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rci2970n2 bias help

Discussion in 'CB and Export Equipment and Accessories' started by cbkidd1, Jun 4, 2011.

  1. cbkidd1

    cbkidd1 Active Member

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    Hi, I have a rci2970n2 I wanted to check the driver and final bias to make sure it is set right.I don't have a DC Ammeter Could i use a dc volt meter to check the bias? I have a dc amp setting. But nothing shows up. Also the main pcb is a ept-695015a Is that board used in any other radio? I want to do a alignment but there is no service manual for the radio. I have read some scary post about the irf520 mosfets in this radio and want to make sure the wattage and bias is right. The main board in the galaxy 98vhp is not the same as the rci2970n2.


     
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  2. Robb

    Robb Yup

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    I use a mA gauge to set the bias for the driver and final, as per spec's.
    I would thoroughly advise getting the right equipment for the job. Otherwise; don't do it! Sears/Craftsmen makes a fine digital multi meter for around ~$45. It is a re-packaged Fluke 17B if I'm not mistaken. I have one, and use the tar outta that thing - and like it too. . .

    AS far as adjusting the final bias on the the N2; what are you trying to accomplish? Hasn't these adjustments already been made correctly? Unless you are using a mA meter; why would you want to change them? How would you know they are wrong? The only way to know is to check it first. I set my radios up when aligning them BY THE BOOK! Including the biasing. (I'm no tech, but I have aligned a lot of my radios and quite a number of locals radios. But I make them work/align them as they should and were designed for)

    Just what are you trying to do - if you don't mind my asking? Lower the power output before the MOSFET's go belly up? If so; then adjust the hi power VR and limit it there. Never worked on an N2; have worked on a 2950. If it is like other RCI chassis radios - it should have a lo and hi power VR. My RCI-2995DX has such VR's too; just sayin . . .
     
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    Last edited: Jun 5, 2011
  3. cbkidd1

    cbkidd1 Active Member

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    Hi, Robb. I have read that the rci2970n2 radio's are coming from the factory with the bias and rf power set way to hi. And because of that the irf520 mosfets are burning up. I just want to make sure mine is not set up that way. I have adjusted the hi and low vr's they were set way to hi for 8 irf520 mosfets. Just want to make sure the driver and final bias are correct. Also am looking to check the gate voltage on the mosfets. There is no service manual that i can fine for the ept-695015a pcb.
     
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  4. GnG8d

    GnG8d Well-Known Member

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    Look at the 2995 maybe.
     
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  5. fodendaf

    fodendaf Active Member

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    I think that when i measured my own n2 that the prongs that u measure the bias from were labelled the wrong way round on the pcb. I cant offer any more as it was so long ago
     
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  6. cbkidd1

    cbkidd1 Active Member

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    I removed the tp7-tp9 jumper board. To check the driver and final bias. My meter as a radioshack 22-810 I used the dca setting but got no reading. So i switched to dcv and got a reading. I am guessing that i can't use dcv to check the bias? If not i will have to go but another meter.
     
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  7. cbkidd1

    cbkidd1 Active Member

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    I also looked at the rci2995. The board is not the same.
     
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  8. cbkidd1

    cbkidd1 Active Member

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    I kind of hit a few wrong keys sorry about that.
     
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  9. AudioShockwav

    AudioShockwav Extraterrestrial Admin Staff Member

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    Your Meter has to be put in series with the points being tested, not parallel.
    what model of meter are you using?
    On mine you must move the leads into a different set of inputs DC+A and DC-A to measure current.


    73
    Jeff
     
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  10. cbkidd1

    cbkidd1 Active Member

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    Hi AudioShockwav. I have a radio shack cat.no.22-810 meter hope that helps. I have dca Dose not have the - sign other then that. I have settings for diode, ohm, dcv, acv, Would any of these setting work to test the driver and final bias settings? And i guess the most in portent part is were do i put the test leads? I can not find ept-695015a pcb in any other radio. I really appreciate the help Thank you guys.
     
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  11. JoeDirt

    JoeDirt Active Member

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    If your meter will not work you can set the bias by voltage, 3-3.4 volts to the irf-520's finals and drivers. I would try to set them all as close as possible since the voltage method is not the most accurate way.


    I wouldn't recommend and voltages over 3.4 volts or under 3 volts.

    And make sure your in side band mode!
     
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  12. cbkidd1

    cbkidd1 Active Member

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    Thank you for your input joedirt. After a lot of reading on different post about the mosfets. That is the only way i could see to set them with the meter i have. So last night i set the driver to 3.4 volts. The factory had it at 3.63 volts. I read that the lower the irf520's are set the cooler they run. But at the same time you get less wattage from them. So i am going to set the finals and will let you know were the factory has them set at. Thanks again.
     
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  13. hotrod

    hotrod Well-Known Member

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    id much perfer a cooler running radio and lose a few watts that noone will notice anyway
    sorry i dont have any info or help for ya. but am curious how it was
    setup from were ever ya got it vs the way your gonna set it up
     
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  14. cbkidd1

    cbkidd1 Active Member

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    When i bought the radio it was putting out over 300 watts. Before i started talking on it i wanted to make sure it was set up right. So i researched the irf520 mosfets. And found that a lot of people had bought the same radio and because the power and voltage was not set right the mosfets burned up. Good thing i took the time and did some research on both the new rci2970n2 and the irf520 mosfet first. Now i hope someone can tell me the right setting for voltage so i can put the radio back together.
     
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    Last edited: Jun 6, 2011
  15. Robb

    Robb Yup

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    If the factory didn't set up the radios correctly before they shipped them out; then they would be deluged with returns and warranty repairs. The ONLY place that I know of - personally - that RUINS radios is RadioActive Radios. First hand knowledge - BTW. Have these radios been getting a bad rep because of being poorly adjusted from the factory? I never heard that yet.

    So long as the driver and final are set up correctly; it should be fine. Is the final - the one before the final power amp - a MOSFET too? If so; then MOSFET's are voltage controlled. In which case, you would want to have the voltage set at a point where it has just enough to turn/switch it on. Then, I would adjust the hi power VR to a desirable level. Preferably to 75% of its potential output - IMO. . .
     
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