A strange case of E0 bankswitch cartridge

[bladawietz]

Hello.
I made a PCB for Parker Bros E0 bankswitch cartridge using schematics on this site:
http://www94.pair.com/jsoper/2600_pb_bs.html
At first I put it in in my Atari 7800 system and it worked perfectly. All games I put in the ROM chip
were playable.
But after this I put this cartridge in Atari 2600 JR and unfortunatelly it didn`t work at all.

Some days after I went on retro gaming convention and tried my cart on various systems. Here are the results:
-On Atari 7800 and on old 2600 systems: works perfectly
-On Atari 2600 JR does not work at all

Apparently, it doesn`t like Atari 2600 JR systems.
Unfortunatelly I dont`t have an oscilosscope in my house and It is impossible to take home one from my work. So I soldered bunch of LED with resistors

to control lines of cartridge EPROM and observed starting sequence with camera with slow motion.  For A7800 (cartridge is working perfectly) and A2600 JR

timings when LED diodes lights up were different. I tried to put some small capacitors on control lines to change timings but with no luck at all.

Does anybody has any clue what is going on? I have Activision`s Decathlon cartridge which works on Atari 2600 JR but do not work on A7800.

Is this the same case? Unfortunately I do not have any oryginal Parker Bros E0 bank switch cartridge.