The AM Forum

Gentlemen
On top of all of the other projects I have going in my radio collecting and restoration activities, this
"pup" came in out of the ether and right into my life, without benefit of warning.
A rather pristine Globe King 500C, complete with tubes and the original cabinet. It appears the SK
in which it came from had it for many years and took extremely good care of it. I will be picking it up
this weekend in Orange county some 30 minutes away. The paltry sum of 350 bucks seems fair considering I never see these things come up for sale. What is even more bizarre is I was the first to call the seller. This almost never happens for me. I can make room for it and will pair it up with a National NC-300 for now.
My preliminary inquiry about modifications only pertain to non invasive type enhancements to make it
perform better and if needed, safer. My initial reading suggests that many like to disable the frequency restricting "Couplates". Does anyone have any examples of what to put in place of them?
Are there any suggestions for improving the modulation characteristics, if needed? I realize this is not a BC rig nor do I intend to pretend that it's anything beyond what it is. Just curious about the "conversation" in being a great performer within certain design limits. I am still rather new to this world so bear with me.
The examples I have heard on the air sounded very good. A couple of guys go into the patch input with external audio processing which sound quite nice. However, I think it could sound just fine with a D-104 using the built in speech amp. There is something fun about grabbing the mic, and push to talk... like my ART-13 rig. I mean, I do have state of the art audio gear in use with my FLEX 5K/4-1000A rig which kicks butt BUT, the point is about using this as close old school as possible while using a modern approach to being "better.
What gives Jeeves?

After reading over the schematics for the modulator/speech amp section, it appears that removal of the couplates will require installing the appropriate plate load resistors and coupling caps. I suppose I can start with published resistor specs for the 6SJ7 & 6C5 tubes. Being that the 6SJ7 is a pentode, I will have to strap the screen together with a 1 meg resistor to the B+ and seeing how I will not be using the clipper stage at all, I can just remove the 6AL5 from it's socket.

  You will get many opinions on this topic.

There are two weaknesses with the GK 500 series on AM. This is my opinion, so take this with a grain of salt.

First is the audio driver to the 811's that uses a single 6L6 in beam power tube configuration. They use a push pull driver transformer with a single ended driver tube. The audio driving impedance when driving the 811 grids is high, so when modulating upward, the grid current of the 811's loads down the drive. This results in high distortion, and limits the peak modulator power.

There is a very simple solution to this, and it is to go back to the GK 400 driver that used the same interstage transformer, but instead of a 6L6 single driver, they used a pair of triode connected 6F6's. This solves a number of issues, and the design stays WRL. Why Leo switched is a mystery to me..

The other issue is the RF linearity of the 4-250/4-400 RF PA tube. Some optimization of grid current, grid voltage, and tweaks to the self modulated screen grid could go far to enhance RF linearity, and to boost the positive peaks.

You could go on and on, like adding audio NFB, boosting the power supply filter capacitors (Mod B+ and RF B+), but going down that road could be a long one.

My vote would be to add a plate over the existing modulator deck, and punch holes for the GK 400 modulator driver tubes..

http://bama.edebris.com/manuals/wrl/king400/
modulator schematic is drawing 'f'.

Jim
Wd5JKO

Centralab couplate circuits from The AM Window!
http://www.amwindow.org/tech/htm/couplate.htm

Two other references
http://pacifictv.ca/schematics/centralabcouplates.pdf
http://anniversary.ipc.org/pdfs/Book112248.pdf

You guys are the best!
Update:
I am picking up the GK-500C tomorrow morning. It seems my trip to Orange will be two fold.
Drop off a 30S-1 and pick up the GK. A fine trade off for space as far as I'm concerned.
I will post some photos to share. It appears from the Craigs List photo that both sets of
HV rectifiers were replaced with those SS plug in units. Fine by me.

http://losangeles.craigslist.org/lgb/ele/4489834184.html

I am likely picking up the other two items as the prices are hard to pass on. The GREEN cabinet
for the SX-28 is pretty hideous. Not sure what that unfortunate knob job is about on the KW MB,
bit it's in nice shape otherwise. What a shame.
Billy N6YW

Looks like pretty fair deals, especially if the SX-28 is in good condition.  A sheet of sand paper and a can of spray paint will fix the cabinet quickly.  bill

I owned, restored and operated a 500B for several years, before passing it on few years ago in my slogging quest to lighten the load around here.  Still suffering from seller's remorse, but it's in good hands.

The 500B/C is a great radio.  Pull the couplates and just use the standard audio RC values from a contemporaneous handbook.  I may still have the values I put in mine  .. if you need them, drop a line, and I'll send you my docs.  It got (and I hear still gets) excellent audio reports.

There are a host of changes you could make, but IMHO, just use the rig.  Even with the couplates, until you get around to replacing them.  I fed line level audio to the phone patch input and the radio sounded great.  No,  it's not a 20V or a KW-1, but it's a good sounding and reliable transmitter.  The only issue I ever had with mine was the occasional buzzing relay, which can be solved by converting to DC.  For the price you paid, you did very very well .... I'm envious  ;D

Grant NQ5T

One other thought about this radio, if you aren't familiar with it.  The key to tuning it up is to use screen current, and not plate current.  Rather than the usual dip and load on the plate, what you want to do is PEAK and load on screen current.  As you increase loading, peak screen current will reduce, which is what you're looking for -- target around 30-40 mils of screen current.  Obviously, the specs on plate and grid current nominal values need attention paid, but tune it up on screen current.

You're really making me wish I still had my 500B :)

Grant NQ5T

Billy,

Congrats on your latest find!  As you said, the GK looks to be in excellent condition.  They do come up from time to time but I have not seen one in that kind of condition for a long time.  I am sure you will give it a good home!  The price that you posted shows that it was a fantastic deal as well.  If I ever found one in that kind of condition, I would pick it up as well. 

I have several pieces of WRL gear around here.  My oldest WRL is a Globe Trotter.  Then I have a Globe Scout and a Globe Chief Deluxe.  Unfortunately no heavy metal WRL pieces though.  My mentor Harry, W3FDY (sk) had a Globe Champion that he used to drive a pair of 250TH's modulated by a pair of 450TL's.  I can still see that Globe Champion sitting in his shack.  They are also somewhat hard to fine in great shape. 

Much has been published on upgrades for the GK-500 so you will have to see in time what you want to do.  Personally, I would keep it in its original physical condition and just do some soft mod's with component changes!  Keep the drill far away from the rig and especially those panels!!

73,
Joe, W3GMS       

Yes indeed. I would likely strip it and have it powder coated. The last one I did came out perfect and is nearly bullet proof. I decided to pick up the KW MB for a friend who needs one, as I already own a
pristine example in use here. I hope he has the shield cage for the RF deck. Maybe there are more items lurking at the SK QTH. I will ask the seller about this.
Getting ready to leave now. Will post later after I get back from the "OC"
73 de Billy

Something to consider about the couplates.  There is little in those things to go bad.  You can check them with an ohm meter and a capacitance checker if you want.  As for replacing them to gain bandwidth, all you have to do is parallel the coupling capacitor leads with another and leave the copulate in place.  Choose the size from the aforementioned tables in the handbook.

That radio was designed for narrow bandwidth so the power supplies and all parts of the set reflect that philosophy.  Without changing a lot you probably won't get 100% modulation, so you will have to decide whether you want to make a lot of changes.  I am with Joe, be sure the carrier and audio is clean and keep the mods to a minimum.  I have an A model and it will modulate with stock iron to right about 95% positive and negative, keeping the modulation deck needle where the manual says. 

But all that is up to you, just remember the manual may differ from the actual set.  There were a lot of changes along the way with WRL equipment and each set could have different tubes or mis-marked diagrams.  Enjoy the set, it works well and sounds good when things are right.  I have owned this one near 20 years and had only one problem.

I do suggest you get the plug in SS rectifiers for it.  Then make sure to disconnect the secondary of the filament transformers and run the HV to it's destination. 

Well looky here... :)

It works. Getting 325 watts into the bird dummy load. Peak outpoot is around 950 peak with good clean modulation before the onset of noticeable distortion. I am very pleased and am inclined to keep it
as stock now. All of the low voltage caps have been replaced before now. I had to install two new
bat switches on the power supply deck. They were broken off when the guy moved it from the SK house.
Fortunately, I had some very heavy duty types that fit in place of them.
Unfortunately, someone had drilled two holes into the front panel of the RF deck. No biggie, I can fix them.
I ended up getting the SX-28 & the KW MB for 150 bucks... silly good price. The D-104 is a little raspy
sounding and the EV 664 sounds better. Both modulate about the same.
Here the pics I promised. All of your comments are extremely appreciated guys, thank you very much!

Some more...

More still...

And finally, put together and installed ready to accept a receiver!  :)
I need to get a dimmer lamp for the VFO, it's REALLY bright!

Fully wired and ready for a QSO. I am in vintage bliss right now... this is so much fun!

Nice!!

Here is the on air recording courtesy of KJ7USA in Oxnard Ca. This was recorded tonight with his TS-590 transceiver. Not bad at all, communications grade audio that leaves me without any regrets.
What do you think?
Billy N6YW

Yeah, my only regret would be that I didn't find it ten years sooner! Seriously Billy, even if you had a roached plate transformer and other, more serious issues than the toggle switches, you made a great find and got a great deal. Those decks look like they were made last week - not covered with the usual decades of crud, corrosion, and other damage often seen on radios of that age.

And I'd say your audio is considerably better than communications-grade. It sounds at least as good as a 32V which is one of the best sounding transmitters of the era out of the box. Your GK sounds pretty darned good! I don't think you need to do much to it.

Now, you got a nice deal on the other two pieces too, but inquiring minds want to know: what about the old wooden 3 dial TRFs in the background? Were there more old radios or were those three and the Radiola speaker it?  ;)

That is a nice set.  One thing you might want to know.  That fan has oil holes for the bearings ,they are on the bottom side and you have to remove it to get to them.  It might be good to put a drop of machine oil in the bearings just for grins.

@Todd
I wish!!!! He had a bunch of wooden radios and all of them are PRISTINE!!!!
Thank you for the compliments. I still cannot believe my good fortune and the biggest thrill is that it fired right up without a single issue. Check this out: We have a small group that we jokingly call "The Venice Gang" because the three of us live basically on the West side of LA and all three of us are heavily into vintage radio. Jay NY6L owns a GK-400 & 500A, Juan KB6KMU who owns a GK-500B and I with the 500C. I say that's pretty remarkable. All three of us got on the air last night to "Christen" my first transmission with it's fellow brethren. Little stuff like this in radio might sound a little corny to some but I get a massive kick out of it. Then John KJ7USA came on and recorded the clip for me. The West Coast AMI guys are always very into it and much like the East Coast folks, are like family. Very supportive of each other.

@Jim
I will do that. The little blower is the smallest of that type I have ever seen and it seems to do an adequate job of keeping the final cool. Of particular interest is that I am getting 325 watts of carrier and RF peak output of 1000 watts on average. The 811-A modulators are pulls I had on hand and the 4-400A is also a pull that came out of a homebrew linear given to me in non working condition. It seems I had all of the parts on hand waiting for this GK to arrive. Serendipity indeed! I even had the DPDT switches to replace the one's that were broken.

For the time being, I am going to enjoy it just as it is. I finally own a piece of gear that I don't have to restore in order to get it on the air. I also got to put the NC-300 through it's paces and it does a good job. One aspect I enjoy about having a SSB receiver for AM use is to be able to make the moronic "Southern Moss" in Texas disappear from my passband. These are SSB mental midgets who refuse to co-operate with us AM er's on 3870. Fine by me. They no longer bother me during the summer months anyway but when propagation is in their favor, I slice them up like Beets. I like that  ;D

What an extraordinary hobby we share!

I can't tell if you removed the filament transformers on the SS plug in rectifiers or not, but if you haven't, I suggest you do so.  That will stiffen the supply a bit and help.  If you have, ignore my bad eyes.  The power reading you are seeing out is probably about right but that is dependent on the meter you are using.

I don't know if you plan to try to use it on 160 or not, but if you do, remember it is designed for 300 ohm output.  If you try to load into a 50 or 75 ohm load, you will burn that coil on top of the RF deck.  I made a modification to mine to allow it to load directly into 50 ohms without a tuner to match the 300 ohms and I don't recommend trying to use a balun between the output and the antenna.

I won't be removing the filament transformers and it's unlikely that operation on 160 meters is in my immediate future without the needed room for the antenna. I wish.

If I removed the filament transformers, you mean just removing the primaries from circuit, and lifting the center tap leads and attaching them to the outputs of the SS rectifiers, correct?
Explain.
Thank you.

I think that's what he means, Billy. I'm a little confused as I thought the plug ins just open the filament circuit anyhow, but it would still be good to remove or otherwise isolate the leads. Not familiar with the circuit so I'm probably missing something [obvious].

Glad to hear you're not going to perform major surgery on the old girl. A lot of us AMers get wrapped up in sounding good and lose sight at times of the fact that we're using amateur, not professional gear designed for HiFi. I'm always willing to make some 'soft mods' as Joe calls them that don't require drilling, blasting, or major surgery. Beyond that, it's easier (and a good excuse) to get something else more purposely designed for the job.  ;)

Those old wooden sets are near and dear to my heart. It's always interesting to see what turns up. And it was a great way to divert my GK-envy. I've wanted a Globe King for years (even have a once-NOS cabinet in the garage)since seeing Brian/W1LYD's highly-modified 'Glob Queen' 400 back in the 90s. Manage to talk myself out of it each time due to downsizing, too many projects, and all that. Sure, Leo's crew cut some corners and used surplus parts or whatever else, but to my eye they are the perfect table-top transmitter and very well laid out visually. Even the Collins KW-1 cut some corners, especially in the audio dept.

Maybe some day I'll find a set of grubby chassis that need a home.

   I live in Texas, and have heard the 3870 issues play out. I am friends to both sides, and I am not laying blame. What I here is that the west coast AM group has big carriers, and low levels of modulation. The LSB or USB from you guys causes little to no interference here in 5 land. What causes a problem is the carrier. The carrier is either low in frequency (like 3869.5), or drifting down below 3870 following a key up. Either way, a beat note is heard. If the west coast AM'ers stayed on 3870 (real close to it), then there would be a much reduced interference issue from two modes coexisting on the same frequency that are in different geographical locations.  The 3870 Texas sSB guys guys do run a lot of power, and some have antennas that are intended to have big signals 1000+ miles out. This messes with the west coast AM'ers. If the beat notes go away, perhaps the Texas SSB guys will drop their power, or switch to a cloud burner antenna. My suggestion is to stay on 3870 exactly (no keyed VFO's), or move up a bit, perhaps to 3875. The frequency of 3875 is used a lot by east coast AM'ers, then being so far away, little QRM from those two areas should occur except late night in the winter time.

Jim
Wd5JKO

For my needs, the GK is a perfect fit on the money. I have a friend who owns a KW-1 that suffered a major problem that is likely going to take a miracle to find the part as it's likely unobtainium. A $20,000 dollar boat anchor with lot's of class and personality is looking to me like a gigantic doorstop. I would love to own one and perhaps someday that will happen. For the time being, The BC-610E and GK-500C make me one of the happiest campers in radio land. Another item I like about both of these transmitters, is they are quiet (ART-13 too) and the GK-500C is very quiet even with the little blower.
My next stops will involve the 30K-1 & a James Millen 500 watt station. That should do it for my AM needs. To me, the thrill is never gone with AM. I wish I could say the same for SSB.

What I am suggesting on the rectifiers is you remove the connections, both primary and secondary and covering them with heat shrink.  Leave the transformer there and run the output of the SS rectifiers to where it should go.   That will take the inductance of the filament transformer out of the loop and maybe keep it from shorting to ground and ruining it.

You don't need that inductance running around in the HV supply anyway.  If you do that then post what your modulated power is.  You stated it is right at 1000 watts with them connected.  I wonder what it will be without those transformers connected.

Jim
I couldn't agree with you more. My station is CONSTANTLY monitored and adjusted accordingly to stay exactly on frequency. Many operators who are rock bound seem to be a little low in frequency. Several of those stations are running high level 1KW BC rigs too. There is a bit of vanity and pride involved with getting a large group like AMI West to move to 3875. Many have tried. The other argument and where I come from is this: We AM-er's have a rather small slice of sub band generously allowed by convention. The 75 meter phone band has a gigantic amount of unused space, yet some individuals cling to a certain frequency as if it belongs to them regardless of interference or gentleman agreements. Not that the AMI folks have any more right than others, but within the sub band albeit the lowest portion, I think a little allowance should be considered. This battle goes back a long way, way before my time here. I go along with the flow, and use my Flex 5K to remove interference. The bummer, is that my beautiful AR-88 & R-390 sometimes go unused because of this unwillingness by the Southern Moss. Both sides are to blame to an extent, but I am an AM convert who spent years as a SSB net manager for several nets. The growth of bigotry, lack of operator skills and manners on 75 meter SSB has reinforced my resolve to tell all of them to pound sand. I have 2 sidebands and a carrier and intend to use it at all costs. While I could increase my carrier level like some do, I prefer to stay under 350 watts and normally run around 275 to 300 anyway. I do just fine.
I appreciate you making a very valid point Jim. The beating of carriers and sideband mixing can otherwise ruin the hobby for some, but not for me. I slice and dice and make everything nice.
73 de Billy N6YW

   I live in Texas, and have heard the 3870 issues play out. I am friends to both sides, and I am not laying blame. What I here is that the west coast AM group has big carriers, and low levels of modulation. The LSB or USB from you guys causes little to no interference here in 5 land. What causes a problem is the carrier. The carrier is either low in frequency (like 3869.5), or drifting down below 3870 following a key up. Either way, a beat note is heard. If the west coast AM'ers stayed on 3870 (real close to it), then there would be a much reduced interference issue from two modes coexisting on the same frequency that are in different geographical locations.  The 3870 Texas sSB guys guys do run a lot of power, and some have antennas that are intended to have big signals 1000+ miles out. This messes with the west coast AM'ers. If the beat notes go away, perhaps the Texas SSB guys will drop their power, or switch to a cloud burner antenna. My suggestion is to stay on 3870 exactly (no keyed VFO's), or move up a bit, perhaps to 3875. The frequency of 3875 is used a lot by east coast AM'ers, then being so far away, little QRM from those two areas should occur except late night in the winter time.

Jim
Wd5JKO
[/quote]

I'd like to raise a friendly horse pucky flag on this one. ;D Caw mawn Jim; there are lots of "golden age of radios" amateur type with VFO's that drift. You want them to stay on a specific frequency, BS. Every xtal in my shack is a couple hundred cycles low, tuff titty. The excuse which you give is just like going to a boxing match and not wanting to see punches traded in the ring. Those that don't want to "hear AM", please skip the frequencies where AM is in use, such as 3.870-3.885 on 75 meters.

Even within the "window"; as the band stretches out AM'er hear each other's heterodynes and either sign off with the close in QSO's or join in with the distant stations. Lots of room on the bands. Some of us have learned to play well with others.

Craig,

I'll sidestep the SSB/AM dysfunction for now and introduce a sidebar of sorts... The GK-500C SSB input.
I haven't done much reading on this yet but there is a switch on the back that allows selection of SSB input, and a corresponding RCA jack.
Now, this site is all about AM, and I am completely down with this but it beckons the question: What SSB adapter should be used? Was this a work around by Leo to let his flagship gear be able bodied enough to support the newer mode of communication to attract the SSB crowd? Is there a specific contraption that is ideal for transforming this little beast into a snotty nosed upstart lacking a carrier?
I am a member of, and a scheduled host for the Vintage SSB Roundtable gang on 3895 KHZ here on the West Coast, so it gives me pause for having a little fun at everyone else's expense... especially my neighbors. Perhaps this is foolhardy and should be avoided. Any takers?
Billy N6YW

I'd think a CE 20A would be ideal.

Well, we're not completely monolithic here, Billy. Plenty of SSB DXers and brass pounders mixed in. And besides - SSB is really just AM Lite, right? An AM signal with the carrier and one sideband filtered, masked, whatever.  ;D

So long as you're working other classic tube stations no one will likely complain. A lot of the newer plastic radio crowd have a really rough time handling any drift on SSB, though. It just drives them nuts, have heard it numerous times (kinda funny to listen in).

For appearance sake, the B&W 51S(?) comes to mind as a good visual mate to the GK. No idea if it would lash up to it easily; keeping the AM stuff working is hard enough on my feeble brain.

I'm guessing your buddy must've lost the vacuum variable in his KW-1? There isn't much else in there that can't be replaced, rewound, or substituted. The vac variable was a custom job as I recall, not many around. Probably a workaround for it, too. Just don't tell the Collins Radio Authenticity Patrol. ;)

  I agree. The GK500 Linear input level should be about right for a 20A that is running about 1/2 to 2/3 power. Of course the 20A power varies a lot band to band (mostly the VFO issue), but 80/20m are the best two bands since they occur without having to multiply the VFO frequency.

  I sometimes get into the "Boat Anchor" net here in Texas where most check in with a vintage SSB rig. This is every Wednesday night at 7:30PM Central time on 3870. I use a modified 20A driving a 8877 based amplifier for ~ 1000w PEP output. I strive to be on frequency, and have went to great lengths to be ON, no matter what mode I run. I attach a system schematic of my Lakeshore Band Hopper VFO effort. More info is in the files section of the Yahoo Group, "SSB Round Table".

Jim
Wd5JKO

Billy,

As mentioned the 20A would be a great driver for the GK-500.  With a grid driven PA in linear mode the CE-10A would probably be enough as well. 

I host an Antique Wireless Net on 160M and a lot of the guys are using either CE-10's or 20's into a linear with good success.  A simple but not vintage solution is to use the N3ZI DDS VFO since that gives great stability.  Those that are using the converted Command sets on 160 as VFO's in general drift quite a bit and for SSB that becomes a problem! 

Being a phasing unit the audio quality is excellent. 

Joe, GMS 

My HT-37 is also a phasing type rig. Perhaps I could use that with a load pad. The CE-20A's are plentiful enough that I could use one with a crystal for 3895 operation. The 458 VFO can be a bit drifty. It's funny, I owned 3 complete sets of 20-A's with all of the accessories and not once did I get them on the air for a QSO. The CE-20A is a very good transmitter and I have several that sounded excellent after a thorough restoration. One guy uses one just about every week for the roundtable and stays on frequency very well. So, about 10-15 watts of RF drive into the GK-500 should do it? I need to do my homework on this subject.
Anyway, I was at the TRW swap meet today and it was great to see a bunch of my buds. Word has gotten around about the GK-500. Seems like people are dumping a lot of BA's. I saw three Valiants sold today, and even a couple of Rangers. One guy was selling an R-388 for $800.00 bucks. I laughed and kept walking. I have to give a big shout out to Bob AK6R, who is Palomar Electronics now. He hooked me up with some ferrite products to help tame my neighbor's angst regarding my AM signal and his sub woofer. Silly wabbit. I'm being nice though and will terminate the issue. The swap meet really has turned into Computers and cheap Chinese tools galore. A few hams selling stuff, much over priced but still some bargains. Juan, KB6KMU bought a Clegg Zephyr receiver in beautiful condition for cheap. He beat me to it by 5 minutes. We are going to put together a 6 meter AM group for the heck of it.
Back on topic:
So far, the audio reports have been quite flattering. The D-104 seems to work just fine. Looking at the schematic of the speech amp, there is a 47K into the grid and a 2.2 meg to ground in the first audio stage. Should I consider adding more resistance or is this okay? Looking at the scope, the bandwidth looks pretty darned good and considering this, it appears that someone may have added some capacitance in parallel to at least one of the couplates.
I sure hope to work some of you guys on the East Coast when conditions permit and I usually monitor 29.010 during the day and perhaps load this rascal up!
73 de Billy N6YW

Billy, a bit off topic but is Palomar back in business under a new owner?  I hope so they had quality products and were a joy to do business with.  The previous owner would send the products and put a bill in the box when I ordered.  How nice that was. 

What's a Clegg Zephyr receiver? Never heard of it. The only two 6 and 2 meter Clegg receivers I know of are the Clegg Interceptor and Clegg Interceptor B.

Bob, AK6R is about as nice a guy as you would ever want to do business with. I believe he carries on the same tradition.

Funny after all the other automatic gizmos on modern receivers, that automatic receiving frequency control in SSB hasn't been added.  Auto RIT.  Of course FM has AFC.

So for those pesky vintage SSB roundtables, "Forward to the Past !"
But then the sweet caché of off frequency dissonance would be heard no more.

Oops, just caught myself. If all in a roundtable are using modern rigs, they're all on pretty much the same freq. anyway, but you know what I mean. Looks like the AUto RIT would be useful to clean up the few unwashed incoming and great for those vintage tube meets.

I guess Auto RIT would be an expensive add-on, if even possible without major surgery for ancient rig receivers, but you wouldn't have to depend on the other guy to have digital VFO's.

So you could have "let's turn off our Auto RIT" days.
Keep drivin' 'em crazy.
Yeah everyone purposely being a few cycles off on even modern rigs in a roundtable would be fun too. Flip on your auto wobulators.

My bad. It's the interceptor. 6&2 meter receiver. What a fine piece too.

It's a nice receiver. I have the original and the "B" models. The 7360 and nuvistor tubes can break the bank if they need to be replaced. The original manual never included the alignment instructions but I got them from Ed Clegg back in the 90's from his personal files.

And now...
The antenna. Yes, a folded dipole with ladder line is reaching into the sky as of this week.
I will now have something other than the vertical (75 meters only) and it will put me on the other bands (except 160).
The property lot is only 90' long so I had to use a compromise but being that it's a Cobra Ultra-Lite Jr
it will at least put out a signal. It will be interesting to see how it works. The tuner is a Johnson KW MB.
So far, the reports on the GK-500 have been excellent again. The D-104 audio processor is doing it's thing  :)

FYI, the Cobra Ultra-Lite is not a true "folded dipole"
antenna...

Yes, its two sides consist of "folded back on theirselves" wires, however the folded dipole is in fact a continuous narrow spaced loop of wire (origionally made with TV twin line) fed with the same TV line or open wire...   

The Cobra is actually nothing more than a center feed Zeep configuration...

Perhaps, but for my needs it's "folded" enough. The first mast was installed yesterday, 43' total height.
It clears the canopy of the tree by 4' ft. A major pain but worth it. Pulling the antenna across the top of the tree will require constant tension with a person at each end. It's going to be a lot of work but once it's installed it will last a long time. I am using the surplus military fiberglass masts that come in 4' ft. sections. Each section has 3 screws to insure as much rigidity as possible. It worked perfectly.
I made two guy rings out of Micarta & installed at the 2/3'rds mark. The bottom 1/3 is supported by a stand off mounts attached to the roof fascia boards on the garage and the house
The antenna will extend from almost one end of the property to the other, which means I might have to dog leg one end downward by a few feet. I don't see much problem with that. At least the antenna will be up in the air as far as I can get it while being practical. I want to put an end to interference issues with my neighbors. It seems that Gary K6GLH maxim on vertical antennas has been true:
Vertical Antennas: "A great way to meet your neighbors"
I am living proof that this is true. Wish me luck. AM is going to rule the roost here at N6YW no matter what I have to do.

Another 3 shots...
As you can see, the Elm tree is not antenna friendly.

Billy,

Looks good and with the amount of guying you have it should stay up for quite some time. 

Verticals have there place and when done correctly can work quite well for low angle work, but It hard to beat a dipole up in the air for general usage. 

Is that a tree laying on the roof shingles in your first picture? 

Joe, GMS

Using that antenna may mean I can hear you this coming winter in the middle of the country.  Good work.

hmmmm 

90' + 40' = 130'

  Run some 1/4 inch Dacron rope through some pulleys and drag some 18 AWG homely despot wire.Sounds like you'd have an inverted eL on 160m. You could pull it back down and leave the other antenna up there.


klc

Joe, yes it's one of the limbs. We are going to cut it off entirely this summer. My wife has been
opposed to it until I showed her that I had to use a piece of plywood to prevent it damaging the new
roof on the garage! Away it goes! :)

Updates:
After purchasing and using the pole saw to remove the tangled mess that snagged my antenna, all went well after that. The Cobra Ultra-Lite Jr. does in fact work quite well considering it's limitations. I am very pleased. Locals and out to 500 miles have reported up to a 3 db increase in signal strength over the vertical which is not surprising. I am not an avid DXer, so arm chair rag chew QSO's are my thing on 75 & 40 meters. So far, it's worked wonderfully.
Now the sad part.
A couple of nights ago, I was using the Globe King 500C and I received reports of distortion on my audio.
I hadn't touched a thing since I had been previously given excellent audio reports. I investigated using the dummy load to re-tune, and modulate my signal while monitoring with headphones and receiver. Sure enough, it sounded like voice peaks were clipping badly with a nasty note, a brief one at that but consistent. Turning down the audio had little effect. I got to thinking audio tube path or bad mod iron.
Then, while retuning in CW mode to make sure it was loading correctly, The plate current shot up and blew the 20 amp fuse on the power supply. Okay. My bad. After replacing the fuse, I no longer get a dip on my plate current meter. I key up and it sits at 200 ma and doesn't move from there.
I pulled the RF deck out of the cabinet just to have a brief inspection of the top sides. Everything is fine looking but I need to remove the bottom cover and see whats up. I also need to measure the HV supply and screen supply to see if maybe I smoked one of the plug in SS rectifiers.
At this point, and because this rig is such a bitch to isolate and troubleshoot without making a custom test harness to spread the work outside of the cabinet, I am left to measuring components at the static level not energized. RF, Mod & supply decks individually. Grrrrrr.
So, what suggestions might the group have to direct me in a manner consistent with good practice concerning this radio?
Man this thing was sounding fine before all of this came about.
Thanks,
Billy N6YW

Take a close look at the switch that is used to switch in fixed capacitance and if all the fingers are there, pull the caps and inspect those.  Be sure the antenna relay is closing, and check the bandswitch for melted contacts.

In addition to what Jim (W5JO) said, I have a couple of comments.

You can set the three decks on the floor making a circle. That way each deck is accessible positioned upside down or upright. Make sure the chassis's are bonded together and grounded. You don't want any surprises.

I would rule out the modulator deck being an issue by routing the B+ straight from the power supply deck to the RF deck. Keep the modulator filaments off.

My bet is that something croaked in the RF deck. With no drive (CW Key UP), there should be no plate current. Tackle that DC condition first. Switch to linear mode (again no drive), then see if you get the usual idle current (50ma?). If the DC tests fail, look at that plate current meter. Is it wired into the cathode side? If so, consider the possibilities. One might be a blown plate choke, and that 200ma you were seeing was screen current!  :'(

Have a plan, and be careful.

Jim
Wd5JKO

Well looky here  :)
It seemed the screen parasitic suppressor (buffer plate) committed suicide. It's a 1 watt 56 ohm
carbon resistor. Can I use 47 ohm without much difference?

I ended up finding a an exact replacement in my stash of vintage parts.
 ;D

Replacement has been completed. I added some rubber insulation tape to the outside of the small transformer next to the solder tab for the PS-1 I replaced. There was evidence of a possible arcing
on the lamination of that transformer. It was indeed very close!

  Remember that the resistor that blew apart had to have seen significant VHF energy to get hot like that and break. This goes along with a VHF parasitic to the extent that the 20 Amp main fuse popped. You are finding peripheral damage, and not enough to explain all the symptoms.

  I have run a GK500B, and I recall specifically dealing with the 4-250 screen bypass capacitor where I replaced what I recall to be a single big mica-mold .002 uf with four 500 pf VHF button capacitors where I had two going to each screen pin, and returning to ground at each of the four socket hold down bolts. That kept the screen at RF ground, and a tendency for the big 4-250 to soar at VHF was dramatically reduced. That RF tube is not neutralized, and it really should be.

  Was that new antenna you put up having a different tuning solution of the GK-500 pi-net? I ask because that might have put the King at a different point such that stability was closer to the edge of carnage.

Jim
Wd5JKO

Jim
You bring up a good point.
First, I inspected and checked all of the components inside the RF deck. No shorts or opens other than the PS-1 I replaced. Having said that, I will put it back into service to see if there is an existing problem not
found through static checks. I have the feeling that the resistor may have been cracked from previous use prior to my ownership... just a hunch.
The new antenna loads up fine. When I had the blow out, I was tuning into a Bird 2KW load, purely resistive, and I used no loading in the tank circuit. I was getting roughly 300 ma. with 345 watts output before all of this occurred. I will advise in a little while what my findings are.
BTW, I oiled the blower motor bearings too following an earlier posting advisement.

I am going to pull the Modulator deck to have a closer look at things to see if maybe there was an arc, loose connection or anything that might point to that distortion issue. It's using an old metal case 6L6 tube which I think should be replaced with something that sounds better. I will see if the bypass caps in the audio chain need to be replaced also.
Thanks again, and more to come.
73 de Billy N6YW

If you did not go thru the radio, checking the values on all the resistors it is more likely that it simply was out of tolerance.

The problem you experience is not totally unknown, I have seen it before.  I would loosen that nut and rotate that terminal board away from potential problem.  Beyond that, check the components around the 6146 to see if you see anything amiss.  

There should be a choke in the plate lead of the 6146, look at it for evidence of heating and problems.  The diagram shows an RF choke feeding bias to that 22 ohm resistor, is it there and what is its condition?  From what I can tell work has been done in that area, be sure all bypass and blocking caps plus other components around the 6146 are good and placed correctly.

Done & done.
I found that way back in the day, someone had replaced the bypass capacitors in the audio stages of the modulator deck (servicing now, removing couplates) and low and behold, the ground of one cap wasn't even soldered... it wasn't even making good contact with the ground solder lug. All of that has been sorted out. I added a 1.5k swamping resistor to the control grid of the 6L6 right on pin pin 5. Even though there is a 500k grid stopper to ground prior to this, that alone isn't enough to prevent audio parasites. Interesting how the 6SJ7 Pentode is being used, and with just a 47K input resistor from the mic input, shouldn't I consider adding like 4 megs for using the D-104? Let me know before I close it up.
:)

Back to the RF deck. No output and the screen meter reading pegs to the right.
On the bench she goes.

I overlooked the obvious...
However, I have an identical spare. Now, should I try repairing the burned one and install a parasitic choke on the anode, or use the new one with a PC?

RF deck fixed. 300 ma. @ 325 watts of carrier.
Back to the modulator deck. It's a comin.

It's fixed.
There was a problem with the print of my schematic that I corrected. Back on the air and it sounds
excellent without the distortion! Maybe I should try one of my EL-37's or KT-66's for the audio driver.
Hmmm.

   It has been a long time ago, but I did something similar to one of Ozana Bob's (W5PYT SK) Globe Kings's.
I used a 6CA7 in place of the 6L6, and added a negative feedback loop from one of the 811 grids back to the driver tube grid using a couple of resistors in a voltage divider.

   If I was doing this again, I'd look at that driver transformer primary. Is there a third wire there that is unused? If so, this is the centertap left over when WRL used a push pull driver with the GK 275's, and the GK400's. I'd connect that center tap to feed the driver tube screen grid. This will act as an "ultra linear" of the beam power tube such that it will act more like a triode (low plate resistance) with the almost the full gain of a beam power tube. Worth a try.

Jim
Wd5JKO

Jim
While I was inspecting the modulator deck, I indeed saw a clipped wire exiting the driver transformer.
It's a rather easy job to remove the transformer & end bells as to extend a new lead for such an application. I will place a bookmark in my brain on this one.
Single ended Class A ultra linear is something I have read very little about, and because I build and restore guitar amps for a living, it's a topology that I rarely consider but have heard of others doing.
I appreciate these ideas and it provokes a lot of thought of maybe doing some extra work to make this beast rock a bit better. However, right now I am just glad I have this wonderful and simple giant working.
One of the aspects of these types of forums that I love a lot, is the way in which the discussions push an individual to use their mind to work through problems, which ultimately result in a fix and sometimes a refinement.
It's quite easy for anyone to assume that just because so and so did this and that to their rig, will equate with the same results for mine or anyone else's equipment. What I am learning a lot about these old pieces, is they all have a character all their own and because their own unique history, (sometimes unknown) and inconsistencies in manufacturing, we end up finding out that we have to learn the particular if not peculiar "personality" of said equipment. This transmitter is certainly no different but I'll tell you what! After the little bugs are scraped away the design "center" starts to become more pedestrian. In other words, a little more predictable.
This learning process is HUGE! Many of the more intelligent naturally gifted electronic guru types might take a lot of this stuff for granted but to us less gifted but equally capable types like me are grateful for the experience.
Having said all of that, my troubleshooting chops got a gigantic boost today and the dividend is large.
I fixed this hairy, heavy old bastard without resorting to a lot of spaghetti. Just a lot heave and hoe.
Thank you very much. This project will continue.
73 de Billy N6YW

The rig is running great today. I am now getting 345 watts of carrier at 320 ma. The audio is nice and clean, free of distortion. The particular D-104 I am using does not exhibit much energy below 200hz, but gives a very full account of itself through 4khz and gently rolling off around 6khz.
Using the display on the Flex 5000 shows a very nice envelope and frequency content.
Jim's comments about the audio driver stage really has me curious.
I could easily do the UL mod but it got me to thinking about using a better grade of SE transformer altogether. Perhaps along with that, exploring the idea of doing away with the 5Y3 rectifier and going SS for the entire audio stage HV rail. I should measure the voltage drop of the 5Y3 under peak conditions.
Anyway, just thinking out loud again but more importantly I want to thank you guys for all of the comments. Getting this rig back on the air has been quite an experience and I happy to report that my body wasn't injured in any way due to repeated moving of the decks during service.
I shall relax with a cold drink tonight and converse with a close dear friend who has made a tremendous recovery from a stroke... on AM of course.
Thank you.
Billy N6YW

Great stuff.

Billy,

It sounded really great on 3870 last night.  Congrats!

Craig, W6DRZ

Thank you Craig! It was good to hear you back on the air. Glad you repaired the antenna problem.
We had 4 Globe King transmitters on the air last night!
K6ZSR, GK-500C
KB6KMU, GK-500B
NY6L, GK-400
N6YW, GK-500C
What a hoot! I hated to go to bed. It was like having out own King Biscuit Flour Hour without the music.
We'll do it again tonight if the conditions are right.
73 de Billy N6YW