Good advices for a newbie (threading tools lathe)

[PJs]

Based on what you said above, the first thing I would do is squirt some cleaner on the FG pots and switches, like you said. Then I would hook it to the TEK scope and run it through the full range (slowly) while watching it on the TEK scope. You should get some indication of any issues with the quality of signal out. Also I wouldn't waste time on the Square wave at this point. It will give you some clues later but not necessary to diagnose where the issues are. If it's clean Sine all the way through you should be Ok to step 2. If not, note the frequencies where it distorts or has sudden drops/increases in amplitude. Another thing with older equipment like this is sometimes the solder joints get a little cold or corroded. Just reflow them and try again.

Next is the probe of the scope to the input of you preamp and its output all while sweeping your FG (if its clean from test/repair above). You will probably notice some slight degradation of signal quality as you move through the amps and to the coil...and you can look at your Real Gain levels and Q.

I didn't notice any new Faraday cage in the pictures like we talked about and that may be contributing to your problem hooking the scope...Or it might be an impedance problem loading from the scope/probe. Do your probes have a 1x/10x switch? Might try the 10x if you do. If they are only 1x it could be part of the problem you are seeing. I see no issue with measuring the KV measurement even at the RF with the TEK scope, but I don't know that scope very well. The TEK is a 60mhz...so it should handle your stuff fine. The probe may also be tired or have slight cracks in the housing? Also unloading the KV for measurement may not give you a real world look, being unbalanced.

What kind of Pot is on your amp - wire wound or carbon, and what kind of volts & ma (watts) is across it? A wire wound on a circuit like this may give you some inductor type issues particularly at the bottom end, by taking on some of the spurious emissions going on in proximity. Might try a quality carbon pot to see if it's any better.

You may have some issues with impedance matching throughout or maybe some distortion issues in the circuit, but I thought what I heard on the videos was pretty good over all with only some minor glitches going up the scales.

Like I said way back in the thread...be as methodical as you can, start at the input, look at and solve one thing at a time, Document the problems and fixes as you go, then to the next till you get it the way You want it at the plasma end!!

What you've done here is remarkable and really hasn't been done in years except for a few wild and crazy guys out there/here who like to Finger it out and make it work. Again, Great Job...Diligence and patience will pay off.

~PJ