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VCO Troubles. [SOLVED]
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VCO Troubles. [SOLVED]

by joper61 on Wed Nov 02, 2016 11:38 pm

Hi all, sorry if i sound like i don't know what i'm doing, very new to electronics but doing my best.

I am having problems with testing my VCO. I have a dso138 oscilloscope that I have been using, I was having trouble getting my sawtooth wave to generate, but after leaving it for a day and coming back it was clear on my oscilloscope that it was being generated.

I proceeded to solder in the components for the square wave generator and now am back to neither the square or saw wave generating properly. I have attached pictures of what it looks like in a 0.5 DC range on pins 1 and 3 of the waveform switch without attaching the ground clip of the oscilloscope. when i do attach the ground clip to 7805 the little waves that i do have disappear.

I've carefully inspected my solder joints, and none appear to be cold or have any shorts between them. I've also verified that my components are all the correct values and should be working properly.

Pins 1 and 3 of J4 have 5.33v and 11.98v my adjustable powersupply (just 2 - 1.5v batteries) is giving out 3.4v.

I'm kindof at my wits end with this, if anyone has any suggestions or could help me but needs more information please don't hesitate to shout out.

Pics:
http://i.imgur.com/nEhuHal.jpg
http://i.imgur.com/T4CMZg0.jpg
Last edited by joper61 on Thu Nov 03, 2016 8:36 pm, edited 1 time in total.

joper61
 
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Re: VCO Troubles.

by antto on Thu Nov 03, 2016 5:00 pm

your picture is with the signal without the ground connected on the scope probe - this looks familiar

that waveform is probably AC aka "mains hum" ... is it 50 or 60Hz?
for a proper measurement you should attach the ground clip of the scope to the ground on the measured circuit, in which case you measured silence, because it's probably silence, sadly

don't know what advice to give
if it has went silent before, and has later came back after sitting - try to reproduce that again
this might be something with temperature involved, or who knows what

antto
 
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Re: VCO Troubles.

by joper61 on Thu Nov 03, 2016 5:30 pm

Thanks for the reply, I will try my tests again when i get some from work today and see what happens. I'm also wondering if there are any common spots to check voltage for these kinds of problems.

joper61
 
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Re: VCO Troubles.

by joper61 on Thu Nov 03, 2016 8:33 pm

antto wrote:your picture is with the signal without the ground connected on the scope probe - this looks familiar

that waveform is probably AC aka "mains hum" ... is it 50 or 60Hz?
for a proper measurement you should attach the ground clip of the scope to the ground on the measured circuit, in which case you measured silence, because it's probably silence, sadly

don't know what advice to give
if it has went silent before, and has later came back after sitting - try to reproduce that again
this might be something with temperature involved, or who knows what



Must've been a temperature thing because as soon as i got home today, both waves were generating as expected!

joper61
 
Posts: 3
Joined: Wed Nov 02, 2016 11:23 pm

Please be positive and constructive with your questions and comments.