PLEASE INFO NEEDED mcs48 adapter question programming 8749

[techy]

Hi forum ,

Has anyone ever build the mcs48 adapter as found on mpu5.tripod.com ??

I am facing a strange problem and cannot find the source of it .

i try to program an intel 8749 , set vpp to 21 volt , choose the correct configuration in 98D12C3.

But , get a strange result when doing a blank check ( chip has been erased ).
0000upto 0400 the fill is 00 , from 0400 to 07F0 it is 04

So , i assume the adapter contains an error but where ??



Any help highly appretiated.



techy