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Yamaha CR-620 receiver - speaker relay problem

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Anonymous
April 9, 2004 4:51:48 AM

Archived from groups: rec.audio.tech (More info?)

I have a Yamaha CR-620 receiver from the 70's -
and it has served me well, allowing me to shuttle audio
between the various ins/outs - it's great -
Well, tonight..went to pop it on and no audio :( (

The sound that I'm missing is the "click" of the speaker relay
after a second or two after the power has been applied -
nothing - nada -
Any common things that it could be ????
I just quickly looked on eBay - and there are CR-620's avail.
That would probably be cheaper
than dragging it to some service center....
I do like the receiver & would miss it -
Phil -
Anonymous
April 9, 2004 5:09:50 AM

Archived from groups: rec.audio.tech (More info?)

>I have a Yamaha CR-620 receiver from the 70's -
>and it has served me well, allowing me to shuttle audio
>between the various ins/outs - it's great -
>Well, tonight..went to pop it on and no audio :( (
>
>The sound that I'm missing is the "click" of the speaker relay
>after a second or two after the power has been applied -
> nothing - nada -
>Any common things that it could be ????

I don't know the details of this model, but in a lot of amplifiers the
speaker-protection relay will not close if there is a significant DC
voltage present at the output of the power amplifier stage. Some amps
also have short-circuit-detection circuitry, which will prevent the
relay from closing if the impedance from a speaker terminal to ground
is very low.

So, the three things I'd check:

- Check your speaker wiring, from speakers to receiver. Make sure
that you don't have any loose strands of wire which might be
shorting the leads together, that you haven't somehow crushed or
nicked a wire, etc.

- Unplug the "upstream" components - e.g. CD player, etc. - and then
turn the receiver on and see if the relay closes. If it does, then
you may have a fault in the CD player (or whatever) which is
putting some DC voltage into the receiver, and the receiver's
speaker-protection circuit is holding the relay open to keep the
amplified DC from damaging the speaker.

- A suitably-skilled technician could open up the receiver and see if
any of the fuses in the DC power supply lines has blown or broken.
Fuses can fatigue with age, and if a DC fuse opens there'll
probably be a big DC offset voltage present at the amp output and
the protection relay won't close.

--
Dave Platt <dplatt@radagast.org> AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!
Anonymous
April 9, 2004 5:55:05 AM

Archived from groups: rec.audio.tech (More info?)

In <Esmdc.13935$Lr5.9815@newssvr15.news.prodigy.com>, on 04/09/04
at 12:51 AM, "Phil Schuman" <pschuman_NO_SPAM_ME@interserv.com>
said:

[ ... ]

>The sound that I'm missing is the "click" of the speaker relay after a
>second or two after the power has been applied -
> nothing - nada -
>Any common things that it could be ????
>I just quickly looked on eBay - and there are CR-620's avail. That
>would probably be cheaper
>than dragging it to some service center....
>I do like the receiver & would miss it -

There is a failure of some sort in the power amplifier section.

If the fuse didn't blow, then it could be a relatively minor problem
such as a solder connection that has broken down.

I'm reluctant to recommend a major repair on a unit of that age. Many
of the parts are past their prime. You could repair the unit and have
an unrelated failure in a relatively short period, or the unit could
last another few years, no one can know for sure.

If you are able, open the unit, top and bottom, and give it a *VERY
CLOSE* visual inspection. Pay particular attention to the soldering on
the PC board associated with any of the power transistors -- especially
the ones that stand perpendicular to the board and use a square tubular
heatsink. In your case I doubt there are any, but look for burned
components. Minor discolorations are normal for a unit with this many
years of good service behind it.

The purpose of that relay is to keep the speakers disconnected while
the amplifier starts up or shuts down, to protect the amplifier from
inappropriate external connections, and to protect the speakers from an
amplifier failure. You are experiencing the latter.

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Anonymous
April 9, 2004 11:33:57 AM

Archived from groups: rec.audio.tech (More info?)

There may be a failure in the output stage or power supply. It would not
hurt to have the unit properly checked by a service tech who is very
experienced in troubleshooting this type of problem.

I would not put too much money in to a set of this age, unless it is to be
kept for an antique collection. It is possible that after servicing it,
there may be another failure soon after. As for finding another used one of
the same age, you have the risk that it will fail as well.

Normally I have very rarely seen used equipment being sold that is in
excellent working condition. I found that they were being sold off because
there was some type of fault condition that was expensive or difficult to
service. I know many people who got taken when buying used equipment for
serious use.

If you want to make a worthy investment, today's receivers are much
improved! If you are a serious home user, look at the Sony ES line, or the
equivelent. If you want to go more exotic or high end, there is some very
good audio gear out there.

Considering the specs of a 70's unit, you would even be much more ahead with
a standard modern consumer receiver.


--

Greetings,

Jerry Greenberg GLG Technologies GLG
=========================================
WebPage http://www.zoom-one.com
Electronics http://www.zoom-one.com/electron.htm
=========================================


"Phil Schuman" <pschuman_NO_SPAM_ME@interserv.com> wrote in message
news:Esmdc.13935$Lr5.9815@newssvr15.news.prodigy.com...
I have a Yamaha CR-620 receiver from the 70's -
and it has served me well, allowing me to shuttle audio
between the various ins/outs - it's great -
Well, tonight..went to pop it on and no audio :( (

The sound that I'm missing is the "click" of the speaker relay
after a second or two after the power has been applied -
nothing - nada -
Any common things that it could be ????
I just quickly looked on eBay - and there are CR-620's avail.
That would probably be cheaper
than dragging it to some service center....
I do like the receiver & would miss it -
Phil -
Anonymous
April 12, 2004 6:40:02 AM

Archived from groups: rec.audio.tech (More info?)

BTW - one of the attributes that was a nice feature of this unit
was the ability to have multiple audio inputs & outputs
that be dubbing while listening to something else,
along with a REC monitor for setting levels -
I have : turntable, cassette, CD, and reel to reel -
or as on the front panel - Phono, Aux, Tape1, Tape2
Anonymous
April 13, 2004 9:27:26 PM

Archived from groups: rec.audio.tech (More info?)

well - I opened it up -
the first time since probably 1978 :) 
Everything looks good except
for some areas around 1 of the 2 tall capacitors next to the transformer.
I was thinking that it leaked....but can't tell... don't know.
It actually looks like soldering flux.
Thought maybe we could un-solder the cap & replace,
but it looks like these 45v 6800uf tall babies might be glued to the board.
So - if an electrolytic leaks...
A - what does it look like ?
B - how does it effect the rest of the power circuitry ?
Now - should I try and rip them out & replace...
or just toss it :( (
Anonymous
April 14, 2004 9:34:07 AM

Archived from groups: rec.audio.tech (More info?)

The fact that a large electrolytic has leaked doesn't mean you need to
replace it right away, but if the leakage accumulates at the cap terminals
sufficiently, it could be a problem. I had a customers' Aragon amp destroyed
by an internal fire. Cause? The cap leakage / corrosion became sufficiently
conductive to start a fire. He was one of those guys who leaves his
equipment on 24/7. He's lucky his house didn't burn down.
In this case the caps were mounted "upside-down", with the terminals UP and
a circuit board placed on top. I've never seen such an occurence with models
where the board is underneath the caps, but it could maybe still happen.

Mark Z.

--
Please reply only to Group. I regret this is necessary. Viruses and spam
have rendered my regular e-mail address useless.


"Phil Schuman" <pschuman_nospam_me@interserv.com> wrote in message
news:2qVec.7990$Lk5.3005@newssvr31.news.prodigy.com...
> well - I opened it up -
> the first time since probably 1978 :) 
> Everything looks good except
> for some areas around 1 of the 2 tall capacitors next to the transformer.
> I was thinking that it leaked....but can't tell... don't know.
> It actually looks like soldering flux.
> Thought maybe we could un-solder the cap & replace,
> but it looks like these 45v 6800uf tall babies might be glued to the
board.
> So - if an electrolytic leaks...
> A - what does it look like ?
> B - how does it effect the rest of the power circuitry ?
> Now - should I try and rip them out & replace...
> or just toss it :( (
>
>
>
Anonymous
April 14, 2004 2:36:12 PM

Archived from groups: rec.audio.tech (More info?)

In <2qVec.7990$Lk5.3005@newssvr31.news.prodigy.com>, on 04/13/04
at 05:27 PM, "Phil Schuman" <pschuman_nospam_me@interserv.com> said:

>well - I opened it up -
>the first time since probably 1978 :) 
>Everything looks good except
>for some areas around 1 of the 2 tall capacitors next to the
>transformer. I was thinking that it leaked....but can't tell... don't
>know. It actually looks like soldering flux.
>Thought maybe we could un-solder the cap & replace,
>but it looks like these 45v 6800uf tall babies might be glued to the
>board. So - if an electrolytic leaks...
> A - what does it look like ?
> B - how does it effect the rest of the power circuitry ? Now -
>should I try and rip them out & replace...
>or just toss it :( (

Many units of that vintage, YAMAHA included, used a very light brown
(some might claim "amber") glue to hold the capacitors in place. By now
that glue has become very dark brown, almost black -- and it is
somewhat conductive! While power supply circuits don't mind a little
leakage, some circuits do and (only in these cases) the glue must be
removed.

I recommend that you give the unit a thorough visual inspection. Look
for cracked pads, especially on transistors attached to heatsinks.

Generally, the first symptom of the large capacitors failing is hum. In
severe cases there might be a blown fuse, but I have not seen that
happen in CR-620s. If the large capacitors failed, it is unlikely that
your only symptom would be the protection relay not pulling in.

If the visual inspection does not yield any clues, you will need some
instrumentation to narrow down the possibilities. Otherwise, you'll be
replacing components blindly.

-----------------------------------------------------------
spam: uce@ftc.gov
wordgame:123(abc):<14 9 20 5 2 9 18 4 at 22 15 9 3 5 14 5 20 dot 3 15
13> (Barry Mann)
[sorry about the puzzle, spammers are ruining my mailbox]
-----------------------------------------------------------
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