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Reviews For: EIMAC 3CX800A7

Category: Electron Tubes

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Review Summary For : EIMAC 3CX800A7
Reviews: 12MSRP: 600
Description:
Hi-Mu TRIODE with Indirectly heated cathode.
Product is in production
More Info:
# last 180 days Avg. Rating last 180 days Total reviews Avg. overall rating
00124.3
N8ECH Rating: 2020-04-22
It's a great tube, until it's not............. Time Owned: more than 12 months.

I remember well when Eimac brought out the 3CX800A7 along with its big brother the 3CX1200A7 back in the early 80's. At the time, pricing was in the $350 range for either one. The 800A7 was seen as an excellent upgrade from the 8873/74/75 series of tubes that were becoming expensive, as demand for them decreased. Broadcast and MRI manufacturers put them to use as driver tubes, or small 1-1.5 KW FM transmitters which helped with demand.
If you ended up with a new one or pair, and treat them right, ie proper tuning, low grid current etc, they will last a long time.

Fast forward to the last 5-7 years. The broadcast and MRI business has transitioned to solid state. All of those wonderful (sometimes) MRI pulls hams have enjoyed are all but gone. A new pair of these will set you back $2-$2.5K if you can find them.

Then, there are the "used" ones that we come across advertised as used but full output, or low(er) power, but still good as a backup .

One very important question to ask is, "What is the the output, and at what grid current?" The key factor here is Ig. The tube(s) may put out "full power", but if the Ig is anywhere near 60 ma per tube to do it, don't buy them. A healthy set of 800's in a properly working amp should put out 1500 watts with no more than 60 watts in, at 30-40 ma Ig or less. As many know, indirectly heated cathode tubes like the 3CX/3CPX800, 8877, etc have a fragile grid structure. Too much Ig will damage the grid overtime, and one good blast can pop the grid leaving you an expensive yet pretty (to hams) paper weight.

As always, YMMV.
KM1H Rating: 2019-07-04
Very fragile grid Time Owned: more than 12 months.
While it is a great tube for HF to VHF it is more prone to fail in ham use due to a very fragile grid along with poor tuning procedures and poor to no grid protection in several amps.

Do not use a 3CPX pulse version to get a lot more power out on ham bands. The grid and cathode is identical and running them hard just results in short life. A pair at 60W drive will do 1500W for many years with plenty of reserve, trying to get 2200-2400W out at 100-120W drive is foolish....use a bigger tube such as the 8877 or 3CX3000A7.
KC6RCM Rating: 2014-08-13
Little workhorses. Time Owned: more than 12 months.
I'm still running the same pair, since purchasing my amplifier new in 1990 and I do use my amp frequently. In 1997 I had purchased an extra pair from Ameritron for $728, but the originals just keep working fine and showing no signs of decline.

Treat them well and they could last your ham radio career... abuse them and you'll be looking for replacements quite quickly.
N4JHY Rating: 2010-10-04
Fabulous tube Time Owned: 3 to 6 months.
My whole ham career of 25 years was using 572B's and Eimac 3-500z tubes. Back in May I bought a sick Alpha 76PA and repaired it. Along the way of the repair, I snagged a new pair of Eimac 3cx800A7's and converted this nice amp to these tubes, rather than buying three 8874's. This is my first venture with metal/ceramic tubes, and I must say I am delighted! 52 watts drive and the amp loafs along at 1500 watts PEP output. The grid current meter just barely wiggles. Also, without all that hot glass, the shack stays much cooler. I am sold! The nicely numbered skirted tune and load knobs allow me to "dial in" to where I want to operate. Set the drive to 52 watts and 1500 effortless watts emanate from these excellent tubes. Yea they are expensive, but if you do the yearly math, they are a great deal.+++++++++
AC5XP Rating: 2008-07-18
Tough as nails Time Owned: more than 12 months.
They are expensive as if they were gold dipped instead of silver plated, but the durability and linearity of the 3CX800A7 is unsurpassed. I have them in my Ten Tec Titan and they perform like gangbusters. Two tubes in parallel are just loafing at full legal power, with an input drive of only 60 watts.
I actually had planned to take the tubes out of the Titan, and buy a Commander HF-2500 without tubes to re-use the Eimacs in it. But the Commander guys hardly gave me any discount on such a deal so I decided to keep the Titan. I now plan to rebuild the Titan by rewiring it using Teflon wiring and coax cables terminating in SMA connectors. That also would require me to re-layout some of the boards in the TenTec to facilitate the SMA connectors. I just cannot believe that TenTec did not do such construction from the start - the price I paid for the amplifier certainly would have justified it!
KO4NX Rating: 2007-01-26
Energizer Bunny of Tubes Time Owned: more than 12 months.
I still have the original set of these in my both of my Titan 425's (Going on 12 years now). 40 - 50 Watts Drive still yields full legal limit. I have made mistakes with overdriving, with no apparent ill effect on the tube performance or life span.

Over the years I have managed to stock two extra sets of these tubes, and have found them at very reasonable cost ($200 - $300 per Tube). Lets assume I paid actual retail for these tubes, $1000.00 per set. I estimate that I spent around $83.00 for the set per year. This is really not too bad when compaired to other brand tubes who are known to have a short life cycle.

Would I consider another amplifier using the same tubes, you bet!


K9RX Rating: 2006-12-20
Great tube Time Owned: more than 12 months.
20 years old now and still easily putting out 1500W with about 60W in. The TenTec Titan IS, contrary to one posting - as are these tubes - GREAT for contesting! Also the one negative about the Titan is it only warns you of overgrid current - it does not fault on this - but i have HIT it hard many times and still no ill effect.
N6AJR Rating: 2006-06-20
Not $1000 each Time Owned: 6 to 12 months.
I have a pair in my alpha 87a and they work. BTW you can buy eimac brand from ameritron( mfj) for $559 and frome rfparts the sevtlanias for $530 each..

ya want to play ya got to pay.
KT0DD Rating: 2004-05-02
Good so far Time Owned: 6 to 12 months.
I'll give them a 4 overall, because I think Eimac is overcharging for this tube just because of ISM customers. I have a pair in my TT Titan 425 that are about 6 years old and still going strong. I don't think I'd contest with this amp at $1000. for a set of tubes, but for extra oomph in casual operation as I do, they work fine.
W7DUD Rating: 2004-03-02
Very trouble free tube Time Owned: more than 12 months.
I have used 2 3CX800/A7 tubes in a Command Technologies Commander HF-2500 for six years now. Still going strong.

Also using a single 3CX800/A7 in the Ameritron AL-800, for about 5 years. Tube performance is still very strong.