I am trying to update the cpu and display program code to 4.0 on my T3. The machine will not work with the new chips. Any ideas? Any help would be appreciated!

Eproms are installed correctly. I had purchased new eproms from Marco with game code installed. The first set didn't work. I ordered another set and they didn't work either. I then purchased an eraser and programmer. Tried programming many different sets of chips and even tried older game code like 2.01 and 3.01. If I program a new chip with the same code that I have on the machine (2.0) It will work just fine. I should clarify that the pinball machine will read the new display code but not the cpu. Yesterday I read the manual front to back and found the following:

CPU Section:
The CPU is a 68B09E (U209) with up to 8 MBytes of CPU Code Space (U210). The CPU code is bank selected
by the use of U211 and each bank consists of 16 KBytes. 8 KBytes of RAM (U212) is available to the CPU. The
RAM is battery backed and has a write protected area. Battery back up is accomplished by 3-AA Cells (BAT1)
which have a TEST POINT VBATT to check the battery voltage status. The write protected area consists of 512
Bytes used for storing game settings. This section of RAM can only be written to when the coin door is open. The
Coin Door switch comes into the CPU on CN6-12 and is fed into the address decoding PAL U213. When this
memory protect signal is low writes to the protected RAM area are prohibited. Address decoding for the system is
accomplished by one PAL U213 and one 1-of-8 decoder U214.

I think the write protected area isn't allowing for the new code. I verified that the coin door switch is working.

Any thoughts? The game works fine with the original code but it's driving me nuts not being able to install the new code.

I've tried removing the batteries and unplugging the machine overnight. Then installed new eprom, then reinstalled batteries. Also tried many different combinations with and without batteries. Still nothing. I forgot to mention that the symptoms aren't always the same. Sometimes just the GI lights will be on. Sometimes the GI lights will flash and the RPG cannon fire at the same time. The symptoms will remain the same until I try other changes like relocating the jumper on JP1, then the symptoms change slightly.

They are identical, 27c040 eproms. I can program a new eprom with the 2.0 code and it will work in the machine. None of the newer versions of code will work.

The schematic for my machines shows a 27co40.

Interesting.. Although the schematic shows a 27c040, the firmware table shows 1m. However, I have programmed a duplicate 2.0 code onto a 27c040 and the game works as it should. Just can't get updated code to work. Is it possible that the original code was on a 27c040 and the updated code requires a 27c010?

The original eprom is so faded that I can't read the part number even with a magnifying glass.

It appears that 3Mbit is empty.

I think I'll erase the original and try loading the new code to it.

Thanks for you help! I am erasing the original and I am confident this will work. Unfortunately my eraser takes many hours and I can't wait to see if this works.

It's a chinese eraser I bought on ebay with no model number. Any suggestions for a better eraser. The original eprom worked with the 4.0 code!