The Apex DT250

Repair of the Tuner

Apex DT250
Apex DT250.  Power Board (PB) on left.  Video Board (VB) on right.  
The IR decoder board is hidden in the front panel.

I have had several units over the years for my old analog TVs, and have found their reliability a bit lacking.  These are the repairs and my analysis of their operation.

Connectors for the boards are on the bottom row in the above image.  PB-CN3 is the larger one on the left (on the PB) and PB-CN4 the smaller one on the right.  The VB has VB-CN8 on the far right.  Pin 1 are always on the right for these.  The pinout of the larger connector on the VB is not shown as it is the same as PB-CN3.

Connector ->PB-CN3PB-CN4VB-CN8
Pin ->6543213215432
These are the voltages and functions on the pins

Repair Log
  • 10/2011 - Repair of C8 (470 uF) on PB (red below).
  • 4/2020 - Same repair on another unit as above.
  • 5/2020 - No video output.  Found bulging CE57 (1000uF) on the VB.  Shows up bright silver in above image near left on VB.  Once replaced the unit worked fine.
  • 5/2020 - Unit would not turn off.  The front panel LED responds correctly to ON/OFF command, but video output stays on and pass-through is not enabled.  It turns out that the front panel board has the IR decoder.  It commands the PB to turn on the 13V bus via PB-CN4-2.  Found PB-Q2 to be shorted.  It is a large plastic PNP 2SA684 bipolar transistor (had date code of 2007).  From top to bottom, their pin order is B,C,E.  I replaced this with a metal can 2N2907 with the pins swapped around and the function was restored (green below).
  • 5/2020 - Low output on PB-CN3 and no video output.  Found two more bulging 470uF capacitors on the PB (see in blue below).  You can see their cans have an uneven silver color in the image.  

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