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Yaesu FT-101E no transmit, no i.c.

Discussion in 'Ham Equipment' started by Champo, Jul 18, 2021.

  1. Champo

    Champo Member

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    Unfortunately there's no one near me that I'm familiar with that has access to a tester. I picked up a weak but functional set of PA tubes that arrived today. Figured it would be a good idea to have a cheap set for testing if nothing else. A known quantity as opposed to an unknown one. I don't have a spare driver tube though so it isn't all daisy's. The tubes in the radio are original...well Toshiba's anyways. The weak set I have are US made. I read there is a cap replacement necessary for neutralization but I figured, even without that, it'll still give me an understanding of where the problem lies while only potentially damaging cheap tubes. I'll run that test here in a few. Thank you for the pointers.

     

  2. nomadradio

    nomadradio Analog Retentive

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    In a case like this, a working part becomes a troubleshooting tool. Good luck!

    Advice to change the mica cap dangling from the neutralizing-adjust trimcap is mostly bad. More important to have two final tubes that came from the same assembly line. The tubes have internal capacitance that determines the setting of the neutralizing cap. If one final tube has twice the internal capacitance of the other one, you'll never get it to set properly. So long as both tubes were constructed on the same assembly line, the internal structures that determine that capacitance should also be the same. And if one tube came from Holland, and the other one was made in Pennsylvania, there's a good chance that the final stage just won't neutralize no matter where the adjustment is set. I'm convinced this is the dominant reason for all of the "I can't get it to neutralize" gripes over the years.

    73
     
    #17 nomadradio, Jul 20, 2021
    Last edited: Jul 20, 2021
    Champo likes this.
  3. Champo

    Champo Member

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    Well that significantly complicates things. It seems like finding a matched set is like catching two rainbow trout with the exact same pattern. I'll probably have better luck catching a leprechaun riding a unicorn than I will finding a matched set lol! So, that aside, is there a solution once all the golden eggs are gobbled up?

    On the other note, there was no voltage present in receiveor during transmit. Adjusting the bias knob didn't change anything. The relay is looking like a strong candidate at this point. This was done with the tubes out (all 3). If they need to be in for the test please let me know.

    Also....ignore my sarcasm lol
     
  4. BJ radionut

    BJ radionut Supporting Member and 6m addict

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  5. Champo

    Champo Member

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    Well I discovered that functional tubes need to be installed in order to get an i.c. value on the meter. The second thing I discovered is the PA tubes in mine were dead. The radio is currently operating. The steps I went through are as follows:

    1. Installed new relay and tested without all three tubes - no i.c. value
    2. Installed new PA tubes and old driver tube with new relay - FUNCTIONAL RADIO
    3. Installed old PA tubes with new relay - no i.c. value

    I'm not sure if the new relay played a role in all of this i.e. multiple problems or not but I did not reinstall the old relay with the new tubes since I do not want to put the new tubes in potential jeopardy. I want to thank everyone for their help and advice through this. I also have one quick question on where the i.c. value should be on the meter after tuning. Should it be in the white, the green or is it irrelevant? Again thank you everyone for your help!
     
    AudioShockwav likes this.
  6. nomadradio

    nomadradio Analog Retentive

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    It's possible that the flat tubes were previously used in a FT101 that did not have sufficient negative grid-bias voltage to shut them off completely in receive mode. The user may or may not notice that the back-right corner runs kinda warm or even hot while receiving, or even wonder why.

    Enough hours of receive time with the tubes pulling current will flatten them. Don't have to key it once to create this failure.

    We got in the habit of changing one half-Watt resistor on the PB 1314 voltage regulator/filter board. The plug-in board bolted to the side of the final compartment.

    R17 gets changed from 4.7k to 10k half-Watt. Turns out the bias pot also causes the shutdown bias in receive mode to change up and down. Changing R17 will boost the shutoff voltage, usually enough to cut off the final tubes completely. Doesn't change anything in transmit. Transmit mode shorts across this resistor through the relay.

    Adopted the policy of changing that resistor on every 101 we saw, just as cheap insurance.

    73
     
    Champo likes this.
  7. Champo

    Champo Member

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    I appreciate the advice. I think those tubes are original to this radio (only one owner - besides me) so I'll need to get on that. I'll need to track down a 10k half watt. I only have 2 watters at the moment (restoring a tube radio). So, I'll swap that mica in the plastic sheeth and R17. If there are any other preventative changes you can think of please let me know. Thank you for all the knowledge Nomad. I am forever grateful. Also, I think you said pass on the neutralizing cap swap for American tubes? That's what are in there now (Toshiba's were the flat ones) with the factory cap and I'm getting the 70 watts the seller promised.
     
  8. Champo

    Champo Member

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    Well that was short lived. Now, after running through the receive tuning I'm having an issue with loading. When you adjust the loading knob you no longer hit a peak and then dip. Now it increases until the knob bottoms out at 10 with no dip. Output increase is minimal during loading. Output has been cut by more than half. It went from about 70 watts out to about 30. Are the tubes dying on me or is there something else at play? Thanks.
     
  9. KneeBiter

    KneeBiter Well-Known Member

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    In the later owners manual there was an update to the tuning. Tune all 3 for peak out in tune unkeying often. No longer than 10 sec at a time. No need to dip plate. But the preseltor should peak at tx out same as the receiver peak. If they differ an alignment is needed. Not hard to do at all. The factory service manual gives step by step and it's not hard to do. Not following what you are describing. Maybe explain step by step what you mean.
     
  10. Champo

    Champo Member

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    During the PO tune up process it has you key with the carrier at 4 and then adjust the preselect for max output. Then adjust the loading for max output. Then adjust the plate for max output. Then repeat with carrier at 6, 8 and finally 10. Yesterday it would adjust preselect for max, then the loading for max which kept it around 3-4 level before the dip and then pull it back to peak. Rinse, repeat with the carrier increase. Today though it tuned up just fine earlier in the day and then I powered her off and went about my business. Later I came back and ran through the tuning sequence but once I got to the loading phase, rather then peaking and then a dip and then bringing it back to its max I barely got any increase and that increase happened from around 3-4 all the way to 10. Long story short, it isn't doing what it was doing before. As a result output has decreased to a 3rd of what it was.
     
  11. Champo

    Champo Member

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    I don't fully understand the relationship between the driver and PA tubes so here is a question. While the PA tubes are new used, the driver is original. Would a weak driver cause the symptoms I'm seeing?
     
  12. KneeBiter

    KneeBiter Well-Known Member

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    What brand tubes did you put in? Sylvania?? I have had over 50 101s and honestly never had one with a bad driver tube. But I remember experimenting with different tubes in one and Sylvania tubes made it load all the way at 10. GE tubes worked good with no mods. Japan NEC, Raytheon, Toshiba and Korean Realistic tubes all worked perfect.
     
    #27 KneeBiter, Jul 22, 2021
    Last edited: Jul 22, 2021
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  13. Champo

    Champo Member

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    One Raytheon, one RCA. Here is the Ebay description:

    "This auction is for a pair of 6JS6C ham radio amplifier tubes..One tube is Raytheon & the other appears to be RCA..

    I tested these tubes in a Yaesu FT-101E..The output showed around 85W on the lower bands 80,40 & 20 & roughly 70-75W on the upper bands..The amount of output you get may depend on the condition of your rig, so there might be some variation..

    The writing is in fair shape on the Raytheon tube, but barely readable on the supposed RCA tube..The only thing you can really see on the supposed RCA tube is the tube #..

    I do not notice any heat discoloration on the glass..I have the boxes for the tubes..

    Hopefully someone can get some good use from these tubes..

    I am selling them as "TESTED, IN WORKING CONDITION" & "AS IS", no returns.."

    Sold by WA5UTK

    The output yesterday was more or less as promised.
     
  14. KneeBiter

    KneeBiter Well-Known Member

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    Try swapping the position of the tubes with each other and see if you get a change
     
  15. Champo

    Champo Member

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    Lol we're on the same brain wave. Yeah I tried that before my original post. With no change unfortunately. I also opened her up to make sure that a cap or something didn't let loose under the final section and everything looks normal. That's what got me thinking about the driver tube but that was me grasping at straws.
     

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