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Heathkit HW 101 transmit trouble

Discussion in '"Boat Anchor" & Classic Equipment' started by WB9UBT, Mar 23, 2012.

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  1. WB9UBT

    WB9UBT Ham Member

    I have good power output on TUNE and CW but not on sidebands. I checked V1, replaced the four diodes in the balanced modulator circuit and checked the mode switch. Any ideas would be great!
     
  2. K9STH

    K9STH Ham Member

    You are talking into the microphone? You are activating the push to talk? Don't rely on the VOX! If so, then try a different microphone making sure it is high impedance.

    If the microphone is OK, then start looking from the microphone jack forward.

    Glen, K9STH
     
  3. KO6WB

    KO6WB Premium Subscriber

    The balanced modulator is placed into an unbalanced condition when you have an audio signal applied to it. The output of the balanced modulator is DSB and then you pass the DSB signal through the crystal filter and you now have SSB. So you don't have an audio signal being applied to the balanced modulator so there is nothing out.
    The manual for the HW-101 is available online at; http://gmcotton.com/Ham_Radio/MISC%20Manuals/Heathkkit/HW-101.pdf. It takes awhile for it to download so be hang in there.
    Hope this helps
    73
    Gary
     
  4. AF6LJ

    AF6LJ Ham Member

    It might be good to start with the basics.
    Check the microphone first.
    See if you have audio....

    With that out of the way;
    See if the VOX circuit works,
    If it does you know the first audio stage is working...

    Also I might add tube failures are rare.
     
  5. KB4MNG

    KB4MNG Ham Member

    I just went thru a hw 101 for a friend. Same problem. I went thru cleaned everything there was to clean, disassembled the relay and cleaned it. 100 watts on all bands!
     
  6. KB4MNG

    KB4MNG Ham Member

    Also retighten all grounds....
     
  7. AF6LJ

    AF6LJ Ham Member

    Always check the grounds.
    :)
     
  8. WB9UBT

    WB9UBT Ham Member

    PTT

    Yep, I am not using VOX, just the PTT.

    I am going to go back and check the mic tonight, might be looking a bit too deep.

     
  9. WB9UBT

    WB9UBT Ham Member

    I believe the relay is working because I am hearing it trip when I push the PTT on the mic.
     
  10. WB9UBT

    WB9UBT Ham Member

    I tried VOX and no luck. I'm going to double check the mic and get that out of the way.
     
  11. WB9UBT

    WB9UBT Ham Member

    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.
     
  12. KO6WB

    KO6WB Premium Subscriber

    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
     
  13. KE3WD

    KE3WD Ham Member

    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
     
  14. WB9UBT

    WB9UBT Ham Member

    I cleaned the relay with paper and contact cleaner and no luck.
     
  15. K9STH

    K9STH Ham Member

    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
     
  16. KE3WD

    KE3WD Ham Member

    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
     
  17. AF6LJ

    AF6LJ Ham Member

    It's always good to start with the basics.
    Glen's suggestion is very good and requires no test gear.
     
  18. WB9UBT

    WB9UBT Ham Member

    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.
     
  19. AF6LJ

    AF6LJ Ham Member

    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.
     
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