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High drive MRF454 amp?
- Thread starter TIN_CAN
- Start date
The terms "HD" and High Drive most of the time are just stamped on amplifiers because it will make them sell better. Very few 2 and 4 final amplifiers are true HD devices. As an example a Texas Star 350 HDV works best with a 1-2 watt AM dead key and 18-22 watts peak drive.
I cringe when I look at the pics of that amp. Hard to say what finals were in there when new. How many different finals have been in there and what was re-worked each time the wrong finals were swapped in is anyones guess.
Amplifier finals are not something you just swap out for larger more powerful ones. Other areas of the amp must then be re-worked so the amp functions properly. I am no amplifier tech but it appears some things are missing from that amplifier.
If the finals are good don't pay more then 50 bucks for that pile, that way at least you can get your money out in the value of the finals. I would start out with a dead key of 1.5-2 watts with maybe 20 er so peak input and see what the numbers are. A 2 pill amp with 454 finals is maybe good for 130-170 honest watts. If you drive the heck out of that amp you might see 190 peak watts. There is no way I would drive it with 50 peak watts.
I cringe when I look at the pics of that amp. Hard to say what finals were in there when new. How many different finals have been in there and what was re-worked each time the wrong finals were swapped in is anyones guess.
Amplifier finals are not something you just swap out for larger more powerful ones. Other areas of the amp must then be re-worked so the amp functions properly. I am no amplifier tech but it appears some things are missing from that amplifier.
If the finals are good don't pay more then 50 bucks for that pile, that way at least you can get your money out in the value of the finals. I would start out with a dead key of 1.5-2 watts with maybe 20 er so peak input and see what the numbers are. A 2 pill amp with 454 finals is maybe good for 130-170 honest watts. If you drive the heck out of that amp you might see 190 peak watts. There is no way I would drive it with 50 peak watts.
Thanks for the info, I was just curious as I have never seen a high drive amp with mrf454's the seller said it was 2879's in it before.
Someone got solder happy. And why would you replace 2879's with 454's. Like said, how many times has that amp been worked on. It really isn't just a take out and put in job for sure when it comes to replacing transistors. I would not purchase that with any intention of it doing much. Maybe a good one to play with and experiment with, but not a good one for daily use IMO. The only hd amps I know of are of the Dave made or x-force HD amps, but a 2 pill still only needs a 2 watt dead key and depending on the way it's built, it can handle up to 100 to 120 watts pep from a 2 watt dead key. I have a magna force 350hd that is built like this, it works best with a 2 watt dead key and about 60-80 watts pep. This puts out around 300-350 pep watts and is still clean. I am currently using the amp with a uniden pc122xl with a 2 watt dead key. Get great audio reports with this setup as well. Radio dead keys 2 watts and pep is around 15-20 watts.
Someone wanted a looks good on the dosy watt meter box there lol. Splatter city baby. Yes sir there are quite a few parts missing as posted. Looks like whoever did the work did not truly know how to fix the amp correctly and probably ripped it apart to get it somewhat working for a customer or something. Or the rest of the parts all got fried and this is all that was on hand to rebuild it. Either way, it's not going to perform like it should and will probably bleed 10 channels either side of the transmitting freq.
Two MRF454's?
Would be OK for an AM-only radio w/2-2.5 watt dead key/10 watts PEP @100% modulation. Amp would draw ~18-24 amps @ 13.8v as a guess. 38 watt dead key with a 150 watts peak output from this amp. Definitely C-class biased from what I can see; so this amp certainly won't work right on SSB. Would sound like garbage on SSB, so don't even bother using it for that. Put 50 peak watts into that amp at your own risk; more like 10 peak watts if you want to keep it alive and working. No offense meant TIN_CAN, but that amp looks like a real hack job. Just because it says 'HD' on it, after the hacking that doesn't apply any more.
MRF454/SD1446 data sheet:
http://www.st.com/web/en/resource/technical/document/datasheet/CD00000618.pdf
Would be OK for an AM-only radio w/2-2.5 watt dead key/10 watts PEP @100% modulation. Amp would draw ~18-24 amps @ 13.8v as a guess. 38 watt dead key with a 150 watts peak output from this amp. Definitely C-class biased from what I can see; so this amp certainly won't work right on SSB. Would sound like garbage on SSB, so don't even bother using it for that. Put 50 peak watts into that amp at your own risk; more like 10 peak watts if you want to keep it alive and working. No offense meant TIN_CAN, but that amp looks like a real hack job. Just because it says 'HD' on it, after the hacking that doesn't apply any more.
MRF454/SD1446 data sheet:
http://www.st.com/web/en/resource/technical/document/datasheet/CD00000618.pdf
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No offence taken Rob, this is not my amp, I just saw it on Ebay as I am there usually looking for older mobile amps in good condition and came apon this one and was surprised by his claim as a high drive amp, I am no tech but do like to get info on the workings on these things, and I collect them, my amps consist of a rebuilt EliteLine TX2250, mint condition Palomar Magnum 6500R and a clean Palomar Magnum 4000, still looking for a clean EliteLine TX5500...just putting that out there...lol