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

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

ad: L-HROutlet
ad: l-rl
ad: MessiPaoloni-1
ad: Left-2
ad: L-MFJ
ad: Subscribe
ad: K5AB-Elect-1
  1. HAMHOCK75

    HAMHOCK75 QRZ Member

    If it were me, I would continue to repeat your test over the next few days to see it the results are reproducible. One other note I might add. My first job out of college was to help design a replacement product for one that had a very high failure rate. Our marketing department complained that it was guaranteed to fail within the warranty period. Studies showed that one of the main reasons for the high failure rate was the plug in boards even though both boards and connectors used gold plated contacts. Contamination caused the failures. Since the VFO gets its +6VDC and the Clarifier input mostly from PB1314, I suggest you pull it and use a pencil eraser to scrub its contacts as a precaution.

    Those results are getting very close to mine.
     
  2. G3YRO

    G3YRO Ham Member QRZ Page

    Yes, although they generaIly don't give any problems, I've always recommended cleaning all the board edge connectors every 5/6 years . . . simply unplugging and plugging in again is often all you need to do.

    The only thing I would say about you noticing less drift now Frank, is that if there is virtually no Temperature change, there should be no Drift anyway. If your room temperature isn't changing, and you only have the rig on Receive, there's nothing really to change its temperature.

    What you WANT to happen is no Drift when there IS a temperature change . . . either because you put the heating on in a cold shack . . . or just because you are generating heat from the Valves by transmitting.

    Roger G3YRO
     
  3. KB3GWQ

    KB3GWQ Ham Member QRZ Page

    The board edge connectors were cleaned back in August, and properly. So not sure what to say about that. Regards to how I did it... I basically would take a microfibre cloth and spritz some DeOxit Red 5% on it and wipe until the cloth stopped coming up black. Then I would dry off the DeOxit with a clean part of the cloth. Then take DeOxit Gold Protectant and spray that on anothe clean and dry part of the cloth and rub it over the contacts and wait until it visible evaporated and put the module back in. I've heard of the pencil eraser "hack" but haven't had to resort to that method yet.

    But, yes, that thing has still been running and it's around 1100hz. So the drift seems to be within spec now. I'm going to use the radio tonight OTA, but tomorrow morning I'll give it a try again and let you know. Not really sure what happened to mostly "fix" it. And if it is this tight it might just be best to leave it alone if it continues to work this well. Unless Roger can give me very exact, detailed instructions on the entire process (including how long do I heat it up? how far away do I hold the blow dyer? how long do i wait to take a measurement? do I cool it down manually? how? etc).
     
  4. KA9JLM

    KA9JLM Ham Member QRZ Page

    If it did not mater they could have saved a lot of the extra parts.

    I do it right the first time. And have the tools to do it.

    Not sure why you think the manual is wrong. Do what you like.

    You should not teach others to do it wrong because you do, And think it is OK.

    upload_2018-7-16_19-20-44.png

    Can you spot the error in the schematic above ?

    73
     
    Last edited: Jul 17, 2018
  5. HAMHOCK75

    HAMHOCK75 QRZ Member

    Not sure if you are referring to the -100 VDC on pin 5 but for some reason Yaesu never corrected that error from the very first FT101's. It is obviously -160 VDC because it is derived from the same winding ( with diode reversed ) as the +160 VDC on pin 6.

    I think I know the reason for the exact value of the +6 VDC now too ( thanks to this thread ). Do you notice the three hand picked ( * valued ) capacitors in the schematic of the VFO posted by KB3GWQ? If I were putting this VFO into production, I would insist that the +6 VDC be very precisely controlled so that those capacitors could be hand picked. The reason is that any change in the +6VDC to the oscillator transistor will change its operating point including the capacitances between the drain, gate, and source. Such a precision made part would require precise control over the stray capacitances as well which means the voltage that gives rise to them. Making it an adjustable voltage in the unit is to reproduce the precise conditions under which the VFO and its selected parts were originally set up.
     
  6. KB3GWQ

    KB3GWQ Ham Member QRZ Page

    I don't know if the 6VDC is that critical. Have you measured yours? How about Roger?

    Also, I went to use the rig for an hour and a half practically non-stop in an hour long CW QSO @ 125W and the whole time it drifted less than 50hz. I purposely started at 7.050 with calibrator tone at 800hz so it would be easy to see the drift.
     
  7. HAMHOCK75

    HAMHOCK75 QRZ Member

    As I mentioned earlier, I restore rigs so if the factory set it to exactly 6 volts, I set it to 6 volts using a Fluke 87 digital multi-meter.

    https://www.fluke.com/en-us/product/electrical-testing/digital-multimeters/fluke-87v

    I don't think engineers in general expect end users to understand why they do certain things. It's important that they know should problems arise. For me, it is part of the fun of the hobby to discover those reasons. I am pretty impressed with the effort Yaesu expended on this rig.
     
  8. KB3GWQ

    KB3GWQ Ham Member QRZ Page

    So you think being as dead-on to 6 volts and readjusting VR4 and Offsets accordingly would stabilize it more?
     
  9. HAMHOCK75

    HAMHOCK75 QRZ Member

    A little about engineering. In first year, we were taught about deviations, particularly "standard deviation". Below is a pictorial representation of "sigma" which is the symbol for a standard deviation. You can see +/- 1 sigma or one standard deviation represents 68.2% of the area under the curve.

    [​IMG]
    Now supposing you are Mr. Yaesu. Your project manager for the FT101 VFO has just informed you that in the first pilot run of VFO's that +/- 1 standard deviation ( 68.2 % ) of VFO's meet spec. You as Mr. Yaesu say that is not acceptable. Your project manager goes back to the drawing board then informs you that by holding the +6 VDC to the VFO at almost exactly +6 VDC, you can achieve +/- 2 sigma or 95% of VFO's will meet spec. Again, you say that is not acceptable. Your project manager returns to the drawing board then informs you that by hand selecting three capacitors in the VFO you can achieve +/- 3 sigma or 99.7% of VFO's will meet spec. You agree to that.

    In the above description you know that 68.2% of VFO's do not need an accurate +6 VDC to meet spec. You also know that 95% of VFO's do not need three hand selected capacitors. You also know that 0.3% will not meet spec even if you do all the above. What you don't know is if a particular VFO like the one you have belongs in the +/- 1 standard deviation, +/- 2 or +/- 3 standard deviation categories.

    In other words, all this work is to ensure that statistically a high % of VFO's meet spec. but it says nothing about whether any one VFO needs any of this work or not.

    It's kind of regrettable but it is the painstaking attention to detail that made Yaesu a household name and marked the beginning of the end for the likes of Drake, Heath, Swan, Cubic, Atlas, etc.

    Why don't you become an engineer?
     
  10. G3YRO

    G3YRO Ham Member QRZ Page

    When you design any piece of equipment, you normally specify what adjustable things should be set at - like in this case setting the Stabilised Osc rail at 6.0 V.

    Similarly, the precise frequencies for the USB and LSB carrier crystals will be specified.

    However . . . in practice, either things really aren't that critical, or else there are things you want to set to your personal taste or operational preference.
    You will find that the precise voltage the 6V rail is set at makes NO difference to the amount of drift.

    I'm sure pedantic people will set it at exactly 6.00V, that's up to them. But bear in mind that when these rigs were first produce (in 1970) 99% of people just had Analogue meters . . . so even if they wanted to set it at 6.0V, it was probably somewhere between 5.5 and 6.5V. Which is fine . . . because it doesn't matter!

    When I worked for Yaesu I personally checked hundreds of new and secondhand FT101s before sending them out to customers . . . every one had to have 100% correct performance. Sure, the vast majority from the factory WERE . . . but the odd one had slipped through the net, and needed something adjusting.

    This included checking VFO drift, VFO linearity, Tx/Rx frequency, Carrier Crystals, Carrier Balance, equal drive and sensitivity on all bands, as well as alignment of various stages, neutralisation, S Meter calibration, Noise Blanker, etc etc.

    Don't you think that working on so many of these rigs (and on old ones ever since) that I know what does and doesn't matter?!

    Anyway . . . I don't expect anyone to follow my advice . . . it's simply out there for anyone who chooses to.

    (now I understand why so many people send me private messages for advice, rather than post on the Forum!)

    Roger G3YRO
     
    Last edited: Jul 17, 2018

Share This Page