Help on Step 6 Please

[Qiaozhi]

Actually, Q3 and Q4 are installed. At one point, I thought I was OK on TP7 and TP8 and I moved on to step 7, just haven't tested it yet with the correct scope settings, but when I tested it with a volt meter, TP4 was reading around 2.5v instead of 500mv. I did adjust R6 to what I believe is the correct 22us delay. I'll post relevent scope images tonight. Again, thanks for all the help. I'm learning a lot with this project, that was the goal.

In that case, please perform the test with U7 pins 4 and 10 hanging over the side of the socket. I highly suspect that the signals on those pins will then look ok.

[Calla969]

OK, here are pics of my results of testing the IC with pins 4 and 10 bent out. Pin 4 looks completely dead. I tested this with 2 difference ICs.
https://goo.gl/photos/kAcFsbUVZT4aFgfu8

Here I tested TP7 and TP8, obviously with the pins in their normal position. This is the same result I had before.
https://goo.gl/photos/qqHfZTXnsLD89J7q9

I had to return the scope to my friend, but I'll be able to get it back soon and I'll continue testing.

[Qiaozhi]

OK, here are pics of my results of testing the IC with pins 4 and 10 bent out. Pin 4 looks completely dead. I tested this with 2 difference ICs.
https://goo.gl/photos/kAcFsbUVZT4aFgfu8

Here I tested TP7 and TP8, obviously with the pins in their normal position. This is the same result I had before.
https://goo.gl/photos/qqHfZTXnsLD89J7q9

I had to return the scope to my friend, but I'll be able to get it back soon and I'll continue testing.

When you get access the scope again, please look at the signals on pins 2, 14, 7 and 9.

Also, I just realised that there will be no signal on pin 4 with it hanging outside the IC socket. This is because I should have asked you to do that test with pins 6 and 10 (not 4 and 10). Pins 4 and 6 are connected together, but pin 6 is the Q output.

So, it looks like the pin 10 signal is good in the test. If you repeat the test using pins 10 and 4, I bet they are both ok.
In that case, something is loading the outputs. There are only two components that can do that: Q3 and Q4, but as far as I can see from your image of the PCB, these are inserted in the correct orientation. Can you re-check that you have the correct transistors fitted there.

[Calla969]

OK, first images are with pins 6 and 10 bent out. Channel 1 (red) on pin 6, channel 2 (yellow) on pin 10. Settings are the same for all images, except I changed the trigger to channel 2 later what I was only using that probe. The only activity I see on channel 6 is a drop to -5v, if I'm interpreting it correctly.
https://goo.gl/photos/qqHfZTXnsLD89J7q9

Here's pin 6 alone, in the socket.
https://goo.gl/photos/qqHfZTXnsLD89J7q9
It is really unstable and moves around a lot, no matter what I do with the trigger. It also displayed nice and clean for a few seconds before becoming crazy and unstable.

Here's pin 2.
https://goo.gl/photos/gN55gjGDdGhAW93q6

Pin 14
https://goo.gl/photos/w7K8VuDT9qgHjMiH8

Pin 7
https://goo.gl/photos/jvm68jw2cxT789vC8

Pin 9
https://goo.gl/photos/QsyU5mThN61W6zPRA

[Qiaozhi]

OK, first images are with pins 6 and 10 bent out. Channel 1 (red) on pin 6, channel 2 (yellow) on pin 10. Settings are the same for all images, except I changed the trigger to channel 2 later what I was only using that probe. The only activity I see on channel 6 is a drop to -5v, if I'm interpreting it correctly.
https://goo.gl/photos/qqHfZTXnsLD89J7q9

Here's pin 6 alone, in the socket.
https://goo.gl/photos/qqHfZTXnsLD89J7q9
It is really unstable and moves around a lot, no matter what I do with the trigger. It also displayed nice and clean for a few seconds before becoming crazy and unstable.

The two images you posted are identical, and are the original ones for TP7 and TP8.

Here's pin 2.
https://goo.gl/photos/gN55gjGDdGhAW93q6

Pin 14
https://goo.gl/photos/w7K8VuDT9qgHjMiH8

Pin 7
https://goo.gl/photos/jvm68jw2cxT789vC8

Pin 9
https://goo.gl/photos/QsyU5mThN61W6zPRA

All these signals look correct.

There may be a problem trying to probe pin 6 (Q output on U7a) with it disconnected, as this breaks the link back to pin 4. Let me check that out here.

Please post the correct images for pins 6 & 10, and also check Q3 and Q4 are fitted properly.
It still looks to me like the Q outputs are being loaded. Especially since the ~Q outputs are ok.

[Calla969]

Ack! I must have had the old images still on the clipboard. These are the images I meant to post for pins 6 and 10.

https://goo.gl/photos/HTrD2gBPUezEqg6n9

[Calla969]

I took a quick look at Q3 and Q4 this morning as well. They appear to be the correct parts (J103 if I recall correctly), they appear to be installed properly, and there are no shorts between the pins.

[Qiaozhi]

I have checked what happens with my MPP if pin 6 is disconnected, and the signal is held at -5V. This is because it needs the feedback to pin 4, so we cannot use that as a test. From your results it seems fairly obvious that something is loading the outputs of pins 6 and 10. Especially since the associated ~Q outputs are both ok.

Next thing to do is remove Q3 and Q4, re-insert U7 in the socket, and put the scope on TP7 and TP8.

[Calla969]

Looks pretty good now.
https://goo.gl/photos/UmAm8MJHdA2fNCMY8
Unfortunately, they didn't come out as nice as I'd hoped and I'm going to need replacements. From what I can tell, the particular ones that came with the kit are now obsolete. Pretty sure they're Siliconix j113 transistors. Know of a suitable replacement, preferably in the US?

[Calla969]

So, I ordered new parts from Digikey. Should I go ahead and install the new parts, or is there some other testing I should perform before moving forward?

[Qiaozhi]

So, I ordered new parts from Digikey. Should I go ahead and install the new parts, or is there some other testing I should perform before moving forward?

Install one first to see if it's working, then install the other one.
You could also try doing a continuity test on the faulty FETs to check for a short.

[Calla969]

OK, finally got back to this. I installed the new J113s I got from Digikey, one at a time. TP7 and TP8 both have a nice clean signal now! Looks much better. Didn't get scope shots, but everything is looking much better. I moved on to testing the voltage on TP4 though and that doesn't look right. I'm getting -4 volts instead of 500mv and the voltage really doesn't change much at all when I move an object over my test coil. I do have pins 1 and 2 shorted on PL3. I had adjusted R6 previously, but maybe I'll check it again? Anything else I should take a look at?

[Qiaozhi]

OK, finally got back to this. I installed the new J113s I got from Digikey, one at a time. TP7 and TP8 both have a nice clean signal now! Looks much better. Didn't get scope shots, but everything is looking much better. I moved on to testing the voltage on TP4 though and that doesn't look right. I'm getting -4 volts instead of 500mv and the voltage really doesn't change much at all when I move an object over my test coil. I do have pins 1 and 2 shorted on PL3. I had adjusted R6 previously, but maybe I'll check it again? Anything else I should take a look at?

Can you show what signal you have on TP3?