Harman Kardon 680i receiver issue

A few quick questions:

Is/are there relays involved? And do they 'click' when this problem occurs? Are there any other symptoms?

Yes. Clean all controls and switches. Yes. Look for loose boards and loose connectors and looms from board-to-board. With the top off, and with a wooden stick such as a chop-stick or drum-stick, poke and prod (gently) here and there - systematically - from one end to the other to see if you can induce the symptoms. Pay special attention to the outputs.

I would also look for swollen, burnt, or leaky electrolytic capacitors, evidence of burnt parts or other visible symptoms. If there are relays, those would be the first thing I tapped.

This does, superficially, appear to be a mechanical issue and/or a power-supply issue if the relays are not receiving enough current to latch (not uncommon).

Good luck with it!

Peter Wieck Melrose Park, PA

I would suspect the relays. Although the problem is not likely to be whether or not they are engaging. The contacts themselves within the relays are corroded. If you can't get to the contacts, replace the relay.

Another quick test is to turn up the volume. If the sound kicks in, the relay contacts are the problem.

Dan

Yep. Should have mentioned this as well! Thank you!

And, I have been known to remove the plastic caps and clean the contacts. Whereas most of these relays are still available, it can me a major PITA to replace them if a large board needs to come up to get to the bottom.

Peter Wieck Melrose Park, PA

Possible problems:

- Bad volume-control pot. It might be very dirty (in which case, rinsing it out with DeOxIt might fix the problem) or the conductive element might be work or cracked (in which case, replacing the pot is the only good solution).

- Bad speaker-protection relay - the contacts may be "burned" or dirty. These can sometimes be cleaned, or the contacts burnished with a proper tool (usually a very-fine-grit diamond polisher) but must sometimes be replaced. [From what I see of the schematic, your HK doesn't have one of these, so you can skip this.]

- A dirty or bad signal-selector switch... either the input selector, or the "tape monitor" switch, tone control switch, tone defeat switch, speaker on/off switch, etc.. Cleaning all of these with DeOxIt or similar may fix the problem.

- A cracked solder joint somewhere on the PC board.

- A bad board-to-board or board-to-cable connection. It looks as if that HK has a bunch of interconnect cables between the boards... a loose plug connection (e.g. from metal fatigue in the socket) or oxidation might cause problems.

- An inter-stage coupling capacitor (typically electrolytic) which has gone bad... they sometimes become leaky and can also fail intermittently.

Before you actually start trying to fix things, you should do some trouble-shooting to identify the specific section of the receiver that's not working right. A good place to start is at the tape-monitor jacks. If you tune to a known-good FM station, select FM as your input, and can see a signal at both "out to tape recorder" jacks, you can deduce that the input half of the receiver is likely OK and that the problem lies "downstream" (control section and amplifier). Conversely, if you can feed another receiver's "to tape recorder" outputs into the HK's "tape monitor" input, then select the "tape monitor" function, and get reliable and controllable output from the speakers, you'd know that the control section and amp are probably OK and that the problem lies "upstream" (in the input selection section).

One useful diagnostic technique: set it up to (try to) play a known-good signal at a moderate volume level into a set of test speakers (i.e. ones you don't care about). Then, start tapping on things - the board, controls, cables, jacks, switches, etc. - with a wooden chopstick. If there's a cracked or intermittent connection, it will probably make itself obvious when you tap on or near its location.

Thanks very much to you all for this wealth of advice. I need to read and digest it all before I do anything else, since I am *not* a tech guy.

Again, thanks, and I'll post again when I understand more.

Greetings-

I have an HK 680i from the 80s on which the volume cuts out. When I first turn it on there is sometimes sound output, but after several seconds it goes silent. If I turn the volume way up the sound will come back, but at ear-splitting levels; when I turn it lower, it goes silent again. I'm wondering if there are any simple ideas I might try? I have a can of Deoxit D5 and a bit of patience.

TIA.

I would try headphones first, this socket often incorporates a switch that cuts the main speakers.

(You don't specifically mention whether both left and right have the same problem at the same time, or whether it is the same or OK on headphones)

Gareth.

stereo?

both channels go out?

Yes, but it started working again (!), for the moment anyway. I had started exercising a few secondary switches (tone defeat/subsonic filter/high cut) and it would make a 'pop' when selecting 'tone defeat' at first, then it started working. It sounds good right now, except, if I may quibble, somewhat sloppy-loose on the lower end. So my next question: is this something that might be improved by replacing capacitors, which I've not done before? For now I'm leaving it alone, but am encouraged by the thing coming to life, even if only briefly (fingers crossed).

Ahhh, replacing capacitors, the new snake oil. Just like valves in the olden days. I think people do this because they look obvious.

No, replacing them is very unlikely to fix your problem. Which sounds a lot like the switches are getting old, oxidized, and could probably use a squirt of contact cleaner and some exercising.

Thanks for the reply. I think I was unclear in my last post, and what I meant to ask is assuming the receiver continues to work, with the help of doing what you suggest, would replacement of capacitors be a possible cure for the loose low-end sound, or is this wrong thinking?

On Thursday, November 23, 2017 at 8:16:57 PM UTC-5, snipped-for-privacy@yahoo.com

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Without putting too fine a point on it, and given that you have a Pacific-R im HK device vs a Long Island, NY device, and given its vintage, I will ris k heresy. It is *unlikely* but not improbable that your capacitors have rea ched the at-risk age. I would put those odds at 30/70, with the 70 that the y are OK. When HK went Pacific-Rim, they went to the lowest-cost-supplier m odel that was absolutely *not* what they were when in LI. But it remains su fficiently recent that the caps are likely good.

But, clean and exercise your switches. Clean your relays if you are of a mi nd to - I have done this. A PITA, but not one that is such that you would d ump the unit in the trash rather than taking it on.

I continue to be glad that I support no Pacific Rim equipment other than So ny & Yamaha CD changers, of which I support 5 + one (1) Yamaha and one (1) Revox. I have obtained all of these Sony devices from thrift stores - and p aid the highest ($25) for two 200-disc changers, complete with remotes. The Yamaha was purchased in the Souks of Al Khobar many moons ago. And been on the front lines since.

Glad that it seems to be clearing itself out. That is often a pleasant resu lt with an item that has been sitting on a shelf for a long while. It acts out until it re-learns how to behave.

Peter Wieck Melrose Park, PA

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-Rim HK device vs a Long Island, NY device, and given its vintage, I will r isk heresy. It is *unlikely* but not improbable that your capacitors have r eached the at-risk age. I would put those odds at 30/70, with the 70 that t hey are OK. When HK went Pacific-Rim, they went to the lowest-cost-supplier model that was absolutely *not* what they were when in LI. But it remains sufficiently recent that the caps are likely good.

mind to - I have done this. A PITA, but not one that is such that you would dump the unit in the trash rather than taking it on.

Sony & Yamaha CD changers, of which I support 5 + one (1) Yamaha and one (1 ) Revox. I have obtained all of these Sony devices from thrift stores - and paid the highest ($25) for two 200-disc changers, complete with remotes. T he Yamaha was purchased in the Souks of Al Khobar many moons ago. And been on the front lines since.

sult with an item that has been sitting on a shelf for a long while. It act s out until it re-learns how to behave.

Well I'm glad to hear that the capacitors probably aren't an issue. I'll ke ep working the switches and hope for the best. I like the receiver, and that i t has a stereo blend control, which is very nice for use with headphones.

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..... Phil

I found this blog post on the 680i, which might be a help to others, too: