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Author Topic: 3CX800A7 Tubes (Low Grid)  (Read 4239 times)
VE3YF
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Posts: 581




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« on: April 02, 2015, 03:43:26 PM »

I see that Alpha sells the 3CX800A7LG (Low Grid) FAC Tubes for $400 a Tube.

http://www.rfconcepts.com/products/transmitting-tubes/tube-3cx800a7-fac-triode-low-grid-current/

However they do not sell them as matched pairs. The fact that they are supposed to be low grid tubes, how critical would be to have a matched pair. I wouldn't think that Alpha would sell them even in pairs if there was the possibility of a problem. The info page does mention they possibly will have some issues in the 87A but fine for other amps like the 86 and 89.

Anyone with some info or insight would greatly appreciated both by others and myself.

73 De Mike
VE3YF
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73 De Mike
VE3YF

http://www.ve3yf.com
KK5DR
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« Reply #1 on: April 02, 2015, 04:54:34 PM »

Matching is only critical in the 87A, due to the automatic function of that model. The manual tune models, no problem.
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K6AER
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« Reply #2 on: April 03, 2015, 09:34:00 PM »

The tubes on the 87A were never matched.
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WB2HJK
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Posts: 6




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« Reply #3 on: August 30, 2015, 10:59:22 AM »

REF: http://www.rkrdesignsllc.com/products/transmitting-tubes/tube-3cx800a7-fac-triode-low-grid-current/

Thanks Mike, I appreciated the reference to this source for 3CX800A7 tubes!!
Would you or any OM know where theirs are manufactured, ie China, etc ?

thanks to all.
73
Jorj
WB2HJK
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KM1H
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« Reply #4 on: August 30, 2015, 05:52:05 PM »

The only reason they are a sometime problem in the 87A is that the current tubes require a bit more drive and higher grid current than the real low grid current YC-238's the 87A used.
Instead of pushing incorrect info try reading the actual details.
http://www.rkrdesignsllc.com/products/transmitting-tubes/tube-3cx800a7-fac-triode-low-grid-current/

And it is correct that matched tubes were never required in any Alpha 8874 or 3CX800 amp.

The current offerings are from China, have a top notch reputation, and are likely produced with Eimac supplied tooling...they want to get out of the small tube business, new developments, and want to slowly fade away on their replacements and rebuilts of the the BIG tubes.

Carl
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KK5DR
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« Reply #5 on: August 30, 2015, 06:04:50 PM »

EIMAC is steady reducing their product line. Soon they will only product and rebuild BC station tubes, commercial, military and medical.
The LH super collider in Europe is currently the largest consumer of power tubes in the world. It consumes about a thousand tubes with each run.
The amateur market has been shrinking for decades.
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