Repair/Restore Process

The Steps to the Basic Repair and Restore

When we get a unit in for Repair, we go through a series of steps.  We try to do all the units the same, so that we do not miss anything, and it allows us to be sure to reach a certain standard of quality in what we are doing.  Our standard is original performance specifications or better, and to get the unit to look as close as possible to the day it was made.  Here’s the basic steps we do.

1)  We carefully unpack the unit, looking for any outside physical damage.  If anything is damaged in shipping, the whole process stops, we contact the owner, and decide how to proceed.  If OK, we read the packing slip, take the covers off and evaluate the rig.  Can we make the customer happy?  This is where we might reject a unit, if it is just in horrible shape or has been previously hacked up or modified.

2) Initial cleaning and lubrication.  With the covers off, we clean/lube all the easy to get to parts such as front panel pots and switches, and some of the rotary switches and variable capacitors.  We do this right away, because many units are sent to us after long term storage.  The sooner some of these parts get some lubrication, the better.  Any use of an electromechanical part that is 30 years old and never been lubed since new, is going to cause a lot of wear and we don’t want to add to the problem.

3)  First Test.  We hook the rig up to our HP8924C service test set and run it through it’s paces.   The 8924C is a large computerized test device, with practically every RF test instrument built in that you can think of, up to and including a spectrum analyzer.  We test all the receive functions first and then all the transmit functions.    All bands and all modes.  ALC, compression, everything.  All the controls are operated and checked for smoothness and quiet.    At this point we know for sure, what needs to be repaired, adjusted, and aligned.

4)  If the unit is going to be recapped, that is done next.  Hopefully, some or all the problems noted in 3) get worked out in the recap.  This means removing all the boards, and careful inspection sometimes reveals additional problems that need attention.

5)  If the recap was done, then a cursory testing of functions is in order to make sure that no mistakes were made, and to see if any of the problems from 3) have gotten worked out by the recap.  The 8924C allows us to check the unit out in a matter of minutes, to see exactly where we are.

6)  Next a thorough cleaning and lubrication occurs.  To me, this is the most important part of the whole process.  Stop and think about this. . . in the big picture, a Kenwood Hybrid will reach the end of its life when irreplaceable electro-mechanical parts get worn out.  Anyone who has restored gear from the 40’s and 50’s has learned this fact.   The electronics can be found and replaced.  Not so easy on all the electro-mechanical parts.  The clean/lube that we do should keep those parts in working condition for the next 20 years.  We really get into this, with a whole range of products, such as De-oxit, De-oxit lube, Corrosion X, TriFlo, various other dry lubes, bearing grease, and oil.  The goal is to get everything feeling and sounding silky smooth. . .  and protected.  Once contacts in pots, switches, and rotating contacts like rotary switches and variable capacitor shafts are clean, we leave them with a coating of Corrosion X.  This product was designed for aviation and marine use, and provides protection and lubrication that lasts  longer than any other product we’ve used.  A noisy pot treated with most of the other products might be noisy again in a couple years.  Parts that I have treated in my own gear with Corrosion X are still quiet after 10 years or more.  We pay particular attention to the VFO gear assembly, using dry lubes, to leave it silky smooth, with no oil or sticky lubricants to dry out and attract dust.

If any of the panel bulbs were out, we will change them all out.  If one is gone, it means the others are not far behind.  Many units are low hours, and if the bulb glass is not darkened, the originals, which were very high quality, will have lots of service life remaining.

We also clean the entire unit inside,

 7) If the customer has ordered the Cosmetic option, while the above is going on, the front panel is removed, and the knobs soaked in a dilute detergent solution for an hour or more, then brushed to get all the grime.  The front panel gets a thorough going over and the dial glass is polished.  We can touch up some scratches, and soon hope to be able to repaint the top and bottom covers.

8)Alignment.  This is where the rubber meets the road, where the performance is put back to factory standards.  Additionally, any problem with the three tubes will show up here.  It’s always amazing how little it takes to bring the receiver into alignment.  Most coils slugs are turned 1/4 turn or less, but getting everything right on, makes all the difference.  This is where the HP8924C shines for us, as we can go through everything in methodical step by step fashion, with frequencies and levels spot on for each adjustment.

The transmitter alignment gives the tubes a real workout. Any problem with the 12BY7A will show up as reduced drive by the time we get to  10 meters.  If it can’t give full drive at 28.5 or if it fails the 5 second test, it is replaced.  Kenwood runs the 6146’s really conservatively, but they do go bad eventually.   The ultimate test is a 5 second key down on 20M with no sag for 100 watts out. 

I check calibration on the VFO and re-align as necessary to get it to track properly on all bands.  RIT and XIT are centered and then the drive control is aligned so that transmit and receive drive track together on all bands.  This means that when you peak the drive control on receive, it will be spot on for transmit also.  This is an area where most units are off the money.  all the foregoing will also show up problems with the ALC, and if we can’t get the full ALC range, it’s another indicator of a soft 12BY7A.

Everything gets calibrated, from the noise blanker in the early units to the S-Meter.  A quick check with the 25khz calibrator on all bands gives a good indication that all is well.

9)Assembly and final test.  We re-assemble carefully, and will use new stainless screws where needed.  Might as well look as good as it works.  I’ll hook up the antenna and listen round the bands.  Sometimes there is not much there and the calibrator can tell you a lot.  If I can, I might make a contact on 20M and get an audio report back.  Then back on the dummy load and we can do an actual two way, with another Hybrid unit about 100′ away which is also set up on a dummy load.  We can get reasonably weak signals that way and actually listen to the output signal.  The final test is a good solid 100 watts out on 20 meters.

back to top

Comments are closed.