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Need clarifications on vco testing
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Need clarifications on vco testing

by xonox on Sun Jun 12, 2005 1:46 am

I'm a newbie.
It is my first project of this size and i have little electronics knowledge. I built the power supply module and everything went fine, it is calibrated at 5.33v.

Since nothing caught fire during the power supply step, i built the vco today. Now i need clarifications for the test routine without a bench power supply. I do not have headphones with enough resistance but my multimeter has frequency detection. Can i use it instead ?

Where would i need to put the red + black probes of my meter ?
What should touch the metal leads of the 200k resistors ?

I might have access to a 3v supply, so i have these questions as well:

Step 2 of the test routine says : With the tuning knob VR2 centered, apply 2.0VDC using your powersupply to R89 (also pin 5 of IC11). Also center TM4 and TM5 to start.
So this means i just hook up the + lead of the power supply to R89, i don't need to connect the - lead, right ?

Step 3 : probe pins 1 or 3 of the waveform switch
Do i just plug one of the leads of my meter(in freq detection mode) to pin 1 or 3 ?

I want to make sure my vco is working

Thanks
xonox
 
Posts: 9
Joined: Wed Jun 08, 2005 5:53 pm

Re: Need clarifications on vco testing

by jcoplin on Sun Jun 12, 2005 12:46 pm

xonox wrote: I do not have headphones with enough resistance but my multimeter has frequency detection. Can i use it instead ?


yes, that's even better. If you replaced the tune pot with one with center detent you are really good to go. The detent isn't necessary but not having one was driving me nuts.

xonox wrote:
Where would i need to put the red + black probes of my meter ?


Put the black lead on pin 2 of J4 and the red on either input post on the waveform select switch. It is handy to have the style probes that clip on so you can keep your hands free.

xonox wrote:
I might have access to a 3v supply, so i have these questions as well:



I would wait to do the final calibration until everything is built as you can use the built in keyboard as your power supply. It should be more accurate and easier to do then.

xonox wrote:
Step 3 : probe pins 1 or 3 of the waveform switch
Do i just plug one of the leads of my meter(in freq detection mode) to pin 1 or 3 ?


The center pin outputs the switch selection. The 1 and 3 pins are the inputs. You can use any/all for the red probe and ground the black to pin 2 J4. Good Luck!

James
******************
If anyone asks of my whereabouts
simply tell them I've gone out the window
for a spot of tea and am not
expected back anytime soon.
******************
jcoplin
 
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Joined: Sat May 28, 2005 11:18 pm
Location: Minneapolis

by Guest on Sun Jun 12, 2005 2:23 pm

Thanks a lot for taking the time to answer.

So i don't have to worry about touching the leads of the 200k resistors just to see if the vco works ?

Any idea on which frequency i should see while probing the switch pins ?

Thanks again :)
Guest
 

Please be positive and constructive with your questions and comments.