HUM - GR-54 & SB-301 & Hasti Fisti

[Fred Finster]

What a great read.   Thanks, sounds like magic to me.  Trying to FIX HUM
problems.
Who would have thought,  Hasti Fisti was coming back to life and haunt you
as a HUM
problem.   What a conincidence to see your wife's voice on the oscilloscope.
Does she
talk LOUD?  Eh, I can't hear you honey, over this annoying HUM problem in
this derelict Heath radio? Honey, Can you speak up?  Honey Did you ever see
how beautiful your voice
looks?

 Wonder if 60Hz HUM isn't the fore runner (foreigner) to the PL Tones.
No Sir, that extra noise you hear is the PL tone in these ancient radios.
They had two
kinds.  Half-wave at 30hz and Full Wave at 60Hz.  Now, if you jest ingect a
leetle of
that PL tone over there into this Microphone, the guy on the other end of
the propagation
wave will hear you better because you are constantly modulating.  Therefore
your
output power will be an the average a bit higher, than the next guy in the
pile up. Now since he is listening with a good quality SSB rig, he might
miss some of that PL tone below 300 HZ.  So you should tell him to switch to
AM reception.  Upon hearing that fine Full-Wave PL tone modulation of your
signal, he can instantly comment on the fine quality of your signal.    For
CW it is even better to add the PL Tone Modulation especially for QRP
operation.  Hams will come out of the woodwork worldwide to comment on your
362 signal.


RST report
3 I can mostly hear you
4 Signal strength is adequate
2 You have that lovely PL tone.  Really makes you stand out in a crowded
pile up.
   Easy to capture that distinctive PL tone by ear.

Hasti Fisti, will we ever hear you again?

The SCREW audit?
You didn't  mention once the IRS in that paragraph.  Too, bad.

Thanks again.  It will give me hope to continue on re-inventing the wheel
when a
set of problems comes my way.

Keep Laughing,  its the best medicine.

Fred Finster WB7ODY

> -----Original Message-----
> From: Heathkit Owners and Collectors List
> [mailto:HEATH at LISTSERV.TEMPE.GOV]On Behalf Of Mark V. Johnson VE3DJU
> Sent: Sunday, January 09, 2000 7:25 AM
> To: HEATH at LISTSERV.TEMPE.GOV
> Subject: HUM - GR-54 & SB-301
>
>
> Hello all. A month ago I posted a note regarding my ordeal with fixing a
> HUM problem on my hw-16. Well its seems I can't buy anything Heath without
> it having a hum problem. The latest is a GR-54 Gen Coverage
> receiver and an
> SB-301. Thought I 'd share my work and invite comments.
>
> The GR-54 worked great but in standby or no volume, there was a hum that
> was very annoying. With this radio, standby removes B+ from the RF amp
> stage...The audio circuit continues to run. I tried new electrolytics, no
> change,  I also changed every bypass and coupling capacitor in the audio
> stages, no change. I isolated the AF amp by removing this input
> lead to the
> 6HF8 and the hum reduced. BUT there was no hum from the previous circuits.
> It was almost as if the input lead (shielded) was picking it up.
> I replaced
> the input lead with new shielded wire..no change. Finally, I put my dual
> trace scope on the audio output and the power supply to see if the hum was
> 60hz from the power supply. Looked like it was.  At that point, my wife
> came in to speak to me and low and behold I could see her voice modulate
> the waveform. Her voice was being picked up through the on board
> speaker...Guess what..Connect an outboard speaker and almost zero
> hum. What
> was happening was the speaker which is mounted right next to the power
> transformer was acting like a mic, picking up the transformer hum  and
> feeding back into the circuit. Don't they (experts from long ago)
> tell you,
> never put a speaker inside a receiver...I now know why! Great that I just
> invented the wheel eh? I also think because of poor high end (15 - 30 mhz)
> sensativity, the audio stage had to be fairly high in gain to compensate.
> This will also make it susceptable to hum problems..Just a guess.
>
> The Sb-301. Got it in a trade. Brought it home, checked for any obvious
> problems and checked for the right fuse. Plugged it in..Got signals and
> HUM. Remember, everything I buy hums. Going back to my Mainframe Computer
> repair days I started doing a pre-install screw audit. Sounds dumb but on
> that stuff intermittent connections was a big problem. First duty on any
> install was a screw audit..Thats is tighten ALL screw connections. Well, I
> started with the 2 screws on the filter cap...One twist bam no hum..Solid
> as a rock and QUIET. Talk about a quick fix!
>
> Hope this helps..Welcome any feedback. Thanks for the space.
>
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