Serit LNB DC supply

A number of people on the BATC forum have reported their Serit tuners are no longer outputting the LNB voltage from one of the F sockets. The cause is inevitably an open circuit inductor (L101 or L102) after the output has been accidently short circuited.

This page describes how to repait the tuner and also a new PCB with DC current limiting available from the BATC shop.

Repairing the Serit DC output

It is very easy to blow up the RF choke feeding DC to the F type inputs before connecting to a dummy load or short circuit antenna - or by just shorting the centre pin to ground. The result is DC on the connector on the main board but no DC on the F type center.

Each F type is fed by a seperate RFC which looks like a ceramic capacitor and is shown in the picture below. These can be replaced with care with a normal leaded RFC or SMD RFC.

Dave M5TXJ posted this modification on the BATC forum using a 10uh wire ended inductor. Note - to repair the other F socket feed, the dc input pin to the NIM is the one directly below the one used in the photo.

LNB power supply with current limit for MiniTiouner

In CQ-TV 265 (Sept 2019) Colin, G4KLB, describes an add on PCB to provide current limiting using the RT5047 device.

The PCB is available from the BATC shop https://batc.org.uk/category/usb-receivers/

Parts list File:RT5047 LNB POWER REV 2-1 PARTS.xlsx

Schematic PDF File:RT5047 LNB Power.pdf

Schematic

PCB fitted to standard enclosure

PCBs

Wiring to MiniTiouner v2.0