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My UCR201 receiver acts weird when I power it from an external supply. The RF level and audio levels aren't correct. Everything works fine on a 9 Volt battery. What's happening?


UCR201 receivers built between the beginning of 2004 and January of 2005 have a voltage divider problem that we became aware of in early February of 2005. External supply voltages greater than 12 Volts overload the analog inputs of the microprocessor and cause all analog readings such as audio level and RF level to be incorrect. This also causes the scan function to work incorrectly and display "interference" in frequency bands where there actually is no interference. 

The quick solution is to run the 201 from 9 Volt batteries or power it from voltages below 12 Volts. The permanent and better solution is to let us modify the unit at no charge, in or out of warranty. This can be done by us at the factory, by one of our servicing dealers or by you if you are moderately handy with a soldering pencil. We will send the surface mount diode, layout drawing and "fix it" instructions to anyone who needs the fix. Check with service to get the package. We include an extra diode because if you drop one on the rug, you'll never find it.

All units shipped after 9 Feb 2005 will have the same fix as described below and the next board rev will incorporate the exact same fix. The fix consists of a small SOT23 surface mount diode from the offending voltage divider to the 5 Volt supply at the micro-processor. The 3 terminal diode is soldered to a copper trace and to two vias on the board. It is necessary to scrape a little bit of solder mask (green screen) from the trace so the solder can bond. This fix, or attempt at a fix, does not affect the warranty. Using a Black Beauty soldering iron and blow torch will, however, result in nasty comments from the repair crew.

  • Here's the S/N for the affected 201's.
  • 4895 to 5649 need to be modified.
  • 4795 to 4894 are in a grey area and MAY need to be modified. This can be checked by operating from a 9 Volt battery, finding a clear RF frequency on the display and then plugging in the CH20 supply and seeing if the RF level goes up 3 or four steps. If the CH20 level is different than the 9 Volt level, the unit needs the modification.
  • Units before 4795 are OK.
  • Units after 5649 are OK

The following units were in our finished gods and have been modified already:
5269, 5304, 5321, 5389-5394, 5417-5419, 5458-5459, 5463, 5465-5469, 5471-5479, 5484-5504, 5508-5515, 5517. Dashes indicate anything between these number are OK.

Another rule of thumb. Anything shipped from Lectro after 9 Feb 05 is modified and any units in for repair after that date will be modified.

Posted 1 year agoby LectroAdmin