Power supply interference

[jw300]

When I first got the QBox, I noticed some interference with another device (Homeplug). I wrapped the mains lead through a ferrite core and this helped enough to restore operation. However, I recently had to replace my ADSL modem/router and the new one seems more susceptible to mains-borne noise (the old one had an AC adaptor with internal rectifier, the new one is the more common DC supply from external, plug-top adaptor). Switching on the power to the QBox produces very high error rates on the DSL, bad enough to affect service, even though the connected PC is not switched on.

Do all QBox supplies behave like this, or did I just get a bad one? The unit has no manufacturer name on the label, just the input/output voltages "85-265Vac 50/60Hz, 7.5Vdc, 2A" and a possible model number "3825A051", though Googling this produces only 12V supplies. The unit bears a "CE" marking, which requires compliance with EMC directives. It was sold in the UK, but with a Euro-style power connector.

Can TBS provide any advice on curing this problem?

[stuey1978]

Hey,

I've just found out that this is the source of my recent ADSL woes! My CRC error rates on my Adsl router have been through the roof since I plugged my qbox boxes in...just unplugged them and my Adsl connection is perfect again!

I found that leaving the power supply unit plugged in resulted in no errors too which implies that the issue might well be with the Qboxes themselves...

Anyone from Tbs want to comment?

[jw300]

The interference will only be seen when the LNB is connected, when more power is being drawn.

Another user in this sub-forum reports interference with MW radio reception (same frequencies as ADSL), so that's at least 3 of us.

From memory, the router stats suggested the interference was mainly affecting carriers around 700 kHz, with additional effects around 1,000 KHz. That suggests the problem is related to the power supply. Smaller switch-mode supplies can operate at switching frequencies in the hundreds of kHz. The unit must not have much EMI filtering.

I looked for an alternative PSU and found only a few as 7.5V is an awkward rating. I won't find out until I buy one if it's from the same source. It would be helpful if TBS could make a recommendation.

[kazimali25]

Switching mode power supply creating problem in many devices.Transformer base adapter working good.