My TP4 waveform ok?

[homefire]

Need to go to bed! Tuckerd out and need to go to the flea market in the morning to sell my fleas! Do you need a 16ft jon boat? Rugger 10-22 stainless with a scope? Wizard Bike moter?

[GT Blocker]

Think I found it

Hey Homefire,
Look at pg 3 of the build instructions, Fig. 5. note that there is no R15, 10K resistor in that schematic.
That is the way I did the build.
Now...take a look at the Rev C2, Option 2, schematic for the same part of the circuit. Hmmm...an R15 10K.
Once I removed the shunt across R15, the scope image looks right (-minus the new ringing problem, but that's a damping resistor problem, I hope).
I'll tweak the damping resistor tonight and post the new trace shot later(Wrong or right).
If this is the problem, it could happen to anyone (and I wish it had, someone would have seen this before ).
Thanks for all the help.............

PS- I'm using the IRF734, which might come into play...

[GT Blocker]

New TP4 waveform...

Here's the new TP4 waveform... .1mSec sweep, ~x10 horizontal mag, .2V/div,



I get it right?

[GT Blocker]

TP2 still has a weird base

TP2 looks just as it did in post 5 of this thread though...wtf?

Must be something simple/stupid......

[gwzd]

Here's the new TP4 waveform... .1mSec sweep, ~x10 horizontal mag, .2V/div,

[ATTACH]6153[/ATTACH]

I get it right?

Nice picture GT Blocker! How do you get it? I have an old scope that goes up to 14GHz, but has an old GPIB port so I take pictures sometimes. Mine are not as good as yours. It would be interesting to know how do you get such nice shots.
Regards,
R.A.

[GT Blocker]

Pics of waveforms

Hey there gwzd,
I use a digital camera, no flash, 1/15 sec, 200iso. Use the IR auto focus in a dim room. A tripod helps at the slow speeds, but I don't bother as you can tell from the first pics in the thread.
Don't focus on the screen! The IR beam glares back on the sensor from the face plate on the scope, much like the flash will. The sensor can't cope, so you'll be out of focus. Focus just to the side of the screen on the knobs, et al. After focus locks in, move back to the screen and grab the shot. Steady yourself and the camera well, or breakout the tripod. I also backlight the grid enough to showup in the shot.
Takes a few tries to get it right, as you can see by following my pics through the post. Hope this helps.
BTW - What is a GPIB port?

Lastly, what about my wave forms? I'm gonna check the emitters on the scope for Q1 & Q2 later. I don't understand why my traces don't look like Carl's. The output at TP4 Dips nicely with metal over the coil though....And the right hand side still starts higher and slides down to the level of that last pic, where upon, it stabilizes. The scope is 'nuts' for a few secs after I fire up the HH, and the settles down to that last waveform post.

Any thoughts? gwzd? homefire? anyone?

[homefire]

Something is wacky! Your not getting the sloping edge to be sampled.

Combination of R-11 and some reactance? Replace R-11 with a heavy duty pot to test?

What schematic shows the use of the second coil? Problems with inductive ballance?

[GT Blocker]

Running one coil atm

Hey homefire,
I removed the damping resistor R14 for the DD coil and the 2nd coil, jumped to single coil config for that last trace shot. I used a pot to find the damping resistor R11 value. I just finished checking the emitter output of Q1 and Q2. The Q2 trace is clean, not so sure about Q1...
My TP1 does show an upwards 'glitch' just before the pulse. Q1 nearly duplicates it, though it vanishes by the gate of Q3. Looking at that atm.
The schematic is Rev D1.

[GT Blocker]

Weird waveforms or not...

Update:
Weird waveforms or not, the beast works.
Nice low motor boat putter until metal gets close, then up goes the pitch (VCO mode). I need to get the pulse width down more than stock and probably limit my coil current a bit, but cool!
bzz....bzzz..bbbzzz.....bzzzzzzzz....wheeeee...bbzzzzz (ya know what I mean).

So what's with the waveforms still looking 'odd'?

Thanks for all of the input and help, guys!

WARNING: I'll soon have a new batch of questions.

[Molzar]

GT,

Your last waveform on TP 4 looks good. Carl's waveform in the artical is incorrect. See http://thunting.com/geotech/forums/s...ad.php?t=12535

Also good idea to read all posts in the HH forum. Lot of information.

Molzar

[homefire]

Link Mozal posted, Carl states he may have taken snap of TP-4 Before adjusting. Maybe with some tweaking, you can make it better!


Bottom line! What to hell happened.

[learner]

I am no way near as good as you guys are on this electronics stuff...but maybe your scope is not working properly..is there anyway to test it?

just a thought.


cheers
dave

[GT Blocker]

Current update...

Molzar, homefire, learner...thanks for the replies!


Molzar - Thanks for that link...I wondered what was going on.
I did a search of the HH forum before I posted this thread, but it looks like I missed it. After the TP1 title and the first few posts of that one I probably scanned through and missed the exact thing I was looking for. Oops.
I went through all of the posts in the HH forum before I started this project, but it's an amazing amount of data to absorb.
I wish there were a FAQ sticky just for the already solved problems (and correct waveforms, schematic errors/changes, etc...). I'm not the best with the forum search function and usually end up with too much data off topic.

Hey there homefire... It's like Molzar said...no problem on the waveform. Since I'm used to worrying about nothing, no biggie. I appreciate all the help. Looks like I have a bad Q11 though, since I have no volume control and have to send the speaker output out to amplified computer speakers to hear it. Even then the volume is low. Signal is good at the base of Q11 though.

'lo learner...Na... the scope's fine. The 'clipping' (?) at the start of the TP1 pulse was from the extreme end of a pot setting. I don't know if the left hand side dip is normal for TP2 or not, nothing I do seems to change that. I'm a digital kinda folk and I have never seen ringing on a scope until this project (pretty cool looking too). I have a lot to learn about analog...


So far:
Nice machine! (If I keep my 'beverage' can nearly three feet away, that is!) Even with all of the noise in the room (computer/printer/scope, etc), and myself unsure as to how to get the most out of it, the un-shielded mono coil picks up a 9 grain little nugget at 4".
I'm sure things will change a bit after I shield the coil(s). Switching over to the DD coil config is next. Understanding that nulling thing and all should be fun.
Thanks again for all the help!

[GT Blocker]

Q11 was bad

Yup..Q11 was bad, guess the magic smoke escaped. The audio is now working fine and can just about be too much at max with the headphones.

What a cool little machine. Now for the tweakin'....

[gwzd]

Hey there gwzd,
I use a digital camera, no flash, 1/15 sec, 200iso. Use the IR auto focus in a dim room. A tripod helps at the slow speeds, but I don't bother as you can tell from the first pics in the thread.
Don't focus on the screen! The IR beam glares back on the sensor from the face plate on the scope, much like the flash will. The sensor can't cope, so you'll be out of focus. Focus just to the side of the screen on the knobs, et al. After focus locks in, move back to the screen and grab the shot. Steady yourself and the camera well, or breakout the tripod. I also backlight the grid enough to showup in the shot.
Takes a few tries to get it right, as you can see by following my pics through the post. Hope this helps.

Thank you very much for your excellent explanation, I'll give it a try when I get a few minutes free of work.

BTW - What is a GPIB port?

It is a communications protocol mainly for measurement instruments. It was developed originally by HP, but nowadays is an industry standard. However, more and more USB is taking over and perhaps some day the GPIB will be just history.

Lastly, what about my wave forms? I'm gonna check the emitters on the scope for Q1 & Q2 later. I don't understand why my traces don't look like Carl's. The output at TP4 Dips nicely with metal over the coil though....And the right hand side still starts higher and slides down to the level of that last pic, where upon, it stabilizes. The scope is 'nuts' for a few secs after I fire up the HH, and the settles down to that last waveform post.

Any thoughts? gwzd? homefire? anyone?

I'm not familiar with the circuit you are referring at, but I'll take a look and post you some ideas back.
Regards,
R.A.