| Author |
Message |
    
Jake
| | Posted on Monday, February 10, 2003 - 4:13 pm: | 
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I would like to find out if anyone has changed the driver pill (2290) to a 2879 and if so how much of an increase did you get or can you expect to get from this exchange?. I know that I can get a texas star1200 and will increase my power but, would like to see how much i can get out of this one with this mod. I'm driving it with 1/2wat swing42. |
Tech671
| | Posted on Monday, February 10, 2003 - 9:05 pm: |
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Unless you're installing a new transformer and hand-winding it and tuning the input/output...you'll do more harm than good. Installing it correctly would yield about 10% increase. |
2600
| | Posted on Wednesday, February 12, 2003 - 1:20 am: |
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The 2290 driver in the 667V already drives the devil out of the four finals. Goosing them harder will only make it fail sooner, and won't talk any farther. Subbing a 2879 sounds like a cheap upgrade, but doesn't pay for itself at all. The smallest step up from a 667V is an amplifier twice this size. Any smaller a step up won't even show up on the S-meters at the other end of the conversation, even if it does make your wattmeter look larger by a third or half. Takes twice (or more) the power you have now to make any difference at all on the other end. 10% is a total waste of time and effort.
73 |
Crafter
| | Posted on Wednesday, February 12, 2003 - 9:17 pm: |
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Jake I think there is a link off of Ear Pluggers web site to HAMBONE in LA and his site has the winding changes on the amps like going from 2290's to 2879's in the texas star amps that someone worked out and listed there on there somewhere. I know I seen them there somewhere. |
Ss8541
| | Posted on Thursday, February 13, 2003 - 10:50 pm: |
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why would anyone want to change the driver in a 667v? the 2290 already overdrives the amp as it is(when driven the way 95% of operators drive a 667v). the 667v has 20db of gain(100 times). 1w gives you 100w out. 6w in 600w out. past this input level, you are really overdriving the amp. so it makes no sense to put in a 2879 as a driver, when the 2290 has too much drive already.
basically an input of 1w carrier and 6w swing pushes the amp to its 'cleanest' levels. it can do a little more at a dirtier level(maybe 700w on a good day). and they can 'show' up to 1000w of swing when 30w is dumped into one. many operators are fooled into thinking that their 667v is doing 1k because of this severe overdriving.
if you think about it logically, if the 667v has 100 times power increase(20db) then if you put 30w of swing into it, then it should be putting out 3000w. since it can't do close to this even with all the bleedover, that is the 1st clue that you are overdriving the amp. it is way out of its linear stage with 30w(pep/modulated) input. heck, it is out of its linear stage at 12w(pep/modulated) input.
just something to think about. |
2600
| | Posted on Friday, February 14, 2003 - 12:43 am: |
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If I were in the business of selling 2SC2879 transistors, I would publish "upgrade instructions" to do just what Jake suggests. Sure would boost sales. The four finals in a 667V are good for several years with the stock 2290 driver. Might get a month or two out of them with a bigger driver stage. Besides, it would sound really nasty to boot.
Had a customer ask how much to put in "that second final" on the radio circuit board in his Galaxy Turbo. The mobile 2950 radio has two CB final transistors. The base version with the built-in linear has only one. He thought putting that second final transistor in the empty slot would be a good idea. I quoted him $350 to do it. Told him "If I'm gonna make a radio sound that bad and have my name associated with it, you gotta make that worth my while". He politely declined. Smart fella.
73 |
Sparkomatic
| | Posted on Sunday, February 16, 2003 - 2:31 pm: |
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I have always been told than you have to double your power to gain 1 S unit. |
Ss8541
| | Posted on Sunday, February 16, 2003 - 10:25 pm: |
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by the books that is incorrect. you have to quadruple your power to gain 1 s-unit. in real life the meters never work by the book, and doubling your power will give you close to 1 s-unit increase(especially on the low end of the s-meter). |
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