Is there a simple way to check (with FTDI cable for example) my ELRS module on the bench without soldering it to FC.
My FC went on Saturday, not sure why, physically can’t see anything and no shorts but it got very hot very quickly with just 5v from USB and lights kept going out. Only thing left connected was the ELRS so before soldering that to the new FC (hopefully arrived tomorrow) be nice to check this. Whilst sorting these GPS tonight it’s a good time?
First thing has to be the power.
Connect it to a 5v supply and measure the current drawn, it should be only a few milliAmps.
If it gets hot, bin in 
Ahhh. Yeah makes sense. Course. Silly question Ive only used my multi meter for continuity and DC volt checking… How I measure a simple 5v/gnd power usage? Serial or parallel em over
Also Stevie… Want those runcam ND filters? See me pm!
Sorry, had family issues and they dropped off my mind.
I’ll send PayPal transfer and postal address now 
That one for current
Switch to DC volts… Black on Ground connection, Red on where you want to measure voltage.
Choose a scale larger than the volts you expect to read.
As Karl says, in series with the circuit to measure current. Though that is usually less useful.
You can get a digital signal analyser to look for actual signals on the TX and RX wires. I have a cheap USB one.
https://smile.amazon.co.uk/gp/product/B00DAYAREW/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
If the FC is getting very hot then checking for any excess current draw from the RX is rather useful 
I guess… though just unplugging it will do that…
Yeah well the FC definitely dead. Very hot one light and yeah…
The elrs doesn’t even power up… Damn. Fortunately vtx seems ok. Frame in good nick too after all the bashing it’s taken.
New FC and I also ordered another elrs or two in case so that’s good arriving tomorrow. Fingers crossed get it built for weekend.
Also another positive note the GPS that @yith recommended worked when connected to PC so can be added to the smaller quads. Yay
Also the ESC seems to make noise with the 4 motors and they all move a little. Guess can plug in new FC and straight off test those without soldering anything up!
Yup sounds like the ESC is fine…
A simple way of testing receivers without having to use a flight battery and some sort of BEC is to use USB power (5Volt) directly to the receiver. For pinned receivers I take a regular USB lead and cut the end off. Then solder the 5Volt and GND wires to a regular servo plug. For the power I use a regular USB power bank.
This setup makes binding regular receivers so much easier than trying to hold down a bind button while simultaneously trying to mate the XT60’s with the other hand.
You can measure the voltage drop and current taken by the receiver with a USB Volt/Current meter. Also most power banks will turn off if the current draw is excessive, a LiPo connected to a BEC will continue supplying current until something catches fire and breaks the circuit.