D+A MDX-200 aka late Maverick 250 amp
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- Опубліковано 5 вер 2024
- Old MDX-200 which is the latest version of the venerable Maverick 250 but modded to get past the FCC during the CB boom of the late 70's-early 80's. D+A took one of the 4 driver tubes and used it as a Pre-driver tube and had a 1 crystal oscillator circuit and sold this as a 20 meter transmitter. Most would remove the pre-driver tube and retap the coils for 10 meters and use this as an 10 meter amp rather than 20 meter transmitter. Since this doesn't use the pre-driver tube it has 3 driving 4 while the Maverick 250 has 4 driving 4.
Interesting to see the creativity used to keep these amps somewhat legal back when they were made. I bet the fcc were pretty frustrated at times.
My thoughts exactly
Interesting history. I just picked one of these up from a guy who moved to hamm radio. Other than dust a pretty clean unit.
Again love the history.
Those are real workhorses!
@@tramdr a little different knobs too than what I am use to. I'm gonna half to find out how to use them. 😂
I have a Maverick 250 can I change my 6AQ5 tube to a 12 AQ5 tube will anything change I watch your videos all the time very educating thank you my name is Robert ???
yes if you change the filament voltage.
Could you show what is required to convert one of these to a 10 meter amp?
Good evening Mr. TramDr. I just came across a d&a mdx 200 20 meter amplifier. I just want to understand that if the oscillator tube is replaced with a filment transformer it has bern converted? Thank you BUG aka 654.
probably, but would have to see that.
So I gave a radio check earlier today. and the guys voice sounded soo familiar. I been sitting here racking my brain trying to figure it out and then it hit me. it is that guy who has all the really cool vintage equipment.. do you operate on crest?
No I don't do crest and except for rare occasions, I rarely talk on the radio. I listen and make vids for the most part.
I have a question what is the final tune used for ? And what is the antenna load used for ? So do I need to set these when turning it up ? And or do I need a watt meter in order to set correctly? Lmk thanks you
They both work in tandem with each other to tune an amps output for max watts (this is simplified so Hams don't bother telling me about resonance and load and stuff). Also, the Tune is the adjustment right after the Tube and it interacts more with tuning the Tube up for max. The Load is right before the antenna and is for the most part tunes the output up to match the antenna. A technical term for antenna, or what ever the amp is keying into (like a dummy load) is the term Load. Hence the common term for the 1st adjustment that tunes the Tube is Tune. The common term for the 2nd adjustment that tunes the antenna (or load) is Load.
One common fallacy is some thing that as long as you tune the Tune up, you then can untune or detune the Load to make the amp do less watts and since the amp is putting out less watts (and the Tune for the tube is tuned up) then the amp is running cool, low, and good. This is dead wrong. When you tune (or load) an amp down from max watts, the tube is still producing the watts even though they are not going out to the load or wattmeter. What happens to those watts then? The tube eats those watts. So lets say you have an amp that does 1000 watts but someone tunes (or load) it down to 500 watts out. Those extra 500 watts go back in the tube and are lost in the tube as heat. The tube eats those extra 500 watts because someone didn't tune the amp for max.
@@tramdr ok so if I had mdx 200 what would u want to tune up first I got it hiting like 375-425 give or take as is now but if I hit the antenna load to the left I'm getting I bleave like almost 600 or atleast hits the 6 milliamperes on amp meter any help would be greatly appreciate
@@everythingvtec Final Tune then Final Load, then repeak a few times, then driver tune, then driver load a couple times, then go thru all 4 a couple of times, if you are already tuning everything for max, then turning the load after that and getting more makes no sense to me. 2nd, there are wattmeters that measure power out, and there are milliammeters or amp-meters that measure tube current. If you are using the D+A milliamp meter to adjust power out, then that is just wrong too.
@@tramdr When I would adjust the antenna load and move it all the way to the left it would punch out more milliamps on the meter on the amplifier but it would make my transmission a little bit more fuzzy so I have to run the ant load in the middle and it seems fine the final tune very little bit adjust the meter ever so slightly so I just set it to Max and left it there and it's been pretty good Seeing if I was doing something wrong or doing something differently I should be doing correctly I'm not sure just double checking with you you seem like you know a lot about your stuff and I appreciate the information
2 more questions are this amp have automatic sbb ? And can it be high drive?
Can I use it in 11 meters?
It would be against FCC rules to do that. It is designed to work on 10-15 meters.