CTM644 new plug

[vasilisk]

Happy new year to everyone.
I have been watching the cpcwiki for a long time, but didnt happen to actively participate.
Hopefully I am looking forward in doing it from now on.
I have an Amstrad CTM644 monitor which needs the plug ,from the attached photo, to be changed.


Is there something specific about that plug? Or I go to any local electronic store just with the diameter? I see there are two cables inside. Is there an order to which goes where?


Sorry if the questions look silly, but I am not very familiar with electronic repairs.

[TotO]

I use 2.1mm/5.5mm power jack connectors for the +5V plug.

[keropi]

also the cables go in specific order - if you put them reversed something bad will happen to the 6128 surely so pay attention to which cable goes to the center and which on the outer contacts of the jack

[TotO]

+5V inside / GND outside.
-12V outside / GND inside.

[vasilisk]

Thank you for your response. Another problem is that I dont have the actual plug. Now the cable is stripped and waiting. Is there a way to determine which cable goes where? Are they the same color? I am not home right now so I wll check later.

[TotO]

Using a conductive tester like a multimeter.
Or your tang... 

[vasilisk]

Using a conductive tester like a multimeter.
Or your tang... 

Ok. I have a multimeter. In setting, to show me what? volts?

[TotO]

Ok. I have a multimeter. In setting, to show me what? volts?

No, using the "diole" symbol. -|>-
Next, testing the conductivity from both side to know what is what... That will display "1" value if both side are the same wire.
(with chance, your multimeter will sound a bip too)

[vasilisk]

What do you mean from both side? The cable inside has one red and one black. If I understand correctly, I need to find which one is the +5 and which is the -12, in order to solder them in the jack with the correct order.

[Bryce]

No, using the "diole" symbol. -|>-
Next, testing the conductivity from both side to know what is what... That will display "1" value if both side are the same wire.
(with chance, your multimeter will sound a bip too)

?

@vasilisk: Set the multimeter to DC volts and connect one probe to each wire. If the meter reads 5V then the wire connected to the red probe goes to the centre of the connector. If the meter reads -5V the wire connected to the black probe goes to the centre of the connector. There is no 12V in this wire, just a +5V and GND. +5V goes to the centre and GND to the outer ring.

Bryce.

[vasilisk]

Thank you Bryce for clearing things up.
So there is no +12v as keropi mentioned.


The 5V reading is (+) or (-)? Because I am thinking of buying something like this to avoid soldering, will I be ok?


https://www.modmypi.com/electronics/power-and-batteries/screw-terminal-2.1mm-dc-barrel-plug-male

The image and site is as a reference.

[Bryce]

The computer get's the 12V via the socket on the monitor through the cable that comes from the computer.
That will work fine. I would assume the "-" is going to the outer ring because that's the most common configuration, but I'd check first with your meter.

Bryce.

[TotO]

?

I have understood that he got the cable (wire and connector) but no voltage to apply on it.
Else, sure... Just to check is 5V or -5V is displayed to know the polarity.

[Bryce]

And how would a diode test help? The wires have a capacitor across them and then go to the output of the voltage regulator circuitry. I can't even begin to guess what result a diode test would give in either direction and would depend on the charge across the capacitor also.

Bryce.

[TotO]

Because it is the easy way to test a wire conductivity w/o voltage. Just read "1" or ear the "buzzer" if OK.
There is no capacitor on a power jack cable... We don't spoke about the same thing.

[Bryce]

Ah, you mean a continuity test, not a diode test. That makes more sense.

Bryce.

[TotO]

Sure. Many multimeters have the continuity test at the same place of the diode symbol. It is why I have said that.

[attach=2]

[Audronic]

Thank you Bryce for clearing things up.
The 5V reading is (+) or (-)? Because I am thinking of buying something like this to avoid soldering, will I be ok?
https://www.modmypi.com/electronics/power-and-batteries/screw-terminal-2.1mm-dc-barrel-plug-male
The image and site is as a reference.

The Plug you will need is a FEMALE plug not a MALE.
Am i correct that you want a plug to plug into the CPC at the back (Socket) which is +5 on the Inner and Ground (0 Volts) On the outer.
Ray

[vasilisk]

The Plug you will need is a FEMALE plug not a MALE.
Am i correct that you want a plug to plug into the CPC at the back (Socket) which is +5 on the Inner and Ground (0 Volts) On the outer.
Ray

I am pretty sure the plug is male. Female is the one behind the keyboard. The one I need is in the photo on post #1

[Audronic]

? On My 6128 and 446 the socket on the back of the Keyboard is Male (Has a Pin on the Middle).
Therefore I would require a Female Plug (with a hole in the Middle)


Yours may be different ?


Ray

[vasilisk]

https://www.modmypi.com/electronics/power-and-batteries/screw-terminal-2.1mm-dc-barrel-plug-male


In the description it says male.  The one I want is this. So I assume its male.

[Bryce]

? On My 6128 and 446 the socket on the back of the Keyboard is Male (Has a Pin on the Middle).
Therefore I would require a Female Plug (with a hole in the Middle)


Your may be different ?


Ray

He's replacing the plug on the end of the flylead from the monitor, not the socket on the CPC.

Bryce.

[chinnyhill10]

Thank you for your response. Another problem is that I dont have the actual plug. Now the cable is stripped and waiting. Is there a way to determine which cable goes where? Are they the same color? I am not home right now so I wll check later.

Use a multimeter. You should have one in anycase just to check the correct 5v is present before plugging it into the CPC.

[vasilisk]

The computer get's the 12V via the socket on the monitor through the cable that comes from the computer.
That will work fine. I would assume the "-" is going to the outer ring because that's the most common configuration, but I'd check first with your meter.

Bryce.

I checked with my multimeter by putting black probe to black cable and red probe to red cable. It showed +5v.


I bought this plug
https://www.modmypi.com/electronics/power-and-batteries/screw-terminal-2.1mm-dc-barrel-plug-male


Where do I insert the black and where the red cable?

[TotO]

"Le fil rouge sur le bouton rouge. Le fil vert sur le bouton vert" !   

OK... So, the red wire on the positive input and the black wire on the negative input.
But, please after doing that, check again with your multimeter. It is expected to have positive (red) inside and negative (black) outer to display +5V.