1965 AM Radio & Reverb System

[Mvannote]

I'm troubleshooting our '65 AM radio that has a reverb system in the trunk and a control knob under the dash just left of the steering column.
It seems both systems work since we've heard it work a few times now but not all the time. We are unsure how the system works, what the reverb does and how to control it. Anyone have knowledge of this system?

[Groover]

I don't have specific knowledge of that system, but there were plenty of them in cars in the late 60's and even early 70s. My understanding of what they really do is create a slight (adjustable) delay (or echo) that comes from the rear speaker. I believe it also removes some of the bass frequencies since they would muddy up the effect (high frequencies being more direct and easier for the ear to locate). The reason it's so complicated and large is that it's pre-computer-chip, so they have to do this with transformers and coils and delay loops, etc. Idea was to give you that concert hall effect (sound ringing off the walls) in your car. Cool if it still works, but I don't think anybody today would be blown away by the effect.

Rabbit hole warning: I grew up about 10 miles from Ye Olde Music Shop in Marissa, IL. Bob Heil invented so many cool things before computers for audio (Peter Frampton's Talk Box). Not saying that Bob invented the reverb for car radios, but that's the sort of stuff they were doing.

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