Radio illumination, need a little help from someone with a working SC80x radio please

Problem is that *all* the bulbs are out, in fact they've never been on
since we have owned the car but I thought I'd finally get round to it
whilst doing a few other illumination bulbs.

I've been round this with a meter and can confirm that none of the radio
illumination bulbs have blown, continuity exists from the power board of
the radio down to the bulbs themselves and I'm pretty confident that
it's the voltage regulator on the power supply PCB that's at fault.

However without a working one, I'd like to confirm the component first.

It's the 3 pin TO220 package on the board behind the heatsink that also
carries what appear to be the IC amps.

The component is marked as DI 764 and then beneath 246 with a logo that
I can't locate, nor can I identify the part directly.

On the left pin is 12v, centre is ground and right pin goes to the DIM
pin on the connector and that finds its way to the bulbs.

That's a pretty standard pin out for a regulator and certainly appears
to match all suspects since on mine there's no output from the output
pin.

Now I did come across a link that suggested that the bulbs were powered
by some odd voltage, 6.5 or thereabouts. I can get a 6v regulator which
won't make any difference but I'd really like to know the actual
measured voltage or confirmation of the part if anyone feels like
popping their radio out and measuring this for me?

Please?

David.

 

The voltage to the lights work a bit funny.
The rheostat for the illumination of the instrumentpanel also controls how
much light you have in the radio.
On the large 14 pin connector on the back of the radio, pin 11 (black wire)
is ground for the lights and pin 10 (pink) is the positive signal from the
rheostat.

Check you have correct power on those pins.

Niels

 

The voltage to the lights work a bit funny.

Thanks, I'll check that. I was looking at this diagram

http://webhome.idirect.com/~rwoodrow/

and it seems that the belief that pink is -ve is possibly because the
lights weren't on at the time of test?

David.

 

I have been looking at a wiring diagram from Volvo from a 1995 Volvo 850.
If you cant get it to work I can scan it, so you can have a look yourself.

Niels

 

On the large 14 pin connector on the back of the radio, pin 11 (black wire)

Sorted with that info thanks. I have a car phone kit with telmute
interface lead and that brings "illumination" out on the wrong pins and
since I couldn't find anything on the pink wire didn't think to check
that one.

I went so far into the radio by this time that all I was finding was
power to the one side of the voltage regulator and assumed that it was
faulty.

Cheers, have an eBeer!

David.

 

Are you sure that doesn't say D1764? TO-220?

Industry Number : D1764
NTE Device Number: NTE2332
NPN,SI DARL W/INT ZENER&DAMPER,TO-220

 

http://www.nteinc.com/specs/2300to2399/NTE2332.html

just in case this is the IC.

 

Sorted with that info thanks. I have a car phone kit with telmute

Further to this, the reason why I didn't think of this before is that we
bought the car about 5 years ago in the summer (light evenings till
about 10pm) and then had the car phone kit installed almost straight
away. I don't think i've ever seen the radio illuminated until this
evening.



David.

 

It does and I'm sure I tried D1764 but just couldn't find anything.
Given that it's coupled to the dimmer circuit, I was wondering if it was
an darlington output transistor.

Irrelevant now anyway but thanks. As of yesterday, I knew nothing about
the Volvo radio illumination, amazing what you can find out within a
day, I now know more about this than I intended to.

David.