Yaesu ft 101E too much heat

Discussion in 'Radio Circuits, Repair & Performance' started by KM4YTW, May 7, 2019.

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  1. KM4YTW

    KM4YTW Ham Member QRZ Page

    My yaesu ft 101e started getting hot between the driver tube and finals. I have chaged the coupling cap between the driver and final with a 1.5kv silver dipped. The metal frame gets hot between the driver and final. I know this area is a hot area anyway. But my God what is getting so hot to heat the matal frame . R37 the 5watt 18k is hot but could that be getting that hot? And should it be getting that hot?
  2. N8YX

    N8YX Ham Member QRZ Page

    Does it get hot when idling, or only when transmitting?
  3. KM4YTW

    KM4YTW Ham Member QRZ Page

    Only when xmit. Something is heating really good. The finals seem normal temp. Hot but not real hot
  4. N8YX

    N8YX Ham Member QRZ Page

    Start by verifying all driver and PA circuit DC resistances (with unit unplugged from the mains) and if nothing is amiss, look at the various DC voltages...driver plate and PA screen being two I'd immediately want to verify.

    Out of curiosity, why was the driver plate blocking capacitor changed?
  5. AA5CT

    AA5CT Ham Member QRZ Page

    Is your fan running - do you HAVE a fan? One of the factory cast-metal fans on the rear of the radio?
  6. KM4YTW

    KM4YTW Ham Member QRZ Page

    Ill check the resistance on all that stuff in the final section. Yes i have a fan on it, i serviced it a little whole ago. New grease. I changed the coupling cap cause this is the 3rd one ive owned and they have shorted after a couple hours of use. So i just go ahead and change them.
  7. N8YX

    N8YX Ham Member QRZ Page

    Did the radio operate correctly (minimal heating) with the old part in it?

    Do you have a way to measure ESR of the new part? I'm wondering if this one is slightly leaky...
  8. KM4YTW

    KM4YTW Ham Member QRZ Page

    Unfortunately i have nothing to measure it. There cheap enough ill change it out again.
  9. G3YRO

    G3YRO Ham Member QRZ Page

    I'm presuming you mean the screening metal plate on the UNDERSIDE of the chassis?

    You need to discover what component is getting hot that is near it . . .

    If it's a resistor, then it will probably be something downstream of the resistor that is causing it to overheat.

    By the way, if the Driver to PA coupling capacitor leaks then you will know straight away as the PA Standing Current will go sky high!

    I've personally never known these fail here in Britain . . . but I suspect they may have failed in the USA due to excessive heat generated by people trying to run high power on AM (on 27MHz). You should also bear in mind that there is also an extra coupling cap switched in on the lower bands.

    Roger G3YRO
  10. KM4YTW

    KM4YTW Ham Member QRZ Page

    R 37 is getting really hot. I don't really understand that , it go's straight to ground. That's the only thing getting hot.

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