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FT-901DE 220v back to 110v

Discussion in 'Radio Circuits, Repair & Performance' started by KE4CQ, Jul 10, 2019.

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  1. KE4CQ

    KE4CQ Premium Subscriber QRZ Page

    I acquired an FT-902DE from an original owner yesterday. Back in the day he rewired the rig from 110v input to 220v input. He had done this to get more drive for his Alpha 77SX. :DIt has been sitting on a shelf in his garage for 20 years....I need to know what to do in order to get it back to 110v. I tried searching but no luck. Is it simply changing the configuration on the power cord and/or moving a tap on the main transformer in the radio? Any help appreciated....

  2. G3YRO

    G3YRO Ham Member QRZ Page

    As with most Yaesu rigs, just remove the bottom panel and change the taps on the Mains Transformer, so that the two Primaries are in Parallel, rather than in Series..

    It's pretty obvious what to do . . . but if you need a diagram, it'slearly shown in the Manual.

    Roger G3YRO
  3. WR2E

    WR2E Ham Member QRZ Page

    Rewiring the AC input for 240 vs 120 won't get any more power output... at least in theory anyhow.

    I think he was telling you a "CB fish story".
  4. G3YRO

    G3YRO Ham Member QRZ Page

    I disagree . . .

    I imagine any rig without a regulated PSU would give slightly more power output when run on 220V, as it would draw half the current, so less voltage drop.

    Roger G3YRO
  5. WR2E

    WR2E Ham Member QRZ Page

    You're welcome to [disagree], have at it.

    What are you thinking? 2 maybe 3 watts?

    Still a "CB fish story" to me.
  6. KE4CQ

    KE4CQ Premium Subscriber QRZ Page no changes required at the a/c input plug....just the transformer tap?
  7. WR2E

    WR2E Ham Member QRZ Page

    If it's wired for 220 it SHOULD have a different plug than if it were wired for 120.

    Use the correct plug.
  8. KE4CQ

    KE4CQ Premium Subscriber QRZ Page

    Yes it currently has a 220 plug at the wall end. But, I am referring to the input to the radio end.

    And, correction on my is a 901DE not a 902DE. Sorry. But I believe it will be the same anyway.
  9. WR2E

    WR2E Ham Member QRZ Page

    Looking at the S/M, it doesn't appear so, but after rewiring the transformer connections and installing the correct plug, and before applying any AC power, double-triple check with an ohmmeter that the input is going where it is supposed to.

    It wouldn't hurt to take a good look at the S/M and see what's going where in the schematic.
  10. KE4CQ

    KE4CQ Premium Subscriber QRZ Page

    All went well with changing from 220 back to 110 on my FT-901DE. I also opened up the back of my 902 to make sure it matched what I had done.

    After making a few checks, I powered on the unit for the first time. It has been probably better than 15+ years since it was last turned on.
    After about 2 minutes, C1004 on the Rectifier A board exploded! This cap (22uf/250v) gets the 120v a/c supply from the transformer :eek: I always wanted to see the inside of an electrolytic cap - now was my chance! Ha!

    I replaced it with a cap that I had removed from one of my FT-101's when I recapped it along with a couple of 1 watt resistors that went up with the cap. Then another cap C1006 I think, started to get really warm. So I replaced it too. Now all seems fine.

    I have ordered some new caps and will recap all the rectifier boards.

    Man that glue that Yaesu used for all the electrolytics is a mess!

    Thanks for the help on the power swap.:)


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