It has Begun

[edgobb]

From there I put two nuts on the bolt and aligned them and stuck the bolt into my variable speed cordless drill.

Up chuck.

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I then attached the wire to the bolt and strung it through the solder port and gave it one wrap. I stuck a clothespin on the two bolts and aligned it with the soldering ports so that I could count rotations.

Pointer installed.

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From there I can keep tension on the wire with one hand and press the drill button to control the speed with the other. Every time the clothespin passes the straight down position, I count out loud.
Be careful when you are done!!! If you let up the tension on the wire, the entire coil will unravel within seconds!@% Then you will curse. And curse you will.

It works pretty well and I don't really think that it has any more potential for turning into a disaster than the hand winding does. Patience and caution will reduce the errors....certainly not prevent them.

Rube Goldberg.

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I've run out of time for now. I hope that everyone's build is going well. More to come, including my embarrassing idea for piece base painting.

Cheers!
Ed G.

[AndrewB]

Hi Edgobb,

To measure the current at the 1k5 resistor you need to place your multimeter in series with the resistor, i.e. disconnect one leg of the resistor from the circuit and connect this leg to one lead of your multimeter. Make contact on the circuit board with the other multimeter lead at the place where you desoldered the resistor leg.

"It should only draw a couple of mA at this point through the 1k5 resistor next to the pic." -> It should only draw a couple of mA at this point in time through the 1k5 resistor next to the pic.

Hope this makes sense.

Andrew

[edgobb]

Makes perfect sense, Andrew. Thank you. I know that it needs to be in true series, but thought there was some trick being described.

Ed

[Tony]

Just to clarify this, the current is measured in series with the + supply to the PCB as at this point the only thing connected to it is the 1k5 resistor feeding the PIC. You don't need to measure the specific current through the resistor and if the total current to the PCB is higher at this point it indicates a fault.

[Tony]

How is the build going or have the coils finally forced you to give up ? - I forgot to say thanks for posting earlier.

[edgobb]

No Tony, I have not given up. I have been distracted as of late. I have 6 minutes of music that I have to write, plus kid's science fair is this week. And blah blah blah.

I will be moving back into this hopefully soon.

I have done some research and experimentation regarding the coloring of the board engravings. I have tried some fabric paint, but I must not be getting the correct stuff. Anyone else out there been trying to fill those grooves in with color???

Cheers,
ed

[edgobb]

I've been away from this for a while, but am now back in gear. Got a tube to light up and everything!

I've got a question about the M3 washers. Where do they go? Are they supposed to be used between the nut and the coil base when attaching board coils to the board pcb?

Thanks, and I'll get back into picture mode here soon.

Cheers,
Ed

[edgobb]

So I don't know what I did, but I created me a really big problem tonight.

I've been working my way down from the "top," meaning the side opposite the power leads. (Refer to above pics.)

I've stuffed that top row of the board pcb. (16 holes worth.) I tested the voltages and amperages as listed in other posts and all was well. I installed the first board coil and finished a piece and BAM! The tube lit up exactly as it should have.

So I wound 7 more board coils and installed each one, testing before adding the next. All 8 went right in and the tube lit uniformly when set on each coil. I was feeling great!

Now once when I had it powered up, the positive alligator clip that I use to apply power to the ferrite filter slipped off and hit something when it released. I saw a little puff of smoke from somewhere, but wasn't sure from where. I reapplied power and tested voltages again as well as whether each coil lit up the tube or not and everything worked just fine. (I thought I had escaped catastrophe.)

So onward! I wound 8 more coils, checked them for consistent inductance numbers and then attached them to the pcb without connecting the coil wires yet. I planned to attach the wires one coil at a time, testing as I went.

I attached the wires from the first coil to the brass screw and bolts, applied power and set the piece on the coil......nothing happened. I then put the piece on every coil in the previous row and it worked fine. Hmph. I'm a pretty experienced builder and can usually troubleshoot my way out of problems, so I start probing with the VTVM. I'm not getting any indication that there is anything at all (good or bad) going on with any of the coils in that second row. I double check the polarity of the diodes and caps...all good.

I started reading the forum looking for wisdom. I wondered if my little alligator slip fried a transistor and found Tony's advice to someone else..."If it has more added now, quickly check the voltage drop across each of the 6r8 resistors, that should show which pair of transistors are in trouble." Now here is where I did something STUPID. I intended to first check the voltage across the top right 6r8 and accidentally grabbed the negative clip of the power supply instead of the one attached to my VTVM. When I touched it to the 6r8, yup you guessed it, I let the smoke out of it. Well bloody hell. So I pulled and replaced it. Powered back up and everything was the same as was before. The top row works but nothing on the next row.

Next I read some more. Tony suggested checking the 2R2 resistors for someone else's problem and I found that the one closer to the second row was completely open. I then decided that was what happened when my clip slipped off last week and replaced that one. So I power up again and same symptoms. Thus far in my "troubleshooting" I had managed to make things worse twice and had somehow recovered from each. So back to the forum reading....

I found a description from Tony that said "Once the pic is fitted the 2 links between the ferrites carry the mosfet drive, check them for about 2.5V or a scope for 70khz" So I went there next. The topmost link was 2.4VDC. The other one gave me nothing...negative voltage, actually. So I figure that I'm getting somehwere. I double check all resistors, get out the glass and search for solder bridges and really just give it another once over for stupid mistakes. I checked the voltages on the diodes that surround the PIC and I'm getting .003V on both sides of the lower right diode. Now I'm suspicious of that PIC so I figure that I'll pull it and replace it just to eliminate it from the list of potential problems. When I got the solder sucker in there it messed up the solder pads a bit, but it seemed manageable. So I replace the PIC and now things are even worse...

Now only one of the coils on the top right group of four are working. Where I was getting 12VDC on both sides of the 6r8s I am now getting 12VDC on one side of each and 11.8 on the other side. Where I used to get 2.4VDC on the jumper by the ferrite, I only get 1.3. While I'm probing around I set my forearm on one of the pads and I got burned. OUCH. Now all of the transistors between the coils in that top row are really, really hot. So now I don't know what the hell to do.

I had reached that point where it was time to kill the master switch on my bench and walk away. Either that or just sit there and cry...or both. Usually when I get myself in a position like this there is something simple and idiotic that I'm overlooking...the simplest and most straight forward solutions often go unnoticed because I feel a need to make things as complicated as I can.

Hopefully Tony, some of this rambling might allow you to offer some help, because I'm baffled here.

Thanks,
Ed

[Tony]

I would guess the first fault was damage to the control line for the second row, either the diode or PIC. The fault you currently have sounds like the drive to the first row is missing (open circuit connection to the PIC) or being pulled low. Check all the connections to the PIC are sound and it's in the right way (possible to miss when you're looking for other problems). You need to get 2.5V across the 2 driver line diodes and 5V across the PIC supply diode. The mosfets may still be OK or one or more may have shoted. Disconnect the 4 6r8 resistors feeding the 8 powered coils so they're not being stressed and let me know what voltages you have across the 3 diodes at this point.

[edgobb]

Thank you, Tony for the response. I appreciate your time.

I have had enough success to get me back to where I was before I started "fixing things." I found a 5V zener that was junked, and replaced it so now I am back to having the first row work but still no power to the second row. I'll trace the power circuit from that jumper that I'm getting null across and see where it takes me. It is obvious that an in circuit test of the 14V zeners is building up power to the coupling caps across it so we'll see if my quest leads me to pulling on side of each of them and testing.

Now that my initial panic and frustration has passed, along with a 24 hour break, I can re-approach this with logic and patience that somehow eluded me when this all hit the fan on Friday.

Hopefully more soon.

Ed