Inside an almost dead Hitecastro hub

[coldlegs]

Some time ago I ignored the cardinal rule about checking the centre pin of a dc connector was +12v and paid the price. I could be forgiven as the cable was a commercially made one in two out cable that had worked attached to my gear for some time until one day I decided I needed to make a seperate dc cable to run a filter wheel and cut off the unused side of the cable. It turned out that somehow the manufacturer had wired the centre conductor to the outside of the plug and I had just been lucky not to use that side. Didn't think that was possible but believe me it is!! Of course there was a bang and a flash and the power supply did its usual trick of shutting down to protect the fuses (!!) . Thought I'd blown up the filter wheel but it was ok although the Hitecastro Mount Hub Pro had stopped working so being a tech I jumped in and opened her up. Inside were three boards. A seven channel usb hub with a small switch-mode power supply and in the other half a main controller board. Five of the usb are outputs and a sixth is dedicated to the main controller with the seventh unused. Turned out the usb hub was dead so I wired the main controller to an output usb plug and everything still works fine through a single port. I could have sent it back for repair but it would have cost as much as a new hub anyway. Speaking of hubs, I really want a hub that can be commanded to electronically shut down and re-boot a single port (both digitally and DC). Do you know of any? Enough chat, here's an inside picture of the Hitecastro Mount Hub Pro.
Cheers
Stephen

[frolinmod]

I opened mine up when I first got it. I wanted to replace the stock USB cable with a different one. My MHP is the same basic design as yours, but the details differ a bit. One difference is that the USB cable on mine is not soldered to the board. It's a regular USB A to B cable and there's a USB B socket inside that it plugs into. That made substituting a different cable trivial. The extra unused internal port in mine also has an actual pluggable port inside. I don't remember if it was mini-b or micro-b. I don't think it was A. I'd have to open it up again to check.

I presume you have some peripherals that are USB powered and want to be able to power them up and down remotely. I suppose you could use one of the switched power ports on the MHP to power a 12V relay whose relay contacts would make/break the +5V line on a corresponding USB port.

[multiweb]

Interesting to see the guts of it. I'm surprised the cabling is running across those small heatskinks on the PCB though. I suspect they're the dew heater channels? Is this something to worry about long term?

[coldlegs]

Frolinmod / Rally
The reason I'm after a hub that can “smoothly (electronically)” turn of a port is the dreaded “Blue screen of Death” (BSD). If you google “usb blue screen of death” you will see this problem going back decades and usually the problem relates to drivers/software updates etc. Most of the time they are right but I'm almost certain there is another hidden problem that relates to what happens when an electronic device is plugged into a usb port causing the crash. Take for example a when a web camera is plugged in. All the bypass capacitors on board the camera start to charge from 0volts to 5volts and even though the camera may use 90 milliamps in normal operation the charging current surge is 1-3 amps for up to 10-20milliseconds. At the same time as this is occurring the power contacts in the plug are making and breaking as the plug is seated, causing the charging current surge to break up into a series of short high current spikes. These feed into the hub and onto the pc and I suspect randomly cause the BSD by either a current overload or some kind of ground current spike the pc doesn't like. In my case there is also about 4 metres of usb cable with associated inductance that will cause ringing and possible negative voltages to be produced which is something you really don't want around digital circuits. For the moment what I have done (and have yet to test) is to take a usb isolator (see attached file) and remove the +5v/+5v isolated supply stopping the pc from supplying power to the hub and to force the isolator to use only the +12v at the mount. This is connected between the hub and the pc so the ground and power lines from the pc are totally isolated. This should prove one way or another if I'm right about these current surges causing the crashing. The other option was to use a clever hub that would turn on/off a port smoothly with a transistor of some kind thereby avoiding current surges. But that may be asking too much from manufacturers.
Marc (multiweb) Don't worry about the cables. If the heat-sinks were that hot you pcb would probably be on fire anyway. Well maybe not on fire but they wont get that hot as the dew output is pulsed – hard on – hard off so it's reasonably efficient.

Cheers
Stephen

[alistairsam]

Stephen,
I'm not entirely sure if the BSOD (as we lovingly refer to it in the industry) is caused by the USB interface
One way to troubleshoot us using the stop error codes
Have you checked that?
It'll show up in the BSOD as stop 0x0xxxxx
Microsoft have explanations for each stop error and resolution
Paging or mem access violations are common causes
I haven't looked it up but the USB standard would allow for surge currents else there'll be millions of devices affected
I use a 5m USB extension lead and a hub with no issues across three different pc's/ laptops
Are you able to repeat the error with a different laptop?
I wouldn't worry about the hub being the issue, but look at the pc/laptop side and diagnose the BSOD
Cheers