Richard I am recommending penetrating oil to clean and lube switches and pots.? Kroil, Deoxit and the like are effective but are also expensive.? Just trying to point out that there are alternatives to name brand items which also do a decent job at a very reasonable price.
Perhaps we should share some cleaning tips on the reflector.? I am sure that there are many products that do a decent job and are less expensive.? I can recommend Bar Keeper's Friend for general metal cleaning, it works well for me.? For wood cabinets, waterless hand cleaner also does a decent job without harming the remining finish. Regards, Jim Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy
The noise limiter in the SX117 is somewhat unusual. It is a diode
noise clipper, similar to the conventional limiters found in many
receivers, but works at IF frequency rather than audio. It is NOT a
noise blanker. The comments in the instructions are very similar to
those for a conventional limiter. In CW it works because there is no BFO
present at the point of clipping or limiting. The same for SSB. The
distortion on AM really traces to the same cause. In a conventional
series limiter the detected carrier sets the clipping point. In most
receivers its set at about the 100% modulation level but usually
produces some clipping below that. In conventional receivers the clipper
will be biased by the BFO. Since for CW or SSB the BFO level is usually
higher than the signal the clipping level is usually well above the
signal so the effectiveness of the limiter is, well, limited. Some
receivers use a shunt arrangement where there is a manual limiting
control. This can be set to produce more noise reduction on CW or SSB
but must be set for AM signals to minimize distortion.
Since the limiter is in the 50Khz IF, before the AVC it has somewhat
the advantage of a noise blanker of minimizing desensitizing by
preventing noise from influencing the AVC.
Why it isn't working? Guesswork, something is causing the diodes to
short the IF signal. Bad diode perhaps, there is really not much there.
Its hard to find on the schematic.
I generally use Deoxit for switches and Fader lube for pots, have
had long term good results. I have never tried Kroil for either and am
not certain Jim is recommending it.
On 6/8/2024 12:42 AM, Jim Whartenby via groups.io wrote: Floyd
You originally said: "Haven't dug into this yet, but wonder what other
SX-117 users see when turning on the Noise Limiter in? USB or LSB mode.
On my receiver, it's like disconnecting the antenna - an S9+20 signal
falls to S1."
If you had only read the SX-117 manual first you could have answered
your own question, see page 11, bottom of the second column.? Cutting to
the chase, the noise limiter is most useful in CW, somewhat useful in
SSB and causes distortion in AM.? Backing off of the RF gain control
will reduce some distortion.
You mentioned that the SX-117 had been repaired in the past.? If that
included replacing the HD6225 diodes then I would check to see if they
are now Germanium.? The HD6225 is a silicon diode from the dim past of
silicon diode availability.? I have not found a datasheet for it but I
would suggest using a high conductance, low reverse leakage, diode.? One
sub would be the FD333 which has 1/10 the leakage current of the
1N4148.? I am sure that there are others.? But the 1N4148 or the 1N914
would most likely be just as good.
As for the use of a spray to clean and lubricate switches and pots, I
found the info below at the Kroil site:
<>
*"What to Expect from a Penetrating Oil*
There are several benefits to choosing penetrating oil over other
products on the market. It offers lubrication, noise reduction, cleaning
power, and is corrosion resistant. Each brand will be slightly
different, but we want to share what to expect from most of the
traditional penetrating oils available today.
* *Penetration*?¨C Penetrating oils penetrate rust and corrosion in
threads, spaces, and small openings of frozen or seized metal parts
that might seem impossible to reach. Penetrating oil can work
quickly to help loosen items that you thought were a lost cause.
* *Reduction of Noise*?¨C If you¡¯re dealing with industrial equipment,
or a deafening suspension, penetrating oils are made to help. The
way the oil is created helps cut down on both friction and rust,
which is often responsible for creating these noises.
* *Lubrication*?¨C Penetrating oil contains lubricant, although the
actual amount depends on the brand and ingredient list. Sometimes
the lubrication is temporary, but it can also last for a long time
with the right components in the mix. The product can be used to
lubricate mechanical parts on various items. In addition, it helps
with loosening stuck parts, removing tight nuts and bolts, and
reducing friction.
* *Resistance to Corrosion*?¨C Penetrating oils are made to protect any
kind of metal surface from the issues related to corrosion. This is
huge since corrosion is a common enemy of metal used in the
construction of mechanical components. The formulation of the
penetrant works to displace moisture, which helps fight against rust
and other situations that create corrosion.
* *Cleaning Power*?¨C It¡¯s essential to look at the product information
to be sure, but many types of penetrating oil are made to be used
for cleaning. They are especially useful for removing grease,
adhesive, tar, and rust. The oil acts as a solvent which means that
the items it is placed on will start to soften. This makes it much
easier to remove what is left with a soft cloth or a wipe of some sort."
My go to spray is Dollar Store penetrating oil.? It is cheap and works
very well on switches and pots.? I have had no problems at all for the
last dozen years using this product.? Just as good as anything costing
10 times or more the new going price of $1.50 per can.? Like everything
else in life, moderation is key.
If your go to spray is WD-40 then I would agree that if one used
nothing, that would be far better then using
WD-40.? This junk turns to gum over a short period of time and makes
matters much worse for switches, pots and gears.
Regards,
Jim
Logic: Method used to arrive at the wrong conclusion, with confidence.
Murphy
On Friday, June 7, 2024 at 04:56:42 PM CDT, don Root
<drootofallevil@...> wrote:
So, guys, where is the formal non-partisan definition of..
"noise blanker"
"noise limiter"
Is there a defined difference between them ? and do the terms define? an
intent or a specific circuit?
Sorry to interfere but my poor education did not address this; at least
not that I remember.¡don
*From:*[email protected]
[mailto:[email protected]] *On Behalf Of *Floyd - K8AC
*Sent:* Friday, June 7, 2024 5:06 PM
*To:* [email protected]
*Subject:* Re: [HallicraftersRadios] SX-117 noise limiter behavior
I had hoped that someone who has actually seen and used an SX-117 would
respond.? I've only been restoring receivers for 40 years or so, but
over that time I've learned that you can save a lot of time by
consulting with someone else who owns the same radio when observing an
odd behavior.? You might be surprised how many times "they all do that"
is the undesirable but true answer.? As I said, I have not dug into this
particular problem yet.? What I do know is that the SX-117 does not have
a "noise blanker" as seen in later or more sophisticated receivers like
the Drake R4C.? It is described as a noise limiter.? This particular
SX-117 has been completely restored with all new tubes and many
capacitors replaced, as well as a few out-of-tolerance resistors.
Spraying old switch sections with anything is a really bad idea.? All
switches in this unit have been carefully cleaned using De-Oxit and Q
tips and tooth picks to apply the cleaner in small amounts where needed. ,_
--
don??? va3drl
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
Jim Whartenby