The AM Forum

OK, rebuilding the power supply on a Globe King 500A that was stripped out ...does anyone out there have a pic of the bottom of the chasis on the power supply portion of this transmitter?   Thanks.. 

73, Tim  K8WBL

K8WBL@yahoo.com

How close is the A to the C?  .. I just dont know if I Can help. Never owned the A model.

Not much difference at all I think.

Tim

The C has the VFO but I think all of the major power supply compoents are the same.

Tim

will this help?

Well, it helps a little, but what I really need is where the parts placements are ... dropping resistor, etc. and general running of cabling, etc.   The chasis I have is from a 500 series but a lot things have been removed.  I have an RF deck that has been unmolested and start rebuilding this transmitter as well as 2 a mod deck from a GK400C.   

Thanks,

73, Tim K8WBL

Ok.   Mine is a 500C and the layout is very different as I have the large VFO sitting in the middle of the chassis. I will ask around to see if anyone I know owns a 500A.  I talk to 4 or 5 people on Kings.

Clark

Thanks Clark, I really appreciate that..mine is a 500A, so any version before the VFO addition is likely similar.

73, Tim K8WBL

I find it amazing that no one has posted ANYTHING about the 500 on Bama.

Bill

Yeah, its pretty hard finding good info on the Globe King 400's or 500's anywhere, this list has been the best place to get info as well as the Midwest Classic AM net on 3885 Saturday mornings in the midwest.

72, Tim K8WBL

I agree. Thats why I made the 500 Document after I got mine up and running.  Without this list I would never have finished mine.

Clark

The manuals for all three of the GK 500 series are on BAMA.  There is a WRL list on QTH mailing lists if you care to join.  It is pretty inactive but there are people there who don't subscribe here.  Someone over there may have a picture but I doubt it.

I have a 500A but getting the power supply out to take a picture is much of a chore.  The layout of the parts is pretty self explanatory and all the wires run around the outside of the chassis.  I do hope you have the spacer for the tube sockets.

Thanks, thats a great idea.  I do have the spacers but will also use plug in SS rectifiers, been easy to get and cheaper than usual lately, Surplus Sales has then for something like $65 each...wow.  Also want this baby to look as original as possible, not a purist at all, believe me, functional!!  But would like to keep the integrity of the Globe King and don't want it to look like a re-do job, even though it mostly is, want it to look stock, as well as interchangable.

Don't hurt your back on removing it...its not worth that, I just thought someone might have a pic of one they put back together.

73, Tim K8WBL

Tim...here's the underside of my 500C deck.  Hope this helps. 

Frank, W4FMS

did some work on the picture to see more detail.

Wow Frank, thanks, that helps quite a bit, lots of similarities but lots of differences too, as expected with the VFO added.  The primary of the HV power supply is at the base of the pics, by the relays?  I think thats I see it.  thanks for all the work and effort on this Frank, its really appreciated!!  This gives me a basis.  There are lots of changes and the chasis was punched out definitely differently, but they kept alot of the same wiring harness to most of the major compoenants intact, added a transformer or two, filaments I suppose and other.

Regards, Tim
K8WBL

Hi Tim,

Here are some fotos of my 500A power supply.  If you need more help let me know.
http://www.qsl.net/w8ujx/GK%20500A%20PS/

Jerry/W8UJX/CA

SWEET....this is exactly what I need, to see and work with...thanks soooo much..what a great guy and group we have here...

73, Tim K8WBL

Just a note that you probably already know..  My 500C had 4UF on the HV supply.  I got a 10 UF cap and replaced it. I saw HUGE gains in overall performance. The rig gained alot of RMS when speaking and really cleared up the pattern.  I dont see that large cap at all in teh 500A. The transformer looks the same though. I wonder what the total is on the HV supply?

Clark

Hi CLark,

My 500A power supply is stock.  It has two 6 UF, 1500 volt caps in series
for a total of 3 UF at 3000 volts in the HV supply.  I agree.  A bigger cap would
give much better performance.

If I was rebuilding the power supply I would try to go with 10 UF as you suggest.

Jerry/W8UJX/CA     

YEah.. Thats what I figured.. I saw the two caps sitting next to each other.. Plenty of room for a 12UF!

I was talking to Timtron one night and he said I needed to change that cap out.. He suggested 14 UF. Then someone on the board here suggested the same.  At a Ham fest, I found a 10UF at 3kv.  It bolted right in.  Better then the old 4uf cap.

The difference was dramatic enough that I had to recalibrate the scope. I was shooting right off the picture tube. 

I also upgraded the one in the Mod decks power supply.  I think that one has a 6 or 8. I cant remember.. I got it from Robert W0VMC.  With the solid state Rectifiers, My mod volts on the 811s is up around 1560. 

Clark

jerry, there are some significant differences in yours and mine, I have 4 toggle switches on the front panel, yours has only 3 toggles...I have a high B+ and Lo B+ switch as well as xmit, exciter and filament.  Other changes as well, interesting.  My RF deck is marked 500A and Number 845 on the top of the RF deck.

Tim
K8WBL

Hi Tim,

I have been working on an old GK 500C.  It was in very bad shape.  Lots of rust and broken parts on all the decks.  I wound up removing all parts from each chassis, cleaning the chassis and reinstalling the parts.

During this process I corresponded with Frank, W4FMS as he was doing the same thing.

Even though our rigs were the same model, 500C, we both found errors on the schematics in all three decks and differences in the hardware.

I found the mounting holes in the chassis were oversize and not deburred in many cases.  I got the impression that WRL used whatever components they had on hand at the time to complete a production run.

I have both a 500A and 500C and in both rigs the HV cap in the modulator is rated at 1000 VDC and the HV on the modulator tubes measures 1000 VDC.  Not good!

It was an interesting and educational project.

Jerry/W8UJX/CA

Yes.. That is normal.. WRL was a cheaper line of gear made for the avg joe. They had finance plans advertised with weekly cost.  I have a stack of old magazines from the 20s through the 60s and you could see adds for each model.

The old story was that Leo purchased alot of surpluss parts in bulk. They used the parts where ever they could. Mind had some serious errors in the schematic. One of which was the push to talk system. This system was never used in my rig because it never worked.  The cap that was installed with the rectifier was the wrong value and the relay would just chatter. You could see this was the original cap. The guys on the forum helped me trouble shoot it. Now the system works. I wired a switch up by the table so I can kick the unit on with a flip of a switch without bending down to the manual key switch.

My modulator deck was an odd ball with a very odd power transformer. It has 11 wires comming out of it and only 8 being used. It was fried as someone installed the wrong modulator tubes in that deck. Some had a 500V supply in the deck and others used a dropping resistor to get the LV for the mic pre tubes. Mine had the 500V supply off a resistor. Others had a tap on the transformer.  IN the end, I ran another HV lead from the power supplys 500V section up to the Mod deck. This took the draw off the weak mod power trans and put it down on the heavy PS decks supply. This allowed me to solid state the mod deck and get 1550 volts on the 811s. Something that really really helped my 500 come to life. The stock mod deck is weak at best.

They are neat old rigs and I sure love mine. Its been working now for 4 months on 75 meters.

Clark

Thanks Jerry and Clark, I have heard the same... I went through a bunch of similar stuff getting my GK400B working, the mod deck was different on every schematic I could find.  My 400B has a pair of 6V6's with a total of 4 tubes in the speech circuit, whereas the 400C I have has a single 6F6 in the final but an extra tube mounted in the middle of the 4 tubes on the mod-speech section.  The 400B has been modified before I got it, Couplates removed, etc,. The 400C does not, and the 500A does not have mod deck at all, will have to build that or use the 400's mod deck until then

73, and thanks all...still finding new stuff.

Tim  K8WBL

I've operated a GK400B for ten years now and one of the best changes which you can
do is to increase the "C" in ALL the power supplies. (I have 12 uF in the Class C supply & 22 uF in the Class B supply)
The suggestion made to use the solid state rectifiers is also a good suggestion but omit the filament transformer used originally with the 866's & 866JR's...
this is a weak link and should not be left in the circuit!

Good luck es 73 Steve
8tow

Thanks a lot for the info guys.  That answers a lot of my questions.  I had the 500B when I was a kid in high school back in the 50's but never really got into it.

One of these days I will go through my A and C models and do some serious mods to the modulator and power supply decks.  My goal is to get it sounding like an AM broadcast station on AM.  Hi... 

As an interesting note the key-up HV on the final in both my rigs is about 2600 VDC and drops to 1800 VDC key-down.  That says a lot about the power supply design.

73's
Jerry/W8UJX/CA

W0VMC Robert sells an inexpensive kit for the modulator deck.  It comes with a schematic and all the parts to install on the preamp tubes.  Its actualy easier to order his kit that it is to sit down and figure the values and order all the caps and parts.

He also sent me the correct Screen and filiment bypass caps for the final tube. You need to change these for full bandwidth audio.

Once this was done, I use the phone patch jack on the rear of the mod deck for the mic input. I use a Low to high level impedance matching transformer (from guitar center). This converts to low impedance to my inexpensive 802 mixer and then to my Large diaphram condensor mic. 

I swept the 500C after all this was done and I ended up nearly flat from 20hz out to 10,000. With some EQ, I reach 12,000. I was suprised the stock mod iron could go that low but it does.  Everyone that has listened to my 500 loves it. Its very wide, full and clear.

Of course,, I can still run the D104 if I want. He even supplies the correct loading resistor for the D104 so you get pretty decent sound from the old mic.

HIs website is  http://www.w0vmc.com/

He is on this site as a user also.  Also.. search for my Globe king 500 under my user name. I posted a full instruction manual on the restoration of my 500 that might help.

Clark