LUXMAN   vintage audio

PrinzSound  T-900 AM/FM Tuner

 

General:

Around 1970 issued tuner for European market, made for the 'Dixons' company, by "Cometro Electric Company" in Japan.

Front on & off ^
 

Owners manual:

(not yet available)

 

Interior, simple yet very well built and good pcb's used, remarkable too simple power supply: 1 diode & 1 capacitor, photo made starting the update process ^
 

special futures:

This solid-state tuner is with DIN socket to be replaced by RCA output sockets.
Nice simple look tuner.
Wood case.
Well build and good parts used.
2 gang variable capacitor.
Good quality tuner with remarkable good specs.
This tuner employs all silicon transistors & 1 fet and 1x PC554C NEC MPX-IC .
The tuner has a stabilzed power supply.
Traditional ratio detector, traditional MF section with coils.
AFC switch at the front, well working and very usefull.


                          

MPX decoder IC with filters & coils: plenty of stereo ^

Stabilizing power supply, from 14Volt to 9Volt: the 2SD261 made by NEC is doing a fine job ^

 

Power supply problems:   

The detrimental power voltage change from 220 to 240V in the EU is no issue here: The tuner has a 240V transformer.
The rectifying in the supply section of the tuner is too simple: only 1 diode is used, and only 1x 1000F capacitor.
This makes the tuner vulnurable to 50Hz hum.
I upgraded the secondary part of the supply to a rectifier bridge with 2 capacitors making 2200F.
I also used the remaining diode for the led's that I replaced the bulb for the scale.
A few extra capacitors may be added to the power supply to get it to modern standards.



Power supply upgrade ^

 

AM antenna ferrit bar inside ^

 

Specifications:

FM IHF sensivity: 1,8 V at 25 dB S/N.
Capture ratio 1.6 dB.
Distortion (THD 20Hz - 16kHz) ~1% at max input voltage.
Signal/noise ratio: 60dB stereo.
Channel spearation approx. 40 dB.
AM works well.

 

Schematic:

click here for the schematic diagram of the PrinzSound T900 Tuner (construction)

                     

Back with new RCA sockets ^
 

Modifications:

This tuner may have some issues. The power supply should be updated.

The stereo lamp should be exchanged for a red color Led.
The scale lamp can also be exchanged by a ledlamp.

The output level pot may be obsolete.

You may replace some capacitors in the power supply and power rail. Check all caps through the whole tuner.
Wiring can be improved too, some resistors may have incorrect values. The output DIN socket is obsolete.
I replaced the DIN for 2x RCA sockets.

The only 2 gang FM front-end variable capacitor could have given a problem in the years from 1960 to end 1990's
when the FM band was a very busy used.
The lack of serious selectivity could ie. in cities with a full FM band make this tuner not the best choice.
Today this is not an issue anymore because the FM band is quite empty, and this tuner in all its simplicity can
outperform modern cheap FM tuners today: it is sensitive, stable and gives very good audio to your amplifier.
Of course its no match for a Hi-performance FM tuner like a Luxman T12 or T14, but it never meant to be.

After modification this is the result:

As new again: Fully updated and upgraded ^

2 gang variable capacitor, but very good performance.  ^
 

Front-end first transistor: FET 2SK37, gives very good FM sensivity ^
 

Very good pcb, typical build of Cometro Japan ^

 

Amplifier that goes together with the T900 ^
 

GB model with different knobs and black front ^

 

Sound:

The sound is remarkably good for this simple and vintage tuner.

 



Dixons price list ^
 

Add of Dixons with the T900 in the list V

 

Hans Hilberink - PE1MMK 2003 - Last update: 04-02-2019.