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Thread: Heathkit HW 101 transmit trouble

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  1. #11

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    What is strange is that right before it went out I was having a nice QSO. Suddenly my power output went away......keyed the mic and was able to carry on fine. A little while later the same thing happened. Finally later that day I turned on the rig and only PO in tune and CW.

  2. #12
    Join Date
    Feb 2004
    Location
    Bakersfield, CA
    Posts
    4,455

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    If your computer in nearby you could take the audio out from the sound card and using some type of attenuation you could apply a signal to the HW-101 microphone in. The audio level at the start would need to be turned down to zero. Slowly increase the sound level until you have a signal on the rig. You can use any audio file you want for this test. It would be best to have the rig on a dummy load especially if the file you use is music.
    The idea here is to get an audio signal into the rig. If this works then your microphone has a problem. You can use this same method to inject the audio anywhere along the microphone audio chain. Just make sure you use a blocking capacitor rated at the voltage the rig can deliver at it's highest voltage.
    Hope this helps
    73
    Gary

  3. #13

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    Quote Originally Posted by WB9UBT View Post
    What is strange is that right before it went out I was having a nice QSO. Suddenly my power output went away......keyed the mic and was able to carry on fine. A little while later the same thing happened. Finally later that day I turned on the rig and only PO in tune and CW.
    Earlier you mentioned that you "believe the relay is working because" you can hear it click.

    Well, the heard click tells us that the relay coil is being energized and the contacts are being moved, but says nothing about the condition of the relay contacts, which can be dirty or corroded and do exactly what you have been experiencing here, including and especially the intermittant operation.

    Clean the relay contacts properly with strip of paper between them, or replace the relay and try again.


    73

  4. #14

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    I cleaned the relay with paper and contact cleaner and no luck.

  5. #15

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    You can put a wire, paperclip, etc., into the audio side of the microphone connector and then touch it with your finger when the microphone gain control is maximum clockwise and the PTT activated. There should be an indication on the "plate" meter showing that there is audio present. If you listen on a separate receiver tuned to the transmit frequency of the HW-101 you should hear a "hum". There is no shock hazard from doing this. It is best not to be holding onto the unit when doing this test because the "hum" level could be reduced.

    Glen, K9STH

  6. #16

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    Quote Originally Posted by WB9UBT View Post
    I cleaned the relay with paper and contact cleaner and no luck.
    Such is the way of the troubleshooter.

    But I would not call it a "no luck" situation, matter of fact, luck hardly ever has anything real to do with it, consider that you have eliminated one of the possibilities on the short checklist, have also added one more potential prolem-solving clue as the troubleshoot progresses, and move on to the next most important item.

    Intermittant operation can sometimes be a tricky troublehoot, but the good news is that the operation is indeed intermittant. This means that the problem can often be pinpointed by performing some rather simple bench testing. For example, with the rig open and on the bench, connected to a dummy load if a transmit problem, I would try mechanical vibratory inputs at various places to see if I could pinpoint an area or a circuit where the fault was. A wooden or plastic "spudger" tool, used to poke, prod, even a light "pop" to a suspected area while observing operation, can often be used to narrow the focus down to a particular area.

    Don't overlook ground points, often done with screws to the chassis in these rigs, that need to be tightened, matter of fact, just going over the entire thing with the screwdriver and simply tightening all screws is always a good idea, as they do indeed become nonconductive over time.

    Solder joints should also be inspected, with the iron already warmed up, tinned and ready for use, suspect an joint that does not appear shiny and otherwise healthy, heating and adding a wee bit more of fresh electronics solder.

    Um, I don't remember this whole thread, but you did use a good spray such as deoxit on every control and switch already, no? If not, you should. Old switches, potentiometers, etc. with corroded or dry contacts can easily exhibit all sorts of problems such as you describe. Tube socket contacts can also show the same symptoms, good idea to pull each tube one at a time, light wipe of the pins with a layer of deoxit, and re-insert the tube in an effort to establish good continuity to all pins. Visual examination can be important here as well, with an eye towards finding a stretched out socket point.

    And when prodding around, be careful of electrical shock, and keep in mind that the prodding may only serve to be the first part of the troubleshoot, there may still be a need to locate or pinpoint a bad component once an area is located.

    73

  7. #17
    Join Date
    Aug 2008
    Location
    SanDiego, People's Republic of California FEMA District 9
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    35,602

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    It's always good to start with the basics.
    Glen's suggestion is very good and requires no test gear.
    "I would rather be free than rich."
    Dick Gregory

  8. #18

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    I'm still working on this.....I checked the DC voltages on V1 and according to the manual I'm supposed to have 50 VDC on pin 6 (plate). I'm getting 270VDC! Any ideas on what could cause this? I checked all of the resistance measurements on the speech amplifier circuit and they are fine. Could a bad capacitor cause this? These may be dumb questions but I am trying to learn how to do these repairs on my own.

  9. #19
    Join Date
    Aug 2008
    Location
    SanDiego, People's Republic of California FEMA District 9
    Posts
    35,602

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    Quote Originally Posted by WB9UBT View Post
    I'm still working on this.....I checked the DC voltages on V1 and according to the manual I'm supposed to have 50 VDC on pin 6 (plate). I'm getting 270VDC! Any ideas on what could cause this? I checked all of the resistance measurements on the speech amplifier circuit and they are fine. Could a bad capacitor cause this? These may be dumb questions but I am trying to learn how to do these repairs on my own.
    Heathkit lists voltages for both transmit and receive on the schematic.
    Make sure you;
    Have the radio controls set to the proper settings given.
    Make sure the voltage you are reading is for the correct condition, transmit receive.
    "I would rather be free than rich."
    Dick Gregory

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