Heathkit SB301

Discussion in '"Boat Anchor" & Classic Equipment' started by KB1FGC, May 27, 2021.

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  1. KB1FGC

    KB1FGC Ham Member QRZ Page

    Hello all,Finally got my 301 on the air.So far it seems OK.
    The frequency maybe about 2 1/2 KC off.I can Zero set it but would it need an alignment or something else.I set the dial up and it works good.Also bands 20 meters and 10 meters are dead.Hiss from the speaker but that's it.The manuel suggests maybe the mixer stage?I maybe barking up the wrong tree here.If the other bands work would think it's not that.Sorry for the ignorance-hihi.
    I dont have a CW filter,Do you recommend just building a simple receive filter for it or sourcing a HeathkitCW filter?
  2. KE4OH

    KE4OH Ham Member QRZ Page

    It's not unusual for a Heathkit LMO dial to be off that far. Usually you will find that the amount it is off differs per band. I believe the usual reason is that the hetrodyne crystals have drifted over time.

    A dead hetrodyne crystal might be the reason for a dead band also. However, I doubt that is the case for 10m on your rig because 10m has multiple crystals to cover the whole band. It would be very unusual for them all to be bad.

    With any Heathkit, it's good general practice to get out the screwdriver and pliers etc. to tighten *every* *single* *screw* that fastens the circuit boards to the chassis. Also tighten every single lug, bracket, etc. that could possibly be a chassis ground. Now, get out your soldering iron. Reflow anything that doesn't look perfect and shiny. While you're doing those things, keep an eye out for modifications. I find them all the time. I personally prefer to reverse all mods before I do an initial power-up. Look for circuit board traces that have been cut (like with a Dremel tool), coax in odd places, big honking resistor/cap that doesn't belong, wires that aren't the standard colors, so forth. It's also pretty common to find traces that have lifted from the phenolic board. You might even cause some of that as you reflow the iffy connections.

    As far as a CW filter, the Heathkit filter is pretty good. IIRC, the center freq is 400Hz. The skirts are fairly steep, but I don't hear much ringing in the Heath CW filters I have. Much better than an add-on audio filter.
  3. KB1FGC

    KB1FGC Ham Member QRZ Page

    Thanks,Also I realized the RTTY isn't to bad.my big concern is:Dealing with high voltages.I need to under stand how to use a Chichken stick,Also have to make one.Heathkit had a lot of testing procedures but nothing on how to safely work on radios so I have to figure something out.
  4. WB2GCR

    WB2GCR Ham Member QRZ Page

    The SB-301 really only has very moderate voltages, at not terribly high currents.
    The SB-401 needs much more "respect".

    You want a meter to check for voltage.
    Shorting stick not required at all for this.

    Download the manual.
    The alignment procedure is there.

    I owned one for a long time, it's a pretty good receiver.
    The dial may or may not be off by a bit.
    Nothing to worry about.

  5. W5RKL

    W5RKL Ham Member QRZ Page


    There's no need for a "chicken stick". The power supplies will bleed down to zero on their own.
    Turn the SB-301 OFF and allow the power supply to bleed down to zero or very close to zero in
    3 to 5 minutes. Unplug the AC power cord from the wall outlet then use your DC voltmeter to
    check the power supply voltages, they should be very close to zero.

    As for the dial being off frequency, you need to check each band and determine if the dial is
    off the same amount. More often than not the LMO (VFO) is not the cause of the 10Khz round dial
    being off frequency. In the majority of the cases where the dial is off frequency, the individual
    band switch selected HET OSC crystals are to blame. There is one HET OSC crystals for the 20-meter
    band and 4 HET OSC crystals that cover the entire 10-meter band.

    14 = 22.895Mhz

    28 = 36.895Mhz
    28.5 = 37.395Mhz
    29.0 = 37.895Mhz
    29.5 = 38.395Mhz

    14 = 22.895Mhz

    As for the loss of 20 and 10-meter bands, the "mixer" is not the source of your problem. If
    the mixer was causing the problem, all bands would have the same problems.

    The mixer causing loss of 20 and 10 meters? The mixer can't be the source of loss of 20 and 10-meters.
    If the mixer were the problem then ALL bands would suffer not just 20 and 10-meter bands.

    Mike W5RKL
    N2EY likes this.
  6. KB1FGC

    KB1FGC Ham Member QRZ Page

    The mixer can't be the source of loss of 20 and 10-meters.
    If the mixer were the problem then ALL bands would suffer not just 20 and 10-meter bands.

    Wow I'm learning something-hihi.Thanks Mike,After I wrote that I thought about it again and thought what you said.I was wondering if the band switch may be the cause.Anyway I'm getting more out of this group than I ever did out of my one year education.That got some basics in but it's like working under tech in this group:.Which is what I wanted to do after I got out of school.But those days are gone I suppose.This was back in 2003.
  7. W5RKL

    W5RKL Ham Member QRZ Page


    Check your local library to see if they have a hard/soft copy of the BASIC RADIO
    COURSE by John T. Frye.

    If there's a used book store near you, try looking there for a hard/soft copy of the book. I found
    my hard copy of "Basic Radio Course" by John T. Frye in a used book store for $4.00 + tax.

    You can also purchase used ARRL Handbooks on eBay. Enter the following search phrase in eBay';s text box,
    click the drop-down menu and select All Categories, then click "search".

    "ARRL Handbook"

    I recommend the older edition of the handbook, they have more vacuum tube topics.

    Another ARRL book on Amateur Radio is:

    "Understanding Amateur Radio"

    There are plenty of soft copy editions on eBay at various prices. Use the same search process but change
    the search phrase to Understanding Amateur Radio.

    There's also a ham club in Waterbury CT that's 7 miles from you. You might consider joining that club
    and asking if there are experienced hams that are willing to help you with your SB-301/401 problems?
    Here's the link to the Waterbury CT amateur radio club.


    Added comment:
    There's a "misprint/typo" on the SB-301 schematic for HET OSC crystals "Y4". The schematic listed "Y4" as
    "14.0" when it should be "15.0 (REC ONLY)".

    Mike W5RKL
    Last edited: May 31, 2021
  8. KB1FGC

    KB1FGC Ham Member QRZ Page

    Thanks Mike,I may have a later manuel.It shows the crystal marked correctly.My radio maybe later 60's as there are some noted corrections in the back of the manuel and it's dated Jan 1969.Will do with the book.I am reading the Army manuel for the 4th time probably,Only sections though.That is pretty good and not a lot of math plus it really goes over signal flow real well.

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