Hi all.
I barely know what I am doing in the world of tuners. I have the above receiver and it has absolutely no FM reception.
When testing, all transistors seem to behave correctly.
I found a chip with some very weird voltages. It's the LA1231 FM IF system chip.
Voltages are:
1) 0.072v
2) 0.06v
3) 0.06V
4) 0v (GND)
5) 0v
6) 0.07v
7) 0.239v
8) 0.237v
9) 0.239v
10 0.237v
11) 13.7 (Supply)
12) 0v
13) 0v
14) 0v (shorted to GND via PCB)
15) 0.017v
16) 0v
According to all info I can find, Including LA1231 datasheet and service manual, all voltages are very off (except pins 11, and 4).
Is this looking like a bad IF chip to anyone? What should I check more/next?
How would you go about restoring the FM receiving abilities of this unit?
BTW:
The receiver had no AM reception and while on FM, the "FM Stereo" indicator was on, permanent. But I found a defective resistor supplying the power supply to KB4431 MPX chip. Now AM seems to work (I think) and the indicator is now null, as it should be.
I barely know what I am doing in the world of tuners. I have the above receiver and it has absolutely no FM reception.
When testing, all transistors seem to behave correctly.
I found a chip with some very weird voltages. It's the LA1231 FM IF system chip.
Voltages are:
1) 0.072v
2) 0.06v
3) 0.06V
4) 0v (GND)
5) 0v
6) 0.07v
7) 0.239v
8) 0.237v
9) 0.239v
10 0.237v
11) 13.7 (Supply)
12) 0v
13) 0v
14) 0v (shorted to GND via PCB)
15) 0.017v
16) 0v
According to all info I can find, Including LA1231 datasheet and service manual, all voltages are very off (except pins 11, and 4).
Is this looking like a bad IF chip to anyone? What should I check more/next?
How would you go about restoring the FM receiving abilities of this unit?
BTW:
The receiver had no AM reception and while on FM, the "FM Stereo" indicator was on, permanent. But I found a defective resistor supplying the power supply to KB4431 MPX chip. Now AM seems to work (I think) and the indicator is now null, as it should be.
Sure is.
I did mention the tuner was out.
Now I am trying my best to tackle this issue as well...
Any help will be appreciated. 🙂
I did mention the tuner was out.
Now I am trying my best to tackle this issue as well...
Any help will be appreciated. 🙂
Thanks.
I've already been to the datasheet. This is one of the sources from which I know my voltages are way off.
But I'm not sure it indicates a bad chip or rather something else...
I've already been to the datasheet. This is one of the sources from which I know my voltages are way off.
But I'm not sure it indicates a bad chip or rather something else...
Could be the internally regulated power supply is pulled down somewhere by a shorted external component.Check for shorted caps around the chip.
If that's not the case, it will be the chip itself.
If that's not the case, it will be the chip itself.