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Reviews Categories | Amplifiers: RF Power - HF & HF+6M | Dentron MLA-1200 Help

Reviews Summary for Dentron MLA-1200
Dentron MLA-1200 Reviews: 8 Average rating: 4.6/5 MSRP: $(missing—add MSRP)
Description: 1.2 KW(PEP) HF Amplifier. It uses one Eimac 8875 tube.
Product is not in production.
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N4JHY Rating: 5/5 Feb 8, 2017 05:00 Send this review to a friend
Super Fun Amplifier  Time owned: 0 to 3 months
Bought my MLA1200 amplifier at a local hamfest. Told it was an untested estate purchase, and they wanted $45 for it!!?!!!!
Got it home and opened the power supply expecting to re-cap it, just to find that it already had been re-capped.
Opened up the RF deck and re-soldered several cold solder joints.
I then set it up to test, and it works just fine.
I see 750 watts PEP out, but have the drive reduced to 45 watts for 550 watts PEP out for good tube life.
SWR if only fair on this amplifier- 1.5 on 75 meters and 1.7 on 40. I am using a TS930sat to drive this amp, and the antenna tuner in the 930 takes care of the mismatch just fine.
Have run this amplifier now 4 days, and am in love with it. Runs cool, runs quiet, and at 550 watts PEP the tube will probably last a long time. It is a keeper. 73, Bruce N4JHY
N1PTA Rating: 4/5 Feb 5, 2014 06:23 Send this review to a friend
Nice old amplifiers  Time owned: more than 12 months
The output can not possibly be 1500 watts unless someone has Re-calibrated ;-) ;-) your meter to read more than it should. Or you may be measuring the output to the antenna with a bad mismatch or a length of coax that is not an odd multiple of the the frequency you are using. Try measuring the output into a dummy load with a known good wattmeter and let us know if you still get 1500 watts out of one tube. Dudes? Come on guys! This is just too funny! Let's pull up our Big Boy pants. Hi Hi!
KI4OVR Rating: 5/5 Apr 25, 2011 16:24 Send this review to a friend
Very good amp  Time owned: 6 to 12 months
This has been a great amp so far, I see a 1kw easily and it does not even get warm, I see amp's that do less selling for double the price. And the tube seems to be very hardy, being as the one in mine looks to be the original tube.
K2DC Rating: 4/5 Aug 22, 2007 12:46 Send this review to a friend
Agreed - Nice Starter Amp  Time owned: more than 12 months
I bought mine used, 3 years old in 1981 and I think I paid $325 for it (that's about $750 in current dollars). It was always pretty dependable. After 7 or 8 years, the filter caps dried out and had to be replaced, and the OEM twist-tab caps in paper cans were like hen's teeth. But drilling the board to install computer grade screw terminal caps was a fairly easy job. I had to replace the caps after an additional 7 or 8 years.

I have to disagree at least a little with Mike, K6AER on the robustness of the tube. While the Eimac data sheet for the 8875 does show a useable output of 587W in "typical operation", I was typically getting close to a KW with 100W of drive. Of course the output was always a little band and antenna match dependant, but I almost always ran it full bore. I started with a TS-520SE with tube finals, but later ran it with a TS-440 and TS-570 and never had a problem with the input impedance - I can't remember ever having to use the rig's autotuner. And I was a little stupid at times - like keying it up with the band switch in the wrong place once in a blue moon.

Still, it took me 18 years to wear out the tube. I was fortunate to get in touch with a former Dentron employee who had a couple of factory test 8875's that were retired after only a few hundres hours, and got a good one, fully tested at a very reasonable price.

The tubes do show up occaisionally on the used market, but not very often. Best advice if you have one with a soft tube is to look into some of the conversions to an 8874 (also discontinued by Eimac, but much more available used and NOS than 8875's, and also new and NOS ones from Svetlana are out there for around $400), a 3CX800 or GI-7B.

Alas, the power supply finally went again. Having and Alpha 78, an AL-1200 and an SB-200 (just in case in case) I decided not to repair. I sold it to someone who fixes and resells dead amps, and I got $200 for it (which he could probably get back just for the tube and transformer. let alone parting it out completely).

Certainly no regrets. I certainly would do it again. After 26 years, it didn't owe me a dime.

73 All,
Don, K2DC
K6AER Rating: 4/5 Jul 9, 2007 21:40 Send this review to a friend
Nice starter amp  Time owned: more than 12 months
I have repaired two of these amplifiers. It is a simple grounded grid design and if the tube has not been overdriven the tube should last a long time. The amplifier is capable of 600-750 watts PEP output with a stiff AC supply. The amplifier model number refers to the input power. With typical 55-60% efficiency and a short duty cycle (SSB) the output should be about 700 watts. There are no protection circuits on this amplifier and it will not tolerate ignorance or abuse.

The 8875 is run in grounded grid and has a non-tuned input. This amplifier was designed for radios with tube outputs that could have the Pi network tune to the amplifier input. Some newer transceivers with auto tunes should be able to match the tube input impedance providing they can tune up to 330 ohms input impedance needed on some bands.

Having the power supply separate is nice and makes for a compact table top amplifier. Maximum drive for this tube is about 25 watts continuous and in SSB duty I would not drive the tube with over 45 watts. Maximum SSB output rating on the tube in AB1 condition is 575 watts out. Although you can get more power out with higher drive you will shorten the tube life. Duty cycle is very important with this amplifier. SSB maximum output should be held to a 700 maximum. For CW the power output should be limited to 500 watts. In CW carrier the maximum output is rated to 370 watts out.
K7PWR Rating: 5/5 Jul 9, 2007 15:43 Send this review to a friend
watt meter works fine!!  Time owned: 6 to 12 months
Its the true *pep* output of this amp *dude*... 3 watt meters cant be wrong. Its a fact. Believe it.
W6IML Rating: 5/5 May 13, 2007 11:48 Send this review to a friend
gud little amp!  Time owned: 3 to 6 months
This little jewel will do 600 to 800 watts out to a 50 ohm load, no problem. The 8875 tube is no longer in production, but you can substitute a 8874 if you modify the cooling. You can also use a 8873, but since this tube is convection cooled, you will have to adapt a heat sink in place of the external fan.
K7PWR, you need to check your watt meter, dude.
K7PWR Rating: 5/5 Apr 2, 2007 00:08 Send this review to a friend
It rocks my world!! :)  Time owned: 0 to 3 months
I bought the MLA-1200 at a swap meet here in Seattle Wa. The amp looked Mint, and the powersupply looked completely unused, and neither one looked faded whatsoever. Both units came with the original owners manual and boxes. It was like going back in time. It appeared that this amp was stored for many years by the older ham who sold it to me for 600 cash. I tuned it up and got incredible output. 1200 watts with 90 watts of input. I know she will do 1500 watts+ output with a little tweaking of the antenna tuner etc, and maybe a few extra watts of input. It really is a solid amp, and i have done ALOT of psk31 and sstv with it, and it runs perfectly.This amp has a large oversized fan on the back for cooling. The only thing i do not like about it is the tube replacement nightmare.The Eimac tube is next to impossible to find.You may get lucky on ebay once in a while...but, they are RARE. I have read many others owning amps with this exact tube, and they claim these tubes last 20-30 years if not driven hard. Hmmmm interesting. Anyways, other than the hard to find tube...This is a solid 10 clean sounding and powerful. I love it!!!! :)

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