Coleco Tabletop Arcade DIY Perma Power

Today I was doing some browsing looking for an answer to a DIY Perma Power for my Coleco Tabletop Arcade machines.

The mini arcades run off of 4 C-cell batteries, 4 x 1.5v.

The Coleco Perma Power Adaptor is 9v.

Does this mean the fake C cells with the Perma Power have resistors in them to reduce the voltage or can the Coleco Tabletop Arcade machines run off of 9v?

I have a 9v power supply and can easily make some fake C-cells, I just worry aboot putting 9v to them wihout checking first, this is not something I want to fry.

I would not assume that the A/C-to-battery adapter is purely a shape change without being able to look at the schematic of the Tabletop Arcade itself. i.e. I wouldn't assume 9VDC would be safe.