[time-nuts] Re: Lpfrs-10 serial port failure

[Gregory Beat]

   Alex,

   The easiest TTL to USB Bridge Chips to use are from FTDI (~25 years
   with OS driver support and ability to program). FT232R originally,
   FT232RN newest.

   [1]https://ftdichip.com/wp-content/uploads/2024/12/DS_FT232RN.pdf

   FIRST, Determine the Voltage Level (5, 3.3, or 1.8) of the TTL DATA
   Lines.

   The Type A USB connector will have 5 V, per standard.

   I will assume a 5 Volt TTL Data Line.

   Sparkfun FTDI USB to TTL (5 volt) Cable.  It uses the FT232RQ IC

   [2]https://www.sparkfun.com/ftdi-cable-5v.html

   Schematic of Cable

   [3]https://cdn.sparkfun.com/assets/b/2/e/e/5/FTDI_Cable_5V.pdf

   FTDI FT232RQ Part Page

   [4]https://ftdichip.com/products/ft232rq/

   Now, the FT232RQ has EEPROM.  It can be PROGRAMMED !

   The Best feature for your LPFRS-10, You can INVERT the TTL Data Lines.

   Download from the FTDI Utility Page

   [5]https://ftdichip.com/utilities/

   FT_PROG 3.12.70.678 programming utility is available for download,

   by clicking [6]here.

   READ to Understand User Guide (You can BRICK Chip with Improper Usage)

   [7]https://ftdichip.com/wp-content/uploads/2020/07/AN_124_User_Guide_Fo
   r_FT_PROG.pdf

   gb

   ==

     From: HB9DRI, Alex Artieda via time-nuts <time-nuts at lists.febo.com>

     Sent: November 19, 2025 11:52 PM

     To: time-nuts at lists.febo.com <time-nuts at lists.febo.com>

     Cc: HB9DRI, Alex Artieda <hb9dri at bluewin.ch>

     Subject:

     Dear friends,

     I am totally new in this list, looking for a solution to a problem
     with my Lpfrs-01.

     I had this unit second hand, in optical an functional pristine
     condition ,

     take only 3min to lock. All looks good, except I cannot connect to
     the serial port, the device specified TTL Rx and TX in the label, no
     response at all when send M, when is

     connected to a USB / UART converter and I send M the TX line show a

     permanent 3.6vdc and a train of pulses show up in the oscilloscope,
     at

     the same time the DX line is clamp to 1.4vdc and nothing appears,

     suspect the serial interface buffer is damage.I will apprecite some

     advice to repair the unit, I try tl fk d a diagram with no success,

     only few tier down photos, maybe some body can point me where I can

     start looking, maybe a IC to replace.

     Any help is welcome.

     73 de Alex,

     HB9DRI

References

   1. https://ftdichip.com/wp-content/uploads/2024/12/DS_FT232RN.pdf
   2. https://www.sparkfun.com/ftdi-cable-5v.html
   3. https://cdn.sparkfun.com/assets/b/2/e/e/5/FTDI_Cable_5V.pdf
   4. https://ftdichip.com/products/ft232rq/
   5. https://ftdichip.com/utilities/
   6. https://ftdichip.com/wp-content/uploads/2025/07/FT_Prog_v3.12.70.678-Installer.zip
   7. https://ftdichip.com/wp-content/uploads/2020/07/AN_124_User_Guide_For_FT_PROG.pdf