FT-101E intermittent TX/RX relay problem

Discussion in '"Boat Anchor" & Classic Equipment' started by KB6MBW, Apr 23, 2020.

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  1. KB6MBW

    KB6MBW Ham Member QRZ Page

    Hoping someone can point me in the right direction with an intermittent TX/RX relay problem. My FT-101E TX/RX relay, RL2, does not disengage some times. RL1, by the VFO will disengage, but RL2, antenna, does not. A quick mic key tap or two seems to get it to disengage.
    After reviewing Ft-101 posts, I understand that RL2 does not fail very often. I will pull it and give it a good cleaning, as per previous post. Before I do, is there anything I should check before pulling the relay? I did clean RL1 three times. Seems to help a little.
    Rig works great when RL2 is working. Output is over 100 watt on all bands (do not use 160). Tunes up with no problems. Unit is in pristine condition. No signs of abuse.
    FT-101E History:
    Professionally upgraded with New Panasonic and Nichicon long life capacitors in 2016. Chassis, power supply section and AC line caps were replaced, as well as recapping the audio and receiver boards. Has its original 6JS6 valves. New Inrad #2011 6 KHz wide A.M. filter installed along with the mode switch professionally wired for the A.M. filter as outlined in the FT-101 service manual
    Thank you for your time
    Last edited: Apr 23, 2020
  2. KA9JLM

    KA9JLM Ham Member QRZ Page

    It sounds like you may have another problem if the relay does not release properly.

    Normally a dirty contact just don't make connection, But the relay should release when its coil voltage is removed.

    Good Luck. No mater what the problem is, You can repair it. :)
  3. G3YRO

    G3YRO Ham Member QRZ Page

    Are you sure the Antenna relay isn't disengaging? Or is it just that receive signals are weak?

    The latter could just be caused by dirty relay contacts . . . and clicking the relay over a couple of times will usually enable a dirty relay to make a better contact.

    Having said that, although I always recommend cleaning the contacts on the Main relay every few years, I have never bothered cleaning the Antenna relay on an FT101, as I have never known it give problems . . . but there's always a first time !

    If you're sure the relay is hanging, you may have a lowish resistance to chassis on the T:0 rail, which may just be enough to keep the Antenna relay on.

    Several things could be causing that - such as a leaky decoupling capacitor.

    Roger G3YRO
    Last edited: Apr 24, 2020
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  4. G3YRO

    G3YRO Ham Member QRZ Page

    The T:0 rail is provided by the Main relay contact C6 going to ground on Transmit . . .

    So if you follow the wires from that contact on the circuit diagram, you will see it goes to various boards, and there are several decoupling capacitors to ground - one of those may have gone leaky.

    Roger G3YRO
    W1TRY likes this.
  5. KB6MBW

    KB6MBW Ham Member QRZ Page

    Thanks Roger and Don for the fast replay,
    With mode set to Tune and Heater off, switching to MOX and back to PPT a few times I can hear both relays engaging and then disengaging. Then the next time I switch to MOX/PTT I only hear RL1 disengage. Switch MOX/PTT again and both relays disengage.
    After reading your post Roger I did not think the relay was the problem. It doesn’t look like any fun pulling it out.
    I was also looking into the T:O rail. And earlier post talked about the T:O rail and those decoupling capacitors.
    Tomorrow I’ll start with the T:O rail and the decoupling capacitors. Will take a day or so before I’ll be able to replay again.
    Thanks for all your help gentlemen.
    Stay safe and healthy
  6. G3YRO

    G3YRO Ham Member QRZ Page

    Removing the Main Relay is dead simple, just lift the lid and there it is . . . lever the retaining wire clip out the way with long-nosed pliers, and then it unplugs.

    Then just lever the plastic cover off, and clean the contacts by squeezing them together and dragging strips of card soaked in switch cleaner/lubricant between them til the black stops coming off.

    This should be done every 5/6 years to avoid any problems. (it's the only bit of regular maintenance the FT101 requires)

    Getting the Antenna Relay out is not much harder - it's in the PA compartment.

    What's great is that these Relays will last forever, as they are high-quality and the contacts can be cleaned . . . unlike the cheap sealed relays used in later rigs !

    Roger G3YRO
  7. HAMHOCK75

    HAMHOCK75 QRZ Member

    Last edited: Apr 24, 2020
  8. G3YRO

    G3YRO Ham Member QRZ Page

    Yes I've heard you mention that before, and this time had a skim through your thread on the other website . . .

    Personally, I have never known this happen on any other FT101 ! The very fact that the main relay switches the Antenna relay should mean that any spike from releasing the PTT should have finished BEFORE the antenna relay drops out (and I presume that's why it was designed that way)

    Out of interest, was your Main relay the original type? (because they're quite different from most relays)

    By the way, the most critical band to adjust the pot for the 2nd Tx mixer is on 160m . . . as the rig was never originally designed to cover 160m, this is where the strongest undesired mixer product can occur . . . but careful adjustment of the pot makes it quite acceptable.

    Roger G3YRO
    Last edited: Apr 25, 2020
  9. HAMHOCK75

    HAMHOCK75 QRZ Member

    I believe you when you say you have never seen this problem but I also believe people who send private emails like this,

    I brought that digital storage scope specifically to test this problem. The details and measurements are in the thread linked above. Normally the glitch would occur after RL1 returned the FT101 to receive but before RL2 changed position but due to randomness in the response times, that did not always happen. The easiest way to test if hot switching is occurring is to pull RL2 and look at the contacts. Mine where black and very pitted.

    During all the power glitch work I had two OEM RL1's. One came from eBay but towards the end of the power glitch work I did replace RL1 with a Potter-Brumfield relay described in the link below. That was the last of the significant problems with the FT101EE.


    I now own a pair of twins, the FLDX400 and FRDX400 which I prefer over the FT101EE. Do you know if the VFO's in the twins have the same variable temperature compensation split capacitor as the FT101 series? One reason I prefer the twins is the receiver covers 6 and 2M plus it has a full set of filters for 600 Hz, 2.4 kHz, an AM filter, and a wide FM filter.

    Also, even though the twins do not use plug-in boards, they are easier to work on simply because they are very roomy compared to the 101.
    Last edited: Apr 25, 2020
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  10. G3YRO

    G3YRO Ham Member QRZ Page

    No, I believe you had the problem . . . and clearly spent a LOT of time investigating the cause . . I have just never seen it or had any '101 owners report it before.
    Well they're mainly Valve rigs, so obviously are very different !

    I always liked the FR/FL400s . . . unlike many valve rigs they had a proper chassis mounting all the valves. (I hate rigs that mount valves on PCBs !) I also prefer the last versions, which used the same Jackson Ball Drive on the VFOs as they used on the FT101. The only disappointing thing is the Tx didn't cover 160m, so never would have interested me !

    I'm pretty sure that the original FT101 series was the ONLY Yaesu rig that had adjustable temperature compensation in the VFO. (I believe only one other manufacturer used this feature on one of their rigs, one of the American companies)

    Roger G3YRO

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