Captain 55 ICF-5500M

The control panel suggests that the meter is VU (audio level) or Tune/Batt. However I can't see by schematic or operation how it shows battery condition. A clue may be that the meter rests at right with power off or batteries removed. I'm not convinced the schematic is correct on meter wiring, looking at how VU works. Or I'm confused.

The VU-meter works from left to right; right being the strongest signal. The battery-meter the other way around, from right to left; left being the fullest battery. It is indicated on the meter by the fat line. In the fat aerea the battery-strength is sufficent. If you use a variable powersupply, and you switch from 4.5 V to 3.0 V, you will observe how the meter goes from 'good' to 'bad'.

Thank you!

I can see now that on any band with no signal, on RF level rather than Audio level, with the batteries getting lower, several weeks use, that the needle no longer rests on zero but near edge of fat part. Plugging in the 4.5V PSU of the Sony ICF2001D makes needle go to zero. No doubt the user instructions explain this, but online I only found a service manual. I then tried with variable PSU (centre of power jack is negative, barrel is positive unlike newer equipment).

Curiously with jack plugged into "DC Out" (lowest socket, presumably to turn on a recorder or power a MPX decoder?) the meter goes to full scale (i.e. the normal off position). A most unusual arrangement! In VU mode the meter is simply driven by a pair of diodes implementing a peak detector across the secondary of audio out transformer.

So with no signal at Tune/Batt position, the lower scale is battery condition with:

• 0 on top scale about 4.5V
• End of fat part about 3.4V (about 4 on top scale)
• Separate pip is 3.0V (about 6 on top scale)

The 1974 UK service manual doesn't seem to mention this, or I may have missed it.

1. Remove the batteries and carefully prise off all knobs.
2. Take out the four rear screws
3. Lift chassis out from battery end. It comes out easily especially if all top switches are at off.
4. Tune past 530KHz till end of scale. There is a small white line on the scale film. Align with slot on mount by gently disengaging the scale film drive cog.

Make sure on VHF alignment that the AFC is OFF and if using a cheap "MP3 FM" transmitter, don't feed audio to it.

There are two slots, one for VHF scale on left and one for AM on the right to show tuned frequency. The VU meter pops out to reveal L3, RF VHF trimmer (88MHz). On my model the CT8 (108MHz ) is beside it but accessed from PCB side. The service manual specifies 86.5 MHz and 109.5MHz as tuning points. If you are using a cheap MP3 player FM TX, use 88MHz (or 87.5MHz) and 107.50MHz (or 108MHz) instead. The Local Oscillator is CT7 (108MHz) and L6 (88MHz). L6 seems to be tricky. Use a plastic tool.

Otherwise follow the service manual. Email me if I forget to upload the rest of it.

As an aside, the power consumption is actually less than a TENTH of a 21st Century DAB radio (30 hours on 4 x Alkaline D cells). It should manage over 150 hours on  3 x Alkaline C cells.

The Sony Captain 55 is powered by only 3 baby cells. The battery current is 50 - 100 mA at normal listening volume. This is a rather large current. Above that, the minimum voltage that the radio needs, in order to function normally, is about 3,8 V. This means that the radio needs new batteries at a point where the batteries are not quite empty (considering that normal equipment can run on lower voltages).

Because of this power consumption I decided to use rechargable batteries.

At the time I bought this radio, the best choice was NiCads. But 3 NiCads deliver only 3 * 1,4 V = 4,2 V at max, right after charging. This voltage lowers rather quickly below 3,8 V. Not enough. So I put in a fourth NiCad in the radio itself, right below the timer. Some plastic had to be removed to make some space there. After that, the voltage was a nice 4,4 V (battery almost empty) to almost 6 V (battery full). The radio can use that extra voltage well and functions better. And, very important: the radio is not harmed by this 6 V.

A miniature electronic circuit was designed and installed in the radio (!) to watch the battery voltage. Below 4,4 V this electronic switch switched off the whole radio. Doing this, the NiCads were protected against too low battery voltage during use, and therefore they live much longer. I will put the schematic on this forum later.

To be able to charge the NiCad battery, the "power in" connector was modified also. This connector was connected directly to the battery. 

Versions of the ICF-5500M exist that have a function of short range FM transmitter/receiver. It can be compared to a CB transceiver. The little plate that says "Captain 55" is not there, but instead there is a push-down switch that switches the radio in FM transmitter mode.

It seems that this was popular in Japan.

This model with FM transmitter function exists also in RMorg: Sony ICF-5500.

I tried to answer to the first version of your post this:

"

My apologies to mr. Salvador Galan-Ocaña.  Because a few minutes after my addition to the Sony model ICF5500M, I discovered that he has entered exactly this model (the model with the FM transmitter) to RM.org.

Bernhard, you can find the model I refered to, here:

http://www.radiomuseum.org/r/sony_icf_5500.html

I have mailed RM.org at once about my mistake. Later this day I will delete my information or (if that is not possible) ask a moderator to do that....

 "

The site would not let me post this. But now I see why: you were editing your post.

P.S. You deleted your first version of your post without a trace - but IMHO it is better not to do that, because that can be confusing to other readers, and myself.

Dear Peter,

since no reaction to my first post arrives, I deleted the post few minutes after recognizing the existence of the Sony ICF-5500 in RMorg. I don't realize that your answer was on the way nearly the same time... You're right, this can be a source of confusing to others, a correction should always be the better way. I apologise this... thanks.

Bernhard

Bernhard,

Yes, that is what happened. A well, things like this can occur. No big problem.

Now about the FM transmitter in this special Japanese Sony ICF5500 model. I would like to see the circuit but that seems not te be available.

This set seems to exist in AM IF 455 kHz and 468 kHz (maybe UK ?) variants, see images of typeplates.

Kind regards Martin Boesch

Yes, the service manual covers both UK (AM 468) and AEP (AM 455) versions of the ICF5500M. This sort of change is common to avoid a hetrodyne whistle on a popular UK station (2nd harmonic?). The differences are now in the notes. I've no idea why the audio output power differs slightly (1.6W vs 1.8W).