DENON AVR3300 no FM reception

Firstly, verify that there are proper supply voltages getting to the tuner unit. If the receiver is digital controlled, check to see if the tuner unit is being properly commanded by the uPC. Check to see that the local oscillator and RF amp in the tuner is working.

If you replace any parts in the FM front end or do any kind of soldering, you will need the instruments and skills to perform the front end calibration if you want peak performance from your receiver.

You will need a good scope and the full service information to properly troubleshoot the front end of your receiver. If you call the parts department for Denon, I believe they will sell you ca copy of the service manual and any parts you need.

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JANA
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"Brasto"  wrote in message 
news:1189445251.055375.150880@g4g2000hsf.googlegroups.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

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.

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...

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.

..Oeps..Got myself in deeper trouble..I had this suspect front-end swapped into a known to be good tuner TU580RD, it performed OK that day. A few days later I reapplied mains to the TU580RD and NO more FM reception. I then reinstalled its original front end and gray hairs...it did NOT work any longer. Measurements showed that B+ had gone. Doing some PCB line tracing ended up to SMD TR23 failed to switch +12 VDC when so commanded. Removed the bug from the board and patchwired +12 VDC to B+, Life returned to the TU580RD. I now have a need to know Type/PN of the SMD switch (No markings left) at PCB location TR23. ?? Who can help ??

So I learned the hardway that my original frontend from the AVR3300 probably developped a short in the B+ over times. I put the suspect frontend back into the AVR3300, disconnected its B+ PCB jumper wire and applied an external 12 VDC. No smoke but a full short..Let me tell you that probing around in the tiny little front end is a challenge of its own. Some engineer must have thought that RF leakage shall be minimized by soldering a tripple housing at all the fingerstocks. Unfortunately the circuitdiagram Mark so kindly provided to me does NOT cover the front end. DENON has classified this part probably as a Black Box....Sealed Do Not Open....

I'll just wait for another FM unit to canibalize its front-end

oorspronkelijk bericht niet weergeven -

Well, it's an A OK, ordered a new Front end (Mitsubishi) and replaced the SMD T105 (RN1205) which failed to switch the 12 V B+ to the front- end. The old front-end had obviously developed an internal short on the B+ line with temperature/time. I still donot understand this because according to some lay-outs there is always 100 ohms in the internal B+ circuit. Probably that a short develops underneath one of the SMD components and a tiny PCB trace.

Anyway, again thanks for your help(s), It saved another fine product from the trashcan...