1. You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.
    Dismiss Notice

XFORCE 12 PILL DRIVE?

Discussion in 'General CB Services Discussion' started by 041, Nov 8, 2018.

  1. 041

    041 Member

    Joined:
    Feb 8, 2015
    Messages:
    20
    Likes Received:
    8
    My BIL purchased a xforce 12 pill and not sure if a driver is necessary to run it, he not a member here so im asking for him. He has a 250amp power supply, driving with just his ranger AR 3500, DK-ing the amp at 300w out and radio swings 100w on am, swings 100w on ssb and hes only seeing 1,000w out of it on both bands. The AR just not enough radio to push it? Amp has issues?


     

  2. OldTech03

    OldTech03 Well-Known Member

    Joined:
    Dec 15, 2017
    Messages:
    246
    Likes Received:
    280
    Well, it could and most likely would show more with more drive but it seems to be doing about what it should. If you consider the specs on 2sc2879's and I'm only assuming that is what is in the amp. They have an average output rated at about 100w each but amps efficiency is only about 80% and there are many variables I don't know about as to how it was tested. And as I said what the actual transistors it is using. The 250 amp supply should be enough but you need to know that it is maintaining at least 12.5 VDC under load the only reason I say that is that most big supplies are not regulated supplies and the load voltage is much different than static load. The drive power will also be divided by the input transformers and most likely each "output pair" will only see around 6 watts "MAYBE" The big boys get tons of power out of amps by running extra alternators and variable line regulators that allow them to run upwards of 18 to 20 volts on the collectors and on top of that would drive an amp like this with upwards of 250 to 300 watts it's just the way they get more out of amps than what you should be if you want them to last. That's my story and I'm sticking to it!
     
  3. 041

    041 Member

    Joined:
    Feb 8, 2015
    Messages:
    20
    Likes Received:
    8
    Sorry forgot some relative info, yes its an older unit with toshiba 2879s, under load the ps drops to about 14,1v and he says it draws around 190a. Just seems kinda low for output, my ts 1600DX loafs along doing more than that with just 8 toshibas.
     
  4. OldTech03

    OldTech03 Well-Known Member

    Joined:
    Dec 15, 2017
    Messages:
    246
    Likes Received:
    280
    Well I didn't go into all the reasons it may not be developing power because depending on it's age parts values can change especially under heavy use and heating. Transistors can become leaky and weak and that can also cause out of balance issues. Best to check the output transformers and matching networks for overheating as well and while you are at it check for bad soldering issues as someone may have tried to repair them without the knowledge or the right equipment. All kinds of things can be issues.
     
  5. Shockwave

    Shockwave Sr. Member

    Joined:
    Sep 19, 2009
    Messages:
    2,591
    Likes Received:
    818
    Check and see what type of capacitors are being used across the tops of the 6 output transformers. If they are the brown style ones and the previous owner drove it hard, they may have lost their value by now. If they are the silver plated metal body style, someone did the job right. They are much more difficult to shift out of tolerance.

    Another problem with amps that have been driven hard is they no longer like to respond as well to lower drive levels. Excessive drive will eat away at the transistor gain and lower the hfe over time. While it still can make good output, it no longer has 13db of power gain and requires more drive to make the same power. The numbers you're seeing now, indicate it is operating with a power gain of 10db.

    The good news is 1000 watts is not so bad at that drive and voltage. One thing you may want to check is what is the SWR that the radio sees while driving this amplifier? If it's not optimal, look inside the amp and see if there is an input trimmer capacitor and adjust it for minimum SWR. That could lower the drive requirements.
     
    Shadetree Mechanic likes this.
  6. 543_Dallas

    543_Dallas Sr. Member

    Joined:
    Jul 25, 2011
    Messages:
    1,668
    Likes Received:
    1,690
    With 100 watts of drive 1000 watts is about right for one of these amps. These amps were designed for competition. They are class C and tuned for 20 volts. It will not have as much gain as a texas star especially at 14 volts.

    Don't mess with the input tuning unless you know how. It's not as simple as tuning for low swr. There should not be any trimmers in it unless some incompetent person installed them. You will have to isolate and check each section and then adjust the LC network. If it works now, leave it alone.
     
    Shadetree Mechanic likes this.
  7. 041

    041 Member

    Joined:
    Feb 8, 2015
    Messages:
    20
    Likes Received:
    8
    Thank you, ill pass on the info on to him and see what he says.
     

Share This Page

  • About Us

    The WorldwideDX Radio Forum was originally established in 2001. We pride ourselves on welcoming Radio Hobby enthusiasts of all types, while offering unbiased, informative, and friendly discussion among the members. We are working every day to make sure our community is the best Radio Hobbyist's site.
  • Like us on Facebook

  • Premium VIP Member

    The management works very hard to make sure the community is running the best software, best designs, and all the other bells and whistles. Care to buy us a beer? We'd really appreciate it!

    Donate to us!