Harman Kardon AVR210, no audio.
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From: Mark Zacharias on 6 Apr 2010 20:57 "David Farber" <farberbear.unspam(a)aol.com> wrote in message news:4bbba75a$0$27750$bd467cd0(a)news.dslextreme.com... > Mark Zacharias wrote: >> "David Farber" <farberbear.unspam(a)aol.com> wrote in message >> news:4bb7fa57$0$16970$bd467cd0(a)news.dslextreme.com... >>> Mark Zacharias wrote: >>>> "David Farber" <farberbear.unspam(a)aol.com> wrote in message >>>> news:4bb51a34$0$27759$bd467cd0(a)news.dslextreme.com... >>>>> 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 here: >>>>> http://eserviceinfo.com/downloadsm/46799/Harman/Kardon_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. |