Eico hf90 tuner dial tube

[Perkinsman]

I have a nice old Eico tuner that still sounds nice and warm is relatively sensitive. My question is if anyone knows how the tuner dial tube is supposed to work. It indicates a beautiful solid blue line "in between stations" but once it locks to a station, the solid blue line separates in the middle leaving 2 shorter lines at either end. I would think that just the opposite should occur, ie, a nice solid line when the station locks in, much like an "eye" tube works..

Does anyone know how its actually supposed to work and more importantly what I need to do to correct it if its not working properly?

 

[wa2ise]

IIRC, that's the way it's supposed to work. Though I would have expected it to do what you were thinking, to get a thicker or brighter on a strong station. One could make that happen with an op-amp to invert the control signal.

 

[larryderouin]

www.magieeyetubes.com

Pull the tube # and match the diagram to the tube #. According to the info I could find it's a DM70, which increases in height as the signal strength goes up. Like an exclamation point. IM3-DM70 on the right in this picture from magiceyetubes.com

 

[cademan]

My HFT-90 also works this way so I figure that it is by design. It looks like a solid line when not tuned to any station and breaks apart in the middle to show signal strength. In the pic Larry posted, it uses the one on the right that looks like an explanation point.

 

[knockbill]

My HFT-90 also works this way so I figure that it is by design. It looks like a solid line when not tuned to any station and breaks apart in the middle to show signal strength. In the pic Larry posted, it uses the one on the right that looks like an explanation point.

Mine works that way also... seems backwards, but....

 

[cademan]

I just remembered my Knight KG-50 AM/FM stereo tuner also uses that tuning tube in the same way.

 

[Perkinsman]

Yep, it's a DM70 but I didn't see an exclamation point unfortunately, just a beautiful glowing, straight line.....So then mine is working properly, thats why I love this hobby-obsession, I learn something new everyday. I like the idea of putting an op amp in circuit to reverse the operation of the tube too!