TP4 waveform wrong?

[Reg]

Ah,

All looks ok now. Also, your pics of the TP without the coil connected explains Carl's pics.

Thanks for clearing that up.

Yes, your pic looks correct.

Now, I am assuming you used aluminum foil tape for your shielding. Is that correct? That would explain the droop or what is the long delay to

[exciter]

okay, now this should be right?
connected my coil...

[exciter]

I connected it to the bridge right from D6..
I have no coil connected. Timebase 0.1ms

[Reg]

Ok,

Now, we have a new problem. You should have a signal that goes positive that isn't there.

Adjust your pulse width pot to maximum resistance and see what happens to the pic. This should give you a pulse width of about 75 usec.

Do you have the scope ground connected to the HH ground?

We still need to make sure everything is correct. Once I know the scope ground is connected to the HH ground and I see a pic of TP 4, I will be able to tell more. From what I see now, I am not sure why your pic doesn't look right. Maybe it is because the pulse width is at minimum. That is why I want you to adjust for maximum pulse width.

Reduce the sensitivity of the scope so the signals are smaller just to make sure the signal I am looking for isn't cut off.

Reg

[exciter]

okay this worked.
picture:

[Reg]

Hi Exciter,

It appears you are using two plain insulated wires for your scope leads. Is this correct? If so, connect the scope ground lead to the pc board ground connection. The scope input then is used to look at TP 4.

Now, if you are using plain wires and not a scope probe, then this is why you probably are having trouble getting your scope to stabilize or sync correctly.

Reg

[Reg]

Exciter,

We need to make sure the scope pics are correct before trying to adjust things. So, we need to get the scope setup right.

Your pic of TP 4 should more like the pics in the HH article. We need to get that to happen first. Once we do that, we can continue

Now, I just saw your latest pic and you should only use one ground. In the latest pic, it appears you are doing that. So, now, try switching the two leads and see if your pic doesn't invert.

Reg

[exciter]

Hi Reg.
Could be also look like in this picture. I plugged my black Ground wire there because if im using my Oscilloscop probe, i use an extra ground.

[Reg]

Hi exciter,

It is hard to tell, but does you scope have banana plug connectors? Also, do you have three different connectors being used? If so, why?

I see a red connector plugged in. What does this do? I also see a plug going into the 1m input. What does this do?

It appears you have a connector on the vert input. What does this do?

I suspect you don't need all three.

If you do not have anything connected to the vert input, then try switching the other two leads and see what happens.

Reg

[exciter]

"For starters, I would try to get the main delay down as short as possible. I would start out with a 100 usec pulse length, a 10 usec sample time and a second sample at a couple of hundred usecs later than the main sample."

Okay this big pulse should be my pulse length, which i can calibrate with R2/R3.
I have set it to 50~75us.
You said 10usec sample time, dont you mean the sample delay????
where should the main delay be, if not there, where i added the 10usec???

[Reg]

Here is your pic with my evaluation of what is what.

[exciter]

i mean its the main sample delay.
picture:

[Reg]

Post a pic of your scope's controls.

Now, when you adjust R 46, you should see a change in distance between the first two bumps.

The area you marked xxx on your pic is the secondary delay.

Getting back to the pulse width, when you adjust R 46, you should see the distance between the first and second bump change as well as the distance between the 3rd and 4th bump. If you reduce R46, the distance between the first two bumps should narrow.

The area you have marked 10 usec is not the pulse width, but just the width of the first bump. So, that is not the pulse width.

Reg

[exciter]

upside down??
i cant see any invert buttons here.
its an old hameg 312 dont know which rev.
have just a +/- Button, but its not an invert...
yes with R46 i can change width of both, main and secondary.
in according to Fig.6 i thought, that the space which i have marked with 10us between the main pulse, and the first bump is the main sample delay.

[Reg]

Hi Exciter,

First, your pic is upside down. Do you have your scope on invert? If you do, you might want to turn off the invert.

Now, when you carefully look at the pic you posted, you will see 4 small bumps. The left trace half shows this better than the right half.

Now, I suspect the first two bumps are actually the pulse delay and the distance between the first two bumps is the pulse width. The later two bumps are the secondary delay and the distance between them is also the width.

To know for sure, look at the same test point and adjust the sample width, R46. You should see the distance between the first two bumps narrow or widen.

Right now, I suspect you have a sample width of about 60 to 70 usec and not 10 usec.

The bumps happen when the gate opens and close, so that is why you have two for each sample. On very short delays, the bumps to not recover and look more like one bump.

Try moving the delay pot and you should see the first two bumps move left and right. If you adjust the sample width, you should see the first two bumps come closer to each other or separate.



Reg