USB connection problems - a closer look

I recently built a new PC and after a few good prints the connection errors just kept piling up, making even short prints impossible.
The usual "cure" seems to be the recommendation to simply print from an SD card and to avoid the USB connection altogether.
As I never liked avoiding a proper fix with a substitute I started to investigate why my new PC could have these problems.
Mind you the old one has done 40hour+ prints with no connection issues at all.

My first round of investigation was to check what happens in the device manager and of course, when the printer stops, the corresponding Com port disappeared.
This was a clear indicator of massive USB problems.
Either the bios or the OS deactivated the entire port, I mean the USB not just the emulated Com port.
On my Gen6 board is a nice green LED and it has a dual purpose.
In normal conditions it just shows you that the power is connected and it goes off if the power is lost.
But if you add another LED directly into the power supply line, or in my case just connect the fan directly to the circuit board, the green LED has an added function.
If the board still has power (fan spinning, additional LED on) but the green LED is off, it indicates the board had communication or initialisation problems.
I was unable to see if the LED goes off before the printer stops or later it seemed to be at the same time.
But the device manager reacted later, which means the problem originated on the pinter and not somewhere inside my new PC.

I could not find any obvious fualts with any part of the power connection but a friend of mine (HiFi fetish) started to laugh about the "flimsy" connections.
He offered to test the power connector and it's connection at his place with some fancy audio tricks.
While he was busy soldering and setting all up I did a search on the web for the power connector and got a bit shocked.
All of them in this size and type are rated for a max of 5A, some for just 1A.
Considering the power demand I started to wonder...
Once the setup was complete we could hear an audio signal from a generator over the power connector (soldered off the board to avoid interference or other problems).
The signal sounded fine and on the oscilloscope there was little difference between the generator signal and what made it to the speaker.
However, when I started to slightly wiggle the plug in the socket the signal on the screen distorted and in some cases you could hear some crackling noise.
According to my friend this indicates a "dirty" connection, like in the old days when people actually cleaned the potentiometers in the HiFi equippment to prevent and problems.

With nothing to loose a destructive investigation of the actual contact areas was performed and no surprise the contacts were discolored, indicating heat stress.
I soldered a power connector from an old laser printer, rated for 250V / 15A onto the board to replace the flimsy original.
This was two weeks ago and since the replacement not a single connection problem happened.

Of course you still have to make sure to use the right settings in the software, firmware and Windows Com port....
But it might help other that started to get USB issues after a long time of no troubles.

In the past few years I have been busy with prototyping electric car batteries upto 400kW/1000A. We always used "conductive grease" for all the power terminal to eliminate the problems you described.

Conductive grease can be DIYed with graphite powder and some thick oil.
The original phoenix contact power connector should be rated for higher amps than 5A, but the counterfeits we might see on the Ramps clones are probably less.

Directly solder the PSU to the Ramps is another option.

I don't think any type of conductive grease will help if the connector in question it totally underrated for the job.
My two concerns with the genral design of these connectors, like on the Gen6 boards and similar, if that there are build in faults.
You need quite thick wires but the screw terminals can't really put enough force on them for a secure hold.
Although the actual pins might be up for the job, the contact area inside the connector is far too small for the power usage - every slight contact problem causes overheating here.
I agree with you though that a completely soldered connection with no plugs should be prefered, especially for heated beds.
But as I said, the main focus was on the USB issues caused by these bad connections.
I really fail to see the point in juggling SD cards if the USB connection is stable for 24 hour+ prints

I agree, conductive grease can´t do wonders.

In the future we will all be able to use Toshiba FlashAir SD-cards. They combine WiFi and SD-memory.
No need to juggle SD-Cards anymore, just send your data right to the printer. Even on_the_fly adjustments thru WiFi will be possible, no more risk of melting USB cables from bad ground loops.
-Olaf, sorry for getting OT

Edited 2 time(s). Last edit at 09/12/2015 02:51AM by o_lampe.