NoobowSystems Lab.

Radio Restoration Projects

Sony ICF-5900W Front View - Click here for larger image
Sony ICF-5900W
General Coverage Portable Shortwave Receiver

The Masterpiece of Japanese Portable in the Middle 1970s

<Japanese Page>

The SONY ICF-5900W

    No explanation of this radio may be necessary for Japanese shortwave fans - This is an export version of the famous Skysensor 5900. Unlike Japanese version, it covers FM band from 88 to 108MHz.

    When I was an elementary school boy, several months of delivering milk bottles in the early morning allowed me to get money for my own shortwave receiver. Then the biggest problem in my life ever arose --- whether I should buy a Panasonic RF-2200 or a Skysensor 5900. The decision whether I should marry to this lady or not, was much quicker and easier choice than that.

    5900 with crystal marker and bandspread, while linear-frequency tuning cap and two speed reduction tuning in 2200 ---- after weeks of wondering about, I chose 2200 which precise mechanism appealed to me.
    Literally I enjoyed 2200, days and nights. But after a year or so, my 2200 suffered several troubles. Most annoying thing was the backlash of the vital precision tuning mechanism. It was caused by my misuse; I accidentally applied mechanical shock to the dial knob. Backlash more than a few kHz really spoiled the pleasure of the shortwave adventure. Another trouble was that when listening 7MHz SSB amateur band the opposite sideband was too strong than desired sideband (possibly caused by the BFO frequency misalignment), I may be able to do something for it now, but an 11 years old kid never knew what to do.

    Following story is a very typical to radio kids of that time; acquire a license and get on-the-air on the 6m SSB. I wonder where is my 2200 now....

    Anyhow, I finally became an owner of 5900, 25 years after that sensational debut --- a monochrome photograph and technical specification sheets including performance curve graph of the "ultimate shortwave receiver soon to be announced" was mailed to all of the Sony Skysensor Club members. Seems like I really stared into the brochure those days; when I opened the UPS box, I even felt that I FINALLY GOT BACK MY OWN RADIO.

Questions 25 years later

    Advanced DXers would consider the ICF-5900 as a beginner's radio, but it was certainly a dream machine for radio kids in the middle 1970s. And, such radio kids had limited knowledge that double conversion was something great. A quarter century later, a middle aged radio kid began reading 5900's circuit diagram with excitement.

    One of the sales pitches of the ICF-5900 was the double conversion system. Then the first question is how much is the intermediate frequency used.

    The answer is 10.7MHz for the 1st IF, and 455kHz for the 2nd IF. Hmm, 10.7MHz IF is identical to ordinary FM radios. Looking at the 5900's dial, we realize that 10.7MHz is in the band gap, i.e. between SW1 and SW2, and cannot be received.

SW1  4MHz - 10MHz
SW2 11.750MHz - 20MHz
SW3 20MHz - 28MHz
MW 530kHz - 1600kHz
FM 88MHz - 108MHz
    In the traditional electrical bandspread arrangement, i.e. having a small tuning capacitor in parallel with the main tuning cap, the effectiveness of the bandspread tuning varies from frequency to frequency. Therefore the bandspread dial can be calibrated only for particular portion of the shortwave frequency range.

    5900's bandspread dial, however, provides constant cover range of plus minus 125kHz regardless of the main tuning setting. This enables to have the precise scale on the bandspread dial. Smooth reduction drive and 10kHz division scaling made "10kHz direct reading" possible, which was a dream before.

    How can this be achieved? The answer lies in the block diagram - the constant band spread arrangement.

Sales copy from the 5900's advertisement - it reads:

From blind tuning to stand-by tuning - Introducing the 10kHz direct readout shortwave dial.

ICF-5900W Block Diagram - Click here for larger image

Circuit Description

1st Converter and 1st IF Amp

    Incoming signal from rod antenna or external antenna terminal goes through the antenna tuning circuit which is tuned by the main tuning knob, and fed to the 1st mixer. There's no RF amplifier in this receiver.
    This mixer is a balanced type; 2 transistors are used. This configuration minimizes the local oscillator frequency leakage to the IF circuit.
    The 1st local oscillator is tuned by the main dial, and the 1st mixer outputs the 1st IF signal which frequency is approx. 10.7MHz. The signal is then amplified by the 1st IF amplifier transistor 2SC1908. Ceramic filters are deployed in the input and output of this transistor. This 1st IF amplifier also works as the 1st FM IF amplifier. It means that the bandwidth of these ceramic filters is same to the typical FM receiver; they are bandpass filters and do not provide selectivity required for the shortwave reception.

    Since the main dial of 5900 should be set to every 250kHz where indicated by the crystal marker, desired signal lies somewhere in 10.7MHz plus/minus 125kHz. Therefore, these filters should have a flat response for plus minus 125kHz. (The 10.7MHz filters used, however, do not have an ideal characteristic of such "flat-top"; causing the sensitivity variation within the 1st IF passband - this is described later within this article.)

2nd Mixer and 2nd IF Amp

    Amplified 1st IF signal is fed to the 2nd mixer. The 2nd local oscillator frequency is varied by the bandspread dial. Okay, this is why the bandspread dial gives a constant coverage, regardless of the band and main tuning setting. The 2nd local oscillator employs one transistor, and the bandspread tuning capacitor is in parallel with a local oscillator coil. When the X-TAL MARKER switch is ON position, bandspread tuning cap is substituted by a trimmer capacitor, eliminating the necessity to return the bandspread dial to zero every time the main tuning is to be calibrated.
    The 2nd mixer produces the 455kHz 2nd IF signal, and it goes through the IF transformer which contains a ceramic filter. The signal is amplified by the 2nd IF amplifier stages, which consist of a transistor and the only IC used in the receiver.
    Shortwave selectivity is provided by the filters and a transformer in the 2nd IF amplifier circuit. This 2nd IF stage also serves as IF amplifier for FM reception. In this case the signal goes through the 10.7MHz ceramic filter, which is in parallel with the shortwave IFT.
Transistors used in ICF-5900W
Desig. Transistor Function
Q1 2SK42 FM RF Amplifier
Q2 2SC930 FM Mixer
Q3 2SC668 FM Oscillator
Q4 2SC1908 FM AFC
Q5 2SC668 SW 1st Mixer
Q6 2SC668 SW 1st Mixer
Q7 2SC710 MW Oscillator, SW 1st Oscillator
Q8 2SC1908 FM IF/SW IF1 Amplifier
Q9 2SC1908 FM IF Amp / SW 2nd Mixer
Q10 2SC1908 SW 2nd Oscillator
Q11 2SC1908 FM/MW IF Amp / SW IF2 Amp
Q12 2SC1363 Meter Amplifier
Q13 2SC710 BFO
Q14 2SC1363 AF Amplifier
Q15 2SC1363 AF Amplifier
Q16 2SC1429 Power Amplifier (push-pull)
Q17 2SC1429 Power Amplifier (push-pull)
Q18 2SC710 500kHz Oscillator
Q19 2SC710 Freq. Divider
Q20 2SC710 Freq. Divider
Q21 2SA677 Voltage Regulator
Q22 n/a n/a
Q23 2SC1363 Voltage Regulator
Q24 2SC1363 Voltage Regulator
Q25 2SC1363 SSB/CW Pre amp
Q26 2SC1908 Local/DX Select
Q27 2SC1908 MW Mixer
IC1 CX075 FM/MW IFAmp / SW IF 3 Amp
The designation of the transistor tells something. Why Q22 is missing; voltage regulator was originally designed with 4 transistors? Why MW mixer is Q27; possibly the other transistor also acted as MW mixer in the original circuit...

Ceramic Filters

   The interesting aspect of this shortwave receiver is that it uses the 10.7MHz ceramic filters for 1st IF stages. By using a component commonly available for FM radios, lower material cost could be achieved. Their center frequencies, however, vary from piece to piece. The 5900 uses 3 of those ceramic filters, therefore the filters used in a particular set must be chosen so that their center frequencies are close to each other.

    Sony production line prepared for 7 ranks of filters and adjustment procedure. Each ceramic filter had a color code mark which indicated its center frequency. All color codes of filters must coincide, and the center frequency applied to the set was indicated by a color label on the back side of the circuit board.

    My receiver has a red label, and the filters have red markings on their top, indicating 10.70MHz is the center frequency chosen at the time of production.
ICF-5900W 10.7MHz IF Frequency Selection
Color Code Specified Center Frequency
Green 10.61MHz
Black 10.64MHz
Blue 10.67MHz
Red 10.70MHz
Orange 10.73MHz
White 10.76MHz
Yellow 10.79MHz


    The output of the 2nd IF amp is always fed to three detector circuits simultaneously. These are the FM detector, AM diode detector and the product detector with BFO. When the band selector is set to FM, FM detector output is selected. When the band selector is MW or SW, AM diode detector output is selected if the BFO switch is OFF, and the product detector output is used if the BFO is ON. Selected output is fed to the audio amplifier. Pre-amplifier is used for the product detector output in order to equalize the audio level between AM and SSB reception.

    AGC voltage is generated by the AM diode detector, and is also used when the BFO is ON. The AGC time constant is unchanged whether the BFO is ON or OFF. AGC control voltage is amplified by a transistor and drives the tuning meter.

SENS Switch

    5900 has a SENS switch which has DX and LOCAL position. This switch may be used when a strong station is to be received, or to avoid the interference caused by strong adjacent signal. You might think this is a simple attenuator in the antenna circuit, but it's much fancier.
    A sensitivity control transistor is located between antenna tuning circuit and the 1st mixer. Normally the transistor is open and the receiver is in full gain. When the SENS switch is set to LOCAL, or the X-TAL MARKER switch is ON, base voltage is applied to the transistor and it shunts the incoming signal to the ground, thus the reduced gain of the receiver.
    This arrangement has a potential failure mode of poor sensitivity; if the shunt transistor failed with short mode, the overall receiver sensitivity remains low even if at the DX position. My unit is okay, but if yours has poor sensitivity and if it does not change regardless of the DX-LOCAL position, suspect the failure of the transistor Q26.

X-TAL Marker

    The X-TAL Marker is used to set the main dial to every 250kHz position for example 15.000, 15.250. 15.500... MHz. The marker circuit consists of a 500kHz crystal and three transistors. Two transistors work as an frequency divider, providing 250kHz and its harmonics. Oscillator output is fed to the antenna circuit. The oscillator is powered up only when the marker switch is ON.

    The X-TAL MARKER lever operates a multi circuit slide switch, and it does many things with a single lever action;
  • Power on the marker oscillator which consists of a 500kHz crystal oscillator transistor and frequency divider transistor.
  • Disconnect the external and rod antenna so that the incoming signal cannot be heard. Marker oscillator output is connected instead.
  • Activate the signal shunt transistor so that the RF signal input is half shortened to the ground. This reduces the receiver's sensitivity, and is the same action as you flick the DX/LOCAL switch to LOCAL.
  • Switch to the product detector and turn on the BFO even if the BFO switch is OFF. It makes the marker signal being heard with beat sound. Also, output of the product detector is attenuated when the marker is on. It makes the marker sound comfortably soft to the operator.
  • Disconnect the band spread tuning capacitor and switch to a trimmer capacitor. This eliminates the necessity to return the bandspread knob to the center zero position.

Audio Amplifier and Output

    Selected output from FM detector, AM detector or the product detector is fed to the audio amplifier through the VOLUME control. The audio signal is amplified by two transistors and the final push-pull power amplifier which has a input- and output-transformer, drives the built-in speaker or earphones.
    Treble tone control is a simple shunt type attached to the VOLUME control. Bass tone control changes the frequency response of the negative feedback loop.

Voltage Regulator

    5900 requires three dry cells, thus the power supply voltage is 4.5V. As a portable but a high performance shortwave receiver, the radio must be stable against the battery voltage variation. ICF-5900 has a voltage regulator circuit which uses three transistors. It supplies stable 2.0V power to the voltage sensitive stages as follow:
  • Crystal marker (only when the marker switch is ON)
  • FM local oscillator (only when FM is selected)
  • AM 1st and 2nd local oscillator
  • AM 1st mixer (MW/SW only)
  • BFO (only when the BFO is ON).
    For circuit blocks other than mentioned above, raw battery voltage or external power input voltage is applied. In another words, there's no overvoltage protection or reverse connection protection provided.
    The external DC power jack is outer-positive, center-negative. It is recommended to supply regulated 4.5V.

    The EXT TIMER IN jack is wired in series with the POWER switch. When no plug is inserted, this jack closes the circuit, thus the power can be turned on or off by the POWER switch. By connecting an external switch to this jack, receiver power can be controlled by that switch. If your receiver is completely dead, check if the contact of this jack is clean and they conduct properly. Inserting and removing a plug several times might make the contact fresh.

Always in sight

    The ICF-5900W I acquired was not perfectly clean, but seemed to have little trouble. The only major and obvious problem was the missing battery cover (which is somehow common to surviving 5900s). As long as the radio is placed on the desk it's not a big deal. Pop-up antenna and LIGHT switch was in perfect condition, which is rather rare case. Although the audio potentiometer was a little scratchy, no immediate service seemed to be necessary.

    Closer look revealed, however, the main dial was misaligned nearly 500kHz. This of course made the calibrated bandspread operation useless. I opened the cover, removed the film dial unit and reassembled again while monitoring the WWV. It looked that the previous owner had opened the cover many times so it was possible that he had misaligned the dial, but the aging might have caused it too.

    Another problem was the poor sensitivity at the high edge of the bandspread dial. It is said that this is a common problem to the 5900s so performing the full adjustment procedure may be necessary.

    Although the reception is good, too fast AGC response results in the noisy sound when the fading is severe. The plastic case is vulnerable to the external noise source such as computer monitors. Since my primary criteria today is to relax and enjoy BBC world service, the 5900 could not beat the Echophone EC-1A with external speaker, which has been occupied the prominent position in my lab. Nevertheless I feel very cozy and happy when this radio is at the corner of my sight. Take time, and let's enjoy the dream receiver for the radio kids in the middle 1970s.

<ICF-5900W and Echophone EC-1A>
    Okay, here is a quiz challenge to Japanese fans. Everyone asked what is the scale at the bottom for. The U.S. version of 5900 has;
Which is it? Look above picture carefully.

Inside of the SkySensor

    Removing the cover of 5900 is easy; all of the components are neatly mounted on the main chassis. Engineers had learned more about the plastic design; the main chassis shape is simpler than 5800, and most of corners has round chamfer which helps the tooling life longer.

    The speaker used is 10 cm in diameter, and is glued to the plastic front panel. I removed the speaker from the panel in order to wash the front panel, and I found grains of sand on the speaker cone edge. Supposedly the radio was once used at a beach, or on a dune. sand grains entered through the speaker grill and were caught on the sticky residue on the cone edge.

    The single-side paper-epoxy printed circuit board has a cheap look. There are many sponge stickers to prevent rattle noise, but it also gives the poor sighting. Sony should not be blamed; after all, 5900 is a low priced, mass produced consumer product.

Examining the Main Dial Alignment

    After mechanically realigned the dial unit, main dial calibration was reexamined by using a signal generator. Here is the result.

Dial Setting Actual Reception Frequency Error Dial Setting Actual Reception Frequency Error Dial Setting Actual Reception Frequency Error
4.000MHz  4.035MHz +35kHz 12.000MHz 12.035MHz +35kHz 20.000MHz 19.970MHz -30kHz
5.000MHz  5.045MHz +45kHz 13.000MHz 13.040MHz +40kHz 21.000MHz 21.005MHz +05kHz
6.000MHz  6.045MHz +45kHz 14.000MHz 14.010MHz +10kHz 22.000MHz 21.975MHz -25kHz
7.000MHz  7.060MHz +60kHz 15.000MHz 15.035MHz +35kHz 23.000MHz 22.995MHz -05kHz
8.000MHz  8.060MHz +60kHz 16.000MHz 16.070MHz +70kHz 24.000MHz 24.025MHz +25kHz
9.000MHz  9.020MHz +20kHz 17.000MHz 17.085MHz +85kHz 25.000MHz 25.080MHz +80kHz
10.000MHz 10.030MHz +30kHz 18.000MHz 18.020MHz +20kHz 26.000MHz 26.030MHz +30kHz
--- --- --- 19.000MHz 18.970MHz -30kHz 27.000MHz 27.000MHz +00kHz
--- --- --- 20.000MHz 20.010MHz +10kHz 28.000MHz 28.020MHz +20kHz

    Result shows fairly good calibration. When the error reaches 125kHz, operator will have trouble calibrating the main dial to the marker signal which is 250kHz apart. Maximum error above was about 80kHz, not perfect but thought to be acceptable.

Sensitivity Variation among the Band Spread Position

    Sensitivity gets lower when the band spread dial position is at high (close to +125kHz). This phenomenon is very common among the surviving 5900s. Here is the measurement result of my unit (before attempting the improvement).

Band Spread Dial Position (kHz) Reception Frequency (MHz) SG output for "S=6"
- 125 14.125 19 dBu
- 100 14.150 19 dBu
-  75 14.175 16 dBu
-  50 14.200 16 dBu
-  25 14.225 16 dBu
    0 14.250 15 dBu
+  25 14.275 17 dBu
+  50 14.300 19 dBu
+  75 14.325 27 dBu
+ 100 14.350 29 dBu
+ 125 14.375 32 dBu

    The sensitivity begins to deteriorate when the band spread is at +50kHz. At the extreme high end (+125kHz), as much as 17dBu of deterioration is observed. Supposedly this is because the center frequency of the 1st IF filter varies for each unit, and the +125kHz portion is at the shoulder of the 1st IF filter. Realignment will be necessary in order to reduce this variation.

SSB and CW Reception

    Flick the BFO switch ON, let's tune the dial to 14MHz amateur band. Here in the very poor receiving environment of typical Japanese apartment house, this plastic body receiver suffers from nearby computer and monitor noise, the tuning meter never gets below half. Tonight, however, several powerful DX stations are calling CQ Contest. SSB audio is clear but slight chirp is noticeable in CW tone.
    Frequency stability is not perfect for SSB and CW, slow drift necessitates retouching the dial every 10 minutes or so in order to maintain the correct pitch. "Hands-off" reception is not possible with this low priced receiver, just as it was either not possible in the medium class vacuum tube general coverage communication receivers.
    Frequency drift trend measurement result is shown on the right. Condition was;
  • Temperature: 17 degC Battery Operated
  • Reception Frequency: 15.000MHz BFO=ON
  • Zero beat tracked by the generator
    The dominant factor of the frequency drift is the room temperature change. This was confirmed by placing an electric desk lamp behind the receiver so that the cabinet got warmed; it accelerated the drift quite a bit. The radio is free from body capacity effect, it's really a good thing in such a plastic body receiver. Swinging the cabinet slightly causes the frequency change, but it is okay as long as the radio is placed on a solid surface.

    The overall performance for SSB/CW reception of this receiver is not perfect, but enough to explore the world of amateur and professional radio communication.
Frequency Drift Measurement Result
Elapsed Time Frequency Drift
00 min  0.0kHz
02 min -0.5kHz
04 min -0.9kHz
06 min -1.0kHz
08 min -1.2kHz
10 min -1.2kHz
12 min -1.3kHz
14 min -1.4kHz
16 min -1.6kHz
18 min -1.6kHz
20 min -1.8kHz
30 min -2.4kHz
40 min -2.6kHz
50 min -3.3kHz
60 min -3.6kHz
70 min -4.3kHz

Image Response

    While listening a Philippine station calling CQ Contest on 14MHz SSB, I used a signal generator to give various frequencies to see the image response. 20dBu output at the reception frequency gave the "6" reading on the tuning meter. Three frequencies were found as image responses; -10.7MHz (84dBu), -227kHz (79dBu), and +889kHz (88dBu). "()" denotes the generator output necessary to tuning meter indicated "6" reading. -227kHz interference was the most obvious, but the rejection ratio was almost 60dBu. If its price is to be considered, the 5900's image rejection performance is very good. The "SW Dual Conversion System" certainly works.


    If an extremely strong adjacent signal (more than 80dBu) is present within the band spread coverage, the receiver's sensitivity considerably drops. Supposedly the 10.7MHz IF stage becomes overloaded, as such adjacent signal is within the 1st IF passband. This is a drawback of the 5900's unique design. Caution should be paid if the extremely strong Radio Peking is not present in the vicinity of the target frequency.
    Also, dial will be filled with bunch of ghosts if external preamplifier is used. The poor antenna system of NoobowSystems consists of mere 1.5m whip rod and a MFJ-959B Tuner/Preamplifier. Usually the preamplifier is left full gain, but in case of 5900 the preamplifier gain must be appropriately reduced.

Audio Quality

    This is quite strange to me. This 5900W plays very well. Volume is ample, no obvious distortion present, tone controls works just fine. Nevertheless, the sound is somehow unclear. When listening a news program, a little bit more concentration or louder volume is necessary in order to understand what the announcer is saying. It does not look like a malfunction of the radio but its audio characteristic. Perhaps the sharper selectivity accounts, could be a speaker characteristic, or the fading distortion may be the reason --- I can hardly tell what's wrong.

Circuit Alignment

    The 5900 circuit requires many adjustments in order to achieve best operation. If you attempt to perform realignment, it is recommended to have the service manual which may be obtained from one of the manual copy services on the Net. Following procedure is just my venture; I'll give you no warranty of correctness of the description.

    List of alignment items is shown on right. Phew.

    A small Adjustment Cover on the rear can be removed by loosing a screw. Underneath this cover, there are 6 trimmers for shortwave 1st local oscillator and 2nd local oscillator alignment. Most of the shortwave alignment can be done by removing the rear panel. To perform the full alignment, front panel must be disassembled.

    The unit in the lab showed sensitivity deterioration when the bandspread dial was at high position. The reason of the phenomenon was supposed to be the 1st IF filter center frequency shift. The unit had a red label on the PCB, indicated the 10.70MHz was chosen as the 1st IF center frequency when manufactured.

  • SW 1st Local Oscillator alignment
  • SW 2nd Local Oscillator alignment
  • Shortwave 1st Mixer alignment
  • Shortwave tracking alignment
  • MW tracking alignment
  • MW Local Oscillator alignment
  • MW/SW 2nd IF alignment
  • BFO alignment
  • Marker alignment
  • FM tracking alignment
  • FM Local Oscillator alignment
  • FM IF alignment 1
  • FM IF alignment 2
MW/SW 2nd IF Alignment

    The first step was to confirm that the IFT-3, located right after the shortwave 2nd mixer, was properly aligned. The designed 2nd IF frequency is 455kHz (468kHz for the U.K. version). The IFT-3 was hidden below the small switch board. By removing the board from the chassis, two cores of the Murata RFT455 IFT were accessible. I hooked up my signal generator to the 2nd mixer collector circuit, and applied 455kHz 30% modulated AM, with output level of 30dBu.

    Slight adjustment was necessary with the black core, to peak the signal. For the yellow core, peak could not be found with the signal generator signal. I disconnected the generator and peaked with yellow core, for the maximum background noise output.

SW 2nd Local Oscillator Alignment

    The 2nd mixer should convert the 1st intermediate frequency to the 2nd intermediate frequency. Assume the 1st IF center frequency is 10.70MHz, the 2nd Local Oscillator must generate [ 10.7 + 0.455  = 11.155 ] MHz when the bandspread dial is at 0kHz.

    By connecting a frequency counter to the output of the 2nd Local Oscillator, its frequency was measured. When the bandspread was at 0 kHz position, the LO frequency was 11.1098MHz. Calculating 11.1098 minus 0.455, I got the 10.6548MHz as the center frequency currently adjusted. However this measurement might be inaccurate, because the frequency counter hookup would cause the detuning.

    Next, I disconnected the frequency counter, and hooked up the signal generator to IFT-2, which is output of the 1st mixer. Set the bandspread to full clockwise and counterclockwise, and tune the signal generator, the 1st IF frequency actually received was measured.

    Seem like the receiver's center frequency was adjusted to 10.663MHz instead of 10.700MHz. Because this was approx. 40kHz lower than it should, the sensitivity dropped at the high end of the bandspread dial.

Bandspread Position 1st IF frequency actually received
Full CounterClockwise (-150kHz) 10.812MHz
Full Clockwise (+150kHz) 10.513MHz
XTAL Marker switch engaged 10.663MHz

    From the measurement result of sensitivity curve, I guessed I need to shift the center frequency to 10.750MHz. I set the signal generator to 10.600, set the bandspread to full clockwise at +150kHz. Then I tuned L21 - the 2nd local oscillator coil - so that the signal generator signal is to be heard. This was immediately found to be too much; the sensitivity got worse at the opposite side (at -150kHz position).

    The 2nd attempt aimed center frequency of 10.720MHz. Set the generator at 10.570MHz, tuned the L21. Then set the generator to 10.870MHz, bandspread at fill counterclockwise at -150kHz. I tuned the CT-11 - the 2nd local oscillator trimmer - so that the signal was to be heard. This time, the sensitivity at +150kHz became lower than at -150kHz.

    The 3rd attempt aimed center frequency of 10.730MHz. Align L21 at +150kHz position for 10.580MHz, and align CT-11 at -150kHz position for 10.880MHz. The sensitivity at both end of the bandspread became almost equal. Bandspread at 0kHz position, the reception frequency was 10.728kHz; close enough to the target. This concluded the 2nd Local Oscillator Alignment.

    Adjustment of L21 and CT-11 was found very critical. Slightest rotation caused the several kHz difference. This means the aging effect of those components might have caused the center frequency shift.

Center Frequency 10.70MHz Standard setting Before alignment 1st attempt 2nd attempt Alignment complete
Target center frequency 10.700MHz ------ 10.750MHz (+50kHz) 10.720MHz (+20kHz) 10.730MHz (+30kHz)
Target frequency Bandspread at +150kHz 10.550MHz 10.513MHz 10.600MHz Peak by L21 10.570MHz Peak by L21 10.580MHz Peak by L21
Target frequency Bandspread at -150kHz 10.850MHz 10.812MHz Not adjusted 10.870MHz Peak by CT-11 10.880MHz Peak by CT-11
Actual reception frequency at 0kHz ------ 10.663MHz (-37kHz) Not measured Not measured 10.728MHz
Result ------ Sensitivity low at +150kHz side Sensitivity low at -150kHz side Sensitivity low at +150kHz side Both side identical

Marker Alignment

    After the 2nd LO is aligned, the maker alignment must be performed. This has two different adjustments. The first thing to do is actually a bandspread substitute trimmer alignment. The next is the marker injection level adjustment.

    As described before, the bandspread tuning capacitor is substituted by a trimmer capacitor when the XTAL MARKER switch is ON. The capacitance of the substitute trimmer must be exactly the same as the bandspread capacitor at 0kHz position. This adjustment can be done by tuning CT-12 trimmer. This procedure requires the bandspread dial scale ring is assembled to the bandspread tuning shaft; i.e. front panel must be assembled.

    Set the bandspread to 0kHz position, turn on the BFO and set the signal generator to the 1st IF center frequency. Tune the generator so that the received sound becomes zero beat.
    Then, keeping the signal generator frequency, turn on the XTAL MARKER switch. Use CT-12 trimmer so that the received sound also gets the zero beat. When this is properly done, exact same frequency is to be tuned whether the XTAL marker switch is on or off.

    The next is the marker level adjustment. Simply, tune the receiver to 28MHz, turn XTAL MARKER on, and tune CT-13 so that the marker signal strength is approx. S=5 to 6 on the tuning meter. In my unit the marker signal level was nice S=5 at 15MHz where I prefer most, so I did not perform this alignment.

The "XTAL" marker switch.

The tuning indicator hand rests on right edge when the power is off; i.e. opposite movement.
Dial light can be turned on by pushing the yellow button on the top. However the brightness is just a joke.

Shortwave 1st Local Oscillator Alignment (Dial Scale Alignment)

    Now the 2nd Local Oscillator has aligned to the new 1st IF center frequency, and the bandspread is calibrated. Now perform the 1st Local Oscillator adjustment so that the main dial scale can be properly aligned.

    Hook up the signal generator to the antenna terminal, set the band selector to SW1. Tune the generator to 4.000MHz, set the main dial to 4MHz, and turn the L12 so that the generator signal is to be received. Then set the generator to 9.500MHz, dial to 9.5MHz. Turn the CT-8 so that the generator signal is to be heard. Repeat this until the dial scale and actual reception frequency matches on both 4 and 9.5MHz.

    Same procedure should be repeated for SW2 and SW3 band, using frequencies and controls shown in the picture here.

    This adjustment went quite smoothly.

Perfect Dial

    After the dial scale alignment, the readout accuracy became almost perfect. Now we can listen to the moment when our favorite stations powering up their transmitter - welcome to the world of 5900!

MOVIE CLIP: Tune to VOA at 15.150MHz

Engage the XTAL marker, zero beat to 15.250, disengage the marker. Then simply turn the bandspread to -100kHz position to listen the VOA on 15.150kHz.
Tuning an exact zero beat may not be necessary unless you are a perfectionist; the spread dial already contains errors of 1kHz or so.

MOVIE CLIP: Tune to WWVH at 15.000MHz

WWVH Hawaii is exactly on 15.000MHz readout! Pay attention that the initial setting of bandspread is not at 0kHz when the XTAL marker is tuned. This demonstrates the bandspread substitute trimmer is properly aligned.

Boy this dial is really COOL. Modern digital models lack this beauty...
There are two versions for the bandspread dial scale ring. The unit here is the later production; 0kHz position is indicated as "0/.250/.500/.750". Earlier production had -125 to +125 indication.

Dial Setting Actual Reception Frequency Error Dial Setting Actual Reception Frequency Error Dial Setting Actual Reception Frequency Error
4.000MHz  3.991MHz -09kHz 12.000MHz 11.997MHz -03kHz 20.000MHz 19.996MHz -04kHz
5.000MHz  5.012MHz +12kHz 13.000MHz 13.009MHz +09kHz 21.000MHz 21.033MHz +33kHz
6.000MHz  6.010MHz +10kHz 14.000MHz 13.985MHz -15kHz 22.000MHz 22.006MHz +06kHz
7.000MHz  7.036MHz +36kHz 15.000MHz 15.016MHz +16kHz 23.000MHz 23.022MHz +22kHz
8.000MHz  8.044MHz +44kHz 16.000MHz 16.056MHz +56kHz 24.000MHz 24.049MHz +49kHz
9.000MHz  9.018MHz +18kHz 17.000MHz 17.078MHz +78kHz 25.000MHz 25.079MHz +79kHz
10.000MHz 10.039MHz +39kHz 18.000MHz 18.023MHz +23kHz 26.000MHz 26.010MHz +10kHz
--- --- --- 19.000MHz 19.003MHz +03kHz 27.000MHz 27.009MHz +09kHz
--- --- --- 20.000MHz 20.033MHz +33kHz 28.000MHz 28.015MHz +15kHz

    You may think the realignment result still contains error. But when I use this radio I usually look down into the dial, not moving my head to the same height of the dial. Having approx. +20kHz of intentional error is practically the best result for me.

    The sensitivity is good, however this is just another plastic body portable. It suffers the noise interference from nearby computers and monitors. Signal strength must be at least 10dBu or more to overcome the lab's ambient noise. If a 5900 with hopelessly miserable appearance, it will be fun and interesting to build a steel case communication receiver using its circuit board.

Sensitivity Variation due to the Bandspread Position - After the Alignment

    Signal level required for "S=6" indication was again measured for various bandspread positions.

    Result is shown here along with the before-alignment result. The graph clearly shows the effect of shifting the 1st IF center frequency. Still the sensitivity variation exists, however, its distribution is much better than before. Maximum deterioration is 8dBu, which has been improved from 17 dBu.
Bandspread Position (kHz) Reception Frequency (MHz) Before Alignment After Alignment
SG Output for "S=6" (dBu) Variation (dBu) SG Output for "S=6" (dBu) Variation (dBu)
-125 14.125 19 +4 23 +8
-100 14.150 19 +4 20 +5
-75 14.175 16 +1 20 +5
-50 14.200 16 +1 20 +5
-25 14.225 16 +1 17 +2
0 14.250 15 0 17 +2
+25 14.275 17 +2 15 0
+50 14.300 19 +4 15 0
+75 14.325 27 +12 16 +1
+100 14.350 29 +14 18 +3
+125 14.375 32 +17 22 +7

Frequent Asked Questions

    This section lists up some FAQs we received.

Problems Common to 5900
Do you have a 5900 service manual?

    Yes I do. However I hesitate to put it here, because I purchased it from a manual copy service. Use WWW search engines using keyword "Sony", "5900" and "service manual". I believe you'll find some services.

Is there any 5900 fan club?

    I don't know. There was a "Sony SkySensor Club" organized by Sony, mainly for sales promotion purpose. I think it ceased operation when Japanese shortwave boom faded away some 20 years ago. I know there are many 5900 fans all over the world, not to mention the Japanese fans. Perhaps you are the founder of a new 5900 fan club. Please tell me, I'll join. :-)

What is the small plastic cover on the rear panel?

    Underneath you'll find the trimmers which you can perform the shortwave frequency scale alignment. Some sources say this cover is not found in the very early production run of the 5900.

Where can I find a new replacement of pop-up rod antenna?

    It was available from Sony service center some years ago. Reportedly, all sold and not available anymore.

What is a BCL?

    Perhaps you have browsed some Japanese web pages in search of 5900 information. BCL is an acronym of BroadCast Listening. Any activity of listening broadcast radio station can be called BCL, but it especially meant the hobby of long distance reception of the broadcast stations. It was very popular in 1920s. I think this word became obsolete long long time ago (maybe by 1930s), and it meant general public who receives broadcast programs until mid 1940s.
    However in Japan, interestingly, the word BCL revived and means the activity of receiving long distance shortwave, especially in the 1970s it was very popular among boys. So the word "BCL" in Japans is identical to "shortwave listening" or "shortwave DXing". Also in Japan the word "SWL" means the activity of monitoring shortwave amateur radio communication.
Many Japanese fans call 5900 as a "BCL radio", which sounds very strange to me, and I do not use that word since it will not be recognized internationally.

Share your valuable information!

    Superior performance, marvelous styling and price affordable even to the radio kids - ICF-5900 certainly drove kids in the middle '70s to the world of electronics and communications. There's no wonder why the enthusiasm still persists with the 5900s in Japan and all over the world.

    Please share your story or valuable information such as restoration topics.
NoobowSystem's Guest Book can be used as ICF-5900W discussion room . Please leave your comment, information, or any words regarding 5900. We have received many emails from all over the world, which I think many 5900 fans want to share.
    Guest Book can be accessed via NoobowSystems Lab. Homepage .
We also want to have a link to your 5900 information. Please let us know your website.

The 5900's logo, appeared in Japanese advertisements. SINPO55555-BCL RX clearly indicates the 5900's target market. Katakana characters above "5900" reads "SKYSENSOR", very famous name for the high performance SONY portables in the 1970s.

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Copyright(C) NoobowSystems Lab. San Jose, California 1999
Copyright(C) NoobowSystems Lab. Tomioka, Japan 1999, 2000, 2001, 2002, 2005, 2006, 2009

Jan. 26, 1999 Created.
Feb. 16, 1999 Revised.
Feb. 17, 1999 Revised.
May. 15, 2000 English version.
Dec. 15, 2001 Relocated to
Feb. 13, 2002 Revised.
Mar. 02, 2002 Revised.
Mar. 21, 2002 Added transistor list.
Mar. 24, 2002 Shortwave alignment performed. Sensitivity at +125kHz improved.
Mar. 25, 2002 Corrected typo, revised.
May. 05, 2002 Revised. Added EXT POWER IN description.
Jul. 27, 2002 Revised links.
Jan. 21. 2005 Reformatted.
Jun. 13, 2005 Retouched.
Jan. 06, 2006 Reactivated Japanese page.
Apr. 07, 2006 Added Links info provided by Galassi. Thanks!
Sep. 02, 2009 Reformatted.
Mar. 23, 2013 Updated.