by newsgroup concerning the audio buzz issue that plagues the Sony ICF-SW1. I
thought my receiver was immune to the problem until a couple of months ago
when I turned it on and it presented the well-known symptom; at volume
settings slightly above a whisper the receiver breaks out into a loud buzz
(some mention that earphone audio is normal and unaffected). Previous to
the buzz I noticed that the quality of the speaker audio was somewhat
degraded compared to earphone audio.
I was determined to repair my receiver; I got it in 1989 and I had carried
it with me the world over. It was a faithful companion, it shared many
adventures with me and it operated flawlessly until now---I just couldn't
toss it. I had taken exceptional care of it yet it had failed on it's own
accord.
I wanted to get a service manual prior to repair but the sources I checked
didn't have them---they must be still available somewhere. Anyway, I
decided to attempt a repair without one.
NOTE: If you are not comfortable wearing a binocular magnifier and using
tweezers while repairing a radio forget about repairing this one---or it
will end up in the trash. Just use the earphone instead and save yourself
from grief.
If you have natural ability but never worked on micro-miniature circuits
before just do a little bit at a time giving yourself plenty of time to
think about procedure and to get familiar with the layout of the receiver.
When you set it aside store it in a place that won't be disturbed and put a
cover over it to keep out the dust.
Disassemble the receiver on a white towel and use a fluorescent or
high-intensity desk lamp. Use a binocular magnifier; OptiVISOR with the 4X
lens plate and the 2.5X OptiLOUPE are highly suggested.
I have included a couple of repair notes from previous posters; they appear
at the end of my repair notes. There may be other repair notes in the
archive besides the ones I've included---check for them as well.
If you have made a repair to the ICF-SW1 please consider posting your repair
notes.
Notes:
1) There are three screws securing the back cover. There is a***under
the black adhesive backed Mylar washer under the volume control. The volume
control pulls off easily but you will have to probe carefully (with a
toothpick) to find where the***is located. I just cut a little hole
into the Mylar enough to get a Phillips head screwdriver into place. There
are two depressions only one has the***beneath it. The little arrow
points directly to it. When the***is replaced it pulls in the rough
edges of the Mylar and looks quite satisfactory.
When removing the back cover be very careful! The plastic is thin and can
break or deform very easily---especially along the edge of the battery
compartment. The back cover pulls off from the volume control end
(carefully using fingernail or finger pressure to unlatch the cabinet
halves); lift it up slightly then slide it off the antenna end (antenna is
collapsed).
2) Carefully remove the screws that hold the boards to the cabinet.
Unsolder the wires to the speaker and remove the ground lug on the speaker
frame leaving the gray wire attached to the lug.
3) You should now be able to remove the circuit boards from the cabinet.
Note that the little dial light push button will fall out of place---just
replace it upon re-assembly of the radio. Similarly, note how the on/off
slide switch on the circuit board engages the green slide button.
4) The keyboard is moved out of place by removing its mounting screws. It
is also necessary to remove the gray ground wire from the ground point on
the main board. The keyboard can now be folded over but still be attached
by its short length of ribbon cable.
5) The display board is folded out next by removing its mounting screws.
Release the display board ribbon cable from the board connector by unlocking
the connector. The ribbon cable can now be removed allowing the display
board to be folded out of the way.
6) You are now looking at the component side of the main board. Off to one
side you will see six cylindrical surface mount electrolytic capacitors that
are located in the audio section. Looking at their values there is only one
that is labeled 33mf 4v; it will be about 1/8" (3mm) in diameter and 1/8"
(3mm) long. In the vast majority of repairs it is this capacitor that has
failed. Like the previous poster, I also had a 22mf 10v tantalum capacitor;
I removed it from the back of a hard drive. I replaced the 33mf capacitor
with my 22mf tantalum. Take care to observe polarity when replacing the
capacitor. Be extremely careful when soldering as there are plated through
holes associated with that capacitor and the traces are very narrow.
7) Re-assemble carefully. Ribbon cable connector; gray ground wires (one
soldered to main board the other on lug to speaker); solder speaker wires.
Carefully locate speaker and gray ground wires to allow back cover to be
fitted into place without the back cover bulging. Everything should fit
cleanly together. Take care when putting the dial light button into place
and carefully align the green on/off button with the board mounted slide
switch. The back cover should snap into place.
At each stage of re-assembly I dust off the boards with a shot of
pressurized air.
When replacing the batteries take care not to move the position of the 9
kHz/10 kHz 'MW CH STEP' switch---it can easily catch on the end of the
battery. If the battery inadvertently moves the switch the radio will
increment in 9 kHz steps on the AM broadcast band.
8) Hopefully your ICF-SW1 is now working.
Maybe someday I will find the proper replacement capacitor and install it
but for now the receiver is working just like it always did, as best as I
can tell, with the 22mf Tantalum.
One poster suggested that all electrolytic capacitors also be
replaced---fortunately for me only the 33mf capacitor required replacement.
Best of luck
R.
Previous Repair Notes:
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Subject: Sony ICF SW1 repaired
Newsgroups: rec.radio.shortwave
Date: 2001-01-25 12:40:14 PST
Despite posing a message in this group a few weeks ago, no one responded
with offers of a circuit diagram for my faulty Sony ICF SW1 receiver. I
therefore followed my instinct and traced the fault out without the piece of
paper. The sound output was unstable at volume levels above a whisper. The
fault was a 33 microfarad capacitor (probably decoupling) in the sound
output stage. It was a very small 4v electrolytic device. The smallest
replacement I found in the workshop was a 22 microfarad tantalum. It appears
to have done the trick and the receiver is blasting away at it's old levels.
Dismantling the receiver was a delicate operation - there are three PBBs
mounted in parallel. Separating them allowed access to the sound output
stage on the main board. There are five electrolytic caps (one of which I
suspected would be the culprit) on the board. I bridged them one by one.
Bridging the faulty one brought the sound output back to it's normal level.
The cap is surface mounted. A hot iron with a fine bit did the job and the
new cap was soldered into place. The hot iron allowed the replacement to be
made quickly - avoiding damage to the printed track on the PCB. In all it
was cheap job - I priced up the new SW100 and it's over 150.00 (Pounds) - a
lot of dosh compared to the price of a tantalum capacitor.
Barrie
York UK
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Subject: Re: Sony ICF-SW1S
Newsgroups: rec.radio.shortwave
Date: 2001-10-27 20:40:36 PST
have: The audio through the >speaker is very distorted although through theQuote:>I seem to remember that someone on this NG had a >similar problem that I
headphones >it is alright. I know it's a electrolytic capacitor problem
Hi,
I believe that would be capacitor C608 (33mf at 4 volts, surface mount type)
on the schematic. It ties between circuit ground and pin 13 of the audio IC
chip IC601 which is a BA5208AF.
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End Notes