What does a K4EAA Kenwood Hybrid Restoration Consist of?
There are several stages to my restoration of a Kenwood Hybrid rig.  Some are evaluation, some are repair oriented, some are maintenance, and some are cosmetic.  I do the same things to all rigs in the same order, so they pretty much turn out to be like peas in a pod.  Any of the rigs I work on would remain a welcome addition to my shack, and trust me, many do.  Here are some of the steps involved in my Kenwood Hybrid Transceiver restorations:

(1) Evaluation - Is this rig suitable for restoration, one that will be "as new" when I'm done and make one customer (or me) very happy he bought it?  If so, that's a candidate for one of my restorations.  Otherwise, I'll sell it to some other restorer,  "as-is," for THEIR restoration.

(2)  Initial Test - What works and what doesn't?  All receive functions are tested including  all bands all modes, and functioning of all controls.   Then I test all transmit functions on all bands, and all modes, and functioning of the ALC, compression, and whatever else applies.  From these initial tests, I know what needs immediate attention and I perform any and all repair work.   When completed, the rig will be fully functional, although not yet cleaned and aligned.

(3)  Electrical/Mechanical Restoration - I will then  go through the entire rig, cleaning, lubricating, and making "as new" all of the connections, controls, switches, shaft couplers, bandswitch alignment, all variable cap rotating connections - Including the variable VFO capacitor, to ensure it is silent and smooth across the entire band.  The VFO gearing assembly is thoroughly cleaned and then lubed with "Tri-Flo," a Teflon based lubricant that dries non-sticky so as not to attract dust, but remain super slick for silky operation of the VFO.  

This takes a while, and I get intimately acquainted with this particular rig at this time! I remove the finals, blow out the final compartment, wash the tubes, clean and lubricate the fan, de-ox the variable caps in the final compartment, and in general, bring the whole rig back in cleanliness and lubrication to what it was when Kenwood first shipped it.

(4) Cosmetic Cleaning - The Front Panel is removed, all knobs are soaked in a mild detergent solution for an hour while the front panel receives a thorough scrubbing, and some of the other tasks are attended to.  The knobs are all  then brush cleaned, and setscrews replaced as needed.  No rust allowed!    The cabinet top and bottom halves are washed thoroughly, and if any worn or scratched areas remain, the cabinet is professionally repainted after prep and priming in authentic Kenwood colors.  They look good.  Please see each individual auction for details on any cabinet work for that particular transceiver, as most do not need repainting..

(5) Re-Lamping  -  Any transceiver that has a burned out lamp, whether they use 3, 4 or 5 lamps, gets a complete re-lamping.  If one went, the others are probably not far behind.    Some rigs are almost new, no significant hours on them, and the lamps are clear and obviously like new.  I do not re-lamp those rigs, as the original Kenwood lamps can last for 30 years or more under normal use.  Good stuff.  I can supply these lamps at $1 each, so it's no big problem either way.  Of course, they are free within the warranty period.


(6)
Re-Tubing
  -  The 12BY7A driver is really worked out during the alignment process,  and if the tube is soft or dying, it always shows up during alignment at 28.5MHz.  Any driver that can't provide full drive+ during the alignment, or if the drive falls off after several seconds of key down, is replaced with a new tube.   The finals are tested for emission, where I quickly run up the grid bias and verify the finals can provide about 300ma+ of plate current.  That condition is held for 5 seconds, and any decrease in plate current shows failing DC emissions.  The tubes are replaced with new finals.  Then the finals are loaded up on 20M and verified to provide 100W of output power to the load.  Those that fail this test are replaced with new tubes.   Kenwood runs their finals conservatively, and they last for many years.  In addition, the ruggedized military version 6146W can be used, and additional life obtained, because the Kenwood Hybrids do not exceed their ratings.  I prefer the 6146W in my rigs.  (WARNING! - Do not attempt to check your finals for DC emission unless you are prepared to perform this test quickly!  You can damage the tubes by boiling off too many electrons if you doddle too long!)

(7) Alignment - Here's where I really bring the rig up to its full performance capabilities, and have an opportunity to check every band and function in detail in receive and transmit modes.  If something is not quite right, or if there is further service work required, this is where it will show up!

For those rigs with adjustable regulators, getting all the voltages set dead-on is the first step.  I check the VFO calibration and realign the VFO as necessary to get it to track properly across all bands.  RIT is centered, and if the rig has XIT, that is also centered. Receiver front-end alignment is next, followed by transmit drive alignment.  It's very important that the drive control tracks on all bands for both transmit and receive. This ensures that when you peak the receiver, the transmitter drive will be peaked as well, or vice-versa. Most rigs I see are pretty far off in this respect; an accurate alignment eliminates that problem.

The previous step also lets me see if there is proper drive on all bands.  If the drive on any band does not travel the full ALC range, it's usually a sign that the 12BY7A needs replacement.  I use only NOS tubes for replacement, never any used parts.  Beware the service center or restorer that says no drive indication on the higher bands is "normal" for the Kenwood hybrid rigs!

Next the IF is aligned, and everything is calibrated per Kenwood specifications.  For the early units the Noise Blanker board is completely aligned as well, as it contains a significant part of the IF system.  S-Meter calibration follows, and a final check is made of the calibrator and drive levels on all bands.

(8) Button-up and Final test - The rig is powered down and buttoned up.  I use new, proper hardware if there is any question as to the condition of the screws.  I order M4 and M3 hardware in the proper lengths, and use the new stuff liberally.  Heck, if it receives and transmits great, it should look great too!

I will then connect an antenna, power up the rig, and listen around the bands.   Any anomalies are compared against my standard rigs, as sometimes the high bands really
don't have any strong signals present!  The built-in calibrator is an excellent check most of the time; if its signals are strong, the Rx is probably doing its intended job. Sarasota has a local 10M beacon that provides an excellent reference for comparing receivers on the highest Hybrid band.

Transmitter power is checked again, into a dummy load, and 100W legitimate RF output on 20M is my pass/fail test.  .

Many of these rigs have been used by me for on-air contacts.  I have a LOT of Kenwood gear, and I've used a lot of it from time to time.  It helps to verify my service techniques, such as "Did I overlook something?", "What kind of Audio (CW) reports will this rig get?", etc.  I just won't sell something that I wouldn't use myself..

73,  Ken, K4EAA

 
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All Photos and content copyright 2005, K4EAA, Ken Kemski.

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