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Reviews Categories | Amplifiers: RF Power - HF & HF+6M | QRO HF-3KDX Help

Reviews Summary for QRO HF-3KDX
QRO HF-3KDX Reviews: 6 Average rating: 4.5/5 MSRP: $$4,595.00
Product is in production.
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W9BHI Rating: 2/5 Mar 10, 2019 12:00 Send this review to a friend
It would work better if it was built correctly  Time owned: 0 to 3 months
I bought one of these used a few months ago.
The first problem I noticed was the hum on the carrier when using it on AM ( you would never see the problem on SSB).
After looking at the unit and comparing it to the schematic,
I noticed that the bypass caps on the cold end of the filament choke that were shown on the schematic were missing from the unit.
They were never installed.
Also, the RF feed to the cathode and filament was connected to the side of the filament that was not common to the cathode.
If you look at the build pictures on the QRO site, it clearly shows the missing caps and the incorrect RF connection to the pins of the 8877.
The hum on the carrier was being caused by the cathode bias being connected to the center tap of the filament transformer.
Fine for a directly heated tube but not for one with a seperate cathode.
Tracing out the side of the filament choke that goes to the cathode and reconnecting the bias circuit to that side of the filament transformer eliminated the hum on the carrier.
Ater making the necessary repairs, the amp performs very well.
This amp suffers from the same problems that my HF-2500DX
had, poor design and lack of quality control (see my review of the HF-2500DX)
Also, don't expect an answer to any emails or calls to Ray.
I never got any after numerous tries.

W1XYZ Rating: 5/5 Jan 16, 2017 06:32 Send this review to a friend
Very Good Amp with a buzz  Time owned: more than 12 months
This review was originally put under the 2500 but it was really for the 3KDX. The one I have exceeds 3KW PEP into the dummy load with enough drive.

I have one of the old 4CX1600b versions of this amp, and when I got it, I realized those tubes were scarce, so I picked up two extras. I haven't had to use them, just tested them and put away in case they are ever needed. Talk about an under rated tube: These things were very powerful and it is too bad they are no longer in production. A more suitable name might have been 4CX3000b!

What can I say about this amp that has not already been said? It is very well made, with larger than average components, heavy iron, and designed for simple easy operation with broad tuning on most bands. So far, over nearly a decade, there have been no problems at all. The power output on some bands with this tube have >3dB available over the limit, and the amplifier simply loafs along. The fan is unnecessarily noisy, considering the little heat this beast creates as it leisurely pumps RF. (NOTE: this observation was incorrect, see below)

The design is easy to understand, and, I presume, easy to repair, should something go wrong. Though a little more costly than its presumed peers, I believe it has no peer, based on my experience with other expensive amplifiers made by vaunted manufacturers.

I have had one problem with this amp: At first I thought I had a noisy fan, and the buzz got worse over time. I discovered that the Dahl plate transformer (I believe it is by them) developed a pretty severe lamination buzz, even with no load. It was so bad I dragged it to a commercial transformer company to have it epoxy dipped, as it did not appear to have been done before. Even with the new epoxy the lamination buzz continued unabated. I asked Ray if there was perhaps another transformer available but he said there were none.

I have stopped using the amp because of the noise, which is annoying.

A possible next step is to make compression clamps that can go corner to corner in an attempt to compress and reduce the buzz. Another step might be to change the bolts that hold down the transformer (one is nearly impossible to get to) to something tighter.

A final step might be to try to acoustically insulate the plate transformer with some heavy micarta or other dielectric material.

I would be very interested in finding a better, less noisy plate transformer.
K5WG Rating: 5/5 Nov 23, 2015 18:17 Send this review to a friend
Fantastic Amp!  Time owned: more than 12 months
I have owned lots of amps over the years, including Kenwood, Drake, Collins and Alpha. I bought this amp based on recommendations from knowledgeable hams that I know and trust. I have had this amp for two years and love it. It's quiet, dependable, and easy to tune. Outstanding design and beefy construction. Look inside of one and you will be impressed. Heavy-duty components throughout. I use it on a daily basis for ragchewing, DX chasing and contests. It's a definite pileup buster! Absolutely the best amp I have ever owned!
Bill, K5WG
K5ZG Rating: 5/5 Jun 13, 2013 07:37 Send this review to a friend
FANTSTIC  Time owned: more than 12 months
WOW, is all I can say, WOW. I got this amp based on previous experience with QRO for both quality and the back up given by Ray...I have owned several of the QRO amps over the yrs and still do. I even got to beta test a pair of 4CX1600's for Ray yrs ago.
This amp is so nice. Tuning is easy and very broad banded. It will put out 3K (into a dummy load of course). I have battered it at 1500 watts out in CW, Fone and RTTY contests without a glitch or burp. It does heat the shack.
Looking back at over 50 yrs of ham radio and all the amps Ive had, Kenwood, Swan, Collins big and little, Heath, Henry big and little, home brew 8877 this is by far the finest amp .Ive ever had. As Pee Wee Herman would say "Im the luckiest boy in the world". Compare the quality and company reputation and Rays backup to all the other amps and then look at the Ray with an order.
If anyone knows me and amps I can say this is "HUD PROOF". See you in the piles...of course you will be behind me.
W5RIM Rating: 5/5 Apr 8, 2013 13:45 Send this review to a friend
FABULOUS  Time owned: 6 to 12 months
Owned lots of amps, this one is a beast. Lots of voltage on the 8877 tube. Runs legal limit plus with ease. Ray is great to deal with. Liked this amp sooo much i bought a hf2500 also. These amps are built like a tank,very heavy duty components. I love it. Buy one you will not be dissappointed.GREAT CONTEST AMP.
Julius w5rim
W7GO Rating: 5/5 Nov 30, 2012 11:26 Send this review to a friend
Powerhouse  Time owned: 0 to 3 months
Wanna bust pileups? This amp will do it.
Very nice construction and easy to tune.
Powerhouse amp and great QSK operation.
Very pleased with this amp so far.

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