Harman Kardon AVR210, no audio.

The .676 at the base of the muting transistors is certainly enough to be considered a symptom. You've tried a reset, yes? If the receiver had been told at some point that no speakers were connected, then all channels might just be muted. Which brings the question, does the headphone jack work? Many modern receivers include a switch in the headphones jack specifically to mute the speakers as soon as the headphones are plugged in. In typical HK fashion, there does not appear to be any speaker relays in this thing, not with a quick glance at page 121 anyway, so if you have not already looked in that area it might not be a bad idea... You could look at the junction of R854 and R855 to check the mute drive which I suspect is active, or just short B-E on one of the muting transistors... Of course there could be an actual circuit malfunction, and if this is confirmed to be the case, frankly without LOTS of patience and a willingness to lose money on the repair, and lacking boards to swap to narrow it down, I would be tempted to just pull the plug on this one. Of course this assumes you have eliminated the usual suspects - the various power supplies, and so forth.

A sign of old age I suppose, but I'm less and less willing to break a sweat on these. The lack of serviceability on the vast majority of late model receivers is almost criminal. The manufacturers don't care that they are difficult to assemble, since they are using cheap Chinese labor anyway, they don't care that it's tough on the warranty servicers, and they certainly don't want them fixed out of warranty. The trend has always been there of course but it's really got much worse the past 10-20 years.

Mark Z.

Hi Mark,

The mute drive at the junction of R854 and R855 is about 3.5 volts iirc. I temporarily did short the mute transistor but I still didn't see signal. Again, there is not much signal coming out of IC706 to begin with.

I looked at the headphone circuit and noticed there is a switch in the jack that goes directly back to the uP, pin 16 of IC201 on page 119, labeled H/P _IN. I assume this either mutes the speakers or puts the receiver in two channel mode. But even if the muting was enabled in error, it still wouldn't explain why there's no signal passing through IC 706, the electronic volume control. You would still need to be able to adjust the volume when using the headphones.

This would be much easier if this model had pre-amp out, main in jumpers. But it doesn't.

I'm leaning toward replacing IC706.

Thanks for your reply.

--
David Farber
David Farber's Service Center
L.A., CA

Duh... I'd forgotten that... sorry.

I do think I'd look at any Data, Clock, and Chip Enable lines going to that chip and see if they are active when they are supposed to. I had one just the other day where the CE line was leaky right through the chip, 450 ohms to ground. They don't work so good that way...

Mark Z.

Hi Mark,

It appears this is all moot now because the TC9482F volume control IC is no longer available from Harman or Sony. Anyone have one sitting on a shelf somewhere?

Thanks for your reply.

--
David Farber
David Farber's Service Center
L.A., CA

Don't know if this is accurate info but B & D Enterprises (bdent.com) website says they'll have it in 2 weeks.

Their phone number is 800-458-6053.

Mark Z.

Good morning all,

MCM Electronics

catalogs this IC as a Panasonic part for a mere $34.90, on backorder. So, you could also try the Panasonic vendor of your choice. However, the TC prefix makes me think its a Toshiba IC, so you could try that route as well.

Regards, Tim Schwartz Bristol Electronics

(MAJOR SNIP)

Thanks Mark and Tim. I've put in calls to both B&D and MCM to find out if the part is still available. I should find out in a day or two.

--
David Farber
David Farber's Service Center
L.A., CA

Hi Mark,

I ordered the part through B&D. It took about 6 weeks to get the part from Japan. It came in an original Sony package. I wonder how it's discontinued in the US but not in Japan?

I installed the new part and smelled a faint cooking odor. I noticed that the color of the bands of R485 looked faded (see page 123 of the manual). It's a 4.7 ohm 2 watt resistor that measured closer to 8 ohms. Then I noticed there was a 1.2 ohm load to ground off of the +5 volt regulator, IC485. I traced that down to a nearly shorted optical 3 input (page 124). That board is buried in the front panel and a pain to get to. I just pulled the connector to the board at its other end and the short disappeared.

When I powered it up again, there was audio but with a background hum. I checked the output of IC 485 and there was noticeable 60Hz noise. Back upstream I found C487, 6,800uF @16V, a bit bulging with an esr of about 1 ohm. I replaced that and all is good now.

Thanks for your reply.

--
David Farber
David Farber's Service Center
L.A., CA

Thanks much for the update. Very often we don't get "the rest of the story".

Mark Z.