Globe King 500 repair and restoration review

[w4fms]

Clark:

What replacment blower did you finally end up using in your GK?  The squirrel cage in my 500C seems to be quite loud and figure it will need replacing one day.

Frank

[Jim, W5JO]

Clark:

What replacment blower did you finally end up using in your GK?  The squirrel cage in my 500C seems to be quite loud and figure it will need replacing one day.

Frank

Try oiling the felts first.

[ke7trp]

I cant find any replacement that is even close. It will be a custom job to rebuild the blower at a machine shop or to mount a larger one.

I took the blower apart, Cleaned it and oiled it.  I used Royal purple Gear lube in a Siringe to inject the oil.   The blower ran noisless for 4 days. Then got out loud again.  This time, Its loud for about 2 minutes on startup but then the noise goes away.. So I am living with it for now.

The GK died on me yesterday.   I threw the switch and heard a LOUD buzzz and no output. I keyed it off fast but the Fuse on the back PS blew. I found the Big HV trans relay was fried.  The unit is rated at 10amps. The Fuse is 20.  On key down with 350 watts of Carrier, I would think that its way past the ability of the relay.  When you UNKEY you can hear it jump across the contacts.  This must have made a Carbon spot on the contacts and then it failed.
 
I stopped by a friends work, an industrial supply house, and purchased a 120 volt 40 amp contactor.  This contactor cost $12 with the discount. I am going to install it today.  I am tired of cleaning and messing with that 55 year old 10 amp relay. Its a nice compact size, But is going to be a bear to fit.  I will take pictures IF I can get it in there.


Clark

[KD6VXI]

The GK died on me yesterday.   I threw the switch and heard a LOUD buzzz and no output. I keyed it off fast but the Fuse on the back PS blew. I found the Big HV trans relay was fried.  The unit is rated at 10amps. The Fuse is 20.  On key down with 350 watts of Carrier, I would think that its way past the ability of the relay.  When you UNKEY you can hear it jump across the contacts.  This must have made a Carbon spot on the contacts and then it failed.
Clark

What you're describing doesn't fit a relay welding shut... The relay welding shut / closed sounds more like a symptom.

I'm betting a shorted rectifier or bad cap somewhere.  I PRAY it isn't an xformer.


--Shane

[ke7trp]

The Relay is not sticking closed.. It fails to HOLD closed and just arcs and buzzes.  If you put a new fuse it, The rig fires up and works.. Then once real warm after talking for 30 minutes off and on, It starts to buzz then hold.. Then finally, It buzzes, arcs to Ground and blows the Fuse.

Clark

[ke7trp]

LEO STRIKES AGAIN!   

My Relays are different then stated in the manual.   Now, I need to find a 6v coil Double Pole, Singl throw 30 amp relay!  My New Contactor wont work.  Great.. Oh well. It was $12. 

It seems on my 500C, The relays are all 6 volt and they Daisy chain so decks and devices come up in sequence.  The Plate supply contacts are TOAST and the other contact for the LV supply, was welded shut.

Anyone got a Nice big DPST 30 amp contact 6 volt coil relay???

Clark

[Jim, W5JO]

Clark go here and find the Form C contacts for DPDT with 6V coil.

http://www.mouser.com/

They are listed under Electro-mechanical/relays/generalpurpose/industrialrealys.  Do their search.  Under 6 V I found three different ones.

Easy to do buiness with if you haven't

[ke7trp]

I got one comming. Thanks!

So the plan now is to wait for the relay...

In the mean time, I got my Screen dropping resistor, HV wire and a huge Jennings screen bypass Cap.  I am going to work on the RF deck:

Mount Screen resistor.
Mount Screen bypass cap.
Run wires to the Plate supply to new screen resistor and cap.
Unhook the original Screen supply.
replace Cracked Millen HV connector.

With new relay, it will key.  With the screen supply, the screen will modulate

Clark

[kd4afp]

Awsome rig... You should be very proud.

[ke7trp]

Just an update. Relay should be here today or tomorrow. 

I have been working on the RF deck.  I used the MFJ 259B.  I fed this into the antenn jack.  I Used a 6000 Ohm Resistor from 4-400 plate cap to Ground. 

I closed the relay with paper.. Then, tuned each band by the chart.  I found that 75 meters was 2.4 to 1 SWR. I replaced the Loading cap and bingo 1.0 at 50 ohms.  Other bands tuned flat.

160 meters requires a 500 PF Silver mica cap from the top of the 160 coil to ground.  Mine had this DONE already.. But if yours does not, 160 meters is just one capacitor away.  Load to 250ma,  Reduce audio down to no more then 100%. Talks clean on 50 ohm antenna.. Just a bit lower output over 75 meters.

This is needed as the King is setup for 300ohm antenna on 160 meters.  The components are small (coils) so only load to 250ma and keep the pep down for safety. 

Thanks to all the advice on this from the guys on the forum!


I also installed a 400PF Jennings Ceramic cap from Screen to Ground. Its huge.. 2.5 inches in diameter. Mounted it to the chassis and ran Coax braid to the Screen pins on the 4-400.  I ran a 1000PF before.. This one got me more highs.

[w4fms]

Hi Clark..thanks for the GK update.

On the 75m match, the "loading" cap you refer to is on in the shorting antenna matching switch with the stacked postage stamp micas?

On the screen bypass, you originally changed from the stock 200pf cap to the 1000pf recommend by VMC.  Now you are back down to 400pf?  Your sweep of the audio shows more highs with 400pf?

Have you seen the article in ER from Dennis, K0EOO regarding the LC network for running the GK on 160m?  Did you opt for the 500pf cap w/o the L just because it was in there and was an easier fix?

Good luck on replacing that 6V relay for the HV, interested to hear your results.

Frank

[ke7trp]

Frank,
   I have tried all kinds of caps on the kings Screen.  The Two 500s or the single 1000 seemed to work well. Yes, I am sweeping from 20 to 20K at the mixing console and the Spec An. I am getting 20 to 10,000 pretty flat. Then it falls off. I can extend this out to 12K with eq. I am going to Try this Big Jennings 400PF and sweep again.  I have a hunch this will be best. If you go back and reread my post, I worded the last sentance wrong.. I meant the 1000PF got me more highs. I just dont think the Mod iron will let the highs through. I am going to try the BIG 400PF and test that. If it does not work, I will go back to the 100PF cap.
   I did not have to modify my King for 160. Someone already did that. I ran the MFJ into the Pi and found 1.0 to 1 SWR at 50 ohms.  Another Ham used a 500PF cap across the Top of the coil to ground and got a 1.0/50 match. He is on it daily on 160 and just recently tested his in the same manner with the MFJ backfed into the Pi.
   I only suggested loading it lighter and keeping the audio down so you do not over do the 160 coil and you dont hurt the MOD iron. I have not seen the article you talk about. But, I have seen all kinds of "fixes".  The trouble is there is just NO room.  The capacitor seems to work and its a simple modification.  In reality,I think the entire RF Deck needs to be rebuilt from scratch.  Then its not a Globe King...

The work is now complete.. The big cap is in, I used RG8 braid to attache it to the screens.  I used a 220 watt 50K ohm Resistor mounted under the deck for the screen dropper. HV wire to the HV socket. Cant test until the Relay gets here for the PS. 


   

[ke7trp]

Part 2:

I am not wiring up the HV wire to the Ultra modulation unit I purchased. It will sit next to the King and hook in using MIllen HV connectors.  If this does not work to my liking, I will remove the Screen dropper, and hook the stock screen supply back up and remove the UM unit from the mix.

Clark

[KD6VXI]

Part 2:

I am not wiring up the HV wire to the Ultra modulation unit I purchased. It will sit next to the King and hook in using MIllen HV connectors.  If this does not work to my liking, I will remove the Screen dropper, and hook the stock screen supply back up and remove the UM unit from the mix.

Clark

I can't wait to hear it.  Was it the GQ you where talking on 40 AM yesterday.

Still can't believe you guys could even HEAR my little station in the mobile!  GOTTA upgrade the antenna, 100 watts AM mobile is NOTHING.  It's REALLY a pisser when you HAVE the linear in the truck, mounted, READY to GO, and have an antenna rated at 120 watts

Anywho, off to make breakfast for little boys!

--Shane

[ke7trp]

Still waiting for my relay!

You heard me on a Globe Champion 300. About 200 watts Am.  Running with a D104 mic.  Only mod is the Couplate is bypassed along with new caps.

I could hear you at times.. But another 10DB would have done it..  Good to hear you shane!

Clark

[ke7trp]

Ok.  Spent all morning with the King. New Relay is in.  Tight fit.. Had to insulate the terminals. The Primary now has three Contacts. The other side has one as normal.

I settled on a 400PF Jennings 4KV Cap for the screen bypass. VMC sent it to me. Sounds the best with stock iron.  Ran the Screen dropper but it dropped to much. I think you need around 15K to 20K.  Robert sent me a 50K. Way to much.. Only has 100 Volts of screen. 

I ended up putting the Stock screen supply back inline. 

After all this the Relay would arc over bad every once in a while.  On the phone with robert and we figured it out. My Dowkey was not latching all the time. This caused the King to key up with NO load..  This in turn arced the contacts out. Took the Dowkey out of line and used the built in Change over relay. Now the King keys like it should. 

Damn Dow key...

Anyways.. I got 370 watts AM Carrier on the bird.  Tallk about 400RMS now. Nice and clean on the scope. Sounds fantastic through my monitor reciever.


Clark

[K8WBL]

This is likely not your issue but my GK400B relay also buzzed and would not close, the problem ended up being a open filament on one of the 5514 modulator tubes.  New tube and all works fine. 

My GK400B sounds great, someone before me removed the couplates...run stock D104 with very nice audio.

73, Tim K8WBL

[ke7trp]

Used the King 500C for a couple more hours of key down time.  One time, I had the relay SNAP when I let off the key.  All other keyups where fine.  I hope it does not start to act up. 

The audio with the external Audio rack is fantastic.  I am using a DBX compressor now. Made a nice difference in the audio.  Here are some recent pictures.

[ke7trp]

Ok that was fast...   It blew out again.

Can someone please explain to me how THREE 20 amp contacts wired together cannot close on a Globe king 500 Primary B+ transformer? 

This is now the third set of contacts fried in less then a year.  The stock set was Torched so I flipped the stack and used the new contacts.. It fried those..

Now on a New Relay Robert sent me.. THREE 20 amp contacts with a Snubber cap and resistor across it.  This is now toast.. dont get it.

When I talk for about 5 minutes and flip the Transmit switch OFF I get a Spark across the Contacts.. BANG.. Then the transmitter unkeys.

Then, If you flip it on you get a LOUD BUZZZZZZ across the contacts and it blows the Main Fuse. 20 AMPS.   Put another fuse in and the thing will fire right up again.

It is NOT a B+ flash over..  I have searched and searched.  Nothing is shorting.. The Relay is arcing on the PRIMARY side.

When Key it, Its a 350watt carrier.. Thats nothing for this relay.  Is it the 14 UF cap I put on the secondary? Is it the Solid state diodes?  Will 866s lessen the blow? 3B28s?  Other then this, The transmitter is Wonderfull on the air!

[N3DRB The Derb]

might wanna test the primary to the transformer with no connections to it. Do the Gito light bulb test on it.     stick a 100 watt bulb in series with one of the primary leads. if it glows with any shine at all, (A little bit of glow is ok) you got a crapped out transformer.

if thats ok, then start hooking your supply back up one piece at a time. Disconnect your leads from your decks and start isolating what's giving you trouble.

if you haven't guessed by now, Leo never used a decent spec'ed part when a cheaper one could be had.

i am starting to think that using any 50 year old transformer or choke in a rig is just a crap-out in progress. They just dont last under typically bad damp storage conditions. (like basements).

My 2 big units were hi-pot tested, so I'm hoping i dont get the KB3AHE transformer blues. I'm hoping I might be able to go up to NEAR-FEST this year, if so I'll offer to take a unit of his choice to KF1Z.

[KD6VXI]

might wanna test the primary to the transformer with no connections to it. Do the Gito light bulb test on it.     stick a 100 watt bulb in series with one of the primary leads. if it glows with any shine at all, (A little bit of glow is ok) you got a crapped out transformer.

if thats ok, then start hooking your supply back up one piece at a time. Disconnect your leads from your decks and start isolating what's giving you trouble.

if you haven't guessed by now, Leo never used a decent spec'ed part when a cheaper one could be had.

i am starting to think that using any 50 year old transformer or choke in a rig is just a crap-out in progress. They just dont last under typically bad damp storage conditions. (like basements).

My 2 big units were hi-pot tested, so I'm hoping i dont get the KB3AHE transformer blues. I'm hoping I might be able to go up to NEAR-FEST this year, if so I'll offer to take a unit of his choice to KF1Z.

A gentleman both Clark and I are familiar with, and I spent MANY a day at his "farm" once instilled in me that it is BENEFICIAL to bake all transformers....  And all transistors if they are to be used out of spec, but that's another story.

He did it to all the stuff he sold from the farm, and rarely if ever had a return on bad iron.  Before they would be hit with ANY voltage after sitting for a long time, they where placed into the oven.

Might be a wives tale, might actually have some merit to it.  I DO know that the transistors prepared in a smiliar method (2SC2879s) would tend to hold a volt to two higher Vcc than non-prepared transistors.  Supposedly, this baked out any residual moisture, which was good.  If this wasn't done, the theory was, the transistors would heat so quickly the residual moisture would heat, boil, and then the top cap of the transistor was cracked, and no bueno.

Clark, I told you before you put that relay in, that wouldn't solve your problem.  1.  No relays for high current.  Mercury wetted contactors are the only thing that will hold up.  2.  No relays where you can get a good arc, mercury wetted contactors are the way to go.

Anything bigger than a 2A transformer that leaves this shop has contactors in it.  Relays are fine for switching the inputs and outputs of linears, where we (hopefully) have sequencers that help us out.  For "hot switching" 60 hz (remember, it's STILL RF), you need something with a lot more oomph.

I STILL don't think it's a relay problem, though.  Those relays have lasted others a lot longer.


--Shane

[Jim, W5JO]

My GK 500A has the same power supply and it has the original relay.  It has never given trouble like you are seeing Clark.  What I don't have is the modifications you have made.

[ke7trp]

Thanks guys. 

How about swapping out the Solid state Diodes with the 866s..  Would this lessen the impact? 

How about inserting some low resistance 5 watt resistors in the primary leads.  This would lessen the blow...

I think its that 14 UF cap charging and discharging everytime I key it and the Big Plug in diodes. 


Clark

[KD6VXI]

Thanks guys. 

How about swapping out the Solid state Diodes with the 866s..  Would this lessen the impact? 

How about inserting some low resistance 5 watt resistors in the primary leads.  This would lessen the blow...

I think its that 14 UF cap charging and discharging everytime I key it and the Big Plug in diodes. 


Clark

Why not go to Grid Block Keying.

Just cut the t00b off during RX, and all is good.

--Shane

[ke7trp]

I would rather just repair it.  It should key fine.. Its only a low power transmitter.

C