Luxman T12 FM tuner

General: 

This Tuner was produced by Luxman in 1980. This is one of the best tuners Luxman ever made,
it has great reception capabilities and sound is excelent. It incorporates great lineair filters in the MF section.
It has some special features, like switchable MF bandwidth and lock of the tuning knob.

 

Photos:

Front ^

interior view of the unrestored T12 ^

bottom view - all photos of the unmodified tuner. ^

Front-end view, 5 gang variable capacitor, input antenna and output to MF section. ^

 

Special features:

Switchable MF bandwidth, test tone, switchable Accutouch, anti birdies filter, multipath switch.

 

Schematic:

The Luxman T12 tuner schematic diagram in pdf format, click here.

 

Modifications:

All electrolytic capacitors in the power supply can be replaced.
Some capacitors can be added to the power supply rail through the tuner,
to improve stability.

C193 of 3.3 uF can be replaced. A better quality cap may improve the sound.

The HA11211 discriminator IC can get defective and must be replaced in some cases, one of the
major symtoms in that case is, that there is no centre tuning possible anymore: the centre tuning lamp stays off.
Also the accutouch is often not working properly anymore in the same case.
Replacing the IC and adding a coil and extra capacitor in the IC's power supply
line may be appropriate to keep this IC up and running.
I used a capacitor of 0.047 uF 50V and a 1 uF 50V electrolytic in combination with a coil,
suppressing noise-instability and HF noise on the power rail.
Also I changed the 22 Ohms resistor in 33 Ohms to get a stable 12V on pin 11 of the IC and reduce max. current.
Max. current through the IC can get high in some cases: caused by the unused AM section that is short-circuited.
A small heatsink on top of the IC is possible, I used a common IC heatsink with thermal grease.

Also a anti birdies filter is employed by some local distributors as in the model above,
can be subject to upgrading or modification. (Audioscript Netherlands)
More simple and also effective anti birdies filters are possible. (Sherwood USA, Denon Japan)
On most of the anti-birdies filter boards low grade caps are used, you may replace them with high grade ones.
I made a modification to this little additional board, that made the sound even better.

Users in Europe must consider to change the mains transformer tap used for the mains connection, it is historically set to 220V.
But since Europe is increasing main voltage to detrimental 240 V over a 20 years time frame, and now being on plus 230 V ~.
So using the 240 V tap is the most sane thing to do now.
Change from the purple or orange (photo above) wire to the red wire of your transformer,
do not wait untill internal voltages of the tuner get too high.
Some transformers may have different coloured wires.
Some tuners may need a internal mains filter to suppress mains noise.

Readjusting the frontend after many years of service may be an option.
Some tuners may suffer unsensitivity because of a worn out front end first mosfet 3SK45,
but most T12's will not have problems in this and are very sensitive.

Some T12's have switching problems with the tiny switches on the front panel, most commonly caused by dust and
by wear of the plastics inside the shaft in the front panel of the tuner. Making a little more room solves this.
Sometimes a little silicone spray helps.
I use a Würth solvent (not avalable in many European countries and some USA states).

In some tuners there is the 300 Ohms connection still working, if you do not need that,
please disconnect internally to improve input sensivity and better rejection of unwanted reception
of very strong interfering signals through the whole FM band.

The Hitachi IC's suffer the same silver creaping desease as their old transistors,
consequently in early 2018 the mpx stereo-decoding IC: HA11223 broke down due to this phenomenon.
I had to replace this IC and after this repair I tracked some other problems again of aging in this tuner.

The Audioscript addition anti-birdies filter op-amp IC's were deteriorating (!),
so I had to address this issue as well, I took the whole pcb out and inserted
a new one with discrete transistors, this improved the sound very much.
Today with less crowded FM bands the anti-birdies filtering may be obsolete.
I experienced that on places where only 3 or 4 broadcasting stations left on FM,
the anti-birdies filter has no important function anymore, you may leave it best out of the circuit.

 

Sound:

When you do the upgrades you can get a fantastic sounding T12 FM tuner that has good sensivity,
good selectivity, good noise figures, good stereo and very well dynamic LF characteristics.
Because of the choice of specific electronic design Luxman made in some sections in this tuner,
the T12 can sound exeptionally well, pity is that some additions by some Luxman distributors and some design
errors Luxman made in the initial electronic design, the sound is not what it can be in the not upgraded T12.
Upgarding & changing some things and removing some additions show how excellent this tuner can sound.
Together with a few other brand FM tuners, this Luxman T12 is one of the best sounding FM tuners ever made,
outperforming many well regarded & well known brand FM tuners.
 

Updated interior of a Luxman T12 tuner, (source: www.tubejack.nl thanks Jack)

 

Concluding:

These Luxman LSS series of audio components soon got legendary by
their outstanding build quality, excellent sound and good durability.

© Hans Hilberink - PE1MMK ® - Last update: 26-02-2018.