The EICO 378 Audio Generator, part 1: Observations.
Friday, September 11, 2026 at 09:22:22
I picked this guy up from an online sales site for next to nothing - I assume because it’s not a desirable Heathkit unit and people don’t seem to care much for these late-model EICO devices. Everyone wants the stuff with eye tubes…but I was just looking at another siggen because you can’t ever have enough of those.
This guy was probably made in 1968, because of the late ‘67 date on the meter.
The underside is decently laid out, but there’s some chaos here.
Of note is the mix of old and new carbon resistors, and the old and new style electrolytics. Those old brown carbons probably need to go, but we’ll check them in a later post.
Here’s the money shot:
I don’t necessarily like lamp being lit like that…but it’s not flickering. Usually when these go bad, you’ll get that circuit trying to balance itself and it will go up and down as the lamp gains resistance from heating up and then falls back when the resistance gets too high. However, the output is rock solid…so maybe this one is supposed to operate like this? Others of this type I have do not do this. It could be a symptom of wildly out of tolerance resistors, so…back to checking those in a later post!
And finally, here is the output. Nice clean signal.
It looks like this won’t need a whole lot, other than some of the potential failures being replaced before they fail. Being 60 instead of 80 years old probably helps there.
Stay tuned for the next part of this series. We’ll dig into the components and see what’s what!
Next part of this series: Coming soon.