DX 60 question

Discussion in '"Boat Anchor" & Classic Equipment' started by KB1FGC, Oct 25, 2021.

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  1. W5RKL

    W5RKL Ham Member QRZ Page

    You should also replace that 2 blade power cord with a 3 wire grounded power cord. Those AC power bypass capacitors are not needed.

    Here's a picture of a DX-60B I picked up on eBay where the builder/repair person appeared to not have the necessary skills to build a
    kit and/or to properly repair a piece of ham gear.

    The point-to-point wiring is too long, component leads are too long, and the overall wiring layout around the speech amplifier V5 and the
    Modulator V4 could easily create feedback problems (Motorboating) in the transmit audio. Wiring to the crystal sockets and the crystal
    VFO switch is incomplete and the wiring around the oscillator and driver stages is a mess including the wiring around the final amplifier
    6146 tube socket. I've seen this type of "messy" kit building and repairs made to a lot of Heathkit ham gear indicating no forethought was given
    to how the radio is built/repaired.


    [​IMG]


    The same DX-60B was stripped down to a 95% bare chassis and completely rebuilt with new components, a new homemade wiring harness
    to replace the original hacked wiring harness, and the wiring layout was rewired with new wiring and component leads cut to fit the connections.
    The 2 blade power cord was replaced with a 3 wire grounded power cord and a fuse holder with fuse is mounted on the rear apron in place of
    the 3 amp circuit breaker. All it takes is to follow simple instructions, pay attention to the foldout pages showing how to arrange the components
    and wiring, cut the component leads to the correct length so they properly fit, use some "common sense", and if necessary ask for help.


    [​IMG]




    73
    Mike W5RKL
     
    KP4SX likes this.
  2. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    The bypass caps DO help reduce RFI. That is their purpose. There is no reason to remove them.

    Modern amplifiers and radios have them in their design. Look at the schematics for Ameritrons for example. Computers have bypass caps built into their Euro-plug jacks.

    Of course modern XY safety caps should be used.
     
    Last edited: Oct 30, 2021
    WA1GXC likes this.
  3. KB1FGC

    KB1FGC Ham Member QRZ Page

    Very nice restore:).I resoldered some of the wires so they aren't over V5,V4.Some of them I was able to bend so that they were clear of the tube sockets..While I was in there,I lifted one of the wires from the secondary to see if I was having the same problem as before.It was mixed results.Overall it cleared up the problem with the light going on in the dim bulb testor.BUT for a second I heard the humming sound that was coming from the relay but it stopped and the relay worked fine.I switched it multiple times and the relay was good.The output of the second was 255vac so that seemed correct.I would think the transformer is good.I again retraced wires and they look good.Maybe the resistor that I installed in the recifier is causing the relay to lag and that is the sound I hear,I don't know.The other issue I don't think is related to the function switch mod.That is some kind of runaway current lighting the light bulb up but something I can't figure out.
    I installed a 3 wire power cord.
    If I can figure what the voltages are for varies areas in the circuit then I can at least rule some things out.My best bet is,getting help and assuming what maybe the problem and them calulating the correct,voltages.I think that is my only chance.My problem is, figuring what I learned in school and applying that in real circuits. I was never able to make that leap.Aside from QRZ and a ham friend ,my best friend has been,the continuity test.That has help me quite a bit.
    73
     
  4. W5RKL

    W5RKL Ham Member QRZ Page


    I've never had RFI problems coming in through the AC power after removing the AC main bypass capacitors. None of my Dx-60s, I have all 3 different
    models of the DX-60s, none of my HW-16s and none of my AC power supplies have those AC main bypass capacitors. I have not experienced any
    abnormal RFI problems. My 80 and 40 meters inverted Vee antennas are about 20 feet from the shack and I've not had any reports of RF on the
    audio in AM or sideband with radios that no longer have those AC main bypass capacitors.

    Yes, computer power supplies have a lot of bypassing not just on the AC main but throughout the power supply AND the motherboard.

    I remove them and as a result, have never experienced any RFI in the AC Main issues in radios that no longer have those AC main bypass
    capacitors. I have experienced arcing noise. My SB-303 has the noise blanker installed from a Kenwood TS-520. Turn the noise blanker ON
    and the arcing noise disappears. Turn the blanker OFF and disconnect the antenna the noise disappears indicating the noise is not coming
    through the AC main but rather being picked up by the antenna.

    The bypass capacitors are to prevent noise from entering the receiver via the AC main by bypassing it to the ground. I don't have that problem.
    I've not experienced any RFI issues through the AC main with equipment that no longer has those AC main bypass capacitors installed. Again, my
    antenna is 20 feet from the shack and I have no RFI issues even with the computer when running 100 watts or 400 watts (Ameritron AL-811
    three 811A tube amp). I can turn one of my HW-16s on that doesn't have those AC main bypass capacitors and the receiver is dead quiet. Connect the
    antenna and I hear atmospheric and surrounding area noise being picked up by the antenna, not fed through the AC main.

    Bill, whether you and/or Richard use those AC main bypass capacitors or not is entirely up to either of you. From my experience and my shack setup,
    I've not had any noise or RFI problems with radios that no longer have AC Main bypass capacitors installed.

    73
    Mike W5RKL
     
  5. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    Madman Muntz is reputed to have randomly removed components from his televisions to force his engineers to prove they were needed.

    You too can remove components you deem "unnecessary".

    In this era of ever present and rising Electro-fog, good engineering practice, particularly good RFI engineering is more important than ever. b.
     
    WA1GXC and KP4SX like this.
  6. WA1GXC

    WA1GXC Ham Member QRZ Page

    Every time your neighbor (or you) starts his washing machine, calls for heat from the oil-fired furnace or air-mover for gas heat, the inductive motor instantaneously causes a voltage spike superimposed

    on your AC line. It was quite a while ago, but I remember Dave W7UUU here showing a histogram of voltage spikes on his neighborhood's commercial AC line power which he believed to be very 'dirty'. Individual engineers

    are not always right, but it is food-for-thought why standard industry practice still compels AC line-bypassing in good-quality communications equipment.

    Standard X-Y rated bypass caps are typically rated well in excess of 1 kV. That's not about RFI.

    "A stitch in time saves nine", says Benjamin Franklin.

    73
     
    Last edited: Oct 31, 2021
    KA0HCP likes this.
  7. K1APJ

    K1APJ Premium Subscriber QRZ Page

    The equipment under discussion was built in the 1960s when TVI was a big issue, it is a non-issue today. Take a look inside a Viking Valiant, for example, it is swimming in chokes and caps designed to keep the RF in the cabinet. You can be sure that none of that stuff would have been included if it wasn't necessary. however, its value in reducing TVI in 2021 is moot.

    There are various RFI/EMI standards today that require actual measurement of radiated and conducted RF levels. Although the effect of the components may not be noticeable to you, they are required for conformance with various standards. Susceptibility to line transients is also a concern but I doubt that a DX-60 is going to have a problem with even the noisiest power line. And, the modern standards aren't binding on old equipment.

    I don't find anything objectionable about proper line bypass capacitors, but if you use them be sure to use correct ones and observe proper chassis grounding procedures as well.
     
    AC0OB and KA0HCP like this.
  8. N8VIL

    N8VIL Premium Subscriber QRZ Page

    I have been restomodding a DX-60B off and on over the last few months and still have a few more things to do. I added a separate HV relay and a PTT relay for AM. This allows the HV relay to function separately from the PTT relay and allows normal function switch operation while saving the contacts. The PTT relay will override the function switch position when PTT activated and put the transmitter into AM mode. This keeps the CW and AM positions from being shorted together if mic is keyed while the function switch is in CW mode. I also added a 4 pin microphone jack following the pinout as used in the Kenwood TS-830. Hopefully my MC-50 microphone will work well with it. I still have to replace some capacitors and resistors. My plan is to try AM on it and perform some audio improvements once I get a baseline on its operation. I also reworked the AC input to put the fuse first in line and removed the circuit breaker. Proper line bypass capacitors were installed along with a 3 wire power cord.
    Posting a few pictures and a schematic of my modifications. May give someone some ideas or may get me some criticism.
     

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    Last edited: Dec 20, 2021
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