"Brasto" wrote in message
ps.com...
On 11 sep, 12:24, "Mark D. Zacharias" wrote:
I have sent a diagram of the tuner section to your gmail address. A quick
glance suggests that pin 5 is the voltage contolled tuning input;
transistors TR 505 and 504 appears to be the AM and FM switches.

Mark Z.

"Brasto" wrote in message

ups.com...



I like to restore the FM reception to normal ops. So far I have
diagnosed that AM reception/tuning is in good condition. In the FM
mode no IF signal is getting to pin 1 of the IC LA1265 so I belief
that the little tuner block is at fault. I managed to remove the
shielding covers to get access to the tuner section which really
exposed a jungle of SMT devices.
To find my way around this multigang-ed tuner I hope that some one can
provide me with a copy of the DENON FM front end or any help to
troubleshoot the receiver

Thanks
Bram- Tekst uit oorspronkelijk bericht niet weergeven -

- Tekst uit oorspronkelijk bericht weergeven -

Mark,
That is great info and probably will lead me to the desired
result......
In the mean time I took another DENON unit apart which is a working
straight forward AM/FM tuner. It's front end is from a different
manufacturer and has a different format/technology, but it also had 8
pins with the same pitch as in the AVR3300. I decided to swapp both
tuners and guess what....the suspect works as advertised and the known
to be good tuner did not function in the AVR3300. So I learned at
least one thing...my front end is OK. I also learned that the AVR3300
does NOT provide the B+ and the Tuning Voltage is stuck at B+ value. I
am still struggling to understand all the *# Note numbers in your
schematic telling that things are OPEN. Is your schematic covering
various versions of the AVR3300 ?.
E.g. top LH corner shows Front End with floating AGC line and
additional pins 9, 10 and 11 which do not exist in my unit and a bunch
of akward connected resiustors.R504...R571)
Am I correct assuming that IC 507 (LC72131 is generating the VCO
voltage to pin 5 of the front end ? and also switches via pin 10 the B
+ thru TR505 ? I am afraid I might end up with a Buss problem in the
PLL circuit ?

Thanks also to JANA who pointed out that the drive signals from the
Uprocessor might be wrong rather than the tuner itself.....


I don't know what the story is on those extra pins - Denon's service manuals
can be pretty crappy, especially these scans of their older ones.
I think the PLL IC is probably bad - this is a pretty common failure.

You can apply an external tuning voltage to the front endm vary it through
the range and see if the tuner tunes, and also that there is an oscillator
output, but of course there should be, since you've pretty well found the
front end to be OK...

Am I correct assuming that IC 507 (LC72131 is generating the VCO
voltage to pin 5 of the front end ? and also switches via pin 10 the B+
thru TR505 ?

I think so; also bear in mind that the AM/FM switch outputs on pins 10 and
12 of IC 507 would each be high and low at any given time - that is, they
should not both be at the same state at the same time. This is another type
of failure the PLL IC could have.

Mark Z.