Technics CD-4 Demodulator SH-3480

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audiomaster

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CD-4 demodulators must have been a repairman's worst nightmare. And given the seemingly endless problems associated with these things I wonder how many of them were never even set up properly in the factory.
I noticed the spec sheet said 100 volts input. Might need to get a stepdown transformer for 120 volts!
 

MidiMagic

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Sounds like the spec sheet was for a version of the demodulator made for eastern Japan.

In eastern Japan they have 100 V 50 Hz power.
In western Japan, they have 120 V 60 Hz power.

It has been that way ever since the reconstruction after World War II. Groups from different countries made the different systems.
 

Wurly1

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CD-4 demodulators must have been a repairman's worst nightmare. And given the seemingly endless problems associated with these things I wonder how many of them were never even set up properly in the factory.
This is the CD-4 demodulator in my Technics SS-1100D system.
No coils, no adjustments, no pll circuits. It uses a lot of transistors and filter capacitors. Diodes are used to detect the FM - PM 30 khz carrier signal.
I recapped it and it work flawlessly! Even if i accidentally set the wrong speed on the turntable, it still detect and demodulate the rear channels.

correction: there are two "seperation adjustment" pot in the final mixing stage.
 

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Soundfield

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I'm amazed how simple it looks - only forty or so transistors. Clearly they didn't make enough money out of those and had to make them much more complicated and expensive.
 

Doug G.

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Hmm, both my SE-405 and SH-400 perform without a hitch after 45+ years. All original parts.

Now, one of my SQD-2050 SQ decoders - I had to replace a diode after 45+ years. :D

EDIT: And now I find Q301 is bad (worked for a few minutes and then back left channel dead) in the same SQD-2050 and will be replaced with a 2SC1845. Maybe I should write Sony and question their parts longevity. :D

Doug
 
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surround.sound.enthusiast

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I noticed the spec sheet said 100 volts input. Might need to get a stepdown transformer for 120 volts!
Indeed. Looking at the rear photos from the actual auction, its a 100V model. I'm not surprised though, as every 3480 or 3580 I've paused to look at have all been 100V. It would be convenient to find a 120V version though. If furui_suterioo has previously already branched into Japanese quad equipment he may already have a 100V step-down transformer.
 

Wurly1

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I'm amazed how simple it looks - only forty or so transistors. Clearly they didn't make enough money out of those and had to make them much more complicated and expensive.
I reverse engineered it. With the sections identified on the pcb, it was easy to understand it's working principle. It is simple, effective and large! About 4 inches x 11 inches.
 

furui_suterioo

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Indeed. Looking at the rear photos from the actual auction, its a 100V model. I'm not surprised though, as every 3480 or 3580 I've paused to look at have all been 100V. It would be convenient to find a 120V version though. If furui_suterioo has previously already branched into Japanese quad equipment he may already have a 100V step-down transformer.
Yep, and the two extra outlets on the demodulator are useful since my step down transformer only has 1 outlet.
 

Owen Smith

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I reverse engineered it. With the sections identified on the pcb, it was easy to understand it's working principle. It is simple, effective and large! About 4 inches x 11 inches.
I noticed in the picture how each logical section of the circuit is clearly outlined and labelled in the silk screen. This was from the days when equipment was designed to be repaired.
 
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