue.

[flashjazzcat]

Is that SAVO connector fully pushed home? Grab the continuity tester and make sure you get beeps between the SCART connector and VBXE itself.

[Beeblebrox]

8 minutes ago, flashjazzcat said:

Is that SAVO connector fully pushed home? Grab the continuity tester and make sure you get beeps between the SCART connector and VBXE itself.

Yeah - it doesn't look all that secure in place in this closeup:

 

[flashjazzcat]

6 minutes ago, Beeblebrox said:

Yeah - it doesn't look all that secure in place in this closeup

That impression might be caused by the fact the plastic sleeve has been aggressively trimmed back to clear the machine's case, but the connector is certainly sitting at an odd angle.

 

The lumpy soldering on the DIN connector anchor doesn't inspire confidence either. On a SAVO board I modified with straight header pins, when I was prising the plastic frame off the existing header pins before desoldering them, a couple of pins ripped clean out of the board without damaging the vias, which was very odd indeed (suggesting that the solder itself was of quite poor consistency).

[macsonny]

23 minutes ago, flashjazzcat said:

Is that SAVO connector fully pushed home? Grab the continuity tester and make sure you get beeps between the SCART connector and VBXE itself.

It looks like the connector is as far as it will engage. See attached pic. I did a continuity test between the SCART pins and the header pins on the SAVO with the cable connected. It got "momentary" continuity buzzes as I figure there must be some capacitors or similar in the cable?