The EICO 150 Solid State Signal Tracer Part 4: It’s the speaker.
Monday, May 4, 2026 at 11:20:37
In the last part, I noticed that the output transformer appeared to be installed incorrectly in the tracer. While the color codes were indeed wrong, the kit builder did install it correctly. This was verified with an impedance check revealing about 136Ω on the primary, and about 5Ω on the secondary. That was measured at 1KHz, and is fine for a transistor output circuit. It was reinstalled in the correct direction.
Moving forward…the only thing left is the speaker. And yes, it’s bad. This should measure 8Ω approximately in both DC resistance and AC impedance. You can clearly see it doesn’t - 0.3Ω is not a good speaker, and I’m surprised there was enough voice coil for it to even work.
I don’t have an 8Ω speaker (one is on order) so I grabbed a small 60Ω unit from a stash of Olson parts and measured it. You can clearly see it reads 60Ω both AC and DC.
Two of these in series would be fine for testing, but I waited until I could get a small speaker for testing. I picked up one at Micro Center and the volume level increase is quite noticeable. It’s too small for the unit, so I ordered a generic 4” unit from an online vendor.
Why did it go bad? The unit doesn’t have any noticeable moisture damage, so that’s probably out. It was mentioned that someone could have used the test speaker function and overpowered it - that seems most likely. It’s only a 400mW unit, so anything modern would blow it apart.
I should have a replacement for this device within a few days. Stay tuned!
Next part of this series: Coming soon.
Previous part of this series: https://wereboar.com … t-3-its-wired-wrong/
Wrapup and final thoughts: Coming soon.