The EWI3020m's "non-volatile" memory battery is soldered directly to the main PCB, which means you have to take the whole PCB out in order to desolder and replace it. I took my newly acquired EWI3020m apart a few days ago to replace the hardwired battery with a coin-cell battery holder.
Every one of the boards are single-sided Phenolic Paper PCBs populated solely with through-hole components and even jumper wires. You can see in the pictures that even some of the ICs (the CEM3374 VCO and EPROM for example) are socketed! Certainly makes repairs a happier experience.
Here are a few pictures of the disassembly and the main PCB itself; apologies for not having a suitable scanner!
Main PCB Images
|EWI3020m Main PCB|
|EWI3020m Main PCB (traces)|
|Composited view of the component-side and trace side|
Re-Assembled with Battery Holder Installed
|Coloured wires are the "instrument in" cable|
|"Instrument In" connection to the I/O PCB|