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Title: Globe King 400 modulator tubes Post by: Detroit47 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 Title: Re: Globe King 400 modulator tubes Post by: Jim, W5JO 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. Title: Re: Globe King 400 modulator tubes Post by: KD6VXI 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 Title: Re: Globe King 400 modulator tubes Post by: w1zb 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 Title: Re: Globe King 400 modulator tubes Post by: WD5JKO 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 Wd5JKO Title: Re: Globe King 400 modulator tubes Post by: Detroit47 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 Title: Re: Globe King 400 modulator tubes Post by: W7TFO on October 09, 2024, 11:54:21 PM The last NOS 808's I sold were a quad on eBay, went for $600. :P
73DG Title: Re: Globe King 400 modulator tubes Post by: Detroit47 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. AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
Thank you Jim Johnathan N8QPC |