[Greggshere]

Hi guys, I have an Eico 324 that I bought off of Ebay a few months ago. It had been recapped (mostly) and a few resistors changed. Anyway I recently got a counter hooked up to it and found that on all frequencys it was a dead at the same point about 430KC and after, like the tuning cap has a short or something. Anyway, I went ahead and changed the remaining caps and resistors that the other guy didn't, tested the tubes and removed the silicon rectifier and replaced it with a 1N4007 diode resistor and new electrolytic caps. Today I started setting the alignment and it is pretty dang close, but I still have a dead spot on all frequencies and then it comes back. On B setting it is dead between 430K - 600KC and then it comes back and it pretty dang close on the counter. It is the same spot on all knob positions. Any ideas as to what is causing the dead spot? I see no contact on the plates of the tuner cap. Does anyone have any ideas?
Terry if you remember when I was using this when you helping set the 60L I was experiencing the drop out.

[bakerm]

You might try using an ohmmeter and measure the resistance of the tuning cap (should be open always) and see if it shorts at those knob locations in questions.
With out power of course.......

[morzh]

>>>>removed the silicon rectifier and replaced it with a 1N4007 diode resistor


Didn't quite get this.
That is I think I know what you meant by that, but .....

[Greggshere]

Hey morzh, I left a few words out, sorry about that. I used the 1N4007 diode and a 2.4K resistor and two .22 electrolytic caps to replace the selenium rectifier. (I also said silicon rectifier). Duh!

[Chas]

The contact of the rotor wiper on the tuning cap may have a spot of corrosion where it sat for years. Using a blade of stiff but very fine sandpaper, slip the paper under the contact blade with the paper side facing the blade. Gently pull the sand paper through. Do that to both blades at the point of the "flat-spot"

YMMV

Chas

[morzh]

It actually needs 2.4K resistor to compensate or is it the combined new value?

[Greggshere]

Hi morzh, I used a 2.2k 1% resistor with the 1N4007 diode. I didn't have a 2.4k. My choices were 2.2k or 2.7k. I was replicating a selenium rectifier replacement a guy sells on Ebay for the 324. I figured I had the parts, so why buy his when I can make my own.

[Phlogiston]

Might not be dead at that spot - might be noisy. The counter I installed won't lock if the signal is too low, too high (level)  or if modulation/noise is above about 20% (mod turned on and about 1/4 turn). On the higher freq settings the unit uses harmonics that can be accompanied by noise and birdies (missing bird imogi) .

[Greggshere]

Ok I got it fixed, yay! It was a slightly bent plate/fin on the variable capacitor. It was a definite dead spot, as my capacitor tester would drop out when I hit the spot and would stay dead until I hit a good spot again.
I had looked at it really closely as best I could with it still installed, but couldn't see any defect. I completely removed it and on my bench got the same result when testing it. Using my large magnifying lens and light, i finally saw one fin on the bottom side that was just slightly bent and touching the one next to it. I carefully straightened it and bench tested it and SUCCESS!
I reassembled everything and got it all aligned using the counter. It is now working great on all ranges.