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Author Topic: I picked up a Globe King 500 missing HV transformer Have a UTC S-49  (Read 5197 times)
W5JO
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Posts: 59




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« Reply #15 on: August 10, 2012, 07:56:00 PM »

The specification for the Globe King 500 A, B and C plate transformer for HV are CCS not ICAS. 

My modulation deck was marked with 5514 also but had 811As installed because the filament transformer was 6.3 not the 7.5.  If you need 5514 then look for my call on the Call Search here and pick up the direct address then send me a message. Couple of other tips, be careful of all manuals for WRL stuff.  They are full of mistakes mostly pin numbering on tubes and such none the less check carefully.  WRL didn't waste anything and you may find mis-markeded chassis in the transmitter.   I am restoring a Globe Champion 300A that all sorts of modifications to enhance the audio.  In the repairs I found the cathode bypass electrolytic cap on the second stage installed in reverse.  That killed the audio out of the second stage to the driver.  Not finding the FACTORY mistake someone put 811s in place of the 809s to get enough modulation and made other modificatons  in the audio.  I don't know how they missed that but be very careful going through the thing.

As for the capacitors I don't recommend spending a lot of money for higher value caps.  It accomplishes nothing but drive up the cost, and in the case of cap input filters which the bias supply on the RF deck is, can damage that transformer if you use caps that are too large.  I used the closest value I could find, ie. 33 for 30, etc. throughout for filters and all others

Check all the resistors.  You probably will find near 80 percent of them of the wrong value.  Also carefully inspect the postage stamp caps.  Some are mica and some are paper.  If they look suspicious at all, replace them  I have seen bad mica caps like that.  You might want to check with Gary/WZ1M about that transformer you lack.  If the core and size is correct for the one you have, he may rewind it for you to WRL specification at less cost than buying a new one or casting about for a long time looking.  Anytime you have one rewound, specify the primary for 120-125 volts.  That helps with stress and heat.

There are other issues on the 500A that should be addressed but this has gone on long enough
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K1YTG
Member

Posts: 199




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« Reply #16 on: August 13, 2012, 09:16:26 AM »

To W5JO
I have supplied 115 volts to the primary of the filament transformer and found the modulator tube voltage at 8.1 volts AC no load.  So the tube for this is as printed on the chassis is 5514.
Please let me know how to arrange the purchase of these tubes from you James  W5JO.
And could you give me a brief summary as to why if I am using a 220 volt line for the HV transformer that it makes a difference if the 115 voltage is taken all off one side or if it is balanced between the two legs.
Thanks, Norm 
You can also contact me at    norm@normangreene.com   
I have some pictures of another AM transmitter at   http://www.normangreene.com/600watts.html
This one also uses a 4-400a  ( or 4-250 )  Every part is at least twice the size and weight of the parts in the globe king.  Makes the Globe King look cheaply made. 
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AC5UP
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Posts: 3822




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« Reply #17 on: August 13, 2012, 10:35:00 AM »

And could you give me a brief summary as to why if I am using a 220 volt line for the HV transformer that it makes a difference if the 115 voltage is taken all off one side or if it is balanced between the two legs.

That's easy.... The advertised current rating of the transformer assumes proper inductive coupling between the primary and secondary. If you use only half the primary winding you can't expect a full strength field (and rated current) in either the core laminations or any secondary winding. Worse yet, remember the windings are stacked in layers. For the sake of a mental image, let's assume the primary is nearest the core (and they almost always are). Visualize two layers of winding, center tap, then another two layers on top of that. If you energize the first half you have two layers of 'dead' copper between the primary and secondary windings. Energize only the second half and the primary winding is now two layers distant from the core and the resultant flux strength will be less than optimum.

If the primary is split into two 120 VAC windings you can parallel them for 120 or series connect them for 240 AS LONG AS THEY'RE IN PHASE!

Get the phasing wrong and the windings will get real hot real fast and there's a chance you won't pull the plug fast enough to avert transformer death by induction. Been there, done that, best advice is to pre-connect a voltmeter or install a lightweight fuse prior to the first attempt at fire in the hole. Hit the switch and any twitch of the meter below what's expected prompts you to shut it off instantly.

BTW: Been my experience that tapped primaries are rare. I've seen it in Japanese equipment with a 120 volt primary tapped at 100 volts for domestic use, but aside from that a split primary is usually on lugs 1 & 2 / 3 & 4 and measure near-identical resistance with an Ohmmeter. Parallel connection is odd to odd (1 to 3) and even to even (2 to 4). Series would be 2 to 3 with AC on 1 and 4. Your transformer could be completely different and what you think is the primary may well be a secondary...... If you have pigtail leads look for black and black with colored stripe. Green is 5 VAC rectifier filament, Yellow is 6.3 VAC filament, Red is HV.

Your Mileage May Vary.  Research and test as best you can before applying power.
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KD0REQ
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Posts: 854




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« Reply #18 on: August 17, 2012, 01:59:12 PM »

the old-timey method of hooking up a same-voltage filament light bulb in series with the primary is also useful.  if the lamp glows full brightness, you have a shorted load, pull the plug. generally half brightness and reddish light, it's not dead yet.  the poor man's Variac.  for instance, I used a 200 watt bulb in series with the CX7, and saved my fuses for later, when I got the transformer replaced.  with the HW101, I used a 100 watt.  at idle, these things do not draw faceplate ratings, so I use a bulb 1/3 or so of the rating.
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