Help plugging old oscilloscope

Thread Starter

burricios69

Joined Dec 14, 2014
18
Hi all,
I recently got an old oscilloscope and (although it may seem a bit sad) I have no idea on how to plug it in. Instead of a normal plug, it has a couple of bananas conectors. Here you have a picture so you can see it:



So, does anyone know how to connect this to a normal outlet?
Thanks in advance
 

DerStrom8

Joined Feb 20, 2011
2,390
If you're sure that's a power cord, you should replace it with one with a standard plug for your part of the world. Looks like a custom rig-up to me.
 

MrChips

Joined Oct 2, 2009
30,452
Show us some more pictures of what the scope looks like, any nameplates and where that power cord enters the scope.
 

Thread Starter

burricios69

Joined Dec 14, 2014
18
Hi,
Thanks for the replies. Here are two pictures of the oscilloscope, from its back and its front. Its an Telequipment D61a (as u can see in the first picture).



 

Robin Mitchell

Joined Oct 25, 2009
819
Hi,

I have two of those oscilloscopes, they are actually pretty good!
Set the rotating switch voltage selector on the back to the voltage of your socket (between 200V to 240V)
Take a normal plug socket and connect the brown wire to live
Connect the blue wire to neutral
Connect the yellow green wire to earth
Im not sure what fuse you will need but 5A should be fine. If it blows use a 10A

All done!
 

Thread Starter

burricios69

Joined Dec 14, 2014
18
Thanks for the answer! I didnt get it completely clear though... The yellow green wire has no end... I understand it is not 100% necessary, but advisable for security issues... Is it in this case VERY advisable?
As well, how can i know, in a normal plug socket, which one is live and which one is neutral? I'm spanish and here the plugs are simetrical...
Finally, you say i will need a fuse. Does that mean that i have to add a fuse between the plug and the oscope?
Thank you!
 

ISB123

Joined May 21, 2014
1,236
Well blue(neutral), brown(hot) and stripped one is ground.You should buy standard euro plug and use it with plug, currently you are playing with your life if you plug it that way.Two holes in the socket are Hot and neutral, ground is two pins on the sides of the socket.
 

flat5

Joined Nov 13, 2008
403
Since the plug can be inserted two ways don't be too concerned about the blue & brown colors.
Just make sure they go to the prongs and the striped one does not! It goes to ground.
 

Thread Starter

burricios69

Joined Dec 14, 2014
18
Thank you all guys! I finally plugged it to the socket as you said, and it turned on. It's a bit worn-out though, as channel 1 has the scale completely wrong and every now and then i get weird things in the screen, but channel 2 works almost decent, the scale is still a bit wrong, and i get some weird things too... But anyway, its more than I expected, as it must have about 30 years and hasnt been used for a long.
Thanks for your help again!
 

flat5

Joined Nov 13, 2008
403
You should buy an aerosol contact cleaner/lubricant from an electrical parts supplier.
Clean the switches and variable resistors.
Google how to use it.
Avoid spraying plastic parts.
 

Thread Starter

burricios69

Joined Dec 14, 2014
18
After playing a bit with the scope I noticed something weird. Im using it with a dsPIC mcu, and although i get to read voltages of 3.3V and 5V with an almost decent precission, when I attempt to read a square signal i get something like this:
--- --- --- --- ---
__________

Where the continuous line is the 0V, and the discontinuous one is more or less 3.3V (which is what I expected). Is this way of representing square signals normal in these old oscopes?

Also, i have another issue:
The MCU is powered through USB, which is connected to a PC. When I make a read through the oscope, i get the typicall windows sound that means an USB has been conected/disconnected. So I am thinking... is the oscope short-circuiting the mcu in some way?

Thank you!

P.D:
You should buy an aerosol contact cleaner/lubricant from an electrical parts supplier.
Clean the switches and variable resistors.
Google how to use it.
Avoid spraying plastic parts.
I'll buy it as soon as I can, thanks for the recommendation. Every care I can give to it, i'll try to do it.
 

RichardO

Joined May 4, 2013
2,270
After playing a bit with the scope I noticed something weird. Im using it with a dsPIC mcu, and although i get to read voltages of 3.3V and 5V with an almost decent precission, when I attempt to read a square signal i get something like this:
--- --- --- --- ---
__________

Where the continuous line is the 0V, and the discontinuous one is more or less 3.3V (which is what I expected). Is this way of representing square signals normal in these old oscopes?
I think you have selected chop mode with a fast timebase setting. You are seeing the chopping frequency and the gaps in the trace are the blanked intervals. If you switch to alternate mode it will look like you expect.

Also, i have another issue:
The MCU is powered through USB, which is connected to a PC. When I make a read through the oscope, i get the typicall windows sound that means an USB has been conected/disconnected. So I am thinking... is the oscope short-circuiting the mcu in some way?
The grounds of both the PC and the scope are connected together through the safety ground wires in the power cords. The scope has the ground side of vertical inputs connected to the chassis which is safety ground. So, if you connect the scope ground to some point in your circuit that is not at the same potential as the PC ground it will short that point to ground.
 

Thread Starter

burricios69

Joined Dec 14, 2014
18
The grounds of both the PC and the scope are connected together through the safety ground wires in the power cords. The scope has the ground side of vertical inputs connected to the chassis which is safety ground. So, if you connect the scope ground to some point in your circuit that is not at the same potential as the PC ground it will short that point to ground.
The problem is that its when I connect the scope ground to my circuit's ground when i get the connected/disconnected sound in my PC. So do you know what could be happening here?
Thanks
 

Thread Starter

burricios69

Joined Dec 14, 2014
18
I've noticed the circuit doesnt get disconnected from the PC if I connect the scope's supply ground to either the circuit's ground or the plug socket's ground. I dont see much sense in connecting it to the circuit's ground, as that requires the circuit to be near the plug, but doing so i get more precise measures. However, if what i do is connecting the scope's supply ground to the socket's ground, the scope gets some weird measures, as instead of measuring 5V it measures about 0.5V, and even less when i attempt to measure 3.3V. Could this be because i am just connecting the supply's groung to the socket's ground by touching it with the ground wire?

Also, shouldn't the ground in the circuit, and the ground in the PC (which is, i guess, the socket's ground) the same, as they are connected through USB and thats what powers the circuit?

Thank you very much again, and sorry if I am making too much questions:(
 

Thread Starter

burricios69

Joined Dec 14, 2014
18
Let's back up for a moment.

Did you get a Euro wall plug and wire all three wires to the plug?
No, i just plugged the two bananas to the socket and left the ground unplugged, and that's what I've connected to circuit's ground (getting nice results) and, later, to the plug's ground (getting weird results).
The problem with getting an Euro wall plug and using it is that the scope is not mine, so I don't want to cut the wire leaving the bananas out.
 

MrChips

Joined Oct 2, 2009
30,452
Then I would talk to the owner and explain what you are trying to do.

Cutting away the banana plugs and installing a proper AC mains plug is your first objective.
 
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