Icom IC-706

Mark 1 - the original “Shack-in-a-box”

• HF 100W
• 6m 100W
• 2m 10W

• From the Silent Key equipment of Peter GM0CXQ

• In poor condition cosmetically, internally and externally
• Intermittent RX performance on several bands, most severely 6m, due to LPF switching relays
• No Power cable
  • ordered via eBay 24/5/23
• No microphone
  • ordered via eBay 25/5/23
• Not “MARS” modified → no TX on 60m

• Sensitivity ok on all HF bands
• 6m shows intermittent “deafness” after changing bands - LPF relays?
• Initially some higher HF bands also showed slow decrease in sensitivity after a few minutes. After transmitting a few times on each band this tendency stopped - have the LPF relay contacts “wiped” themselves clean by carrying more significant signal current on TX?
  • 6m still suffers random RF signal loss on RX
• TX power ok on all HF bands, and 6m, with 100W FM carrier at setting “H”
• All controls work correctly
• Fitted FL-223 “Narrow SSB” filter option appears to work (TBC)
• Frequency calibration not checked but appears to be acceptable.

• All knobs removed and washed in warm soapy water and all grooves in knobs scraped clean with toothpicks.
• Front Panel cleaned, all recesses around buttons/controls cleaned with toothpicks and warm water (being careful….)
• Covers from main unit removed and washed to remove build up of dirt from inside and outside.
• Inside of main unit vacuumed and blown to attempt to remove as much loose powdery dirt deposits as possible without damaging any connectors or components. Some cleaning of surfaces done where possible.
• Re-assembled

• To cure signal loss on RX I removed the LPF board and was able to pop the clear plastic tops from the 2 relays, used on either side of the 6m LPF section.
• Contacts in RL2 and RL3 were cleaned with Contact Cleaner spray, and wiped with paper soaked in cleaner, to remove any dirt/contamination build-up.

• Tops replaced on relays and LPF board replaced into radio.
• Receive sensitivity now good and does not vary with time, or following band changing.
• The relays used on the other HF bands are of a different (more easily sourced) type and can't be opened in this manner. Fortunately they all seem to be healthy at the moment.

• To allow use on the 60m band I carried out the simple modification to remove “D59” from the Main PCB, which removes the “TX only in Ham Bands” restriction.
• Radio now transmits across the whole HF band, including 60m

For Digimodes using fldigi and a Signalink USB soundcard requires a simple Cat5 ethernet cable to connect the IC-706 Mic socket to the Signalink USB soundcard. The Jumper information is here : https://tigertronics.com/sl_wirebm.htm

Connect serial RS232 from laptop to IC-R75 and then C-IV cable between IC-R75 and IC-706. The IC-R75 will convert between RS232 and C-IV. Separate C-IV hex addresses means each radio can be addressed individually through one serial connection (/dev/ttyUSB0)

rigctl -m 3009 -s 9600 -r /dev/ttyUSB0

gm4slv@laptop:~ $ rigctl -m 3009 -s 9600 -r /dev/ttyUSB0
 
Rig command: f
Frequency: 10147600
 
Rig command: m
Mode: USB
Passband: 2400
 
Rig command: q
gm4slv@laptop:~ $

• User Manual

• https://groups.io/g/IC706
• http://www.hampedia.net/icom/ic-706-enables-out-of-band-transmit.php
• Possible alternative Microphone HM-152 hm152schematic.pdf