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Author Topic: Globe King 400 modulator tubes  (Read 1176 times)
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Detroit47
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« on: October 08, 2024, 11:20:37 AM »

I have started into my recently acquired GK400. I noticed
the 5514's where changed to 811's not even the A variety. One of them turned into a snow globe. I then noticed it still had the 7.5 filament transformer. Has
anyone used 811s successfully? I would obviously have to change the filament
transformer. I am going to put a want add in the proper category for 5514s. Just looking for others experience my Johnson 500 uses 811A"s so. does my GK500.

Johnathan N8QPC
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Jim, W5JO
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« Reply #1 on: October 08, 2024, 11:36:22 AM »

I have started into my recently acquired GK400. I noticed
the 5514's where changed to 811's not even the A variety. One of them turned into a snow globe. I then noticed it still had the 7.5 filament transformer. Has
anyone used 811s successfully? I would obviously have to change the filament
transformer. I am going to put a want add in the proper category for 5514s. Just looking for others experience my Johnson 500 uses 811A"s so. does my GK500.

Johnathan N8QPC

I have seen this before.  Obviously the 811 or A version will not last as long because of the higher filament voltage, but the specs for any tube is +/-10%, making the top at about 7 volts, and maybe a bit more.  That means the 811s will last longer than you expect.

You can add a resistor to the input side of the filament transformer to lower the voltage if you don't come across the 5514s.  Don't be concerned about the difference between the A version and the plain 811.  In this application they will be fine.
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KD6VXI
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« Reply #2 on: October 08, 2024, 12:29:09 PM »

Cathode emissions will be hotter since the cathode will be hotter.

Watch idle currents, but otherwise I'm with W5JO.  I think you'll be fine.

I once did a Valiant that someone had modded to 811s..  Good lord that was an audio monster.

--Shane
WP2ASS / ex KD6VXI

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w1zb
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« Reply #3 on: October 09, 2024, 12:02:52 PM »

I changed the modulator tubes to 811A's in my GK400 about 5 years ago and they work great. I also changed the filament transformer to 6.3VAC 8A. Those 5514's were just too expensive and hard to find.

Jerry W1ZB
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WD5JKO
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WD5JKO


« Reply #4 on: October 09, 2024, 12:13:22 PM »

Lots of options here. If you have some stock of type 808 tubes, they have the same 7.5v@4A filament need as a 5514. It would require a jumper from the side grid cap to the socket base. The bias should be close, but might need a slight shift. The 808's are great tubes. For decades, Fair Radio Sales had them 4-Sale at 75 cents apiece, NOS! Likely very scarce today.

Jim
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Detroit47
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« Reply #5 on: October 09, 2024, 11:07:00 PM »

Lots of options here. If you have some stock of type 808 tubes, they have the same 7.5v@4A filament need as a 5514. It would require a jumper from the side grid cap to the socket base. The bias should be close, but might need a slight shift. The 808's are great tubes. For decades, Fair Radio Sales had them 4-Sale at 75 cents apiece, NOS! Likely very scarce today.

Jim
Wd5JKO

That sounds like a great idea. Buy another rare tube that I would have to modify the rig for.

Johnathan N8QPC
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W7TFO
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« Reply #6 on: October 09, 2024, 11:54:21 PM »

The last NOS 808's I sold were a quad on eBay, went for $600. Tongue

73DG
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Detroit47
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« Reply #7 on: October 19, 2024, 07:28:00 PM »

I have to give credit when it is due. Jim WA2MER came to my rescue with a pair of 5514"s.
Thank you Jim

Johnathan N8QPC
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