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FT101 later series low or no output on 80 and 40

Discussion in '"Boat Anchor" & Classic Equipment' started by ZL1TIU, May 13, 2018.

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  1. ZL1TIU

    ZL1TIU Ham Member QRZ Page

    hi, i have been working on restoring an old FT101. it's coming along well and despite tired output tubes I do get 100w out on 20 and a slow slide to about 80 watts on the higher bands. receive is good on all bands. after considerable alignment. However the first part of aligning for 80m requires peaking both T106 and T105. T106 peaks nicely and I get about 5 watts out but I can't get T105 to peak at all. I've had the board out and the slug appears ok and is easy to move through it's range but it has no effect on the output. The switch S1h looks ok as well. Has anyone any ideas? The switch should short out T105 on the hiher frequencies bur it doesn't seem to come back in to circuit. Continuity all looks good.
    Dave ZL1TIU
     
  2. HAMHOCK75

    HAMHOCK75 QRZ Member

    Not sure what you mean by S1h does not come back in to circuit. It should not be shorting T105 on 80M. An ohmmeter test should confirm whether it does or not.
    To resonate, it also requires S1g connect C9 and TC6 in parallel with T103 and T105. Did you check if S1g is doing that?
     
  3. ZL1TIU

    ZL1TIU Ham Member QRZ Page

    Thanks for the swift response. I wasn't very clear in my description. I could see that T105 is shorted out except for 80 and 40. That is working Ok. however you lead me in another direction. TC 6 looks damaged. There is piece missing from the roter. I'm following that lead. There seems to be a few differences from the circuit I have to this actual FT101 though all the differences appear to be factory made ones. There is a capacitor across T105 which is not shown in my circuit. Just measured TC6 out of circuit, the maximum capacitance it will make is 22pf. I see it should be 100pf. Now to track down a suitable replacement! Thanks for giving me steer in the right direction.
     
  4. ZL1TIU

    ZL1TIU Ham Member QRZ Page

    Further follow up, replaced the trimmer with a 80pf (a bit lower than the 100pf original). After a alignment 110w out on 80m. So all good. Thanks for your help.
     
  5. G3YRO

    G3YRO Ham Member QRZ Page

    Why did you touch T106 or T105 at all? This is never normally necessary, unless they have been replaced ! And T105 should not have a capacitor permanently across it, so remove it, and then re-adjust the Driver trimmers on 160, 80 and 40m..

    All you ever need to do is adjust the trimmers on each band. But as the Driver has no 10m trimmer, you should peak the Preselector on 10m Tx FIRST, and then adjust the trimmers on the Mixer and Rx Front End to correspond with that position.

    If any Trimmers don't peak properly (or peak at max or min capacity) then either you have a faulty trimmer, or else you need to change the fixed padder capacitor across it. These are often selected on test when the rig was built. You will also find resistors across some, to equalise the Drive level from Band to Band.

    This goes for ALL the trimmers . . . the Rx Front end . . . the Mixer . . and the Driver . . as well as the trimmers that resonate the the Crystal Mix oscillators on each band.

    With good PA and Driver valves you should be looking at 130 watts output on 160 - 15m, maybe 120w on 10m. But if your valves have lost emission a bit, and the power is a little lower, that's no big deal . . . it's still more than you get from a pair of 6146 PA valves!

    So what model do you have? If it says just FT101, then it's either a Mk1 or a Mk2. The Mk2 has LOTS of circuitry differences from a Mk1 . . . but the changes to the B and E versions from a Mk2 are pretty small.

    You can tell if you have a Mk2 as it will have 160m printed on the front panel Bandswitch. (It's quite easy to modify a Mk1 to cover 160m, but that will be in the Aux band position)

    Roger G3YRO
     
    Last edited: May 15, 2018
  6. ZL1TIU

    ZL1TIU Ham Member QRZ Page

    nnections on the So first the transceiver is a FT101 series 2 s/n 134351.I got it as a total basket case. It initially did not receive at all but after fixing some dodgy connections on the NB board it received badly on 40m but not much else. No Tx at all. Pretty obviously every single screw that could be turned, had been. Also some strange mods which I could find no reference to at all. The actual hardware is quite tidy. I decided that it was going to become a project. I removed all the mods and have been slowly working through a complete lineup. It now receives quite well on all bands. Tx is improving (obviously the tubes are weak) . I am now getting nothing on 160m, (suspect c131?0 110w on 80, 45w on 40, 75w on 20, 100w on 15 and it drops to 55w on 10. I would be happy if I could get about a little over 100w on 160, 80, 40, and 15 I don't mind it trailing off at 10m. I've replaced one trimmer so far, it had a piece broken off! I'll follow your advise on the cap across T105. It wasn't on any schematic I could find. Thanks for the help so far. One question on the trimmers for the drive from the crystals. Adjusting the trimmer adjusts the frequency as well as the drive level. There seems to be enough drive from all crystals but I adjusted them to be on frequency rather than peaking their drive level.
    thanks Dave ZL1TIU
     
  7. G3YRO

    G3YRO Ham Member QRZ Page

    Sounds like you've had a job on your hands Dave!

    The good thing is that the FT101 is one of the best engineered rigs ever made . . . it's really easy to work on, especially with all the plug-in boards. I bought my FT101E new when I worked for Yaesu, and it's never had a single fault, despite being my main rig for nearly 40 years. (recently bought a second one, as it was going really cheap)

    You should peak the Crystal trimmers for maximum drive on Tx . . . if the output is the same when the frequency aligns from band to band, then it's OK to try and achieve that.

    If the receiver is just as sensitive on 160m, yes I would suspect the grid trimmer.

    I'm sure you're aware, but the important thing with these rigs is always keep the full power Transmit (with carrier) to short 2-second bursts. When aligning circuits on Tx, keep turning the carrier level back down, so you only have about 100mA of PA Current.

    As long as you do that, the PAs will last a long time (much longer than 6146s in my experience).

    But do make sure the Fan is working properly - Most Mk2s had a computer style fan . . . but all the later rigs had a simple fan (as used in their Linear Amps) you can take apart and clean and lubricate if it's not spinning freely.

    You may find that your reduced power is due to the 12BY7A, rather than the PAs, so given that it's readily available I would replace the Driver. (you will have to re-align the RF circuits again)

    Roger G3YRO
     

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