Digital oscilloscope project/kit

[John Swift]

Hi Roy

the voltages measured will depend in the input current into pin 13 of the micro controller
but this picture shows  what I expect

   John

[wheeltapper]

Typical! I get that fixed and now the trace is stuck at the bottom of the screen.
It won't any how I try.

Roy.

EDIT
test point V1 is now -1.4V instead of 0.test point V2 has also gone negative.

[John Swift]

Hi Roy

what did you re work to fix the original problem ?

with switch 1 grounding the input
pins 1 , 2,  3 , 4 on switch 2 (SEN1) should all be at 0V
 the switch common (pin2) is connected to the input pin 5 of the unity gain buffer U2B
the voltage at TP 2 should be the same

possibly a splash of solder is shorting some thing to the negative supply AV-

  John

PS

how negative is TP2
just noticed U2 negative supply pin 11 is next to pin 10 U2C's input
 which is connected to switch SEN2 's common

[wheeltapper]

Yippee.
I think I've fixed it.
the first thing I did was reflow R18, that fixed the AC problem.

I just reflowed pins 1 to 7 on IC U2 and all the voltages are correct now.

PHEW!

thanks for the help.

Roy.

[John Rudd]

Yippee.
I think I've fixed it.
the first thing I did was reflow R18, that fixed the AC problem.

I just reflowed pins 1 to 7 on IC U2 and all the voltages are correct now.

PHEW!

thanks for the help.

Roy.

Excellent! Glad you fixed it...

[John Swift]

great news

your perseverance paid off


   John

[shipto]

I am cracking on with mine but ran into a problem on the surface mounted resister 20. I couldnt get the solder to take and after a few tries the pad came loose.
It looked to me like the connection is to the large area under the R20 so I scratched a little of the paint away and bridged the solder to that but it would be nice if someone could confirm that this is the right thing.

[John Swift]

I've not found a good photo showing the PCB without R20 and R21 fitted
but I've highlighted the connections you should have

If all else fails it should be possible to fit wire ended resistors directly to the terminals on switch SEN1 to replace the surface mount resistors

   John

[sparky961]

I suspect the resistors are the wrong way round....

Sure this doesn't belong in the "cruelty to apprentices" thread?

[kayzed1]

i have not started mine as yet, my Iron has too large a tip to get into these small spaces so i need to order a new small iron 30w i think it said. My only good iron is 60watt and big, from my BT days.

[wheeltapper]

I suspect the resistors are the wrong way round....

Sure this doesn't belong in the "cruelty to apprentices" thread?

I had a chuckle when I read that.
I know he meant I may have transposed two resistors, it just came out wrong. ...........................................................at least, I hope that's what he meant.

unidirectional resistors, whatever next.
the mind boggles.

Roy.

[John Rudd]

I had a chuckle when I read that.
I know he meant I may have transposed two resistors, it just came out wrong. ...........................................................at least, I hope that's what he meant.

Roy.

Yes that is what I meant...10k at the bottom, 3.3k at the top.....

[shipto]

Thanks John I will check that later when I am in shop.

[John Rudd]

Thanks John I will check that later when I am in shop.

Just to be clear here......

I thought you may have got the two resistors transposed, and that was why the readings were wrong....but as you said in a previous post, the joints were not good and you reflowed some of them.

So as the resistors appear to be correctly placed, that is the 10k is connected to 5v and the 3.3k is connected to 0v, the junction provides the third state for AC indication.....

As it is all working ok now, you dont need to fault find anymore....

[shipto]

No John your confusing me with someone else I just had pad come loose is all so far

[John Rudd]

No John your confusing me with someone else I just had pad come loose is all so far

Hmm...so I have.... my apologies....in my defence, I plead a senior moment..

[shipto]

No John your confusing me with someone else I just had pad come loose is all so far

Hmm...so I have.... my apologies....in my defence, I plead a senior moment..

My fault couldnt figure out how to quote message with tapatalk.

[kayzed1]

Whilst on the subject of Banggood stuff, i made the PSU but am short of the 22volt AC input...still looking for that.
So i moved on to the trany tester and have it all together barring one item missing, the  ( i think ) ceramic cap with
104 printed on it, i do have one extra three leg with a number that includes 104 so i think they have dropped a thingy.
I also have what looks to be the same thing spare in another kit with 104 printed on it but it is a little bigger and a
more yellowy Orange, the original item is a more Orange orange if that makes sense..
Lyn.

[John Rudd]

So, you mean you need a 22v ac secondary transformer?

Which psu is this?

Can you post up a picture of your 104 thingy?.....Generally speaking a 104 thingy with 2 legs is going to be a capacitor with a value of 0.1 mfd or 100 nF, if the board reference begins with C....three legs....hmmmm not sure what that could be .....A mutant 100n cap...with 3 legs... 

[DMIOM]

..........three legs....hmmmm not sure what that could be .....A mutant 100n cap...with 3 legs... 

Oi !        we're unique on the Isle of Man, not mutants!

[John Rudd]

If the BG psu is the one Rob referred to, it has some flaws.....
The max ac input is 24 AC, rectified will give around 36 v at the reservoir cap.....this is right on the edge for the TLO op amps used in the design.....

[kayzed1]

that is it John the one Rob has, can't do pics as my internet is soooo slow, but will try tomorrow some time late when the kids are in bed and the net not so busy,, tis a little diddy cap.  It uses three that look the same but have the number range 101, 103 and 104, as said will try a pic tomorrow.
Thanks.  Lyn.

[drmico60]

With a few more legs and a tyre you might have invented the wheel!
Mike

[PekkaNF]

Clacking bell!

I was minding my own business, measuring DIY spotwelder controller with a transformer and doublecheccked each time all is fine....Then it got time to measure thyristor and ofcourse I checcked that scope body was "zero" and same "zero" that line that feeds the thyristors.

I put the shuko on 

Yup this outlet could go either way...I though I did not fiddle with it. Wife noticed that fuse blew, because outlet from that bedroom went off too. I was affraid that that I fried the scope, but noooooo.....Just good oldfachioned scope "ground" to phase error

OK. This scope is nowwhere as good as these beauties, but maybe it's easier to float.

Pretty german Phillips (Two tubes, othervice transistors) does not sync. I got one nearly as old UK made one and that mostrly works...

Where you get 1:1 and 1:10 scope probes?

Pekka

[RobWilson]

Whilst on the subject of Banggood stuff, i made the PSU but am short of the 22volt AC input...still looking for that.

Lyn.

Hi John

I think Lyn is referring to  the 0 - 30 v PSU    http://www.banggood.com/0-30V-2mA-3A-Adjustable-DC-Regulated-Power-Supply-DIY-Kit-p-958308.html  , info attached .

My 0 - 30 v psu kit arrived yesterday along with the frequency meter kit 






Rob