I purchase 6 x QBOX3 (TBS 5921) a month ago after having very stable performance and good build quality from TBS 8920 for over a year. Since then, I have been unable to get them to work properly when going through any type of distribution multiswitch. My problem appears to be similar to this:
https://shop.tbsdtv.com/forum/viewtopic.php?f=21&t=196
I believe there has there has been a design error in the TBS 5921, just like the TBS 6920 (notice that the rep never reported back at the end whether the returned card was indeed defective be design, and just quietly replaced the unit with an improved , or should I say corrected, TBS 6921 card). When using 22Khz=on, the device sends some disruptive signal that shuts down the multiswitch, causing signal loss on all ports until the device is off, reset or unplugged.
Before we continue I wish to remind everyone the 22khz switching is a VERY BASIC and universally used distribution switching method found in SMATV systems, universal LNBs, DirectTV multiswitches, etc. If a DVB-S tuner product does not work with 22khz tone, switching, it might as well be an empty box.
I was told by support to test one card at a time. In the first week I was reluctant to do this, as, if it does world that way, what does it mean? That I can only use one QBOX3 in the SMATV network???
After spending a week trying Windows XP and Windows 7 on two machines (one Atom, one i3, clean installs - nothing on them) with DVBLink, DVBViewer, TBSViewer and SageTV, I was unable to get a working setup for the 22khz=on port (the 22khz off ports always workd fine). Sometimes is will scan about halve the channels, sometimes none. With DVBLink, I once manage to scan all the channels, but actual use is not reliable - just switch the channel a few times between 0/22Khz channels and boom - stops working. Restarting does not help. 2 days wasted.
In the second week, I thought, maybe I will follow the advice of support, so I try just one device - same results - another 2 days wasted.
In the third week, I thought maybe it is my hardware. So I got out by regulated linear lab PSU, set it to 7.5V, and plugged it into the Qbox3. I then got out my Promax TV Explorer (Prodig 5), and painfully verified the signal quality (50dB<power<85dB, VBER < 1E-7) of each transponder on all my 4 LNB signal lines - both before the inputs and after the outputs of my DirectTV approved, top quality Zinwell MS6x8WB multiswitch (which by the, way, has been running an Openbox S9, Mediastar HD1100s and a Mediastar HDX9100 with zero pixelation of dropout, throughout these weeks). I when and got an Intel D525MW mainboard with integrated Atom CPU, 2GB a Kingston RAM, and a Kingston S100 SSD. After installing windows and the Intel official drivers, plus all updates, I rebooted, and downloaded the latest TBSViewer and 1.0.0.2 drivers off tbsdtv.com. After plugging in Qbox3 and installing the drivers, I rebooted and ran TBSViewer to do a scan of Chinasat 6B, I set LOF1=5150, LOF2=5150, LOF SW=3400 (min C-band freq) as I have the V/H independent outputs from my commercial LNB connected to the 22khz=on ports of the Zinwell MS6X8WB. After doing a scan - same problem - no lock on about half the transponders. Exited TBSViewer, rebooted and tried again - this time, the same problem as the other guy with his TBS 6920 - signal loss on all ports of multiswitch until Qbox3 is shut down. Unplug the same cable and plug straight into the Mediastar HD1100s - perfect picture - 99% signal quality.
One of the many transponders that it fails to lock on 22khz-on port is Shanghai (3808Mhz, H, 8800Ms/s), but the bigger problem is the emitted signal that causes multiswitch to fail. I will try to measure this with my scope - by why waste so much time on the faulty hardware - where is you test Engineers TBS? Your hardware is great quality - with solid caps, well moulded cases and overengineered 265V PSU, why waste all the hard work on these little problems. They are probably just a little bug in you driver - but look, you did admit to any problem with you product, and now I have wasted 3 weeks, which I could have used elsewhere. We could have done a lot of business together, but you ruined it badly.
Just a note: I have just tried a 2 year old TT-budget S2400 unit, which worked straightaway after plugging in to the same USB port on the same PC and installing drivers. but Qbox3 have much better chipset and S2 support, plus better build quality - but does not work - such a waste, such a pity!