The AM Forum

I wanted to make a post in hopes that someone down the line would search and find this information usefull in restoration of a Globe 500. Many of you have helped me and know the story but I would thought it would be worthwhile to type up some documentation for the group.

My Globe king 500C was not working when I purchased it. The owner before me installed the wrong tubes in the modulator Rectifier sockets. This sent AC voltage through the mod deck.

Modulator:
1. Every tube in my deck was bad. The 811s where shorted. New tubes installed.
2. The HV power trans for the modulator deck was shorted. I got a used one from W0VMC robert. W8QBG George came over to my house and helped me wire it in.. What a guy!
3. I converted to Solid state plug in Rectifiers. Now with 1600 Volts on the 811s.
4. Replaced all old capacitors with higher values.
5. Performed the W0VMC Modulator Speach amp kit.  Kit came with Schematic and all parts for hi fi audio. No more couplates.
6. His mod Also allows me to use the Phone patch cable  for use with external audio gear bypassing some of the preamp tubes.
7. Replaced HV connector on back. Used to have old Standoff types. I used Screw on Amphenols from Henry radio with Spark plug cable.
8. Cleaned switches and pots with Deoxit
9. PTT was not working. Found that the Electrolytic near the Selenium rectifier was bad. Replaced cap and used 1 amp diode in place of rectifier.
10. Replaced 6UF Oil can cap in HV section to a new 12 UF from W0VMC Robert. It fits in, I had to extend the clamps with custom made brackets.

At this point The mod deck was up and running.

Power supply Deck:

1. Cleaned chassis
2. Cleaned relays.
3. Replaced 866s with plug in solid state diodes.
4. Replaced Broken 866 plate caps.
5. Replaced Cracked power cord with Large side cable and large high amp plug.
6. Replaced various Paper caps.
7. Replaced High voltage standoffs with Amphenol Screw type from Henry radio.
8. I had a Burned Relay contact on the PTT relay. I unscrewed the contact "stack" and flipped them so I had a new contact in use.

At this point, the deck was now safe and working.

RF deck:

1.Replaced all paper Caps in screen supply and through out the deck.
2. Found Cracked 500PF Doorknob.  Replaced with 1000PF unit.
3. Found Burned Parsitic Resistor on 6146 and a dead tube. Replaced both.
4. Cleaned Tank coils with Tarnex metal polish.
5. Replaced the Screen Rectifier tube with new one.
6. Found one side of the 12ax7 dead. Replaced with new tube
7. Replaced Screen bypass cap with Silver mica block style cap to ground 1000PF (w0vmc mod)
8. Replaced Filiment bypass caps (005s) with .01 large diam caps to ground (w0VMC mod)
9. Cleaned Switches and controls with Deoxit.
10. Replaced HV standoffs with scew on types from Henry radio.


As you can see, This was a basket case.  After getting the rig up and running I found I could not load to 330 MA. I could reach 280 to 300.  Power output was about 250 to 290 watts AM on a Bird 43.

I had one melt down about a month into useing the rig.. The 6CB6 tube shorted. This is the VFO Buffer tube that drives up to the RF deck. This tube cased the Solid state diodes on that supply to fail. A new tube and a 5R4 plugged in got the rig back up and running.. Now I can load to 330MA.  Its imperative that the VFO has enough drive or you will never get full output. Check or swap the 6CB6 tube and the 6au6 tube out with others until you can reach 330ma. Power output jumped to 340 to 350 watts AM after this at 330MA.

Later, I changed the 4-400 bypass caps. They are WAY to small for the job. They used tiny little disk caps. Mine where dark in color from the heat. w0vmc told me to change them and it made a big difference in power and audio response just as he said it would. Now with the .01s on the filiment and the 1000PF mica on the screens Power output is now 375 watts at 330 MA. If you turn the Grid Drive up a bit it will do 400 easy. I run it around 320MA at 350 watts with a Grid of 15 ma. 

Its important to go back and tune the Buffer knob for max plate current. This is stated in the manual. If you forget this you might be leaving some power on the table.

I run my Globe king 500C on a Seperate 30 AMP wall box with number 6 cable to a 30 amp breaker. This seemed to really help. The standard wall socket is not enough really. At least not in my house. Very stiff supply and it shows in my output.

I run a Behringer 802 mixing board.. Cost $69.  I also run a Marshal MXLV57M large diaphram condesner micphrophone. This mic requires 48 volts from the mixer. This caused me to buy the 802 mixer. The Drawback is that the 802 DOES NOT Have high impedance output. It has the 1/4 jacks but in the manual it states 150 ohms out. This resulted in low Audio. I purchased a Low to High impedance matching Transformer and a Right angle 1/4 inch plug. This matched the 802 to the high impedance on the modulator deck. Just buy a mixer with high impedance out.

Future mods?  The only thing that stands out is the HV Oil can cap. Its only 4UF. I woud like 10 to 12 UF in there and at least 3 people told me to get at least 10UF.  I have purchased some 10 and 12 UF caps and will try to get one of them in.

Results:

When swept at the mixing console to the modulator deck with 20hz to 20,000HZ, the audio is Flat from 20HZ to 9000. Its 3 DB down at 10,000 and past 10 it rolls off hard.  Not bad!

Power output is now 375 watts At 330MA. Modulated 100% it actualy goes forward to 400 RMS on the bird 43.


Many, many people on this board have helped me. I am very greatfull for all of those who have helped!  Hopefully someone will come to this site with a Globe 500 that needs a list of things to check and this post will help! I am no expert.. I have basic skills. Many of these people where very patient with me during this project!

Ke7TRP
Clark

Outstanding, Clark!

You gotta wonder about rigs like that.  Most times one things craps out and the rig gets shelved.  This one sounds like it was a trailer park after a tornado hit.

BTW I didn't get your turret out today, I went to the York PA 'fester instead.  Will get it out this week sometime, depending on when I can sashay over to the post office.

and what all you learned during the process is priceless.

Any after pix?
Any before pix?

 ;D  ;D

We love pix!!

           _-_-bear

I did very little cosmetic. This was just to get the rig up and running. I plan on painting the Chassis back to Hammer tone grey. Here are some pics of it though!

Clark

Always liked the Glob Queens, nice size and layout. Looks the way a table top transmitter should look, although the table better be stout.

Derb's absolutely right about the learning part: the symptoms and problems will vary from set to set, but the knowledge you gain along with the support and encouragement such a post brings to others is priceless. Obviously it wasn't a simple case of having the cabinet powder coated and claiming a full restoration!  ;)

Nice work, Clark.

BTW - is that a halogen lamp in the corner, and if so - does it raise hell with your reception?

That a king!  The Queen is the 400 :)

Thats a Floresent lower power lamp. Its just the camera acting up. Our power company gave us those for free so I installed them. No difference on or off on recieve.  Its not variable.. Just off and on.

I wish I had some nice metal tables or a desk to put it on.  It will have to be on the floor for now!

Clark

Clark, the turret went out today parcel post, expect 8-10 days.

Apparently it's a well-kept secret, but shouldn't be: check your local state or gov't surplus sales site for some excellent steel tables at very reasonable prices, Clark. If you saw the post I made in QSO about my radio room project, it shows one of the two tables I picked up. Think I paid $25 for one and $35 for the other. Steelcase, AllSteel and others made these for commercial use, and they are quite stout. Some have Formica tops, some have the same rubber found on the Johnson Viking KW desk. I go with the rubber top since they are more in keeping with the age of the gear and things stay put. Not only that, they sell for less since most prefer the Formica tops for writing and so on. Both of mine have adjustable leveling feet, and a nice sized drawer too, for odds 'n ends like connectors, hardware, whatever.

You can also find them online at some of the retro furniture sites. Just make sure you're sitting down, as $700 and up seems to be typical pricing.

If you can score one of the large metal conference tables, well then you'll be livin' in the tall cotton! Those things are sweet, but quite hard to find.

Ok thanks.. I have a friend that attends all those auctions. I will check the online ones.  Old metal tables would be sweet.  I want the one my 9th grade Science teacher had. LOL 

Ok..  Onto the cosmetic restoration of the Globe king 500.   I purchased the sander, sad paper, Metal primer, and Grey hammer tone paint yesterday.  I am going to pull it all apart in a little while and get started. The hammer tone paint looks a bit darker then the original but its the best I could find.  I also got some Red paint and masking tape. I am going to tape off and repaint the Red stripe on the two aluminum bar pieces.

Clark

Can you share the information on the VMC changes (speech amp, other)?

Grant/NQ5T

You can ask Robert for it. I purchased it as a Kit with Schematic and all the parts. This made it easy for a lite skilled guy like myself. It was cheap and worth it. 

Clark

Cosmetic restoration is nearly complete. 

I chose to not repaint the face plates and resilk screen. The faces are pretty nice as is so we left that alone. This weekend we sanded the Bud case down to metal. We used an orbital electric sander with 100 grit. Then 150.

After this, we washed the case and let it dry. 

We primed the case and then used Hammer tone paint.  This paint came out MUCH darker then the can stated and darker then the original hammer tone by a mile.. Oh well.. It sure looks fantastic in person though!  The old case as pictured above was painted with Silver paint and it was a horrible paint job.

We polished the two aluminum bars at the top and bottom and put them back on the case.  I am going to replace all the screws with SS hardware tomorrow. I am going to call this transmitter done now.

Here are pictures.  Keep in mind that for some reason, the flash on the camera causes patches to show on the case. Whatever is in the hammer tone paint is reflecting the light back.  This case looks smooth and solid color in person from your eyes. I tried all different methods to try to get clean photos..  Its just wonderfull in person!

Clark

more pics

I forgot to add:

When I had the 500 apart, I replaced the 4uf Oil can cap in the HV power supply.  I installed a 10 UF at 3000 volt unit. Same dimensions. It went right in. 

Now, The Radio does 125% positive Modulation. I had to recalibrate my scope. The Bird 43 RMS meter now goes forward nearly 100 watts when I talk. There must have been some major sag on that supply with the old 4UF cap. It made a world of difference.

Clark

Looks real good Clark. Very clean. I also noticed the big rig wasnt sitting there in the purple room. Does that thing have wheels on it? I gotta hear that thing since you added more C.

I was not on this weekend. I came down with the Flu over night. Worst case I have ever had.  Feeling better this AM. Finally got some food down.

The Big transmitter is on wheels yes.  We rolled it outside to clean it out. Its drying in the backyard sun.  This week, I am going to plug it in and see if it comes up.

Clark

I forgot to add, on the subject of the parasitic suppressors on the monster.  You can also get a plate current / voltage reading, and call/email Rich Measures.  He can sell you a toaster wire suppressor kit that will work great.

--Shane

Just and update to the original Restoration.. In case someone comes along that is restoring a King 500.


I ditched the 6al5 clipper stage.  Simple remove the tube and Connect a jumper from the Cathode Pin 5 to the Suppressor Grid of Pin 3 on the 6sJ7 preamp tube.  This helped alot with the audio.

Next,  I installed a 2.2 Meg resistor from the mic jack to the Grid pin of the 6SJ7.  I used a 500K from the Grid pin to Ground.  This matched the D104 much better. The Stock 47K is better for a dynamic mic.

For some reason, You cannot get past 75% to 80% mod with the Globe king and a D104.  Many of complained about this over the years. I found that if I run a powered D104 I can get over 100% without flat topping.  Run the D104 about half way and keep the Gain control on the king down around 3.  The difference is amazing. The First tube does not have enough gain to hit 100%.

Clark

Good update, Clark. Did similar things to my big transmitter years back. Ditched the clipper, swapped out the grid resistor (1M IIRC) for a 4.7M, huge improvement. Later I fattened up the coupling caps from .01s to .1s and beefed up the eletrolytics a bit. Seems fairly universal on these old rigs.

My memory of past GK discussions is mention an audio amp/driver weakness that can be overcome exactly as you've done. Looks like you found your way there handily.

Wouldn't mind picking up a GK to play with one day. Always liked the looks of 'em.

All that is done..  :)   With outboard audio I have it sounding fantastic. With the D104 it sounds nice and smooth. This element has alot of mid and not much highs.. But I kinda like the sound.

GKs are nice if you always wanted a GK. As long as you can accept the fact that it has low B+ on the 400, and the mod deck needs alot of work.

Clark

Clark...did you ever find a solution to your banging meter movement on the mod deck?  Did you change it to read plate current or maybe dampen the movement with a little capacitance?

Frank

I put a cap across it but it did not seem to work.  Its a real problem. I have backed my audio down to 100% mod so I dont slam it but on peaks it will still hit all the way over. The Meter is acurate.. I tested the Idle current on the 811s.. Got a suggestion?

C

Did you try maybe 1000uF and adjust up or down from there?

Frank

No.. No 1000F... I tried a 10, 20 and I think a 100.  I was unsure of the voltage and just clipped it on there.I would like the static current to stay the same so I can watch that..Or maybe just cut the reading in half would be cool!

Clark

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.

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

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

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

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

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

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

Awsome rig... You should be very proud. ;)

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.

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

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. 


   

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

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

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

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

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.

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!

might wanna test the primary to the transformer with no connections to it. Do the Gito light bulb test on it.   8)  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

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.

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

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

C

And so are every other transmitter you have, sans the Motorola one.

Grid Block Keying is how a LOT of the Johnson's end up, as it's easier on the relays and the rest of the iron.  Keying B+ requires quite a jolt.  If you have iron that is nominal (like I hear ALL iron in Globe products is), then you can quite literally, shock the crap outta it every time you key.  By going to grid block, there is no "slamming" the rectifiers and transformer into that 14uF cap.  It's charged all the time.

Or, another way to look at it is:  How many 1500 watt amplifiers do you own, or have you owned, that DIDN'T cut the tube off in RX?  How many have / do you own that DO?  Isn't the Globe King pretty much in the same Pout arena?

Admittedly, I don't know everything about the xmitter you're working on, but it is DEFINATELY not a relay problem, if others aren't having the issue.  BUT, fact remains.  Hot switching anything is bad mojo.

--Shane

Another way to look at it is:

Cutting B+ on TX requires switching 1500+ watts.

Cutting grid requires switching 30 watts???  BIG diff.

Also, if you are cutting the TX B+ on and off, you might be suffering from secondary inrush.  This was covered by the guys running LARGE xformers on the yahoo ham_amplifiers forum a few months back...  The SECONDARY inrush can be as large, or larger than the primary inrush.. IE, AFTER the step-start CLACKS and goes into "shorted resistor mode", the inrush current at THAT time can be as great, or greater than the inrush if left to attend to itself.

Again, I don't think that's your problem...  It would seem to me to be closer to something like a HV breakdown:  Something doesn't like the initial inrush of the TX.  Maybe a scope on the pins being switched could enlighten you....  As well as find a Hi-Pot tester to test your iron and caps.  Could be something like a feedthrough (not sure if they use those crappy things on that chassis or not) breaking down.  A lot of times, the inductive kick on key up and key down causes GREATLY increased B+...  Think the "anti spike" diode that you can series more diodes in on the AM CB chassis....  It's THERE to kill the inductive kick, and those radios aren't even switching the B+....  Does the Globe HAVE an anti-spike type diode on the mod line to the RF deck?

--Shane

Not a fact at all. Probably every transmitter made from the 40's-60's used the switched primary method of powering up the HV when in the transmit mode (same arrangement at the Globe King). Such an arrangement is generally not a problem with a choke input supply. I'd be a little suspicious of the GK power supply since they used very minimal filter capacity. Increasing the capacitance significantly may cause a problem. You'd need to look at the inductor value to determine the inrush current. You may be able to simulate all this with SwitcherCad or some other Spice based software.

I believe this is another case of not all mods are good mods.  If I were looking, the simple thing to try is put the old filter cap back in the PS and see what happens.  That will eliminate one potential problem and allow you to move to something else.

I am going to try the 866s.. I loose alot of power.. But if thats what it takes thats fine.

Clark

What was the original cap value?  4 uF?  I think is what I read.

Going from 4 to 14 might not be that great of a thing:  That's nearly 4 times as much C, and can cause all kinds of problems.  You might want to try the cap first.

The rectifiers might make it work again, but I'd be willing to bet it's the hit the xformer takes every time you key the thing up.......  Going back to vac tube rectifiers might make the transition a lot better on the contacts, but doesn't address the real problem, and a problem that could cause those "expensive" rectifiers to also be blown / screw things up / etc.

Try a vac relay on the OUTPUT of the supply, rather than switching the primary?  If you must keep HV keying, that is, and you want to keep the high C.

You're welding contacts.  That means too much current.  What is causing the current draw?  The rectifiers don't, it's something else...  The rectifiers are softer than solid state, though, and can band-aid the fix.  The associated "BANG" also means high current.

I'd much rather keep the solid state rectifiers and lose a bit of C, especially since they give you more Pin to draw from.

--Shane

I think its a 12 uf.. But still.  The original was 3 or 4..  Thats not enough. I got big PEP gains with that big Power supply cap.  I really hate to take it out.

Let me try the rectifier tubes.. I will use it for a day like that.. Then if it works, Its fine. If not, We will step start it..  That should fix it right?

Clark

Before you jump to conclusions do the math on ripple using the original cap and choke values.  If it is 5% or less then I don't see a problem.

Most of the hum on the GK series has to do with electrostatic shielding not lack of filtering.  I would have used a bit more C myself, but I believe you will find the original values are enough.

Jim. You are correct. I Had no hum before.. But this big cap is keeping the voltage up and really increased the peak output. I can remove it if it is infact, the problem.

C

I would give it a try to see what happens Clark then plan from there.  Some mods simply do not work.  Some day ask John/K5PRO about published mods to the DX 100.  That is a real eye opener.

You really don't need 125% positive, 100 percent works fine and is smooth and easy on the ear.

Very true.. 

I got the 866s out.. Found two RCAs and Two GEs.   Put them in the TV7 tube checker for 5 minutes each..  GEs tested 65 each (40 minimum).  RCAs tested 45.   

Kinda neet to see the Tubes turn to chrome metal before your eyes.  I put the GEs in the Globe king.. I am going to bake them for a few hours before throwing the switch.. 

Clark

You may be asking for trouble with those merucry vapor rectifiers.  Be careful.

After an hour of cooking.. I put it on tune and flipped the transmit switch.   BZZZZZ POW  blew the Primary fuse.  Put a new fuse in. Tried again.  Slight pop and another fuse.. 

Oh well.  Its not the rectifiers.. Time to yank the PS out and start over...

Clark

Time to check that filter cap, and any feedthrough caps.

You might also be checking the cap under low voltage (like any decent modern cap checker would be doing, since battery powered usually), and it might be breaking down under HV.

Replace that cap, I just have a bad feeling about it.  And, if it does fix it, and you still want the bigger cap in it, then a step start would fix it, but it would need to be robust, as you're not switching onto an unloaded power supply, you hit it full tilt.

I do NOT like HV keying.  Yes, nearly every transmitter made in the 40-60s had it, but has technology and our intelligence not moved beyond some things considered "good engineering practice" by 50-80 years ago principles?  YES, it does work, but it sure is HARD on your iron.  Commercial Mfg's could have cared less, they where ALWAYS ON.

--Shane

Keying the primary of the HV transformer is not the problem.  It is the mods.  Put the original cap back in and work from there.  I hope you haven't shorted the choke winding or the winding to ground.

Pulling the PS now.. Going to fire it up on the table by itself.   No load.. Go from there..  I am going to study the PS again to make sure nothing on the high side is arcing.  Once keyed, I can talk for an hour... Full power. I think the iron is ok..

Clark

Maybe

Power supply looks perfect.  No arcs anywhere...   

Set it up on the table. Locked the pets up.  Put a clamp on probe on HV output.  Plugged in the wall. Flipped Filaments on.

After about 5 minutes, I flipped the Transmit switch with a long pair of lineman pliers. Loud gutteral (deep) Clicking and the over head light DIMMED almost out.  Flipped it out of transmit.  Tried it again and it made the normal click and came up fine. No arc on relay.. I was looking right at it. 2000 volts or so.. 

Clicked it out of transmit,  Then on 5 times..  Normal click and 2000 volts. Then on the last time, I heard the Low thumping sound and the lights in the room dimmed out.  Fuse blew.

No idea what in the hell is causing that Thudding sound.. Must be the big cap?  No smoke, No smell.. No Arcs.  Sounds like a Thud thud thud... Then fuse blows.

I really hope its not the damn iron. 

Clark

I hope this is at least entertaining to someone.. LOL.

I put the Solid state diodes in..  2200 volts. No GLUG GLUG GLUG sound.. No dimming if lights. No sparks at contacts. Clicked it on and off 30 times.. 

So the big draw is happening somewhere else.. Mod deck or RF deck.. 

Clark

Or the choke

Nope.. I put BIG resistors on the output of the PS.  Used ohms law to figure 250 mills.  Flipped the switch.. Current Draw.. Sounds normal.  Operated it for a few minutes into a load. No issues..  Resistors getting warm.  Volts Dropping to 1800.  Keyed it 35 times over and over. Not one spark or flash. 

This must be a flash over on the HV side of the mod or RF deck.  This PS is fully functional on the test bench. 


Clark

You mean, like HV Breakdown. :)

I thought in another post, you had pulled it out.  I took that to mean, you pulled it out, and only had primary VAC hooked up, nothing on the secondary (output of the supply, input to the Mod and B+ RF deck) hooked up, outside the cap / iron and rectifiers?????

If so, and it still thumps, then it's in the cap(s) or the like.  If not, then ......  It's time to put the tech hat back on.

--Shane

:(

Starting to resemble the Motorola rig, it sounds like...  MIGHT be a good thing.  Fix one, learn enough to get them BOTH goin!

Best of luck, I'm out for the night.  Vertical up tomorrow, HOPEFULLY.

--Shane

The PS was operated on the bench at 300 MA.  For minutes.. Switched 35 times.. No sparks.   To me, That means the PS is not the proplem.   This means that somwhere in the mod deck or the RF deck must be arcing over.. That would make a HUGE Draw on the Primary side relay and buzz the contacts.. Right?

C

Ok..  I found the left 866 socket BLACK as hell and covered in soot.  The right socket is clean and white. This must be the problem.  I am going to order two new sockets, Clean everything and install new.  Crossing fingers.


Clark

Mine are recessed.  About 2 inches below the chassis with metal screws and Black plastic insulators.  I cant go any lower as the bulb of the tube will not allow full contact.  I am going to get new sockets, clean everything and re wire it. Maybe that is all I need to do?   What about putting some Transformer Dope on the chassis around any spot where it can arc?

The left socket is so bad it looks like someone held a Blow torch on it.

Clark

Its bare and open connections.  I am getting Ceramic sockets  I will look for Nylon screws. Kinda long through... I will use heat shrink for sure. 

I cant believe it was a B+ short.   Classic mistake on my part.. I focused on the effect and NOT the cause.

Clark

I just finished running some hv ceramic feedthrus through the dishwasher (only the ceramic parts) a few times. cleans them up like new. gotta force dry them to make sure you dont have any dried water tracks on any unglazed portions, but the cleaning is great.

I think fully one half of any restoration project is spent cleaning. At least, if you're doing it right.

I'm going to be boiling up some breadslicers in acid when I get back home.  8)

(down at my dad's place for 2 days)

Yeah..  I am going through the PS deck now.. Insulating here and there..  I got some Corona Dope along with my new Military style ceramic sockets.  I am going to dope up the areas where I think it might flash.  The other thing I noticed is the Mains come in through the fuse to a 22 AWG wire that runs all the way to the power switch.  Its crispy and stiff.  I cant believe they used 22 awg wire on this radio. 


Clark

Ceramic sockets installed. New stand offs, New wire, New hardware.  New Power wire runs. Corona dope on HV section of rectifiers. All is well.  More power now. Tunes up higher. No flash over.  Sounds awesome.  Time will tell if this was the entire problem.

Thanks to HRO and others for all the help.. 

Clark

All leads are insulated now wiht Shrink wrap.  Seems to be working perfectly now.


Clark

Station as of Aug 2009. 

GK500C, SX110, DBX rack, mixer, Condensor mic, Ultra modulation unit.

Clark

Where are the bungee cords suspending your chair from the ceiling?

LOL

 ;D

(http://images.icanhascheezburger.com/completestore/2008/6/20/rotflol128584571459354136.jpg)