Tuner problem

[Zeljko]

I know that it is hard to fix tuner section without scope, but I don?t
have it, so if someone can help me without using scope, this would be
fine.
I will write what I did until now about non working tuner:
- First, now I can catch two FM local station but signal is very weak, I
have some movements on tuning meter when I seeking stations from 88 MHz
to 108 MHz, but signal meter is always on 0 (because FM signal is always
weak). Because of that I mean that local oscillator is good on front
end.
- I have changed FET01 with new one
- I have changed TR01 and TR02 on F2714 and TR01 on F2919 with the same
2SC1674
- All resistors are good (I checked) and I have replaced C02, C07, C14,
C25 and C28 on F2919
- I have replaced IC03 on F2919 HA1137W

After all, the tuner doesn?t work!

Here there are results of measuring on F2714 Board:
TR01
E-1.3Volts
B-1.98Vlots
C-13.42Volts

TR02
E-7.26Volts
B-7.89Volts
C-13.42Volts

And here http://public.carnet.hr/~zekalini/G8000FM_tuner.jpg I have
schematic diagram of FM part of Sansui G8000 tuner

I finally I have one more question, If I damaged FET with ESD (but I
have shorted all legs of it with one wire, and when I connect it on
board, I removed this wire, I am only asking if?), doest it damaged FET
can pass FM signal or it cannot pass signal?


Regards!

 

[Zeljko]

I know that it is hard to fix tuner section without scope, but I don?t
have it, so if someone can help me without using scope, this would be
fine.

As you probably seen, it is tuner of old Sansui G8000 receiver.

Regards!

 

[JANA]

You will definitely require the proper test equipment to determine if your
unit does not have any more defective components. Going through the
alignment procedure of the front end is a way to sort of prove if there is a
fault.

For the alignment, you are going to require a FM type calibration signal
generator that can operate in the range of 80 to 110 mHz and 10.7 mHz, with
both carrier, and modulation mode. You will also need a scope, DVM, and if
you are not experienced with the particular model, you will need the
alignment instructions from the service manual.

Trying to troubleshoot and align a device without the proper test gear is
like trying to drive your car through the streets blind folded. You have
absolutely no way to know were you are going.

I have never yet seen someone be able to perform an accurate alignment
without the proper setup. There are some experienced techs that can sort of
do this by ear, if the receiver is not too far out in the first place.

Your only other alternative is to give the set out to a service centre that
has an experienced tech who can work on the front end of FM tuners.

--

JANA
_____


I know that it is hard to fix tuner section without scope, but I don?t
have it, so if someone can help me without using scope, this would be
fine.
I will write what I did until now about non working tuner:
- First, now I can catch two FM local station but signal is very weak, I
have some movements on tuning meter when I seeking stations from 88 MHz
to 108 MHz, but signal meter is always on 0 (because FM signal is always
weak). Because of that I mean that local oscillator is good on front
end.
- I have changed FET01 with new one
- I have changed TR01 and TR02 on F2714 and TR01 on F2919 with the same
2SC1674
- All resistors are good (I checked) and I have replaced C02, C07, C14,
C25 and C28 on F2919
- I have replaced IC03 on F2919 HA1137W

After all, the tuner doesn?t work!

Here there are results of measuring on F2714 Board:
TR01
E-1.3Volts
B-1.98Vlots
C-13.42Volts

TR02
E-7.26Volts
B-7.89Volts
C-13.42Volts

And here http://public.carnet.hr/~zekalini/G8000FM_tuner.jpg I have
schematic diagram of FM part of Sansui G8000 tuner

I finally I have one more question, If I damaged FET with ESD (but I
have shorted all legs of it with one wire, and when I connect it on
board, I removed this wire, I am only asking if?), doest it damaged FET
can pass FM signal or it cannot pass signal?


Regards!

 

[Tim Schwartz]

As you probably seen, it is tuner of old Sansui G8000 receiver.

Regards!

Zeljko,

I have to agree with JANA that an alignment is absolutely necessary.
As soon as you replace the FET, or even remove and reinstall the old one
you will need to realign at least the front end. Even moving the
position of parts in the front end can effect the alignment drastically.
In general, replacing parts in the front end, unless you know that
they are defective, causing a problem and must be replaced is a bad idea.

Regards,
Tim Schwartz
Bristol Electronics

 

[Zeljko]

Your only other alternative is to give the set out to a service centre that
has an experienced tech who can work on the front end of FM tuners.

I have Service manual for this receiver, and because of that I know
alignment procedure but I don't have any equipment than FLUKE Digital
multimeter, so I will do what you suggestion me and bring this beauty to
qualified service.
Thank you and best regards!

Zeljko