Radio and Equipment Issues I have Experienced

ICOM CIV and Yaesu CAT Control USB and USB to Serial cables

Many of the cheaper USB ICOM CIV cables use the counterfeit Prolific chips and don’t always work reliably, especially with Windows 8 and 10.    Ebay store bluemax49ers offers cables at reasonable prices that work and also provides support for them.  I’ve also experienced more severe issues with Yaesu cat control using USB to serial converters and recommend purchasing your cables from this Ebay vendor.  If you have to use a USB to serial for serial control, look for FTDI chip based converter.  It may cost more but you will have less headaches.

A Death Threat on your ICOM 706MKIIG HF/6 meter PA

Heard horror stories of the 706MKIIG having blown finals and there are no OEM replacements available?   There is an issue that needs to be addressed that might save yours from an untimely demise. This dosn’t apply to a 706MKII so you don’t have to check it.  I am not sure about an original 706.  Over time the repeated insertion of the PL259 pushes the center pin back until it shorts out against the radio frame. This only happens on the HF/6 connector.

Remove the top cover (the one with the speaker).  At the rear of the radio where the HF/6 SO239 connector is located, remove all the screws on the circuit board covering that area and gently lift up slightly and slightly to the side. Do not try to remove it entirely, just enough to look into the area at the back of the SO239.  See the center pin with the wire soldered to it?  How close is it to the extruded frame of the radio to the rear?  Almost touching?  Mine was. There isn’t much space between the pin and the frame when the pin is properly seated.

The Fix – Push the center pin forward into its original position. Insert an insulator of some sort behind the pin so it cannot move backwards.  I use a piece of Teflon block wedged behind the pin.  Reassemble and no more worries on shorting out your PA.

ICOM/YAESU/KENWOOD Power Output Issues

Recently one of my friends called and said his Icom was shutting off on transmit.  I told him to change out his power cable.  He argued with me it was not the problem.  He lost that argument after I convinced him to try a spare power cable.  This was the third time I have seen this issue. The first time I experienced it with a 706MKIIG I noticed the fuse holder got hot.  A little reading uncovered what was causing it.  The crimps on the wires to the fuse holder clips develop resistance in the connection over time.  Soldering the crimped areas  cures the problem.  This could also happen on the power plug end as they are also crimped.   Also the pins of the power connector itself can be at fault.

Swan Radio Issues

I’ve repaired a lot of Swans.  SOP for any tube Swan that crosses my bench is replace all electrolytic capacitors including the can capacitor.  After a half century of deterioration, it’s nothing but a ticking time bomb if you don’t change them.   Don’t forget the power supply capacitors.  Radial lead capacitors with long leads can be used to replace the OEM axial lead capacitors in the power supply at a much cheaper cost than new axial lead capacitors.  Also, radial lead capacitors can be used under the chassis and the ground point can be any convenient ground point available if it won’t reach the original.  Watch that polarity as there is a -130 volt bias circuit where + does go to ground.  I’ve also used small circuit boards to replace the can capacitors with individual capacitors.  In some models, the can cap only has 2 caps inside the can so its easier to just hang 2 caps under the chassis than try to replace it.  Get a squeal/feedback when volume is turned up?  Almost always bad can capacitor for any of the Swans.

There may be some 160 volt capacitors in your radio and these should be replaced with at least 250 volt rated parts.  All other capacitors are fine with the OEM rating unless you just want to put ones with higher voltage ratings in.  Also its OK to substitute an electrolytic capacitor  with the next higher value if you can’t find one that is similar in value/voltage rating.  OEM 100 uf caps in the power supply were 350 volt, I use 450 and usually replace with either 120 uf or 150 uf capacitors from my supplier. It makes for a bit more PEP output.

Check all 1 and 2 watt resistors and replace if out of tolerance if more than about 10% to 15%.  You can almost be assured the 2 watt 150K bleeder resistors in the are out of tolerance.  You can get 3 watt metal oxide resistors to replace them and they are same or less size than 2 watt carbon.    1/2 watt resistors that are problematic are 100K, 270K, 470K, and 1 meg ohm. The 100K ohm resistors in the balanced modulator circuit are usually cooked pretty bad.  Replace with 1 watt metal oxide as they will last longer.  DO NOT DESOLDER A RESISTOR TO CHECK IT.  If it doesn’t read within tolerance in-circuit, clip one lead where it can be tacked back together and read it.  Heating the resistor lead seems to make most of those that read high move back into tolerance.  How long it will stay is not worth having to work on the radio later to correct the issue so replace it if the reading is off.

The only bad tubes I have consistently  found are the finals (6HF5, 6LQ6, 8950) and to a lesser extent, the 6GK6 tube that is used in both the audio and driver stages.  Examine any 6GK6 tube that is used as a replacement to make sure Pin 6 does not have a internal connection going somewhere inside the tube.  If it does, either do not use that tube or you must make sure that pin 6 of the socket under the chassis does not have anything tied to it.  If I find one of those tubes with the internal connection, I cut pin 6 off flush with the bottom of the tube so it does not make connection to the socket and if plugged into another Swan it won’t cause an issue.  If you or someone else has plugged one of those into your Swan and something is connected to Pin 6, it will take out a couple of parts and require more repair.

If someone has used light oil,  WD40, or some other solvent/lubricant to spray the Jackson Drives, I feel sorry for you.  Nyogel  damping grease is the only thing available I have found that will fix it and it will require a lot of work to remove the Jackson Drive from the VFO compartment to clean and replace the grease in it.  Don’t waste your time trying to substitute something else, it just doesn’t have the same feel.

if your meter needle is sticking somewhere in it’s movement, its usually because the plastic scale has warped.  This requires front panel removal, taking the front meter cover off, removing the 2 screws holding the scale, removing it, and then reforming it so it lays flat.  I put the scale between 2 pieces of paper, place that between 2 aluminum plates, place in a toaster oven, then turn the heat on while observing progress.  As soon as the plates fall flat, off goes the heat and then allow to cool for awhile before touching them and removing.  This also works great on the dial if its warped. Don’t over cook it!

That black/brown spot on the plastic behind the dial is caused by using the wrong lamp.  This can be replaced with translucent acrylic sheet that is cut/filed/drilled using the old plastic as a templet.  That can be purchased on Ebay. To reduce the heat and prevent future damage, replace the #47 lamps with #44/47 LED lamp replacements. sells them in different colors. I prefer the cool white over the original yellow lamps.  They are very bright! Both lamps must be replaced with LED lamps as they are in series and only replacing one lamp with a LED lamp will result in burning out the LED lamp.

Got drift?  It’s a Swan.  FIRST – Check the bandswitch phenolic wafers and see if its soaked in oil from tuner/contact cleaner. If so, you have to remove it using denatured alcohol or other non-contaminating solvent. Once all the oil is washed away, hope it’s fixed.   Then its a shot in the dark.   Could be issues with zener diode regulator circuit or 2n706 transistors.   One thing that will help reduce the drift if its not one of the above problems is replacing all the resistors on the VFO board with 1% metal oxide.  This has made great improvements in the radios I have worked on.  Also I found that most if not all the carbon resistors on the VFO board were usually out of spec quite a bit unless it was in an external VFO.