Will this DSUB inhibit a continuity check?

blueflyer · #1 03-29-2015, 08:28 AM

I have this DSUB I took apart because I couldnt get it to pass a continuity check. After opening it up, Im not sure it will pass a continuity check without power supplied to it. Can anyone confirm this or help me figure out why I cant get a continuity check from the pins to the wires at the other end of the circuit board?
Sorry for the terrible picture:

DaleB · #2 03-29-2015, 08:31 AM

I would put the chances of that board passing a continuity test at approximately zero. What is it? It looks like a USB to serial converter or something

Mich48041 · #3 03-29-2015, 10:35 AM

Some sensitive electronic circuits can be damaged by a continuity check. An ohmmeter or test test light puts out a voltage and attempts to send a current through the circuit under test. The circuit might not like that.

blueflyer · #4 03-29-2015, 12:06 PM

How can I determine which DSUB pin corresponds to which USB pin?

Dale, your post was funny. I got a chuckle. Yes, its a USB to serial cable.

Mich48041 · #5 03-29-2015, 01:12 PM

Here is schematic of a USB to Serial adapter (not yours). There is no direct connection between the input and output. Depending on the computer operating system, a driver might need to be installed. What are you trying to connect to what? Did any documentation come with the adapter?

Mich48041 · #6 03-29-2015, 01:52 PM

USB
1 +5VDC
2 Data -
3 Data +
4 Ground

DSUB Signal Name
1 DCD Data Carrier Detect
2 RXD Receive Data
3 TXD Transmit Data
4 DTR Data Terminal Ready
5 GND Signal Ground
6 DSR Data Set Ready
7 RTS Request to Send
8 CTS Clear to Send
9 RI Ring Indicator

USB to RS232 conversion

DaleB · #7 03-29-2015, 02:52 PM

Yeah, there is no direct USB to serial connection. It's not a "conversion" at all, in the sense of those we used to see for RS-232 to some other serial interface specs. The "converter cable" has an embedded processor that implements a USB slave device and a serial I/O port, and passes data between them. The only thing the two sides have in common is ground.

What's the problem you are trying to troubleshoot? USB to serial interfaces are pretty rugged for the most part, but they do fail... and they are also cheap and plentiful.

blueflyer · #8 03-29-2015, 06:23 PM

thanks everyone for the education. I wasnt having problems with it. I just got curious and ended up cutting it open after it wouldnt pass a continuity check. I couldnt understand how it was working but I couldnt get it to show continuity. Its a serial/USB cable that ties together my EFIS system and IFLY 720.