65xe Issues with Cartridge (I've replaced Ram, plus OS & Basic masked roms)

[Gaetznes]

Back Story

Last month I received this in trade. It was known dead, or at least it was a pure red screen of death. Previous owner plugged a C64 psu into it. I replaced the ram, which got me to the black screen of death. After which I replaced the masked os with a eprom. Everything seemed to work at the time. Though I had not tested it with a cartridge. I only performed a few simple commands on the screen. After It booted into basic with no problem.

 

Current Status

After attempting to play a cartridge game. I received a multitude of different results. In rare cases Blue Max did appear on screen. however it has not worked after hitting the reset button. Other results range from black screen, frozen at the blue screen (Ready not showing up), a bunch of random characters appearing on the blue screen, and varied result from the self test.

 

Self test prior to inserting cartridge will state both roms are good. After inserting cart and after removal of cart. I will get a black screen, if the game doesn't boot. I then have to use the option key to boot into self test. At this point both roms are red. I have tried this with two alternative OS and Basic masked roms and one burned OS on a eprom. The masked roms are out of known working 800xl's. All having the same effect. After forcing the self test, I can generally get back to some other resulting screen. That i've stated above they generally have been frozen. I can only get back to the normal basic screen with ready if I unplug and turn off and on the system several times over a min or leave it sitting for several mins.

 

Each hard restart is followed by at least 10-20 second, prior to another attempt.

 

Other points of note

I've followed the instructions for he Black Screen post by brensk

Tested all the caps, and they are good

PSU 5.12vdc

Once a shipment of sockets arrive, i'm considering swapping out the the MMU from one of my 800xl

I don't own an oscilloscope

 

Does anyone have any advice ?

 

 

 

 

Plus this screen came up once.

 

[shoestring]

Each hard restart is followed by at least 10-20 second, prior to another attempt.

 

Does your PCB use 8 DRAMs or the 2 x 4464s ?

 

4464s can take time to clear in between power cycling. I've definitely noticed this with my 65xe ( which uses 2 x 4464s ) and my Apple 2e platinum after power cycling or hitting reset.

Edited March 15, 2018 by shoestring

[JR>]

Did you check the power supply voltage under load? I've had similar issues with marginal power supplies that supplied much less voltage under load.

[+DrVenkman]

I'd be checking the MMU and the 6520 next.

[Gaetznes]

Ok to answer the above questions.

 

The ram is a quantity of 8 (4164)

Voltage with a load on it, is 5.08v.

 

I'd be checking the MMU and the 6520 next.

 

That is also the plan, well the mmu was a consideration. I hadn't considered the pia chip. Good thing I have spares to follow that recommendation.