Yamaha TX-900U Tuner Bulb Voltage Anyone?

[wajobu]

Hi there all,

One of our sons has a Yamaha TX-900U tuner (I know, I know...not entirely "Vintage"). All of a sudden this afternoon the digital display went out...oh oh I thought...digital module is gonzo, but the tuner still worked. So I opened it up and much to my surprise the digital display is backlit in a dual projector-like housing with two bulbs. The bulbs were indeed burned-out. All I have is the typical Yamaha CR/CA era 12V 60mA bulbs and they work for now, but are rather dim.

Does anyone have a TX-900U schematic or could advise what the bulb voltage/mA is?

Thank you!

 

[wajobu]

Found this thread...looks like 9.2 volt--though not sure the mA.

http://audiokarma.org/forums/showthread.php?t=52685&highlight=TX-900U

 

[the-real-mandak]

It seems to be a common problem, my TX-900 did the same. I think Yamaha uses the same bulbs in most of there gear from that time, if so it will be an 8V150mA L = 300 (data from the bulbs in the M-85).

 

[wajobu]

Thanks for that t-r-m...guess I'll contact good ol' dgwojo

 

[the-real-mandak]

No, problem. But it does look like joelongwood got the info from Yamaha, try to look at the base of the bulb - there might be some data.

 

[yamaha]

I measured the TX-900 bulbs to be 8.2 volts AC with a multimeter.

I replaced each bulb with the following parts:

10mm White LED RadioShack#: 276-005
270 ohm 1/2W resistor RadioShack #: 271-1112
1.4A, 100V Full-Wave Bridge Rectifier RadioShack #: 276-1152

For each bulb, the existing tuner leads were fed into the AC point on the rectifier with the positive leg of LED to the positive lead of the rectifier. The resistor was placed between the negative lead of the rectifier and the negative leg on the LED.

The LED needs to be scuffed up pretty good to keep it from forming a hot spot on the display, but it works, and it's plenty bright.

 

[avionic]

This thread is back from the dead..