Mark Zacharias wrote:
"David Farber" wrote in message
...
Mark Zacharias wrote:
"David Farber" wrote in message
...
Mark Zacharias wrote:
"David Farber" wrote in message
...
This Harman Kardon AVR210 receiver has no audio output in any
mode. Customer
said it just went out all of a sudden. I was able to find a copy
of the service manual he
http://eserviceinfo.com/downloadsm/4...on_AVR210.html
It's in four parts and you'll need a utility that can unpack a
rar file to see it. The manual is 135 pages so when referring to
it, I've included the page numbers.

I performed the part modification as suggested on page 19. It
didn't correct
the problem.

Then I traced signal as shown in the chart on pages 25-26. Using
the direct
input, I was able to get audio out of the tape output jacks.
There is no output from the preamp output jacks. There is no
protection relay that I can
see and there is no dc offset at the power amplifier output.

Referring to the signal flow chart on page 26, the audio input
signal is present on pins 4 and 25 of IC 706 (electronic volume
control) but missing on pins 3 and 26 of IC 706. The schematic of
this circuit is on page 116. However when I rotate the volume
control, the audio will appear as long as the knob is moving. As
soon as the control is left alone, the audio mutes. The output
pins are 3 and 26, of IC 706. The signal appears to be clean
though I estimate the speaker output to be about 30dB less than
where it's supposed to be while it is present. If I bridge the
input to the output pins of IC706, an attenuated signal appears
but it's too low for any
output to register at the speakers.

Now, referring to the block diagram on page 30, you'll notice IC
716 and the
muting transistor(s) that follows. Back to page 116, there seems
to be enough forward bias on Q716 and Q717 .(676 volts) to
possibly mute the output if there were any input to amplify.

So in light of all these observations, do I just replace IC706?
It's about $30 but I'm wondering if there's some muting going on
behind the scenes that
can be contributing to this problem.

Thanks for your reply.
--
David Farber
David Farber's Service Center
L.A., CA




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






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.

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.

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