FT-101E Intermittent Audio level/S-Meter level

Discussion in '"Boat Anchor" & Classic Equipment' started by KB3GWQ, Jun 26, 2018.

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  1. G3YRO

    G3YRO Ham Member QRZ Page

    No, the best position will vary a lot from rig to rig . . . (that's why you have the adjustment, to correct it for YOUR particular rig)

    No rig (of any kind) should drift once it has reached a stable temperature . . . but the whole point of good Temperature Compensation is to stop it drifting REGARDLESS of the temperature change.

    Once you have it set for optimum, the rig shouldn't drift at all from cold switch on to fully warmed up after transmitting for an hour or more. (mine doesn't!)

    And no, I wouldn't go changing any of the capacitors. The only capacitor that I hear has SOMETIMES failed in the very early FT101 Mk1 was the Driver to PA coupling capacitor (this was later changed to a higher voltage rated cap).

    I've personally never come across ANY capacitors failing in the FT101 . . . not even the electrolytics!

    Roger G3YRO
  2. KB3GWQ

    KB3GWQ Ham Member QRZ Page

    OK. Well for kicks I'll be a little more aggressive on how far I turn it and make some notes see if there's a difference. It would be nice to get it so I can just start using it right away after being on for a minute. Well, I do now and for quick exchanges that's fine but really needs about 30 minutes to stabilize. I'll give it a try again tonight and let you know how I make out. I got plenty of time.

    I'll leave the caps alone in the VFO cage. I've replaced all the electrolytics back in August on the modules and the ones I could easily see by the HV cage. I left the two large filtering caps alone as I don't have any hum and my audio reports are good. If those were bad, they would've been a problem by now. They also look like they're very unfun to swap out.
  3. KB3GWQ

    KB3GWQ Ham Member QRZ Page

    What is your exact procedure here. I just spent another 2 hours on this. I don't even pay attention to how much it drifts when cooling it down if I just let it continue to cool down the cage... Here is what I do...

    Set it at 1000hz on the calibrator. Low heat with gun about 8-10 inches away heat it up for exactly 10 seconds (or close enough while counting 1-one-thousand, 2-one-thousand, etc.). Note how much it drifts up. Set cool and only cool it down until it reaches 1000hz again. Turn the cap and try again. I found a point where one extreme or the other would make it drift way too much and started narrowing it more and more basically the best I can get it now is about 200hz drifting up. When it got to this point I noticed bumping it just basically enough to make it drift about 5hz in the tone was enough to change it pretty wildly. So it's almost impossible (for me) to get it more precise than that. You're talking that's basically putting pressure on the screw is enough to make it do that it's very difficult to get it tighter. You also have to be very careful to be consistent on how far the gun is held and how long you do it or this will veer the results. If you over-cool it too much then you must wait until it goes back to 1000hz or the results are skewed again as well.

    So basically, how are you doing this? How far are away are you holding the gun? How long are you doing it? Are you just cooling it down enough to get back where you started and making sure it's relatively stable when back at that point? When you are as close as I am how much are you turning it?
  4. G3YRO

    G3YRO Ham Member QRZ Page

    Firstly, it doesn't matter at all how much the VFO moves in frequency when you turn the Compensation trimmer. In theory, the total capacitance across the tuned circuit should stay the same, as it's a split-stator variable, with equal pos and neg caps to ground from each end.

    But inevitable tolerances will mean that in practice the net capacitance will vary by a few pF, so the VFO frequency will move slightly when you turn it. So just turn it the amount you choose, then re-tune the Calibrator in BEFORE you start applying heat.

    I'm a bit worried if you're using a Heat Gun, as really that is way too hot! I only ever used a Hairdryer for this, as the heat is far more gentle - you need to heat it up gradually for a couple of minutes, not a few seconds from a heat gun! (or else you may be "shocking" certain components, rather than a natural warming up)

    Also . . . if having moved the Trimmer when you heat it up it Drifts MORE, you need to turn the Trimmer the opposite way! And for example, if it goes HIGH when you heat it up, you should be able to set the Trimmer so it goes LOW. You then gradually find the position where it goes neither High or Low.


    Roger G3YRO
  5. KB3GWQ

    KB3GWQ Ham Member QRZ Page

    I'm not literally using a heat gun... I keep calling it that from when I used to work in a garage. But, no, it's the XYL's hair dryer!

    So, you are holding the blowdryer for literally a minute or two about what -- 8-10 inches away? I noticed holding it longer than 20-30 seconds seems to be mostly useless. But so far, just experimenting with ridiculous points on the capacitor I have never found a setting where actually heating it up would LOWER the calibrator tone/frequency.

    I'm still confused on the cool down process. Are you just cooling it down until it stops drifting? If you over-cool it I noticed it can go fairly low then take a minute (maybe more) to drift back up about 100-400hz (depends) and stabilize. This also makes it difficult.
  6. KB3GWQ

    KB3GWQ Ham Member QRZ Page

    Also, you're saying this trimmer shouldn't vary the VFO frequency much. Are we looking at the same trimmer here? If I'm looking at the top of the radio and the front panel is facing me TC-2 is the trimmer on the RIGHT? It corresponds to a split stator air cap in the VFO compartment. Just to make a point here... if I turn that thing a lot I can start out at say 7.050 (on my dial) and can actually make it end up on the dial closer to 7.060-7.065 range. Small turns in this trimmer makes it drift about 100-200hz or so in whichever direction. There are certain points you reach where it will go real high like 7.060 then the next turn will make it end up somewhere around 7.048.
  7. G3YRO

    G3YRO Ham Member QRZ Page

    OK about the hairdyer.

    The technique is to try and heat up the WHOLE of the VFO compartment, not just particular components. So use it further away, but for longer.

    And yes, cooling down is only really to get it back to the frequency it started on . . . but again, it's important to cool the whole VFO, not just particular components.

    I can't remember exactly where the Temp trimmer is . . . but if you look you should clearly be able to see the fixed vanes split in two halves . . . and with 2 differnt types of capacitor hanging from each side to chassis. (it's very different from a "normal" variable capacitor)

    By the way . . . once you have finally found the BEST position for this trimmer, if the VFO has moved from it's original frequency very far, it's a good idea to bring it back on frequency by adjusting the other Trimmer (or else dial linearity may be off a bit). But don't keep doing this - only when you have finished!

    Roger G3YRO
    Last edited: Jul 13, 2018
  8. KB3GWQ

    KB3GWQ Ham Member QRZ Page

    Well the book shows this... Capture.PNG

    So, then it appears TC2 is the one you are talking about right? If yes, that's the one I've been experimenting with but I have just been unable to find a setting where actually heating it up LOWERS the calibrator tone. Is it hard to find, will it be in a small window where it can be found?

    It appears like I am doing it right from what you are describing. But, should I just be heating it up briefly and if it drifts HIGHER at all just stop, cool it down to the tone of choice then turn it more and more (and readjust the VFO if needed if it drifts out of the filter) until I find a point where it actually goes LOWER when heated?
  9. G3YRO

    G3YRO Ham Member QRZ Page

    Yes to your last question.

    Look at the Trimmer - you see the two halves of the split fixed stator?

    Move the variable vanes so they ONLY cover one side . . . that will be full compensation one way. Then try moving it so it only covers the other side . . . that will be full compensation the other way.

    In one of those positions, you should be able to get it to drift the opposite way.

    Do you get it?

    Roger G3YRO
  10. KB3GWQ

    KB3GWQ Ham Member QRZ Page

    Yes, but this doesn't work. I am doing it right now as we speak and so I moved it so it covers one full side (you mean so the "half-moons" are aligned all the same on one side or the other right?) and no matter what every time I put some heat in that compartment it just drifts up.

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