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Kenwood TS-520S and Accessories

Downloads

If you have the PDF plug-in in your web browser you'll have to "Save File To Disk" to save a PDF copy. You can do this with the "Save A Copy" icon on the left of the PDFViewer plug-in tool bar, OR in Windows, outside-click (well, everyone says "right click" but I'm left-handed and "outside" works for both) on the link and pick "Save Target As.." or "Save Link As.." On the Mac, hold down the mouse button on the link and select "Download Link To Disk."

Jump down to: [ Transmitter Tuning ] [ Tune-Up Procedure  ] [ Tips ] [ Tubes ] [ Remote VFO Notes ]

Notes about the Manuals

Chuck, KE5FIK, just (Sep 2005) set me a scan of the 520 manual (via BAMA). The 520 was the first radio in the series, followed by the 520S, and finally the 520SE.

Hank, VK5JAZ, from Australia just sent me an original scan of the user manual for the AT-200 antenna tuner in November 2003. He writes

"I have located a manual locally (VK5) for the AT-200 (which by the way, was not available anywhere on the Net, hence my interest in your site... I was looking for one). ... I would imagine a lot of hams would be appreciative for the AT-200 as it is such a workhorse.

Well, "amen" to that -- I am just such a ham since the AT-200 is what I use here. Many thanks. (If you pull up Hank's QSL on QRZ.com you can see his AT-200 on top of a big stack of more modern gear. Excellent!)

Sam, WA5JAW, sent me the service manual for the 520SE (The last of the 520 series when Kenwood removed the 12v input and transverter output.) Not sure of the origin. It is about 8 pages with part list and schematic, if you pair it with the (big) 520S service manual you should be all set..

I just (October 2003) scanned and posted the manual for the Heathkit RF-1 from 1959. I also sent it to BAMA to give back and say thanks for the MC-50 scan (see next).

Rafael in Madrid, Spain sent me a PDF of the one-page manual for the MC-50 microphone, that he snagged from K4XL's Boat Anchor Manual Archive (BAMA) . Thank You.

Malcolm, G0UMP in the UK, was kind enough to send me a photocopy of the VFO-520 manual, which I have scanned and posted above. This should work for the VFO-520S as well -- the 520S has a redesigned tuning dial, but is otherwise identical. Also, John, KD7SLM, sent along a JPEG of the schematic of the VFO-520s specifically. Many thanks.

All of other scans are by me. I made a new scan of the User Manual for the 520S (instead of the one that has been floating around the web), because I wanted the covers, schematics, and photo plates. I also wanted photo pages to be in grey-scale so you could see the pictures.

Troubleshooting

  • No transmitter output? Make sure the "SG" ("screen grid") on the back of the rig is ON. (This switch is used when "neutralizing" a new set of finals. The "H.SW" in front must also be ON. See "Tuning" below
  • No receive - just constant white noise? If you are not using an External VFO you must jumper pins 8 and 9 of the brown external VFO plug on the back of the rig to get the receiver to work. 8 and 9 are the two holes clockwise right after the big space in the pin hole. There is a picture in the User's Manual (download above) at the bottom of page 8 that shows this in the "blow up" section. You can take a paper-clip, cut it into a "U" shape with 1 inch legs, and jam it into the plug. The original, very nice Kenwood plug is sometimes available on eBay. It is part E05-0901-5 "9P Plug (EXT/VFO)" -- but a paper-clip works just fine too. (Several people wrote that these plugs are still available from at East Coast Electronics -- kenwoodparts.com. They have a rather poor PHP session setup on their site that keeps me from linking directly into their catalog, as well as a finicky search engine with very low usability (no telling how much business this has cost them), but this magic search string string (from James, KE4DRN, thanks!) will call up the part if you can figure out where to enter it! E05-0901-05 TS-820 9P VFO PLUG TS-520 . The price is around $5. Web site usability issues aside, serveral writers say these are good folks to do business with - though I have not done so myself.)

Transmitter Tuning

For a digital computer guy like me, being confronted for the first time with tuning the final tubes on the 520S was a daunting and mysterious task.The manual's description wasn't all that great, and I was very afraid I would fry something and render the radio useless! Obviously, there is a generation of hams who can tune up a tube set in their sleep, but I found most of their discussions self-referential and steeped in a lot of background knowledge of vacuum tube technology I didn't have. (Kind of the way software engineers like me explain computer technology to people these days, except its computers and not tubes!)

Fortunately, Jim, N2EY, posted a good plain-language discussion of the process on USENET in 1998. I have taken his original text and combined it with notes from my own experiences to produce the text below. If you find something here that is inaccurate or confusing, lemme know. I'm not an expert by any means and am still learning this stuff.

Transmitter Controls

  • H.SW This is the heater switch for the tubes. This must be in "ON" position or you will get no output, but the receiver will work normally. When turned "ON" a filament will heat the cathodes in the 12BY7A driver and 6146B finals and electrons will bake off into the vacuum and start to fly to the plate. This switch is on the rig for mobile/battery operation, since less power is used if the tubes are not being heated. There seems to be some debate about whether turning off the heaters when you're not going to be transmitting prolongs the life of the tubes or not. Some argue the thermal shock of repeated heating and cooling is worse than just heating all the time. There are also arguments about how long you should let the tubes warm up before you start transmitting. I've seen folks advocate everything from 30 seconds to 3 minutes. The reality is you'll probably flip it on in a panic when you realize it is off and you want to transmit right now. I've gone as little as 15 seconds in this situation and it seems to work...
  • CAR Carrier Control. Adjusts the amount of signal applied to the final amplifier. Clockwise to increase. Though it seems obvious to me now, it took me a while to figure out this is the "output power control" when using CW. (The "mic" control in the center does the same thing for SSB.) Bad news is that it goes from full power to nothing with a tiny amount of counter-clockwise turn and can be tricky to twiddle with on the fly. The Kenwood manual wants you to start tune up with this control at 12 O'clock. I usually have it at about 9 O'Clock. It has to be up a little or the S-Meter won't give a reading when you try to peak the drive (see below).
  • Drive Resonates/peaks (tunes) the grid (input) of the final amplifier, and also the receiver input. Proper setting will always be somewhere in the middle of the knob setting. A proper setting for receive will also be right for transmit and vice-versa. Adjust for loudest static on receive and you'll be in the ballpark for the band and frequency. You are adjusting the operation of the 12BY7A DRIVEr tube. I think!
  • Plate Resonates the 6146B power amp tubes -- which means minimum current is coming off the plate and you're not frying them!
  • Load Jim writes: Adjusts the amount of loading of the final amplifier. Minimum loading = minimum power = knob turned ccw (to the left). I'm not sure what he means. As I wrote above, the CAR control varies the CW output power. My understanding is the Load control runs a small Pi network on the amplifier output that adjusts the final amplifier output LOADing, and can be used, something like an antenna tuner, to match the transceiver to the antenna system so you can drive the most power into it. The Plate and Load controls interact and are adjusted one after another during tune-up (see below).
  • Meter Controls what the meter displays. (Took me a while to figure out that when the rig is in receive mode, the meter is always an S-Meter, no mater what this switch is set to. Also, the receive S-Meter is only accurate if the RF Gain is wide open and the AGC switch is on "fast" or "slow.")
    "ALC" = (automatic level control) amount of drive to final amplifier. Useful in SSB to see your voice peaks (adjusted with the "mic" control. I just realized that AGC (for receive) and ALC (for transmit) are not the same thing! Doh! Scale is the black ALC at the bottom of meter -- the lowest of the scales.
    "IP" = (current "I" plate) Final amplifier plate current, read on mA scale
    "RF" = (Radio Frequency power) Relative power output (not a wattmeter, but useful)
    "HV" = (High Voltage) Final amplifier plate voltage - normally reads about 800V (8 on the red HV scale)

I guess my current "mental model" of how the these control work goes something like this: CAR/MIC injects the amp, DRIVE peaks up the 12BY7A to juice the finals, and PLATE resonates the 6146 finals and LOAD tweaks the inductance and resistance the final tubes see as they pump RF out of the radio . All these controls interact in various ways, with PLATE and LOAD being the most important, and twitchy!

If you can think of a better/clearer expression for this circuit syllabus lemme know.

Tune-Up Procedure

The User's Manual (downloadable above) has the "Kenwood Approved" procedure for tuning up the rig starting on page 20. In particular it has a nice chart of initial settings for ALL the controls, which is useful if you have never done this before. The procedure presented here differs in some respects.

  1. First, fire up the rig and tune to the band you would like to transmit on. The rig needs a load that is fairly close to 50 ohms. Less than 2-1 SWR is good. If your antenna has been trimmed for the band you are going to transmit on, you're probably all set. If you are using an Antenna Tuner to load up a random wire or mis-matched dipole, the procedure is to connect a dummy load (rated 100 watts or better) to the 520 and tune the rig into THAT perfect 50 ohm load, THEN switch in your antenna tuner and adjust it for minimum SWR. You might want to use a dummy load to practice this tune-up procedure anyway, since part of it involves putting a signal on the air.
  2. Make sure the H.SW is on. Warm up the tubes.
  3. Make sure the FUNCTION switch is in the VFO position. Make sure RIT is OFF (out). Make sure RF ATT is OFF (out).
  4. Plate idle current: Kenwood wants to be sure the idling current of the plate is at 60ma before you begin. Generally, you only have to check this once in a very long while. Set the METER switch to "IP" (current, plate), tune to the band of interest, set the MODE switch to USB or LSB. Flip the rec/send switch to "send." You should read 60ma on the top scale of the meter. If you get a different value, you need to open the little door on the left of the rig and turn the bias pot until you get it. See the manual.
  5. Get the DRIVE control into the ballpark: If you have an antenna connected, you can turn the DRIVE knob until you hear the loudest static (with the MODE switch on USB or LSB). If you are working with a dummy load, or just want something easier to work with, flip the FUNCTION knob a click to the left to the Cal 25 Khz setting. Then tune to the nearest 25,000 HZ division (i.e. 7.125, 7.150) so you can hear the tone then turn the DRIVE knob until the tone is loudest. Be sure to set this switch back to VFO when you are done. (The marker is every 25khz, but, like CW, you have to offset to hear it -- or my radio is out of whack! -- for example, at 14.150 I use 14.152.5.)
  6. ALC adjustment: Turn the CAR and Load controls fully counter-clockwise. Put METER switch in "ALC" position. Put the Mode switch in the "tune" position. (If you are not using a dummy load, find a quiet place on the band.) Flip the send/rec switch to "send." Turn the CAR control slowly clockwise until you get a half-scale deflection or so. (The original instructions and manual are unclear, I turn for a half of the ALC scale, or S5. I think this is right.)
  7. Fine tune the DRIVE: With the rig still set to "send", turn the DRIVE control to peak the ALC meter reading. I wind up at S9 on the ALC scale. Put the send/rec switch back to "rec" and breathe. (Try keep the rig in "send" as little as possible -- less than 15 seconds at a stretch -- and let the tubes cool down between time.) Franky, I've been skipping this step lately (Oct02), since the right setting is good for both xmit and receive you can do either this step or the ballpark step above and be OK. I think this is harder, so I've been using the 25khz tone and peaking the receive side instead.
  8. Dip the PLATE: This is my favorite step, if only because of the name! Put the Meter switch in the "IP" (current,plate) position. Set the PLATE for the middle of the band you are tuning on. With the MODE switch still in "Tun", flip the send/rec switch to "send." Quickly adjust the PLATE control for minimum meter reading. (I think the dip is bigger on the higher frequency bands.)
  9. Peak the output: Everything is close now. Put the Mode switch to CW, the Meter switch to "RF" (or, if you have an antenna tuner, read the actual RF power there). Be sure you're on a dummy load or quiet place on the band. Put the send/rec switch in "send." Key down. Quickly turn the LOAD control for maximum RF output. Jump to the PLATE control and twiddle it for maximum RF output. Alternate back and forth between the two quickly and "walk" the meter up to the most RF you can get out of your rig. (Right now, I get around 100 watts on 40m, maybe 90 on 20m.) Key up between jumps. Don't do this for very long. When done, put the send/rec switch back to "rec." Breathe.
  10. Final adjustment: send/rec to send, key down. Twiddle the DRIVE control to see if you can get anymore RF out of the thing. Probably not if you've done the previous steps properly. Leave DRIVE at the strongest meter reading. Adjust the CAR control to where the RF output just starts to drop. Again, you should already be close. Key up. Flip the METER switch to IP. Key down. The plate current should be about 240ma. Mine hits this exactly if I tuned into my dummy load properly. If the current is more, you need to reduce the loading -- turn LOAD to the left and re-dip the Plate control.
  11. Congratulations, you are resonating! If you have an Antenna tuner, switch from your dummy load to it and make your final antenna tuner adjustments, if necessary. The rig has to be re-tuned if you change frequency by more than 1-2% or so, and want to transmit. This means 25-50 kHz on 80 meters, and progressively more on the higher bands.

Later (October 2002): I've been doing this a lot now, so I have a short version if you understand the basics above, and have an outboard RF wattmeter (like the one in the AT-2x0 antenna tuner series...)

  1. Pick a frequency. Select your dummy load, turn on the 25khz marker, peak the DRIVE control on the meter at the nearest 25khz division. (When the 520S is in receive the meter is always an S-Meter, no matter what the METER switch is set at.) You might have to crank the CAR a little to get a reading. Also, the AGC switch should be on FAST or SLOW.
  2. Turn the LOAD control down (CCW). Put the METER switch in "IP" position. Select "tune" on the MODE switch. Flip to "send." Dip the plate.
  3. Walk it up: Put the MODE switch on "CW" and key down. Raise the LOAD for maximum RF on your outbound wattmeter. Now adjust the PLATE to lower the "IP" current shown on the transceiver's meter. Repeat, back and forth, back and forth, until you can't get any more RF out or plate dip. I say to myself, "this meter goes up, this meter goes down, this meter goes up, this meter goes down" -- silly, but it works. Go back to "REC."
  4. Select your live antenna and adjust your antenna tuner for lowest SWR if necessary.

Tips

  • When receiving CW, turn the AF gain up almost all the way, turn the RF gain down, and turn the AGC off. Use the RF gain for the volume control. This method helps fight QRM and receiver overloading.
  • Although the 520 has semi-break-in, it is more of a hindrance than a help to a beginner. Use the manual SEND/RECEIVE switch and you won't be distracted by the clicking relays while trying to send. (On the other hand, at very slow speeds, the VOX timing can enforce character spacing...)
  • I just (September 2002) built a LogiKit CMOS-4 Keyer from Idiom press. It keys the 520S just fine if you set the JP-1 jumper to the outside, close-to-edge pins: " grid blocked keyed, negative voltage, keyed to ground."

Tubes

Types: KGHM writes: Even a regular 6146 works just fine for any Kenwood radios.

  • 6146 - normal old type
  • 6146A - uses dark heater, works better when the filament voltage drops below 6V otherwise same
  • 6146W- to be used under severe vibration like mobile radios or military, otherwise same.
  • 6146B - has 25% more plate dissipation otherwise same
  • S2001A - exact copy of 6146B by Japanese companies like Matsushita (Panasonic) and NEC and Hitachi. In my experience, it is not as rugged as 6146B. [I'll add that it is a little taller than the 6146B, and what you will find in a TS-520S that is still on its original finals. --ww]

Output Power:
Someone else on USENET wrote this about output power:
First item is the power. This radio uses a pair of the Japanese equivalent of the 6146 beam power tetrode called the S2001, and a 12BY7A as the driver. This was at one time (back in the '60s) the de-facto standard combination in a lot of radios. A pair of 6146 or 6146A tubes were rated at 180 Watts PEP INPUT or about 100 Watts output. A pair of 6146B tubes had a bit more plate dissipation and were capable of 240 Watts PEP input and about 115 Watts output provided you could also raise the plate voltage to about 850 volts. Otherwise, if you plugged in the "B" tubes you only got the benefit of a bit more plate disapation and no change in output. The output varied a bit downward as you went from 80 to 10 meters usually because the drive dropped off from the 12BY7A and with a well used driver and pair of 6146s you would commonly go from 100watts at 80m to 75watts on 10m. The bottom line here is, don't expect more than 100 watts output MAX from your TS520, that is all it is capable of. On 10m, more like 75 to 85 watts depending on the age and condition of the finals and driver.

BTW, the Kenwood rigs (TS820-TS520 etc.) that used these tubes were one of the very few who actually went from class AB2 linear service to class C when you switched from SSB to CW. Result: greater output on CW and cooler tube operation. If that doesn't mean much to you then get an old '60s or early '70s ARRL Handbook and read up on vacuum tube operation and it will make more sense to you.
End Usenet.

Getting ready for CQWW, I crudely measured my CW output into a 50 ohm dummy load with the two radios I have here. The results:

FrequencyRadio OneRadio Two
28.25061 watts57 watts
21.30085 watts 80 watts
14.22590 watts 95 watts
7.325 91 watts 98 watts
3.850 100 watts 105 watts
1.900 90 watts 95 watts

I was surprised to see the output vary by band. I thought "soft was soft" and that radio two would be weaker at all frequencies, not better on 20M and below.

Replacing:
Ward here again. Because I can't leave well enough alone I decided to replace the finals and 12BY7A driver on the 520S I have here, just to go through the process. I also took a shot at aligning the radio, which was time consuming but straightforward, and seems to me to be a lot like tuning up a piano! Anyway, some notes:

  • Removing the 12BYZA: This little tube is just outside the metal box at the rear of the radio that holds the final tubes. (The one with the dire "high voltage" warnings into which the long "drive" "plate" and "load" shafts go into.) In my radio it was inside a black metal jacket that had a flat braid going up the inside. I guess this acts as both a heat-sink and grounded Faraday cage. I did a crummy job pulling this tube because I didn't understand the layout. I didn't break anything, but I could have messed up the socket. If I had to to it again, I would remove the metal jacket first, using a a finger to keep the tube down, and perhaps spreading the metal apart a little with my other hand. I'd also try to not put too much strain on the ground braid coming out from under the socket because I don't want to break it off. Once the metal jacket is off, the tube comes right out. I did a better job of putting it back together, just plugging in the tube, placing the braid against the glass and lowering the metal cylinder back down over the tube.
  • Unknown tubes, and other mysteries: I bought a pair of "NOS" (supposedly) Sylvania 6146Bs on eBay. I opened up the high power box and pulled the original S2001As and put in the Sylvanias. I put the plate cap on each tube. I tacked the box shield back on with a couple of the screws. I turned the radio on. Immediately there was a nasty blue/white arc over the tops of the tubes and the 6A power supply fuse blew. Were the tubes bad? Did the fact that the 6146 are shorter than the S2001A mean the plate cap didn't seat correctly? I don't know, and still don't! But the next day I got some 6A fuses, pulled the Sylvanias, and put in two RCA 6146Bs I got with some used equipment. This time I winced as I threw the switch, but this time, no smoke. Then I flipped the heater switch on. Both tubes started to glow. I began tuning the rig up in preparation for neutralization. Then I started working on how to do the neutralization step. I left the rig on for about 15 minutes during this time. Suddenly there was a crackling noise and the 6A power supply fuse blew again. Dang!
     
    Finally I had two (new? hopefully) S2001A tubes from the used equipment I bought. I put these in. They heated, tuned up and neutralized just fine, and I'm running them still. I gained maybe 10 watts on the old tubes, not much differences, but at least I know the history and status of the tubes in my radio now. I do NOT know what went wrong with the other two sets of tubes.
  • Neutralization: I didn't have a "sensitive RF voltmeter" for neutralizing (I assume they mean a VTVM), but I do have an old Leader 100mhz scope. I couldn't figure out a good way to connect it. In the end I wound up opening up my MFJ 300 Watt dry dummy load and clipping the probe just inside the connector where the wires go from the case to the big resistor. Next I had to find the screw to adjust. It is the fairly big one in the high voltage box toward the front of the radio. There are two holes in the shield, One lets you angle a tool down onto the screw, and the other lets you look straight down and see what you are doing with a small flashlight. None of my alignment tools were big enough to turn this screw so in the end I used a screwdriver. This seemed to work if I didn't ground it against the shield. I thought there would be all kinds of capacitance effects, but this was not the case. The voltage with the SG switch down is tiny, I had the vertical deflection on the scope wide open. Still, once I started turning with a fast auto trigger going it was easy to twiddle the screw until the trace became its narrowest (voltage minimized). So I THINK I've neutralized the tubes. Nothing blew up -- yet -- anyway!
     
    Be careful! If th SG switch goes up, you will fry your scope with a direct connect. (You can make an inductive pickup by sticking a BNC connector on some coax, screwing it into the scope, and then stripping the outer jacket off the other end, bending the insulated center conductor into a loop 3-4 times around your feedline, and then striping and soldering the center conductor to the braid. Makes a nice "station scope.")

20 Feb 03: I've had a couple of folks write me about why my tubes blew up. One fellow suggested letting the RCA tubes heat up while out of neutralization blew them up. The other (Allen, W5TCH) said that sometimes these radios are modified (by CBers) to increase the plate and screen voltage for more power output. Apparently the S2001A can handle the higher screen voltage and the 6146 cannot. I'll update this section if I discover anything further -- but since the radio has been working well, I don't want to open it up!

Remote VFO 520S

One of the reasons that I bought a 2nd complete 520S station on eBay last year was to get the remote VFO-520S. It worked fine with the 2nd radio, but when I moved it to my original 520S it stopped working. (This caused me some distress in CQWW SSB since I could not work split on 40M and was pretty well shut down at night.) Then I moved it back to the radio it came with and it no longer worked there either. Dang! I opened it up and fiddled around, but it sure seemed like something had broken and the whole thing was fried.

In the meantime, the colleague who gave me my original 520S radio found the Remote VFO-520S for it when he was cleaning out his house to move to Colorado. So now I had two remote VFOs. But when I plugged this new one in, it didn't work in either radio either. Since the only thing common to all of these setups was the connection cable, I finally had the "ah ha!" (or "doh!") moment. Sure enough, a wire had snapped off inside one of the 9 pin cable end connectors from all the twisting. A little solder and both VFOs started working again. Whee. Some random notes:

  • The Remote VFO-520S my friend gave me has a much higher serial number than the one I bought on eBay (1,110,018 vs 620,628) and the tuning knob on it has the little high-speed twisty post on it like the tuning knob on the 520S itself. The earlier Remote VFO just has a plain, flat, brushed aluminum center disk. Don't know whether this indicates a mid-production run revision (and possibly other internal changes) or a one-off modification by someone on the units I have here. I'm going to keep an eye of eBay to see what sorts of knobs the models for sale there have.
  • Hey, this is super-dumb, but for a long time I thought the "function" switch on the 520S was set to VFO.R to use the "remote" VFO. But Noooooo -- the "R" stands for "receive" not "remote." (doh!) VFO.R ("vfo receives"), FIX.R ("fixed crystal receives") let you work split with crystals (if installed) and control whether the 520's VFO or the crystal control the receive frequency. The FIX setting uses crystals for everything. (So, in practice this probably means you never use ANY of these three settings!) To use the remote VFO, you just turn it on, and leave the the FUNCTION switch on 520S set to VFO (as always). Easy.
  • I only have one connection cable, and it is a fragile thing marked 1975. There is no strain relief on the ends, so twisting it around eventually snaps off the wires. The ends unscrew. You can lay a jewler's screwdriver between the pins to hold them, and then turn the black enclosing body counter-clockwise to unscrew. The cap then slides back onto the cable and you can work on the pin connections.
  • Most of the wires in the cable are straight-thru hookup-wire type, maybe 18 gauge? There is one shielded wire with a braid (for the high-frequency stuff). If I were looking at the FEMALE plug on the back of the RADIO (not the male plug on the cable) and counting clockwise from pin 9 (after the big space in the pins, at about 8 O'Clock -- per the picture on page 8 of the User Manual), the connections are:
     
    9: Red
    8: Orange
    7: No connection
    6: Yellow
    5: Green
    4: Blue
    3: Shield braid
    2: Black (center of shielded wire)
    1: No connection
     
    All of the wires are straight through, so the colors are kind-of irrelevant, but I wanted to have a note of my setup somewhere! Note that the schematic diagrams for the VFO-520S count this way too. That is, when you read them, you are virtually standing "inside" the VFO-520 and looking "out." (You are not on the outside looking at the female side of the socket, but are looking at the header pins where the wires are soldered onto the inside.)
  • Gary, N5OMO, writes that these 9 pin plugs and sockets were used in old Sanyo car stereos (also sold as house brands by Ward's, Seares and JC Pennys). You might be able to dig these up at flea markets and yard sales.
  • May 2005: W9GB writes: "Well Kenwood Parts and PacificCalifornia - the 2 parts distributors for Kenwood USA ... have them and still have them ! 9-pin VFO jumper plug is missing on the back panel this is available from Kenwood Parts (E05-0901-05 TS-520/TS-820 9P VFO PLUG):
I'm always interested in hearing about any other replacement sources for these 9 pin male connectors, and any ideas for strain-relief lash-ups to protect the wires (maybe something under one of the machine screws holding the sockets to the cases??). Finally, I should add that Since I finished building my Elecraft K2, I have just (Oct 2003) auctioned my VFO-520S on eBay. (*sniff*)

On an unrelated note, my sister, Gayle, is a Board-certified Audiologist. Thought I'd put a link to her site here to throw traffic her way. And if you need your hearing worked on in the Sacramento area, you should give her a shout at Hearing Sense Audiology,

Revised 04 Nov 2014.