Is it possible to reverse a HDMI switch?

Jourei

I meant to get a HDMI switch for my PC, so I can switch between a monitor and TV.
Didn't realize I got a 2 in, 1 out switch which turned out to be one-way (I had no idea that would even be relevant).
Since the store won't accept it back as I already opened the package, I decided if I could put my electrician's skillz to good use and found out there's really only one switch and one diode for each input.

My question is, can I modify the switch to work both ways or reverse it completely?
I reckon something should be done to the diodes, but I don't have any hardware that I don't mind breaking...

Philip4242

Have you actually opened up the device and seen this for yourself ?

I'd be curious to see a picture of the circuit board and components.

Jourei

Not exactly sure why I didn't do that already...

HAMA HDMI Switcher 2x1 - Imgur
The device is HAMA HDMI Switcher.

noiseboy72

Looks entirely passive, so give it a go.

Just switch it with the power off, to avoid any hot plugging issues. You may also hit EDID issues, as the card will need to detect the new display and set up a correct resolution for it. Usually, you just get  blank screen for a few seconds, but it may crash the card - I have 1 laptop that you simply cannot hot plug, as it crashes every time.

Jourei

I've been hotplugging my devices every time I wanted to change the device.
When I plug that device in between my PC and TV or monitor, it just flat out doesn't work.

Would be nice if someone with great knowledge in electronics would stumble upon this thread.

noiseboy72

So far as I can see, there are just 2 diodes, I assume to prevent the active voltage pin being driven by another source.

You could try removing and bridging these, or spinning them the other way around?

Jourei

I reckon that's the only thing that can really be done, just wanted to be sure since that could be an expensive mistake.
Will bypass one of the diodes to see what happens.

Jourei

Okay, f this...
So I jumped the diode with a simple piece of wire, and the screen got a signal.
Seems like it only needed a pulse.

Why would they make a device like this? What's the potential harm that could happen if you used a device like this backwards, which is why they would prevent it functioning like that?

tl;dr: bypassing the diode even for a moment works as a solution.

Update: Not exactly after all. Seems like the other device needs some pulse to start listening that port? It seems to work only with which ever screen is plugged first. This requires a bit more tinkering. :l

plm61

If anybody is still interested, I found a HAMA HDMI Switcher 2x1 and modified it in order to make it work in reverse mode (1 input, 2 outputs). Actually, bypassing the diodes is not the correct solution and may be dangerous for the attached devices. Since in the passive switch there is no room for all the HDMI channels, the  5 V wires are not switched, but connected in parallel through the diodes which avoid current flowing from one power supply to the other. Please note that the  5 V channel is required since it is often used to enable the input port. To make the HDMI switcher correctly work in reverse mode, the diodes' polarity must be reversed (remove them, turn 180 degrees and put back on the PCB - this requires some soldering skills). This should overcome the Jourei's issue.
Hope this helps.

globe1701

Thanks plm61, works like a charm although soldering those small SMD diodes backwards was a bother.
For other people that might be not so skilled with soldering (like me), before you start, mark both diodes on one end (make a scratch with a needle) and you'll avoid some hassle if you drop them during the procedure.