Sunday, August 26, 2018

New RF frequency generator for the shack

Nothing build here, next time!

Before going on holidays I had the idea to get an rf frequency generator of good quality to be used as a reference when testing circuits.
Previous I built one based on an Si5750, also used at times an AD9850 or a quick crystal circuit but nothing permanent and referenced.
Searching online, I found probably one of the cheapest 1Gz frequency generator available  that an ham near my QTH was selling. The looks are not perfect, it had in the past a not so caring previous owner but gives a precision frequency output. Now developed a fault in the output circuit which I suspect probably due to calibration data missing, so I hope. Still it outputs a constant signal but still need to measure to confirm specs.

Here it is:

The knob is not the original one and the bezel around the power button is not in good shape, parts that I probably replace one of this days:

Knob: 0078.1192.00

The fault that it has is error 4 and according to page 11 of SMY Service Manual

Error message "Err. 4"
Level control does not work correctly:

- Level overrange
- AM overrange
- Overrange with AM EXT DC
- 'Level-Preset' calibration faulty

I just hope it was not me making any wrong setting (did it once when selected external reference and was error'ing since nothing connected), in any case will check output and run the calibration details to see if it goes away....

For reference the routine and troubleshooting areas are

Service manual Level Error
A5 Output Unit OPUY01/02
A12 Power Module option SMY-B40
A6 Attenuator ATT01

Page 18 - Level-preset calibration is special function 45.

And some more pictures. By the way the frequency is bang on, only the level, still not measured, looks a bit low when an S9 is generated and connected to an uncalibrated radio in any case.

Have a nice week!