Denon AVR-2310

This was a sort of impulse buy as I'd been thinking of renewing our ancient Teac AG15D with a better surround sound amplifier as well as tackling a new repair project. I spotted this as a "spares-repair" item for a fair bit of money (£73). I offered about 75% of the asking price (£55) and was a little surprised to spot next day that it was due to be delivered in a couple of days. It turns out that Paypal has added a tick into a box of which I wasn't aware to seal a deal without my involvement. Anyway, I suppose it saved a few days but nevertheless they are more than a bit remiss in doing what they did.

At this moment I stopped typing to meet the delivery man at the gate....

It was pretty heavy and, as advertised, in its original box. I opened it and again, as described, extra bits and pieces were included. I'm very puzzled because the thing looks brand new. The remote looks new also except for slight scratches on the back. The front of the remote and the rear buttons under a cover look unused and there are no batteries fitted. Why should an amplifier of this age (circa 2010) look so new and why was it described as having "no power"? I checked the mains lead (this is the original Denon lead complete with plastic cover) and looks to have never been used. Both 13-amp prongs had continuity to the 2-pin IEC socket, but plugging in the mains lead and pushing the ON button resulted in nothing at all hence "no power". I checked the rear mains input connector and saw no continuity at all... seemingly open circuit. More and more puzzling. Did the equipment suffer a mains overload not long after it had been purchased or is it a "customer return" that's been lurking somewhere for many years? Could its history be simply that it didn't work because batteries hadn't been fitted in the remote and it just died after being abandoned in someone's loft? I checked for a rear fuse but there's none to be found but I did notice there were no scratches or marks of any kind at the back very odd.

Is it for 110V, but no, it's marked 230V 600W

I removed the top cover (9 screws). The mains transformer has a thin covering of dust suggesting it has seen some service.

This is the power supply area with its circuit board and thankfully it's not a switching type, just a common or garden mains transformer with rectifiers, capacitors and linear regulators.

Two fuses are hidden away in an awkward position, and you can just make out a power relay connecting the large mains transformer to the mains input.

At the bottom of the board where it connects to the motherboard I spotted a tiny yellow standby mains transformer (under that white wire).

To examine the board and attempt to find the fault I had no real option but to remove it.

Removal of the board seemed to be possible after freeing it from two multi-way edge connectors mating it to the motherboard, however that bulky mains output connector (seen below) prevented straightforward removal.

Firstly I needed to remove or slacken dozens of rear panel securing screws. Not all because I could lever the end of the rear panel just enough to clear that mains socket. I also needed to pry apart the unyielding motherboard connectors with a flat bladed screwdriver.

Then, once loose, finally detach two mains cables and that red/black cable plus the two connectors at the right side (blue plus yellow wires)

That white plastic peg was a trifle awkward especially when it came to refitting the board.

I started fault finding by checking those two fuses (both were OK) then the primary of the large mains transformer at the rear of the chassis. This measured a low 2.9 ohms (low because it's rated at 600 watts) and is not visible from the mains input connector because it's fed via a relay. The amplifier's brought out of standby by activating the relay (on the right marked "DLS1U").Top right is a tiny mains transformer used for supplying enough power for the standby circuitry used for recognising the remote control.

As the standby transformer wasn't electrically visible from the rear mains input socket it suggested to me that it may be open circuit which was why I'd chosen to remove the board and check further. These small transformers are a fairly common point of failure in lift equipments with which I'm quite familiar because they're often designed for 220 volt mains and in the UK our mains is nominally 240 volts.

The amplifier is definitely not repairman-friendly as dozens of screws need to be removed or at least slackened before this power supply circuit board can be unplugged; but eventually I had it on the bench and was able to comfortably check its various parts.

When I came to test the standby transformer its primary was a bit peculiar because my ohm meter flashed on and off although this seemed to occasionally accompany a resistance reading of 5.3kohm. With my meter in diode mode I was able to read a solid 1.6 volts indicating the winding was likely to be OK. I checked continuity from the mains input to the transformer and found one leg was open so traced the wiring and came to that red 2-pin plug (top left)

This had connected to the cable carrying red and black wires visible in the previous picture.

Where did these wires go? An ON/OFF switch, but not the outer one.

Suddenly the penny dropped. The amp was dead because its ON/OFF switch was set to OFF. That red connector is wired to that tiny switch on the front panel and because everything is black with off-white lettering and the lighting had been poor I'd missed this. I'd actually spotted the ON/Standby switch and assumed its function was ON or Standby! Clearly the vendor had made the same mistake.

I refitted the board, switched on, and the amplifier came to life with a nice bright display (I'm lucky because these displays often go very dim after lots of use).

I selected "Tuner" but then had to download a manual before I could figure out how to tune a station (the user manual was missing from the box!). After puzzling for a bit I realised that the tuner was set up via buttons under the flap on the back of the remote.. not the front.

A pair of headphones and a couple of feet of wire later and there was Classic FM loud and clear. So, unless there's a hidden problem, say in the loudspeaker circuits, the thing is working as it should.

Next, I'll stand down my Teac and install the Denon, complete with its HD video switchery.

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