Games Not Running! Screen Glitching! Why?

[SainT]

Bad ROM Sets

Headers for ROM's HAVE to be correct! If you have ROM's with incorrect headers (and there are a LOT out there!) then you will likely run into problems. Trebors ROM set is recommended as being well checked and actively being updated and fixed all the time.

 

Console Region

The 7800 has two different Maria (graphics) chips, the PAL and the NTSC version. The chips both expect different length display lists from the game, which means unless the game was designed to be multi-region, games are rarely interchangeable between consoles. For an actual physical cartridge, PAL games will never run on an NTSC machine due to the security mechanism of the NTSC console, however the GameDrive does allow these games to boot. NTSC cartridges *can* be run on a PAL machine however, but are still very unlikely to run.

 

The region for which the game is intended is set in the header of the ROM and the GameDrive warns you if you are trying to run a game of the wrong region by displaying "WARNING: Wrong Region!". Any of the original commercial titles of the wrong region will definitely not work properly, homebrew gets a little more complicated.

 

Some homebrew was intended to be multi-region and adapts the display lists to work on both region consoles. There is an additional bit in the header to allow these games to be marked, however not all games will have been correctly flagged yet. So the current rule of thumb is that if the GameDrive warns of wrong region, expect the game not to work. If it does work, great! You have found a multi-region game. Over time these will all be correctly flagged and you can guarantee a wrong region message will definitely be followed by disappointment.

 

Break Issues

One issue which will crop up from time to time is screen glitching when BREAK is enabled on the cart. BREAK is the functionality which allows you to return to the game menu with a controller button combination or apply cheats to the running game.

 

The way BREAK works is the cartridge takes over execution of the code from the game once per frame to do it's own thing and apply cheats and check for button presses. For some games this happens at a very crucial moment and causes graphical glitches. One common example is Ms Pac-Man (NTSC) and all it's mods, this game has very noticeable screen flickering / glitching with break enabled.

 

Until there is a work-around for specific games with issues the best option is to disable break for the game. This does mean you will not be able to enable any cheats (if they exist) and you will have to power-cycle to return to the game menu, but the game will be glitch free.

 

To disable break, press right trigger on a standard controller or B on a Mega7800 controller and press left / right where it says BREAK ENABLED to change this to BREAK DISABLED. Move down and hit START.

 

Incorrectly Installed AV Mod

If you are connecting your 7800 to a TV or monitor via a composite mod and are seeing very bad interference in the video signal when playing games which support some kind of external audio (POKEY, YM2151, COVOX, BupChip), then you will most likely have a wiring issue with AV mod install. 

 

There are several different variations in instructions on how to connect the audio from the 7800 to the AV mod, some only connect the TIA audio, some recommend replacing resistors to adjust the mixing balance and some just recommend lifting one end of a pair of resistors (which are the TIA and external audio signals) and connecting them together to create a clean mixed audio signal. I recommend the latter option.

 

If you are seeing screen interference when playing games with external audio I would recommend not continuing to play any games which have these issues. To be fair, you generally wont be able to see them, so this probably doesn't need saying! But depending on the installation of the mod you could potentially damage the TIA or the GD audio driver as both outputs are being incorrectly coupled and causing both audio drivers to potentially fight. However, if there is no external audio active, the audio driver on the GD is disabled, so any other games will not pose a problem. I would strongly recommend fixing or having this problem fixed to be able to enjoy the GD fully. A temporary work-around is to set the global audio settings (press START on the Mega7800 pad or SELECT on the console at the game menu) such that all external audio is at volume 0.

 

Please see the detailed description below!

Edited November 13, 2023 by SainT

[CommodoreCEO]

Hey folks, I had some screen glitching and along with @SainT noticed that it was dependent upon POKEY sound.

 

 

Thankfully SainT suggested that it could be the composite/AV mod that was done on my PAL console (see below).

 

 

Upon investigation, I re-modded the console with two resistors being lifted on their 'left side' and joined together with the white wire (see below... It's not pretty!)

 

POKEY games etc now work properly on the 7800GD!

 

If you have on-screen glitching with the 7800GD and have an AV mod installed, double check the wiring of your mod.

[Greg2600]

Do these issues occur via the RGB out on the cartridge?  That's my intended method, and I have little faith my AV mod was installed properly given all the past issues I've had with it.  Lol. 

[SainT]

3 minutes ago, Greg2600 said:

Do these issues occur via the RGB out on the cartridge?  That's my intended method, and I have little faith my AV mod was installed properly given all the past issues I've had with it.  Lol. 

It wont affect the RGB out from the cart, but it is possible, depending on how the mod was installed, it could damage your console or the GD audio driver. I'm trying to figure out exactly the cause of the issue!

[+-^CrossBow^-]

41 minutes ago, SainT said:

It wont affect the RGB out from the cart, but it is possible, depending on how the mod was installed, it could damage your console or the GD audio driver. I'm trying to figure out exactly the cause of the issue!

This is why I have it listed in the UAV install procedures to either lift the north legs of the resistors and attach them with another capacitor before running them out is because if you just attach directly, the TIA ends up overpowering the external audio on the NTSC consoles. Not sure how it differs on the PAL consoles but I know that PAL consoles used different resistor values compared to the NTSC machines. The external audio line on the NTSC machine is a 6.8k 1/4 watt resistor and the TIA is an 18k 1/4 watt. That is quite a difference and there is a reason for that.

 

So yeah. just grabbing the audio directly off the source pinss is going to cause signal issues and that was seen with the Dragon Fly carts as well and I also suspect a large reason why some folks complain about such low volume with their HOKEY enabled Concertos.

 

I think the stereo mods are also partially to blame on this given how those are wired up, and a large reason why I don't offer them. I know I've had to replace a few TIAs that developed audio output issues due to such work in the past.

 

For those that might be concerned, if I've done your console with a UAV upgrade or you sent it to me for audio repair, then you should be good given the method I've always used was to either lift the original resistors and use those, or add another set in tandem with the originals and wire the audio from the new set of resistors when RF output is still wanted. Also for those that order the 7800 UAV mount boards from TBA or myself, those mount boards include the extra set of resistors and capacitor on it already to simplify that issue.

 

Good info to know SainT and good to know it can be corrected for pretty easily.

 

[SainT]

The PAL machines have 6.8K resistors for both TIA and POKEY. I think the NTSC ones may have been modified (maybe later revisions?) to make the POKEY audio a bit louder? I remember you saying about the issues with AV mods... now I'm understanding more... 😆

So far today I've been trying to replicate the issue, without success. I have copied both audio coupling methods used by the two consoles I know of which showed a problem, neither resulted in an issue on my PAL console.

 

Initially I thought it was shorting the outputs of both AC coupling caps before the resistor and therefore feeding some current back to the TIA. I tested this, no noticeable issues. I then thought perhaps one of the AC coupling caps had shorted (seemed unlikely.. but) and was causing worse fighting issues, tried manually shorting both caps (C10/C17 below). No issues.

 

 

However, both consoles which had issues had a TFW8B composite mod fitted and appeared to have followed the install guide as they had a lot of other components removed from the mainboard. So my current train of thought was then it's a combination of factors, including removing a load of components which are currently present on my mainboard.

 

The only source I can see in the schematics which would result in video interference from the audio is the modulated audio section which adds the audio signal to the video signal. If this was to become connected directly to the audio signal this would cause problems, and in fact if I short R33 (R5 above) (on PAL), I DO get very bad interference akin to what has been reported. So I think the cause is a connection of the POKEY audio to the composite video SOMEHOW. The question is.... HOW?! As if you remove R62 (R1 below) then it also DOES NOT cause an issue even shorting R33 (R5 above).

 

 

The TFW8B install guide recommends removing the marked components. This isolates the RF AUDIO OUT (which connects to the composite video) such that audio should not make any difference. Likewise the AUDIO IN is actually disabled by pull the left side of the two resistors, however it is left floating.

 

So far I cannot see any reason why the mods above should cause video interference and a I cannot replicate it on my console in a way which would make sense for the actual mods seen. I'm very confused as to why this is happening, tbh!

[+-^CrossBow^-]

7 minutes ago, SainT said:

The PAL machines have 6.8K resistors for both TIA and POKEY. I think the NTSC ones may have been modified (maybe later revisions?) to make the POKEY audio a bit louder? I remember you saying about the issues with AV mods... now I'm understanding more... 😆

 

All NTSC consoles used an 18k for R6 from the TIA and 6.8k at R5 from the external audio line. Now variances in those resistors as they used 5% spec'd ones at the time could account for subtle volume differences from one console to the next, but still not enough to really notice in most instances.

 

Again, I'm not familiar with the PAL side of it, but I know that I used to replace both resistors on the older Magic Knight s-video boards because they weren't the right values initially for NTSC 7800s. And again, I've redone the audio on a number of 7800s that had been done by others in methods similar to what you've shown where audio is just being grabbed straight off the pins pretty much.

 

[CommodoreCEO]

44 minutes ago, SainT said:

The PAL machines have 6.8K resistors for both TIA and POKEY. I think the NTSC ones may have been modified (maybe later revisions?) to make the POKEY audio a bit louder? I remember you saying about the issues with AV mods... now I'm understanding more... 😆

So far today I've been trying to replicate the issue, without success. I have copied both audio coupling methods used by the two consoles I know of which showed a problem, neither resulted in an issue on my PAL console.

 

Initially I thought it was shorting the outputs of both AC coupling caps before the resistor and therefore feeding some current back to the TIA. I tested this, no noticeable issues. I then thought perhaps one of the AC coupling caps had shorted (seemed unlikely.. but) and was causing worse fighting issues, tried manually shorting both caps (C10/C17 below). No issues.

 

 

However, both consoles which had issues had a TFW8B composite mod fitted and appeared to have followed the install guide as they had a lot of other components removed from the mainboard. So my current train of thought was then it's a combination of factors, including removing a load of components which are currently present on my mainboard.

 

The only source I can see in the schematics which would result in video interference from the audio is the modulated audio section which adds the audio signal to the video signal. If this was to become connected directly to the audio signal this would cause problems, and in fact if I short R33 (R5 above) (on PAL), I DO get very bad interference akin to what has been reported. So I think the cause is a connection of the POKEY audio to the composite video SOMEHOW. The question is.... HOW?! As if you remove R62 (R1 below) then it also DOES NOT cause an issue even shorting R33 (R5 above).

 

 

The TFW8B install guide recommends removing the marked components. This isolates the RF AUDIO OUT (which connects to the composite video) such that audio should not make any difference. Likewise the AUDIO IN is actually disabled by pull the left side of the two resistors, however it is left floating.

 

So far I cannot see any reason why the mods above should cause video interference and a I cannot replicate it on my console in a way which would make sense for the actual mods seen. I'm very confused as to why this is happening, tbh!

It should also be noted that my console was completely fine with standard POKEY cartridges. There was no interference when putting Crystal Quest or Commando carts into my console, but the POKEY based ROMs on 7800GD gave me interference. 🤔

[+-^CrossBow^-]

8 minutes ago, CommodoreCEO said:

It should also be noted that my console was completely fine with standard POKEY cartridges. There was no interference when putting Crystal Quest or Commando carts into my console, but the POKEY based ROMs on 7800GD gave me interference. 🤔

Similar was reported with the older setups with original carts working just fine. When the Dragon Fly was released is when some audio issues started to come up and I even offered to correct those for others on their consoles for only cost of shipping, even though I hadn't done the work on them originally and a few folks took me up  on that offer.

 

I had issues with original carts not working well as I couldn't hear the Pokey when I was using the older audio wiring methods laid out in the original LHE and similar AV upgrade docs years ago. 

 

[Greg2600]

Mine is an old, crappy, Longhorn.  I have a Concerto with Hokey, it works though.  However as mentioned, the Pokey games are not very loud.  

 

 

Edited July 20, 2023 by Greg2600

[SainT]

1 hour ago, CommodoreCEO said:

It should also be noted that my console was completely fine with standard POKEY cartridges. There was no interference when putting Crystal Quest or Commando carts into my console, but the POKEY based ROMs on 7800GD gave me interference. 🤔

This is exactly the bit which I want to get to the bottom of! 😄 As much as, in my opinion, mods which are bypassing resistors are ultimately potentially damaging to the system in the long run (Atari did these things for a reason), people have systems with these setups. I want the GD to behave exactly as you would expect a physical POKEY.

 

I have more theories to try out tomorrow. I WILL get to the bottom of this. 😂

 

However from my testing so far, you must have to remove quite a lot of components from the PCB for this issue to manifest! It’s definitely not an issue on a stock or even moderately modified system.

[SainT]

41 minutes ago, Greg2600 said:

Mine is an old, crappy, Longhorn.  I have a Concerto with Hokey, it works though.  However as mentioned, the Pokey games are not very loud.  

I suspect this will be absolutely fine. The AV mods I’ve done on my systems, which haven’t involved removing components from the PCB, work absolutely fine. I can even massively abuse them by shorting out all sorts of components and it doesn’t cause an issue.

[+-^CrossBow^-]

1 hour ago, Greg2600 said:

Mine is an old, crappy, Longhorn.  I have a Concerto with Hokey, it works though.  However as mentioned, the Pokey games are not very loud.  

 

 

Send it my way and I can get those audio issues resolved at least...

 

[SainT]

Well, I've removed everything recommended by the TFW8B installation guide and it's still working fine even with directly shorted AC coupling caps. I'm at a bit of a loss as to what is causing the issue with the two cases that have been reported. 

 

The issue is definitely to do with the low impedance coupling of the external and TIA audio, but why it's resulting in composite video interference on some consoles I cannot explain. The only thing I can think is as well as the above there also needs to be other component failures, or even possibly different TIA revision? Or PCB revision?

 

 

[Trebor]

35 minutes ago, SainT said:

The only thing I can think is as well as the above there also needs to be other component failures, or even possibly different TIA revision? Or PCB revision?

For PAL, C300633 is the only PCB motherboard that has been publicly spoken of and taken note, AFAIK, unlike NTSC which is known to have either an NTSC C025233-001 or C025233-002 PCB board.   

 

However, like the NTSC C025233-002 motherboard, wondering if there may be a few different varieties on component inclusions.

 

For the PAL C300633 motherboards, component inclusions might vary, especially considering the daughterboard addition with the French units.  Similar to NTSC consoles and the Expansion Interface scenarios, there may be some units that vary slightly in motherboard appearance, or in the case of PAL units, vary with components.

 

TIA may be a factor, as at least TIA versions 8, 9, and 10 are known to be leveraged for 7800 consoles, each having quirks of their own.

 

Spoiler

Version 8 was used in most PAL JRs and all PAL 7800s that reveals a problem with PAL Centipede and the 1987 re-release of Millipede.  Using the Activision work-around method of avoiding the HMOVE lines doesn’t work on some PAL 2600 JR (all-black) models.  Also, like the 3-in-1 2600 JR chip, the TIA chip in PAL versions of the VCS only have mono sound output.  According to Joe Decuir, the PAL version of TIA was called PAULA.

 

Version 9 has an issue with Frogger II: Threeedeep! and is found in certain 7800 systems.

 

Version 10 is found in 2600 "JR" consoles (both NTSC and PAL) that are made in China after late 1989. The signal timing in the TIA for the shifting pulses for the movable objects seems to be a little off from older versions of the TIA. Therefore when a game starts the shifting process in such a way that some of the shifting pulses happen during the visible part of the screen, the movable objects might be positioned slightly differently. This affects all PAL 7800 consoles, too.

 

 

[SainT]

1 hour ago, Trebor said:

TIA may be a factor, as at least TIA versions 8, 9, and 10 are known to be leveraged for 7800 consoles, each having quirks of their own.

 

Absolutely could be a TIA difference.

 

Mine is a C398052-001 in the PAL machine. No idea what revision that corresponds to?

Edited July 21, 2023 by SainT

[Trebor]

Checking the Master List picture of TIA chips (~1/4 of the way down) from the aforementioned webpage and compare it, hopefully will provide a match.

 

Spoiler

Below is the current master list of TIA chips:

American MicroSystems (AMI)

C010444-01 7749FF -- Found in a Rev 8 (1977). "2 or 3" shows 2.

C010444-01 7750XG -- Found in a Rev 8 (1977).

C010444-01 7801BA -- Found in a 4-switcher.

C010444-01 7812MS -- "2 or 3" shows 2. Pac-Man/Pesco issue with stray dots.

C010444-01 7814QA -- Found in a Rev B (1977). "2 or 3" shows 2. Pac-Man/Pesco issue with stray dots.

C010444D-01 8010TL -- Found in a Rev B (1977). "2 or 3" shows 3. Pac-Man/Pesco issue with stray dots. Slight issue with Cosmic Ark starfield (V1 PIC).

C010444D-01 8027PX -- Found in a Rev B (1977). "2 or 3" shows 2.

C010444D-01 8028MS -- "2 or 3" shows 2.

C010444D-01 8029CU -- Found in a Rev B (1977).

C010444D-01 8031CS -- Found in a Rev B (1977). "2 or 3" shows 3.  Slight issue with Cosmic Ark starfield (V1 PIC).

C010444D-01 8031QU -- Found in a Rev B (1977). "2 or 3" shows 2.  Wall Ball exhibits issues.

C010444D-01 8033BB -- Found in a Rev B (1977).

C010444D-01 8035IR -- Found in a Rev C (1977). "2 or 3" shows 2.

C010444D-01 8036DAG -- Found in a Rev B (1977).

C010444D-01 8051AHH -- Found in a Rev C (1977). "2 or 3" shows 2 at first, and then 3 after it warms up.

C010444D-01 8051ALR -- Found in a Rev C (1977). "2 or 3" shows 2.

C010444D-01 8105DAC -- Found in a Rev C (1977). "2 or 3" shows 2.

C010444D-01 8108DAL -- Found in a Rev 9 (1980). "2 or 3" shows 3. Pac-Man/Pesco issue with stray dots. Slight issue with Cosmic Ark starfield (V2 PIC).

C010444D-01 8108DAO -- Found in a Rev 9 (1980). "2 or 3" shows 3. Wall Ball exhibits issues.

C010444D-01 8111IAJ -- Found in a Rev C (1977) and a Rev 8 (1977).  "2 or 3" shows 2.

C010444D-01 8115KZ -- Found in a Rev 9 (1980). "2 or 3" shows 2.

C010444D-01 8116XP -- "2 or 3" shows 2.

C010444D-01 8117BBQ -- Found in a Rev 12 (1980). "2 or 3" shows 2.

C010444D-01 8117MAE -- Found in a Rev 12 (1980). "2 or 3" shows

C010444D-01 8119BAB -- Found in a Rev B (1977). "2 or 3" shows 2.

C010444D-01 8119BCR -- "2 or 3" shows 3.

C010444D-01 8119FZ -- Found in a 4-switch.

C010444D-01 8132MBT -- Found in a Rev 13 (1980). "2 or 3" shows 3.

C010444D-01 8132MBX --  Found in a Rev 13 (1980).  "2 or 3" shows 2.

C010444D-01 8135BIK -- Found in a Rev B (1977). "2 or 3" shows 2.

C010444D-01 8135MCZ -- Found in a Rev 13 (1980). "2 or 3" shows 2.

C010444D-01 8135MDD -- Found in a Rev 12 4-switch.

C010444D-01 8136MDO -- Found in a Rev 14 (1980) 4-switch.  "2 or 3" shows 3.

C010444D-01 8137DAI -- Found in a Rev B (1977). "2 or 3" shows 2.

C010444D-01 8137MEJ -- Found in a Rev 13 (1980).

C010444D-01 8138MEW-- Found in a Rev 14 (1980).  "2 or 3" shows 2.

C010444D-01 8140MEY-- Found in a Rev B (1977).

C010444D-01 8140MFG-- Found in a Rev C (1977). "2 or 3" shows 2.  This chip exhibited a heat-related problem that affected the title screen graphics on He-Man (V1 PICS).

C010444D-01 8144MFX -- "2 or 3" shows 2.  Pac-Man/Pesco issue with stray dots.

C010444D-01 8150MAJ -- Found in a batch of items that the Irish service center Peats/Emcee tossed in 2009, so this version is likely PAL.

C010444D-01 8202MAP -- Found in a Rev 14 (1980). "2 or 3" shows 3.

C010444D-01 8206MBM -- Found in a Rev 13 (1980).

C010444D-01 8209MCD -- Found in a Rev 14 (1980). "2 or 3" shows 2.

C010444D-01 8211MCP -- Only works in a Rev 12 4-switch if pin 36 is lifted, and even then there's issues. "2 or 3" shows 2.

C010444D-01 8214BKR - Found in a Rev C (1977). "2 or 3" shows 2.

C011903 8214MBM -- Found in a PAL 2600AP Rev 6.

C011903 8215MBN -- Found in a PAL Rev 6.

C010444D-01 8216LO -- Found in a Rev 16 (1980). "2 or 3" shows 3.

C010444D-01 8222MEN -- Found in a Rev 16 (1980). "2 or 3" shows 3.

C010444D-01 8224BQJ -- Found in a Rev 14 (1980).  "2 or 3" shows 3.

C010444D-01 8224RP -- Found in a Rev 14 (1980).  "2 or 3" shows 2.

C010444D-01 8225EOW -- Found in a Rev 16 (1980). "2 or 3" shows 3.

C010444D-01 8227JG -- Found in a Rev 14 (1980).  "2 or 3" shows 3.

C010444D-01 8228MFN -- Found in a Sears Video Arcade II (1981).

C010444D-01 8231BMH -- "Found in a Rev 16 (1980). "2 or 3" shows 3. Has issue with Ebivision's Pac-Man and Pesco, and an issue with Cosmic Ark's starfield (V1 PIC).

C010444D-01 8424LI -- Found in a non-socketed Rev 16. "2 or 3" shows 3.

C010444D-01 8712MIT -- Found in a Rev A (1984) 7800 "Action" 0287 pcb. "2 or 3" shows 2.  Pac-Man/Pesco issue with stray dots.

C010444D-01 8715MJF -- Found in a Rev A (1984) 7800 "Action" 3187 pcb. "2 or 3" shows 3.  Slight issue with Pitfall II (PICS). Both BurgerTime and He-Man do not work using a Harmony cartridge.

C010444D-01 8725MJQ

C010444-002 8811TAH -- Found in a 2600 JR, Rev F. "2 or 3" shows 2.

8123MAB -- Found in a PAL 6-switcher.

8419ABI -- Found in a PAL "Vader".

 

IMP

C010444-31 8835WEA -- Found in 2600 JR.

 

Intersil

C010444-23 8131 -- Found in Rev C (1977).  "2 or 3" shows 3.

 

"MA" (?)

C010444-11D 7812 -- Found in a "heavy sixer" Rev B.  "2 or 3" shows 3.  Has issue with Ebivision's Pac-Man and Pesco, and an issue with Cosmic Ark's starfield (V1 PIC).

C011903-11 7934 -- Found in a PAL 6-switch Rev A.

CO11903-11 8008 -- Found in a PAL system.

C010444-11D 8013 -- Found in a Rev B (1977).  "2 or 3" shows 3.

C010444-11D 8015 -- Found in a Rev B (1977). "2 or 3" shows 2.  Issue with Cosmic Ark's starfield (V1 PIC).

C010444-11D 8020 -- "2 or 3" shows 3. Wall Ball exhibits issues.

CO11903-11 8045 -- Found in a 6-switch.

CO11903-11 8102 -- Found in a Rev B (1978) PAL system.

 

Motorola

C010444D-05 8138 -- Found in a Rev 13 4-switch.

C010444D-05 8144 -- Found in a 4-switch. "2 or 3" shows 2 until the chip warmed up and showed 3.  Slight issue with Cosmic Ark starfield (V1 PIC).

C010444D-05 8147 -- Found in a Rev 12 4-switch with pin 36 lifted up. Not sure what the reason was, as it worked fine with the pin in the socket. "2 or 3" shows 2.

 

National Semiconductor

C010444D-19 B201 -- Found in a 6-switcher.

C010444D-19 B204 -- Found in a Rev C (1977).

C010444D-19 B208 -- Found in a Rev C (1977).  "2 or 3" shows 3.

C010444D-19 B219 -- Found in a Rev 13 (1980).  "2 or 3" shows 2.

 

OKI Semiconductor (OKI)

C010444-22 M3980 1Y42 -- Found in a Rev 14 (1980). "2 or 3" shows .

C010444-22 M3980 3563 -- Found in a non-socketed Rev 16 "Vader". "2 or 3" shows 2.

C010444-22 M3980 4560 -- Found in a non-socketed Rev 17 "Vader".

C010444-22 M3980 4561 -- Found in a non-socketed Rev 17 "Vader". "2 or 3" shows 2.

C010444-22 M3980 4653

C010444-22 M3980 6904 -- Found in a Rev A (1984) 7800.  "2 or 3" shows 2.  Slight issue with Cosmic Ark starfield (V1 PIC).

C010444-22 MSM3980 0Z71-- Found in a Rev 12 (1980).  "2 or 3" shows 2.  Slight issue with Cosmic Ark starfield (V1 PIC).

C010444-22 MSM3980 1151 -- Found in a Rev C (1977).  "2 or 3" shows 3.  Has issue with Ebivision's Pac-Man and Pesco, and an issue with Cosmic Ark's starfield (V1 PIC).

C010444-22 MSM3980 1374 -- Found in a Rev B (1977).  "2 or 3" shows 2.  Slight issue with Cosmic Ark starfield (V1 PIC).

C010444-22 MSM3980 1742 -- Found in a Rev B (1977).  "2 or 3" shows 3.  Has issue with Ebivision's Pac-Man and Pesco, and an issue with Cosmic Ark's starfield (V1 PIC).

C010444-22 MSM3980 1953 -- Found in a Rev 13 (1980).  "2 or 3" shows 2.  Slight issue with Cosmic Ark starfield (V1 PIC).

C010444-22 MSM3980 1955 -- Found in a Rev 14 (1980).

C010444-22 MSM3980 1957 -- Found in a Rev 14 (1980).

C010444-22 MSM3980 1Y58 -- Found in a Rev 13 (1980). "2 or 3" shows 2.  Slight issue with Cosmic Ark starfield (V1 PIC).

C010444-22 MSM3980 1Y64 -- Found in a Rev 13 (1980). "2 or 3" shows 2.  Slight issue with Cosmic Ark starfield (V1 PIC).

C010444-22 MSM3980 1Z55 -- Found in a Rev 14 (1980). "2 or 3" shows 2.

C010444-22 MSM3980 1Z56 -- Found in a Rev 14 (1980).

C010444-22 MSM3980 2247 -- Found in a Rev 16 (1980).  "2 or 3" shows 2.

C010444-22 MSM3980 2259 -- Found in a Rev 16 (1980).

C010444-22 MSM3980 2263 -- Found in a Rev 14 (1980). "2 or 3" shows 3. Has issue with Stay Frosty (PIC).

C010444-22 MSM3980 2445 -- Found in a Rev 14 (1980).  "2 or 3" shows 2.

C010444-22 MSM3980 2461 -- Found in a Rev 14 (1980).  "2 or 3" shows 3.  Has issue with Ebivision's Pac-Man and Pesco, and an issue with Cosmic Ark's starfield (V1 PIC).

C010444-22 MSM3980 2469 -- Found in a Rev 16 "Vader".

C010444-22 MSM3980 2473 -- Found in a Rev 16 (1980). "2 or 3" shows 3.  Has issue with Ebivision's Pac-Man and Pesco, and an issue with Cosmic Ark's starfield (V1 PIC).

C010444-22 MSM3980 2551 -- Found in a non-socketed Rev 16 "Vader". "2 or 3" shows 2.

C010444-22 MSM3980 2584 -- Found in a Sears Video Arcade II.

 

Synertek

C010444-03 7732D -- "2 or 3" shows 2.

C010444-03 7742D -- "2 or 3" shows 3.

C010444-03 7743S

C010444-03 7749S -- Found in a Rev B (1977) "heavy sixer".   "2 or 3" shows 2.

C010444-03 7801S -- Found in a 6-switcher.

C010444-03 7808S

C010444-03 7810D -- Found in a Rev B (1977).

C0104440-03 7814S -- Found in a Rev B (1977).  "2 or 3" shows 2. Wall Ball exhibits issues.

C010444-03 7817D

C010444-03 7820D -- Found in a Rev B (1977).  "2 or 3" shows 2.

C010444-03 7823S -- Found in a Rev B (1977).  "2 or 3" shows 2.

C010444-03 7829S -- Found in a Rev 8 (1980).  "2 or 3" shows 2.

C010444-03 7836E -- Found in a Rev B (1977).  "2 or 3" shows 2.

C010444D-03 8007D -- Found in a Rev A (1984) 7800.

C010444D-03 8015D -- Found in a Rev B (1977). "2 or 3" shows 2.  Slight issue with Cosmic Ark starfield (V2 PIC).

C010444D-03 8019E -- Found in a Rev B (1977) and a Rev 12 (1980). "2 or 3" shows 2.

C010444D-03 8031E -- Found in a Rev B (1977) and Rev 5 (1980). "2 or 3" shows 2.  Has a heat-related issue with Stay Frosty.

C010444D-03 8034E -- Found in a Rev B (1977).

C010444D-03 8036E -- Found in a Rev 5 (1980). "2 or 3" shows 2.

C010444D-03 8108 -- Found in a Rev B (1977).  "2 or 3" shows 2.

C010444D-03 8113D -- Found in a Rev 12 (1980).  "2 or 3" shows 2.

C010444D-03 8114D -- Found in a Rev B (1977).  "2 or 3" shows 2.

C010444D-03 8115D -- Found in a Rev 12 (1980).  "2 or 3" shows 2.

C010444D-03 8117 -- Found in a Rev 12 (1980).  "2 or 3" shows 3.  Stay Frosty issue with starfield (but not with Cosmic Ark).  Wall Ball exhibits issues.

C010444D-03 8130 -- Found in both a Rev B (1977) and a Rev 13 (1980). "2 or 3" shows 2.  Pac-Man/Pesco issue with stray dots.

C010444D-03 8139 -- Found in a Rev 12 (1980). "2 or 3" shows 2. Slight issue with Cosmic Ark starfield (V2 PIC). Also has issue with Stay Frosty (PIC).

C010444D-03 8143 -- Found in a Rev 13 (1980).

C010444D-03 8144 -- Found in a Rev B (1977).

C010444D-03 8145 -- Found in a Rev 14 (1980). "2 or 3" shows 2.  Pac-Man/Pesco issue with stray dots.

C010444D-03 8146 -- Found in a 6-switch Rev C (1977), Rev 12 (1980), and Rev 13 (1980).  "2 of 3" shows 2.

C010444D-03 8147 -- Found in a Rev C (1977).

C010444D-03 8208 -- Found in a Rev 14 (1980). "2 or 3" shows 3.  Pac-Man/Pesco issue with stray dots.

C010444D-03 8212 -- Found in a Rev 14 (1980). "2 or 3" shows 2.

C010444D-03 8214 -- Found in a Rev 14 (1980).

C010444D-03 8216 -- Found in a Rev 14 (1980) and a Rev 16 (1980). "2 or 3" shows 2.

C010444D-03 8222 -- Found in a Rev 16 (1980). "2 or 3" shows 2.  Also found in a Sears Video Arcade II (1981).

C010444D-03 8223 -- Found in a Rev 16 (1980). "2 or 3" shows 2.

C010444D-03 8225 -- Found in a Rev 16 (1980). "2 or 3" shows 2.

C010444D-03 8229 -- Found in a Rev 14 (1980).  "2 or 3" shows 3.

C010444D-03 8310 -- Found in a non-socketed Rev 16.  "2 or 3" shows 2.

C010444D-03 8319 -- Found in a non-socketed Rev 14 (1980).

C010444D-03 8321 -- Found in a non-socketed Rev 16.  "2 or 3" shows 2.

C010444D-03 8325 -- Found in a non-socketed Rev 16.

C010444D 8404 -- Found in a non-socketed Rev 16. "2 or 3" shows 3.  Also Found in a 7800 with different results - "2 or 3" shows 3. Pac-Man/Pesco issue with stray dots.

C010750-03 7739D -- Found in a "heavy sixer".

C011903-03 8138 -- Found in a "Vader" 2600AP (PAL) Rev 6.

C011903-03 8222 -- Found in a "Vader" 2600AP (PAL) Rev 6.

C011903-03 8307 -- Found in a "Vader" 2600AP (PAL) Rev 6.

 

TSU

C010444-11D 8141 -- "Found in a Rev B (1977). "2 or 3" shows 3. Has issue with Ebivision's Pac-Man and Pesco, and an issue with Cosmic Ark's starfield (V1 PIC).

C010444-11D 8142 -- "2 or 3" shows 2.

C010444-11D 8145 -- Found in a Rev 13 (1980). "2 or 3" shows 2.

C010444-11D 8203 -- Found in a Rev 14 (1980). "2 or 3" shows 3. Has issue with Ebivision's Pac-Man and Pesco, and an issue with Cosmic Ark's starfield (V1 PIC).

C010444-11D 8309 -- Found in a Rev 16.  Chips are socketed.

C010444-11D 8318 -- Found in a Rev 16.

C010444-11D 8348 -- Found in a Rev 16.

C010444-11D 8410 -- Found in a Rev 16 (1980). "2 or 3" shows 2.

C010444-11D 8413 -- Found in a 7800, Rev A 1984. "2 or 3" shows 2.

C011903-11 8151 -- Found in a 4-switch 2600AP (PAL) Rev 5.

C011903-11 8344 -- Found in a PAL 2600 JR, Rev. B.

 

United Microelectronics Corp (UMC)

UM6532 8611C -- Found in a 2600 JR, Rev C.  This chip exhibited a heat-related problem that affected the score counter and timer in Kool-Aid Man.  As the chip got warmer, the digits slowly moved to the right (GIF).

UM6526N 8637C -- Found in a 2600 JR, Rev D ("ACTION" not printed on pcb). "2 or 3" shows 2.

UM6526N 8639C -- Found in a 2600 JR, Rev C.  "2 or 3" shows 2.  Slight issue with Cosmic Ark starfield (V1 PIC).

UM6526N 8717S -- Found in a 2600 JR, Rev C. "2 or 3" shows 2.

UM6526N 8639C -- Found in a PAL 2600 JR, Rev F.

UM6526P1 6936S -- Found in a PAL 2600 JR.

UM6526P1 8846S -- Found in a PAL 2600 JR, Rev F.

UM6526P1 9134S -- Found in a PAL-B 2600 JR.

UM6526P1 9212T -- Found in a PAL 2600 JR, Rev F.1.1.

UM6532 8650C -- Found in a 2600 JR.

 

(UN)

C010444-20 8203-003 -- Found in a Rev 14 (1980). "2 or 3" shows 3.

 

("unknown")

C011903-11 7834 -- Found in a 6-switch (PAL) Rev 1.

CO10444-8637 -- Found in a JR, Rev C. "2 or 3" shows 2.

C010444-20 8001 8116-582 -- Found in a Rev 12 (1980). "2 or 3" shows 3. Has issue with Ebivision's Pac-Man and Pesco, and an issue with Cosmic Ark's starfield (V1 PIC).

C010444-20 8001 8123-618 -- Found in a Rev 13 (1980). "2 or 3" shows 3. Has issue with Ebivision's Pac-Man and Pesco.

C010444-20 8001 8126-641

C010444-20 8001 8152-A002 -- Found in a Rev 14 (1980). "2 or 3" shows 3.  Has issue with Ebivision's Pac-Man and Pesco, and an issue with Cosmic Ark's starfield (V1 PIC).

C010444-20 8706 -- Found in a Brasar Brasvision clone.

C010444-20 8001 8210-010 -- Found in a Rev 14 (1980). "2 or 3" shows 3.

KSC131 9024S -- Found in a Rev B 1/90 Dactar Video Game.

KSC131 9038S -- Found in a Dactar Video Game.

KSC131 9038T -- Found in a Dactar Video Game.

 

(VTI)

VF4013 4583 -- Found in a Coleco Gemini, Rev C. "2 or 3" shows 2.

E4002 8251 -- Found in a Colecovision Expansion Module #1, Rev G (1982).

E4002 8253 -- Found in a Colecovision Expansion Module #1.

E4002 8304 -- Found in a Coleco Gemini, Rev F. "2 or 3" shows 3. Issue with title screen graphics on He-Man (V1 PICS).

E4002 8313 -- Found in a Coleco Gemini.

E4002 8403 -- Found in a Coleco Gemini, Rev F. "2 or 3" shows 3. Pac-Man/Pesco issue with stray dots.

 

 

 

[+darryl1970]

I do not have any mods. I am running through default RF-to-channel 3. Whenever Pokey music plays, it's full of static.

 

I was able to play 1942 with Yamaha sound. I copied some Yamaha and Covox demos from my Dragonfly. They run in silent. Likewise, the two Covox demos are without sound. I believe they crashed to there I had to power off the system. 

 

Am I doing something wrong? Does the bad static sound like I could have a problem with my cart? 

[SainT]

The covox demos you cannot exit from, it’s just how they are written, so that’s normal. The audio on the covox demos are also very quiet, you would need to turn the volume up to hear it. And the headers need to be setup correctly (see below).

 

Could you provide me a video of the issue? Is there any problem with the video at all? My feeling is it could be a failed component on the 7800 currently, as this isn’t something I’ve come across. Although you have a dragonfly as well? No issues using that?

 

And this may be a daft question, but are you sure there are no mods to your system at all? These kinds of issues I’ve only heard of on modified systems.

 

Oh, and one final thing, make sure you are using Trebor’s ROM pack for any of the covox, ym or pokey demos. The header absolutely must be setup correctly for the ROM to work. You will see at the bottom of the game selection menu what mapper options are enabled. If it’s a covox demo for example, it must say COVOX at the bottom of the screen for it to work. I think with the dragonfly you have to manually enable different audio rather than it being picked up from the rom header?

 

And i’ve just noticed you say you can play 1942 with Yamaha audio just fine? This is sounding more and more like badly setup rom headers. Can you DM me the rom images which gives you pokey static?

Edited July 23, 2023 by SainT

[Guitari]

Hi SainT, further to our discussion a couple of days ago I have now located the MegaDrive 2 DIN to SCART cable. The colour is superior to the S-Vid mod but the screen image is off centre to the left and the far left of the image is therefore clipped.

Ideas?

 

Further - the 7800 does tend to crash the image (like an out of tune 2600 on a CRT - or sends the screen totally black) - this happens on the rare occasion with regular carts (tested again yesterday) - but is happening every time guaranteed after about a minute with the Game Drive.

 

2600 ROMS on the Game Drive are not running through the S-video mod (out of tune), but run ok through the GD's AV out (image to the left - with crashes after a minute). 

 

Pics of the S-video mod (taken today) attached.

 

Any ideas?

 

(Ballblazer music (POKEY) is fine now through the proper cable but still have to turn the volume up on the TV.)

 

Many thanks.

 

 

[SainT]

The AV out on the 7800 is very jittery, if you’re plugging directly into an LCD TV (which I think you are) then I would expect issues. Unfortunately the 7800 and the way it deals with backwards compatibility with the 2600 means the sync is very unstable. Modern TV’s do not like this at all, but CRT’s are fine with it.

 

I think the image is clipped because it’s set to 16:9 — can you set it to 4:3? It’s spot on with a CRT and the sync is as provided by Maria.

 

Unfortunately the best solution to this is to use a decent upscaler, I recommend the retrotink5x pro for the 7800 as it handles the sync jitter very well.

 

As for the audio volume on POKEY, I can’t see where the audio has been taken from. If you look at the 2nd post in this thread you will see r32 and r33 are the audio. Looking at the pcb with the board facing you such that the cart slot is at the back you should be taking the audio from the left side of the resistors not the right. 

Edited July 23, 2023 by SainT

[Guitari]

Thanks Saint,

 

4:3 still clips the edge! Now that I was not expecting! (Also 14:9.)

See pic. 

 

I'll try the upscaler. So you think this may solve the image crashes too? It is LCD I think. From 2009.

During crashes the 7800 is still nicely powered on. 

[+-^CrossBow^-]

16 minutes ago, SainT said:

The AV out on the 7800 is very jittery, if you’re plugging directly into an LCD TV (which I think you are) then I would expect issues. Unfortunately the 7800 and the way it deals with backwards compatibility with the 2600 means the sync is very unstable. Modern TV’s do not like this at all, but CRT’s are fine with it.

 

I think the image is clipped because it’s set to 16:9 — can you set it to 4:3? It’s spot on with a CRT and the sync is as provided by Maria.

 

Unfortunately the best solution to this is to use a decent upscaler, I recommend the retrotink5x pro for the 7800 as it handles the sync jitter very well.

 

As for the audio volume on POKEY, I can’t see where the audio has been taken from. If you look at the 2nd post in this thread you will see r32 and r33 are the audio. Looking at the pcb with the board facing you such that the cart slot is at the back you should be taking the audio from the left side of the resistors not the right. 

He has the magic knight s-video board. Those have an extra set of resistor (Obscured by his wiring in the pic), so that is why he likely took the audio from where he did. I've not really looked over the Magic Knight PAL install instructions since I don't service PAL consoles, but as I stated before, I would have to change the resistors the board came with to match the values of the NTSC consoles I did install a few of these into years ago.

 

[SainT]

11 minutes ago, Guitari said:

Thanks Saint,

 

4:3 still clips the edge! Now that I was not expecting! (Also 14:9.)

See pic. 

 

I'll try the upscaler. So you think this may solve the image crashes too? It is LCD I think. From 2009.

During crashes the 7800 is still nicely powered on. 

I don’t really know what an image crash is, but an upscaler will take an old TV signal suitable for a CRT and make it work nicely on an HDMI input. They do a fantastic job and look waaay better than trying to plug an old SCART cable into a modern TV. And the 2600 video issue — the 2600 has sketchier sync than the 7800 in some ways. The vsync is software definable, so can also be very jittery and again modern TV’s have big issues with this.

 

And I’ve just realised above you mention that Ballblazer is quiet through the proper cable. I assume you mean the MD2 SCART? In which case, that’s just how loud the output is. 🙂

Edited July 23, 2023 by SainT

[Guitari]

Thanks Saint. 

I wouldn't know about how the magic knight mod has been done as the creator of the mod did my installation. 

Yes the MD2 scart cable is what I'm using and I assume it's carrying RGB. It's a full pin scart plug. 

My 2009 flat screen has always been fine with every retro console I feed it.. And I have a lot of them! 

I've just tried to tune the analogue signal from the 7800's original RF out but it won't work so I think the modder has disabled it. 

I've been running the built in Asteroids (no cart inserted) and it doesn't crash/glitch the image to a black screen like the Game Drive does. 

Also tried without the seagull adapter and just the old fashioned joystick but still the screen glitches. I think the problem is my 7800 has a propensity for this intermittently, and the GD is just highlighting it on every boot. Whether the 7800 needs a service /recap etc I don't know. Maybe someone in the UK could take a look at it after I explore this upscaler option. 

 

EDIT - I can't spend $390 on the upscaler! But thanks for the recommendation. Inbuilt Asteroids has now been running for an hour and no glitches. I think the issue therefore must also be related to the cart slot.

Edited July 23, 2023 by Guitari