French (SCART/Peritel) Atari 7800 - no color in 2600 mode

[+slx]

I finally got around to set up my prized French 7800 on a B&O MX4000 CRT TV just to find it doesn't show color in 2600 mode. 7800 mode is fine but regardless of ROM and PAUSE button setting it only shows B&W when using VCS carts.

 

I have searched here and found the VCS color pot but this is hidden beneath a daughterboard that would need to be unsoldered to reach that pot (which seems to be glued in position anyway, at least the 7800 pot is).

 

There are two more pots on the Peritel daughterboard. Moving one of them (the lower one on the pictures which is connected to the VID point on the motherboard below) changes brightness in both 7800 and VCS modes while moving the other has no visible effect.

 

I have PMed a couple of declared SCART 7800 owners to ask about their experiences.

 

Any hints welcome.

 

I add some pictures as I found no information about the internals of this model online.

 

Serial No. label (out of warranty by now )

 

Rev. C motherboard (CO300633-001) overview:

 

Daughterboard hiding VCS color pot (CO300452 Rev.C):

This is mounted to the mainboard at the position marked CS2 and with the pins around the U4 outline. It's hard to peek beneath but as it doesn't budge when moved I assume it is soldered at all position (no socket).

 

Peritel Daughterboard (CO301645-001 Rev. B):

 

Sorry, can't seem to get the top and bottom pics to rotate correctly.

 

P.S.: while having a VCS colour blind 7800 would be a great excuse to finally mod and set up my light sixer, I'd really prefer to have a single console for both VCS and 7800 games to save space.

Edited April 2, 2018 by slx

[Djoulz]

Hi,

Did you finally find your answer ... Because I've also trouble with this machine !

[+-^CrossBow^-]

I could be wrong here..but I'm pretty sure that hole in the PCB covering the color pots at the lower left of U2 is to access the 2600 TIA color adjust. Might hit that with a torch and see if you can then see the slot to put a screwdriver in there to adjust it. Also they aren't really glued, they used loctight or glyptol to keep the wheel or adjustment in place but you can easily crack it loose. After making such adjustments I will usually apply nail polish back over the wheel and corner to keep it in place and still be easily cracked loose in the future if needed.

[ongikong]

Yes, you can reach the pots from the underside of the mainboard. There are 2 holes where you can put a small screwdriver in.

There was another thread 4 days ago which talks about the B/W-2600-problem on a 7800 SECAM machine:

http://atariage.com/forums/topic/291151-atari-7800-secam-question-and-information-help/?p=4274489

 

I have a similar problem with my S-Video modded PAL machine but not on all devices :-(

Please keep us updated here.