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Reviews For: Dentron MLA 2500B

Category: Amplifiers: RF Power - HF & HF+6M

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Review Summary For : Dentron MLA 2500B
Reviews: 32MSRP: 1200.00
Description:
2 KW PEP Amp 160 80 40 20 15 10 m
Product is not in production
More Info: http://
# last 180 days Avg. Rating last 180 days Total reviews Avg. overall rating
00324.7
KD8JMQ Rating: 2012-01-27
I have two Time Owned: more than 12 months.
Ok here are my thoughts;
If you find one in good shape with the original tubes(8875);and you see no less than 1kw and no more than 1300 watts; the amp is a buy.
Make sure the electrolytic caps are either new or replace them.
Never try to drive the amp past the alc.
Tune the amp and bring up the drive until you reach max output and set the radio for that wattage.
Use common sense

If you have ANY amp with original tubes and it still is putting out full power; It won't get any better.
Most 2500 amps that survived this long already have all the mods done!
I have two MLA 2500 amps. One I have ran for two years non stop with 1250 watt pep output,the other was just purchased with in new condition and not even a trace of dust inside on the fan.
Both amps put out Exactly the same output!
I paid 500 for the first amp
I paid 1200 for the "NIB" amp

My point; If it's working and you operate it with the Dentron protection mods in place; You won't have to worry about substituting some other tube.

Things I love about this amp

lightweight
small
lots of power
smooth tuning
can run on 110v with good line current
clean output
attractive
CHEAP (A new amp doing the same will cost you big bucks and probably end up blowing something)

In my opinion; If the 8875 was put back into production; you would see everyone flooding the market to buy them and building amps around the MLA 2500!

Unless I "Kick the bucket" sometime soon or you kick my door down at gunpoint; YOU WONT GET MINE
73
K9MHZ Rating: 2012-01-16
It works, and it's OK Time Owned: more than 12 months.
Sorry to veer away from the glowing reviews about this amplifier. I owned and operated one for 10 years and found it to be OK at best.

The swamping resistor input circuitry is an absolute joke. It was clearly cheap in design, allowing Dentron to avoid putting in a tuned input circuit into the small cabinet.

The cooling air was sufficient only until you operated with more than a small amount of duty cycle. I personally wouldn't ever use it on any mode other than SSB with lower, uncompressed drive.

The grid current was a mess.

It did "work", and the tube choice is a good and solid one, but Dentron definitely went on the cheap trying to cram it all into the small cabinet.
KB8YIJ Rating: 2011-08-03
5.5 Time Owned: more than 12 months.
Im a RF engineer and I see all the things that are said about the Dentron MLA 2500 amp. I can tell you of course their amp has issues but for the size and the punch it has find a better one!

I own a few of these and I can tell you they will run with the best of them for the money.

Just watch the grid current and let her rip for the size and what it is (Really) It will outperform a SB220 like nothing!
VK3OT Rating: 2011-07-29
Oldie but a goodie Time Owned: more than 12 months.
This is a short review about an old MLA2500.
It started life in Australia in 1979 at the CQWW VK2ATZ/Lord Howe Contest station after which I transported it to Xmas Island as VK9XT and ran it into a QUAD 1000 feet above sea level and worked 65000 contacts between 1980 and 1982.
If you have a light blue or dark blue VK9XT card then you worked this amplifier.
It never missed a beat and when it cme time to ship it back to VK, the post master would not accept it back the way it came so I was forced to carry it in my luggage in with my clothes. It was used at my home QTH to set a 5th word high score on 10 mtres in the ARRL and then by VK3AKK to set high score on 40M. Then in mid 1980s sold it to Jeff VK8GF who used it until he left VK8 in the lates 2000's, he sold it to Eddie VK4AN who sold it to Peter VK5PJ who just sold it back to me (VK3OT).
Its the original amp in original condition and is back here after 25 years. It still has the original tubes and I know that because when I hand carried it back through Singapore to VK3 the tube fell out and rattled around in the tank area and I had to use some straight nosed pliers to get the dents out and you can see the plier marks. I have jst pulled the tank circuit apaart and linished the silve rplating on the switch and lubricated the bearings and cleaned out all the red centre bull dust. I ran it into a load and get 1000 watts out for 65 watts of drive and it goes 800 mA key down at 100+. Original tubes, original caps, and the original well travelled case. Date codes on tubes are 1975. You can still see the engraving under the corrosion and rust spots. As someone said at $500-$600 good dollaars per watt. Pity about 9975's being obsolete, but then Im obsolete so what the heck. Just need to stop the power transformer humming and change the fan over to new 120mm 12V late design with modern blades to get the fan noise down at high speed. Need to find out if the Nulon shield has been left out of the power transformer mounting.
JUNKMAN Rating: 2011-02-20
Worth every penny Time Owned: more than 12 months.
I've owned several of these amps over the past few years and I just acquired another one last week. This one is the MLA-2500 non B model and is in like new condition inside and out. Even the tubes still look new. 50 watts will produce about 1100 out and 80 watts will produce 1500 watts out. A full 100 watts in will get you 1800+ out! I just ordered the soft start kit from Harbach to make it easier on the tubes at start-up. Considering the ever increasing prices of the new amps these older amps are looking better and better. A simple upgrade to the power supply board with new caps and diodes is all that is needed to make these amps last for many more years of service. I know of no new amps that cost less than $600 and puts out 1500+ watts to the antenna. In my opinion these are a smart buy and worth every penny that they cost now.
N4EDX Rating: 2009-12-30
Great service Time Owned: more than 12 months.
I bought one at the Asheville, NC (Waynesville NC)Hamfest from a private owner, it was a great buy. It has provided a couple years service with no problems. I know the tubes are original but its been a well cared for unit. 1800 out on 80 meters down to 1200 on 10 meters. Best purchase I've made at a hamfest!
73's
Ed (N4EDX)
KG8DP Rating: 2009-02-13
Great Amp. Time Owned: more than 12 months.
For a number of reasons I made swing from Commander amps back to the Dentron. I now within 2 months own 2 of them plus a WP-1 watt meter and MT-3000A. match a 2500 and a 3000a and load up the box spring in your mattress just dont lay on it. LOL. To top it off, i have found 2 people that work on the stuff locally. One of the dentrons I purchased I sold to a guy back in the arly 90's and he did not use it anymore. thats why I marked it longer than 12 months. they are on e-bay all the time. good amp and good buy beats paying thousands for the 1.5 kw amps. Mark
ZL4TGH Rating: 2009-01-05
Bang for the bucks Time Owned: more than 12 months.
15 years ago I swapped a TNC for the non-working amp. It came with 2 new valves and the originals also like new. A quick tweak on the voltage relay (about 5 minutes work) and in business. Put it in storage for 5 years and when I turned it on, bang! HT cap blew. Well tonight I replaced them all and with extra 0.01uF across them and 10 ohm on the HV B+ in case of arcing. Removed my GLA-1000B and put my sweetheart back in line. First contact with the repaired amp, over the south pole long path to Germany on 40! The guy was so excited it gave me a buzz also. Other ZL4's tried but he just could not hear them. My FT-2000D was only putting out 30w. What a great amp, before it's time.
KA9TZU Rating: 2008-11-21
Best amp I have owned Time Owned: more than 12 months.
An extra class friend of mine bought this amp new in the mid 80's. I always thought is was great. When he moved he sold it to me for a song.

It sat on my shelf for over 5 years before I used it. Worked like a charm even though the caps arced now and then. The problem stopped on it's own, so I never replaced them. Put it away when I moved a year later and brought it back out 12 years later. Still worked great.

I have 2 sets of 8875 tubes I had bought back then in case I needed them. Not so far, originals are still at full power. I can easily get 1400 pep on 80 meters with a 40-50 watt drive. The swamping resistor is still in place. I have used this amp with numerous radios and it always has preformed for me. I am currently using it with an Yeasu 897D

I am converting a solid state medical research amp for amateur radio use. The amplifier uses 16 MRF150 MOS FETs in 8 push-pull output stages, which are driven by a push-pull stage using two additional MRF150s. Even when this amp is up and running, I will never part with my Dentron!!!!
W5VIN Rating: 2008-03-11
Retube Time Owned: more than 12 months.
I just finished doing a retube on this great amplifier using the GI7B Russian triodes and W4ZT sockets. It will crank out well in excess of 1300 watts of power with less than 100 watts of drive power. To those that have this amplifier and it's tubes are going south this is a working modification that is not all that hard to do. It gives the MLA-2500 amplifier a new lease on life.
Charlie W5VIN

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Earlier 5-star review posted by W5VIN on 2007-05-19

I purchased a Dentron MLA-2500 with bad tubes. I replaced them with three 4CX-250B operating in modified grounded grid with screen and grid bias voltages. Both grids are at RF ground through coupling capacitors. I sort of followed the old QST article which used a Russian GU74-B. It was my initial choice but produced a less than stellar output. I redid the bias supplies using an LM431 and series zener for the negative bias. The screen bias uses an LR8N3-G high voltage regulator feeding a high voltage MOS transistor. For input matching I use an LDG 100Z Ultra externally between the antenna switching relay and the tube cathodes. It simplified impedance matching and is battery powered with memories. The amplifier will load to 1200 watts output and is quite comfortable at 1 KW out. There are several mistakes in the QST retube article article both in design and on the schematic.
Charlie W5VIN