All About Circuits Forum  

Go Back   All About Circuits Forum > Electronics Forums > General Electronics Chat


General Electronics Chat Discussion forum for general chat about anything electronics related, including asking questions about material in the All About Circuits E-book, Worksheets, and Videos.

Reply   Post New Thread
Thread Tools Display Modes
Old 04-01-2008, 03:08 PM
Danielsix-five's Avatar
Danielsix-five Danielsix-five is offline
Junior Member
Join Date: Dec 2005
Location: Colorado
Posts: 20
Default Rca Wo-505a

Bought a surplus RCA WO-505A Oscilloscope. Got everything working okay, except the Horizontal Amplitude (the test circle thing). I can get the internal source to display a test circle correctly with 24VAC on the vertical input, but in external mode, I connect the AC Source (24V Transformer) to both the vertical and horizontal inputs (common ground) and I get back a loopy-cornered skewed rectange. Any idea what's going on or how to fix it??

Reply With Quote
Old 04-01-2008, 04:07 PM
SgtWookie's Avatar
SgtWookie SgtWookie is offline
Expert Member
Join Date: Jul 2007
Location: In the vast midwest of the USA; CST
Posts: 22,038

What are you using for test leads?

Try swapping the leads.
If the loopy-corner skewed rectangle is then drawn in a mirror image, the problem is in one or both of your test lead(s).

Your transformer may be going into saturation. This is pretty common with the cheap transformers you get nowadays. But it sounds more like you have a good bit of capacitance in there somewhere.

With the secondary windings of a transformer connected to the X and Y inputs, you should wind up with a straight diagonal line.

If you have a signal generator around, set it to output a 1kHz square wave @ 1v, and observe it using your test probe(s). It should look nice and square. If not, the internal caps need to be adjusted.

If you have a CMOS 4000 series IC around that has Schmitt inputs, like a 4093 or 40106, you could build a simple square wave generator using a small cap (around 8.2nF) and a resistor (around 100k). That should give you in the vicinity of 1kHz output. See the datasheet for either IC for the oscillator diagram. Once you get the oscillator running, you should see close to a perfect square wave on your scope if you look at the output of the oscillator with a 10x probe.
General info:
If you have a question, please start a thread/topic. I do not provide gratis assistance via PM nor E-mail, as that would violate the intent of this Board, which is sharing knowledge ... and deprives you of other knowledgeable input.
Reply With Quote
Reply   Post New Thread


Related Site Pages
Section Title
Worksheet Electromechanical relay logic
Worksheet Design Project: Simple component curve-tracer circuit
Worksheet Oscilloscope trigger controls
Worksheet Mixed-frequency signals
Worksheet Basic oscilloscope operation
Textbook Frequency and phase measurement : Ac Metering Circuits
Video Lecture System Notations - Electronic Systems
Textbook Polar and rectangular notation : Complex Numbers
Textbook Boolean Relationships on Venn Diagrams : Karnaugh Mapping
Textbook Waveform analysis : Ac Circuits

Similar Threads
Thread Thread Starter Forum Replies Last Post
RCA Selector Switch Build Zatarra64 General Electronics Chat 1 07-21-2014 04:50 PM
s-video and RCA component ? Mathematics! General Electronics Chat 0 02-12-2010 05:31 AM
VGA and RCA ? Mathematics! General Electronics Chat 13 01-29-2010 09:00 AM
Using RCA audio adapters with bare wire speakers Gdrumm General Electronics Chat 1 01-11-2010 04:45 AM
wiring RCA and TRS jacks haditya The Projects Forum 5 06-22-2006 04:58 PM

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

All times are GMT. The time now is 03:54 AM.

User-posted content, unless source quoted, is licensed under a Creative Commons Public Domain License.
Powered by vBulletin
Copyright ©2000 - 2014, vBulletin Solutions, Inc.