Yaesu FT-411E Repair Help (No turn ON)

Discussion in 'Radio Circuits, Repair & Performance' started by F4GXS, Mar 14, 2021.

ad: L-HROutlet
ad: l-rl
ad: MessiPaoloni-1
ad: Left-3
ad: L-MFJ
ad: abrind-2
ad: L-Geochron
ad: HRDLLC-2
ad: Left-2
  1. F4GXS

    F4GXS Premium Subscriber QRZ Page

    Hello everyone,
    Few days ago, i buy from an OM an old non functioning YAESU FT-411E, X2 MH12A2B and an empty FNB-11H Shell, all of that for only 30€ (35,86 $ / USD)

    I was interested to get an eye on my FT-411E to repair it, the problem is it won't turn ON, It doesn't turn on with a battery fully charged and i ask you for help to be able to fix it if you have some ideas of why it won't turn on with fully charged battery.

    Does anyone have an FT-411 ?
    Someone has already had to do with this HT that does not light up ?

    I'm waiting for a response.
    Take care everyone !!

    73's F4GXS Pierre
     
  2. US7IGN

    US7IGN Ham Member QRZ Page

  3. F4GXS

    F4GXS Premium Subscriber QRZ Page

    Hello US7IGN !

    I check the page 5 (mother board unit circuit diagram) on the FT-411 Technical Diagram you just send me, thank for that. :)

    The contact between the battery to the power button are OK, the power switch are OK too, no cut detected, the current pass thru with no problem.

    Cordially.

    73's F4GXS Pierre.
     
  4. US7IGN

    US7IGN Ham Member QRZ Page

    Good. In the next step, please apply the supply voltage to connector J103 and check for the presence of voltage on pin 9 of the motherboard connector J102.
     
  5. F4GXS

    F4GXS Premium Subscriber QRZ Page

    Ok, voltage supply to J103 = OK, presence of voltage on pin 9 to J102 FINDED, all OK
     
  6. US7IGN

    US7IGN Ham Member QRZ Page

    Please check Q202 and Q203 (transistors inside) one the control unit board. But first what is voltage on pin 1 of Q202 when you turn on and off radio.
     
  7. F4GXS

    F4GXS Premium Subscriber QRZ Page

    I just check Q202 and 203, it seen to me OK but when i check the voltage on pin 1 of Q202, it's not OK, no voltage out, 0V

    an website tell me this, for checking PNP and NPN : (https://vetco.net/blog/test-a-transistor-with-a-multimeter/2017-05-04-12-25-37-07) :
    When i check that, it's not OK, i've got someting on my multimeter.

    I think we find the culprit.

    This is why it's not turning ON ?
     
  8. US7IGN

    US7IGN Ham Member QRZ Page

    I want to specify. Does the voltage change when radio turned on and off?

    It is important that between base and collector and base and emitter the meter should show a voltage drop between 0.45V and 0.9V depending on the type of the transistor (NPN or PNP). I put the multimeter in diode measurement mode and put one of the probes on the base, and the second to the collector and emitter. There must be the correct voltage drop. If nothing else, then I swap the probes and repeat. Of course, the transistor must be unsoldered before measuring.
     
  9. F4GXS

    F4GXS Premium Subscriber QRZ Page

    When the radio is OFF, the voltage is between 0V to 0,30V, when i turn it ON, the voltage is 0V

    Due to a microscopic size of this chip, i can't unsoldered that type of component, because i don't have the hardware to do this.
     
  10. US7IGN

    US7IGN Ham Member QRZ Page

    it is OK.

    Further more difficult. It is necessary to find out how the processor controls the radio when it receives a signal that voltage has appeared and whether it is working properly at all. I need time to think.

    And... What is on pin 2?
     

Share This Page