New Build Gone Awry

[geoscash1]

Ok, I got a kit from silverdog and went through all parts so good to go.

I began by making a copy of the build doc, read thru it, and then started my build. Now I know enough
to get through these builds but am not very good at trouble shooting when a problem arises.

I followed my copy of the build doc as I built,

Step 1 - Apply 12v (tested with both bench supply and 8AA pack) = 12v - good.
Step 1 pt 2 - MM red probe to TP10 and Black probe to pin 4 U8 = -4.98v - good.

Step 2 - MM black probe to TP10 and red to TP2 = +4.96v - good.

Step 3 - Scope probe channel 1 to TP1/probe gr to TP10, scope set to 5v div/10us delay = 54us pulse,
reset time delay to 1ms to check kHz, a line/dot on each division (or close to each) on scope scale so is close to 1kHZ.
Also attached a speaker to TP1 and 0v (TP10) to test as well, got a nice clean low volume high pitch tone in the speaker.
Checked sync with channel 2 probe at U2 pin2 and both traces were synced or very close to being near identical.

Step 4 - Attached one of my test coils 354uH and proceeded to test flyback, set probe to 10x and scope
shows an approx. 350/370v flyback (scope clarity) - good. Double checked with headphone test and could definitely
hear a nice clean high pitch audio tone in the headphones - good.

Step 5 - Dc voltage at TP3 moves slightly (few millivolts). Tried using a crushed pepsi can but it does not change the
voltage reading or tone from speaker. Tried to check with MM and it shows a +.06 reading. I assume this to be close or
correct as I am not seeing a reference voltage to go by - good?. Moved to step 6 based on that.

Step 6 - shorted pin 2 of delay/reject pot to pin 2 first and then pin 3 to see if there was a difference from either, same with either.
channel 1 probe to TP1 and channel 2 probe to TP5. Tried adjusting R6 with no response. It looks like on the scope the sample pulse
is right around 24us but adjusting R6 does not change it in either direction with PL3 shorted. Now when powering on, I get a constant
tone from the speaker at PL5, tried adjusting the threshold pot but it will not slow the tone down, stays continuous.

Step 7 - thinking I am maybe just not adjusting the scope correctly, I moved to step 7 based on the build doc to try using the MM
as well as the scope. At this point I am unable to slow or quiet the threshold or adjust R6 whatsoever. Nothing passed over the coil changes
anything, no detection, does not change the scope trace or the voltage on my MM.


Problem - Constant tone coming from speaker at PL5. Tried adjusting R6 with no response anywhere on scope. Back tracked and
rechecked my first 5 steps, now it seems step 2 only shows a minimal + .73v so I have to assume I shorted something that shouldn't
have been shorted or ???. Also must assume since the voltage is short at step 2, I may have either fried U3 (78L05) or something else has
gone awry. Rechecked the steps 3, 4 and 5 and they are the same (or close to) as they were during initial testing and building prior to whatever I have done.

Am lost now so any help would be appreciated. This seemed pretty straight forward and quite frankly seemed simpler than the barracuda but for whatever
reason I have screwed it up somewhere...

[Qiaozhi]

It appears that the -5V supply is kaput. You'll need to fix that problem first.
In Step 5 you said "Tried using a crushed pepsi can but it does not change the voltage reading or tone from speaker.".
I don't understand this statement, as the speaker is not connected at this stage of the project.

[geoscash1]

Hi Qiaozhi,9

I removed U3 and replaced with a new 78L05 and ran the tests again but it still is not correct, I get a reading of .071v, same as before. I tested the regulator using my bench supply and it worked as intended so somthing else is causing the low voltage. I think you meant to say the "+5 supply is kaput".

As far as step 5 and the crushed can, I mis interpreted that test, assumed I should be able to hear a coil change as well, so added the wafer plug and speaker thinking it was just overlooked. After reading your comment and re-reading the step 5, I see now that I wasnt supposed to be able to hear anything and the pepsi can is just used to see a voltage change on the coil. Either way, it is still incorrect, I will look at the LT1054 and replace it as well and then check the TL071 and 72 (came with kit in place of 61 &62).

[geoscash1]

Ok, replaced U3 with a new 78L05, no change, gets .71v. Changed LT1054 with a new one (different batch) and still the same. Went thru and double verified resistors, all 39 are correct.

I tested the + supply diodes with power on (using bench supply set at 12.0v) and D1 = -.05v and D2 = +9.29v.

[Qiaozhi]

Ok, replaced U3 with a new 78L05, no change, gets .71v. Changed LT1054 with a new one (different batch) and still the same. Went thru and double verified resistors, all 39 are correct.

I tested the + supply diodes with power on (using bench supply set at 12.0v) and D1 = -.05v and D2 = +9.29v.

Yes, that was a typo. I (of course) meant +5V.

If I understand correctly, the input to U3 is at +9.29V, but the output is +0.71V.
In this case, I suspect you have a short somewhere on the +5V line - either a physical solder short, or a faulty IC.

[geoscash1]

Yes, that was a typo. I (of course) meant +5V.

If I understand correctly, the input to U3 is at +9.29V, but the output is +0.71V.
In this case, I suspect you have a short somewhere on the +5V line - either a physical solder short, or a faulty IC.

You are correct, +9.29v at U3 input and +0.71v out of it. I rechecked all solder joints, re-soldered any that looked suspect (2), changed the TLC555's that came in the kit for NE555's and also changed the LT1054 again and I even put another new 78L05 in after testing it with my bench supply before installing so I know the regulators are working. Re-soldered the caps, resisters & diodes on the +5V line and it is still the same, +9.29 in/+0.71v out. Completely confused as it worked through to step 7 and after powering down and back on later yesterday afternoon this was the result.

Not sure what else to check or do...

[rickb]

Remove power and measure resistance from u3 output to 0v (gnd or common terminal of u3). You may measure a low resistance that is overloading the regulator and shutting it down due to thermal overload. (does it start getting hot as soon as you apply power?) You may have an ic in backwards or a shorted capacitor. Is u3 in backwards?

Rick

[geoscash1]

Hi Rick,

Hey thanks for the reply, its appreciated.

I have checked and rechecked the Ic's, they are all in correct, U3 is also in correctly. As far as a shorted cap, I'll have to do a double check on that, may just replace all the caps on the 5V line. As far as the resistance, I set my MM to 20k and tested U3 output (red probe) and ground (black probe to middle pin U3) and meter gives a reading of 4.12

I get No heating at all on U3 or any of the surrounding Ic's.

[Polymer]

Hi geoscash1,

I have not built the MPP yet, but have had some odd problems with the Bara & Surf and
will take a "pot shot" at this, literally.

I found that often the external wires to pots and such have broken inside, but not visibly.
After turning the pcb only a few times during soldering & experimenting this has already happened to me.

I only use servo wires now and glue the wire ends down like there's no tomorrow.
Do check your external wire connections with multimeter and wiggle them too. Hope this can help you!

Good Luck, Polymer

[rickb]

meter gives a reading of 4.12

4.12 what? ohms, Kohms? You need to be consistent when making measurements. Were the voltage readings made from the same reference point? i.e. middle pin of the regulator? if not, do so. Both input and output of the regulator.

Very ImportantThe quality of answers/help you receive is directly related to the quality/accuracy of the information you supply.

[geoscash1]

Hi geoscash1,

I have not built the MPP yet, but have had some odd problems with the Bara & Surf and
will take a "pot shot" at this, literally.

I found that often the external wires to pots and such have broken inside, but not visibly.
After turning the pcb only a few times during soldering & experimenting this has already happened to me.

I only use servo wires now and glue the wire ends down like there's no tomorrow.
Do check your external wire connections with multimeter and wiggle them too. Hope this can help you!

Good Luck, Polymer

Hello polymer,

Yep, that is a habit I got into when building trail cameras, had quite a few stump me as well so it is something I do check but sincerely appreciate your reply, as at this point any hint or guru tips help with the learning curves. You never know, when you forget something little it always leads to other issues later.. Thanks and I'll keep that in mind as I proceed.

4.12 what? ohms, Kohms? You need to be consistent when making measurements. Were the voltage readings made from the same reference point? i.e. middle pin of the regulator? if not, do so. Both input and output of the regulator.

Very ImportantThe quality of answers/help you receive is directly related to the quality/accuracy of the information you supply.

Sorry bout that Rick, I mentioned the MM setting at 20k so assumed... Anyway, yes, it is 4.12k measuring the output pin of the 78L05 with the middle pin or common used for ground with blk probe. I measured the input pin the same way, blk probe to middle pin (common) and red probe to the input pin but the difference is it roams, meaning when first probed it shows 3.56k then bounces to 9.2k then to 15.4k then off or zero's out. Tried different settings with the meter but it still shows 0 with other settings.. hope that clarifies any misunderstanding I may have caused. I appreciate your interest in trying to help, a little goes along way some times.

I seriously keep feeling like it is something right under my nose, something so simple but for whatever reason I am missing it...

[rickb]

Were the voltage readings made from the same reference point? i.e. middle pin of the regulator? if not, do so. Both input and output of the regulator.

The voltage readings at the regulator are wrong if you are using +12v and measuring from the reg center pin.

The rising resistance readings are just the capacitors charging from the constant current generator in the multimeters ohms function

[geoscash1]

With some help from the master himself (Qiaozhi), We have figured out that the problem lies beyond U3/C4 on the 5v line. As per instruction, I isolated the 5v by cutting the trace between C4 and the via at U4 and have found now, I get a nice 4.98v at TP2. Then tested voltages at U6, U7, U8 and U9 after removing each individually and all measure approx. 5v (4.97 to 4.98v) at the respective input. So, now I know the issue is elsewhere and not the regulator or cap...


Back to the drawing board...or should I say the minipulse board...

[6666]

I isolated the 5v by cutting the trace

No need for the hammer just yet then ?
Here is an oldtimers tried and tested tip, after you first build the +5 and -5 supply install a led on both -5 & +5 rails at the end of the longest tracks and after you install a component that is even remotely close to a power rail, test it, and if you introduce a fault you will see it.

[Polymer]

How much current is flowing in the "non-proper-working" mode and what
would normally be expected? I am sure there are experiential values from other builders
as to approx. how many mA with & without coil, speaker etc.

Do you have any hidden metal in your coil test bed? That happened to me

Is there a chance of you putting a hi-res photo of front and back of pcb on the forum?

Just trying to help and sharpen my skills.

Good Luck again, I know what it feels like to want to let the big hammer hit a fangled mess with a big crunch,
preferably multiple times ...