Testing the TK Tar Baby

[picowatt]

The waveshape is broadly similar but becomes more sinusoidal as the amplitude increases and the relative contribution of the distortions decreases.

For this run here, as I thought I said in the post, I am using the regulated PS and the pot/10R series resistance, no 50R, and yes, the bias is floating. I am not, therefore, using the inverter, just straight DC from the PS, hooked up "backwards" to the FG inputs at the board, so that the negative supply lead goes to the Q2 sources and the Q1 gate and the positive supply lead goes to the Q1 source and the Q2 gates. The power supply is set to about 5 volts or so and is adjusted to make osc amplitude increase and to regulate the current through the system as indicated on the CVR and the inline ammeter. This is the easiest and most stable way to make the oscillations and the waveshapes that result in negative mean power products.
A battery can be substituted for the PS and the only difference is that the bias voltage is no longer regulated and will decrease. The inverter running off the PS or external battery, ditto. The inverter running off the lowest of the main battery does cause some differences in the waveshape but as I've shown the negative power product still emerges.

So I have the A channel probe at the battery itself, tip to +48 V nominal, reference at 0V right at the battery terminals with no intervening wires and no decoupling capacitors, and it stays there. And I have the B channel tip directly on the CVR right at the body of the resistor, on the transistor side. And I am moving only the B channel reference lead from one point to another.

The effect of moving the probe reference lead on the CVR trace is about the same when I am using decoupling caps, which do smooth the battery trace considerably (but not yet perfectly) or when I am not.

I made a video but I'm hesitant to post it because it will start another three-page rant from YKW. Oh.... what the hell. I'll process and upload it. Should be viewable in half an hour or so.

TK,

Sounds like strays, added inductance, or possibly, if you were to add more L, you are resonating a real or stray C.

You should never have used a green wire.  As in the JT vid, , green wires are magical.

PW

[TinselKoala]

By the way, all....

I realize that the YT video quality is not all that great. I shoot the videos in 16:9 full-res HD on my Panasonic camera and they are typically 500 MB-1GB in size in .mpg format. Then I downconvert them to .avi using WinFF which compresses by about a factor of 10. Then YT does its own thing converting and compressing to .flv or whatever.

Anyway, I have the full resolution copies of most of the videos still available and they do look much better than what's on YT. If anyone wants a particular high-resolution version of something you've seen on YT from me, let me know and I'll upload it to a file-sharing site and you can download it for your viewing pleasure.

[TinselKoala]

TK,

I would suggest you keep the probe gnd leads as short as possible, and together at all times.

Gladly.  Would you mind making the same suggestion to ...er..... never mind.

Whatever is happening in the probe leads it's also causing real changes in the oscillation amplitude in the circuit, as shown by increased load heating and the real current on the inline ammeter. So the increase in the CVR amplitude is a "real artefact" in the sense that it is actually happening and causing more current through the mosfets, but is caused by the fiddling with the probe ground positioning.

Right?

[poynt99]

Agreed.

If waving your hands around the circuit can affect the oscillation amplitude and heating, it's not unreasonable to expect that probe grounding can have an equal effect on things.

[picowatt]

Gladly.  Would you mind making the same suggestion to ...er..... never mind.

Whatever is happening in the probe leads it's also causing real changes in the oscillation amplitude in the circuit, as shown by increased load heating and the real current on the inline ammeter. So the increase in the CVR amplitude is a "real artefact" in the sense that it is actually happening and causing more current through the mosfets, but is caused by the fiddling with the probe ground positioning.

Right?

TK,

Right?... Right

I've always felt that the osc amplitude could be increased for a given Ibias, which I assmue is remaining constant.

As to the rest.. smart ass.

PW