Kenwood TS-430s: SSB RX with very low AF volume and S-meter stuck at S-0.

 Repair Brief – Kenwood TS-430s – bad SSB RX.

 

DISCLAIMER: the following instructions are provided only as a report of my hobby experience. In no way I am responsible of any damage you or your device can suffer by following this procedure. Lethal voltages are present in the device!! Qualified personnel only! You know what you are doing and you are proceeding at your own risk!

 

Symptoms (RX only):

• In USB and LSB low volume and no S-meter deviation.

• Strong (local) SSB station are demodulated OK and can be heard with very high volume setting. IF-Shift and RIT working OK as well as NOTCH.

• AM and CW are OK.

 

Findings:

• In USB and LSB, the ACG line (gate of Q13) stuck at 2.5V, no matter of signal strength.

• Q17 (what is it useful for?!) voltages: 2.6V all terminals as per schematics.

• SSB line goes high when USB or LSB are selected (as expected).

• On AM S-meter is well calibrated for S-0 and S-9.

• CAR signal present @305mV RMS in USB, CW (8.8314KHz) and LSB (8.8284KHz).
  It disappears in AM.
  

Signals at IF board connector 27 seem not to be OK. it seems the SSB filter is never selected, leaving the signal path open.

 

The fault:

The SSR (SSB Receive - connector 27, pin 6) signal is driven HIGH in USB or LSB. That's ok.

It is then routed to the NAR/WIDE front panel switch through the IF board connector 27. It should come back as SSW (connector 27, pin 4) with the switch in the WIDE position, or SSN (connector 27, pin 2) with the switch in the NAR position. 

 

 

Neither SSW nor SSN go high regardless of the switch position: the switch is not working or the switch board is not properly connected.

S18 found not working.

Restoring S18 solved the problem.

TOWER 5 Transistors Walkie talkies from the 60s - The ones that ignited my radio/electronics hobby.

Tale of my first transmission : 27.125MHz - CB Channel 14.

When I was young (late sixties, first seventies) I got a couple of black TOWER walkie talkies.
They were shiny and looked like rocket science objects.

My actual units

It wasn't long before I realized they weren't usable: communications with a friend were difficult, if not impossible, even between rooms.
On the other hand, however, one evening, I heard voices coming out of one of the radios. They were people who chatted about this and that using esoteric language...as well as coded words (CQ, QTH, QRZ, YL, 88, Roger, K, ...).
I tried to make myself heard, but no one could listen to me.
Suddenly, while I was desperately trying to make myself heard, (are you listening? Hello, ready, are you listening?...) one of those voices answered me. He greeted me, welcomed me and ... explained to me that I had a "super regenerative" radio in my hands and that it could simultaneously listen to many frequencies but only transmit on a single one. That's explained me why I was hearing many voices but I had difficulty make me listen.
After a few days I met that person: he was an OM with a shack that looked like a spaceship to me.
BINGO. Since then I have been CB for years and have become passionate about radio and electronics.
Eventually I also got an ham license.

A DIY bench RF step attenuator with Arduino and Aeroflex-Weinschel step attenuators

A while ago I made a bargain purchasing a couple of Aeroflex-Weinschel step attenuators (models 150T/11 and 150T/70) for 20EUR each.

The idea was to implement a bench step attenuator for my lab.

Here is the project.

Those attenuators offer serial and parallel digital interface. I choose to use the parallel interface protocol.

Each attenuator is controlled by 4 bits (a nibble), so, with the help of the following map, I built an Arduino sketch to drive the attenuators by a rotary encoder:

The table on the left simply lists all the wires coming out of the attenuators with color and function.
The two tables on the right show the parallel protocol details for the 150T/11 and the 150T/70 respectively: what attenuator setting corresponds to which nibble value. They also show the Arduino micro<->attenuator physical interface (what Arduino's pin goes to which attenuator wire).

The attenuators were cascaded by mean of SMA to SMA RF rigid cable; the input and the output were brought to the front panel by mean of a couple of SMA to N Bulkhead rigid cables.
If it has been built following all RF precautions, the final product would be capable of reaching a DC-18GHx bandwidth. I suppose my implementation should be able to reach a couple of GHz, ...far beyond my actual lab upper limit.

The rotary encoder has been programmed to step the attenuators up and down. Pressing the knob, toggles between 10dB and 1dB steps.

If you want more details I suggest you to have a look at the Arduino sketch that contains a lot of comments. Despite making every effort to correct the problem, the encoder occasionally misses a beat.

The enclosure has been recovered from a previous project and the front panel layout has been designed using Kicad:

The 7 segment display has been recovered from an old industrial control board.

The switching power supply used in this project has been recovered form a faulty LAN switch. It provides the necessary 12V and 5V rails.

Here is the final product:

Have a look at it, live, during testing...

I had fun, I spent few bucks, I eventually have a bench step attenuator form my lab.

Hope this content can help other makers..

Ciao.