Hi,
I am working on placing a 1 mb simm into a nms 8250 according to instructions posted on Hans Oranje and Hans Ottens website.
First thing I did was taking out the ram chips and after that I tested the machine if it still worked. Replaced the ram chips with sockets and the machine is still in perfect shape.
Then I placed the extra ttl logic ICs into the machine and connected the simm.
When switching it on it gives the relais click so something is wrong.
I then tried to start with external memory which did not work.
Removed the simm and booted with external memory and everything works.
Even with 2 ram chips placed in the sockets with the mapper circuit still intact the machine boots.
What could be wrong? I don't know of the simm is working, purchased 4 cheap ones and according to seller they should work ....
Can try another one but don't think it will work. Is there any way to test the mapper circuit for the simm without placing one?
If necessary I can show a picture of the used simm.
Erik

