Need some input - unusual receiver overheating issue

amplifiers, receivers and loudspeakers
lbls1
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Re: Need some input - unusual receiver overheating issue

Post by lbls1 » 08 Jul 2019 15:35

You can leave receivers on for hours and have no impact (I've done that to amps that I still have today). I don't feel that you should leave them powered up all of the time (you can with computers, but they have auto shut down features). It could be a component that went bad that could cause excessive heat.

Check it out, and also check the air ventilation around the unit. Proper ventilation can make a difference.

Adamo0926
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Re: Need some input - unusual receiver overheating issue

Post by Adamo0926 » 08 Jul 2019 20:21

After going over to my friend's place, and asking more questions here is what I think happened.

I don't anything was wrong with the receiver that caused this. My friend has a Thorens TD-145 which he was using but he hasn't had it checked out and tweaked yet after buying it. There is some hum coming from mostly the right channel. Didn't sound to me like there was any hum coming from the left channel.

I noticed that the hum is present even if the turntable is powered off but the receiver is still set to the phono output.

We turned on the Yamaha CR-2020 and tested it with the AUX output to use the CD player. There was very little output from the right speaker, left speaker sounded good although I seemed to detect a little distortion in the bass. We both assumed that the CR-2020 was the cause and that it was damaged from getting so hot.

But then I hooked up my Yamaha CR-620 to his speakers, ADS L810s by the way, and the result was exactly the same. I was 100% positive that the CR-620 was fine, short of needing some contacts cleaned internally. So now it seemed the right channel not playing was due to blown drivers in that speaker. Well there was some musical information coming out but it sounded like only from the tweeter.

My theory. When the receiver was left on with the volume at around 2 or so and with the PHONO output selected the hum was going through that right speaker for the whole time. I asked my friend if he was positive that the very loud hum was coming from the receiver or if maybe it could have been coming from the speaker, he told me it could have been coming from the speaker. This obviously shed new light on everything.

Now why the hum got extremely loud from the right speaker I have no clue. But since they didn't hear it until early morning my friend guessed that the hum could have been happening for as much as 6-7 hours. I've already established that the 2 8 inch woofers of the L810s are shot. You could tell just by pushing in the cone and feeling the rubbing. At least I have been told you can tell by doing that.

Both the receiver and the pair of ADS L810s are at the tech's to be checked out. He is going to test all the drivers of the speakers and determine if any or all of them are blown.

So the good news is that the far for expensive piece, the Yamaha CR-2020, may actually be fine. The bad news is that at least one of those lovely ADS L810 speakers probably has blown drivers.

Anybody have any idea on how that humming/buzz could have gotten so loud as to damage the drivers ? To me that is a head scratcher. To me, someone would have had to turn the volume knob up to get that sound to get that loud. Or am I wrong about that ?

circularvibes
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Re: Need some input - unusual receiver overheating issue

Post by circularvibes » 08 Jul 2019 21:30

That still sounds like my filter capacitor problems with two receivers. I lost two speakers ther first time after my landlord called me at work and said he could hear it from below and outside. Your tech should be able to determine it fast enough.

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Re: Need some input - unusual receiver overheating issue

Post by pivot » 08 Jul 2019 21:49

Sold ADS, Sold Yamaha.

If the Yamaha got too hot to comfortly touch it is malfunctioning in some manner. Quite possibly the channel in question failed in some catastrophic way that damaged the speaker. Contact the tech who did the rebuild and ask EXACTLY what he did to rebuild the unit. Ask if there is any warrantee on his work. If there is no warranty DO NOT return the unit to this tech.

Do you have the expertise to remove the bass drivers from the ADS?? If you do - remove the drivers and test with a meter if one of the drivers tests as infinite resistance/open circuit. My bet is one if the two drivers has a blown voice coil. The 810 woofers are wired in series so one driver out would kill both drivers. Does the midrange test good? Do the crossover components look blackened or scorched?

Do NOT connect another valued pair of speakers to the damaged Yamaha. Do NOT connect the damaged speaker to another amp.

I suspect you will find, with the help of a competent tech, that the power amp section of the receiver failed taking the coil coil of one of the woofers with it. I do not think the turntable or the time the unit was left on contributed to the failure. An issue with rebuild may have contributed to the failure.

lenjack
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Re: Need some input - unusual receiver overheating issue

Post by lenjack » 08 Jul 2019 22:21

I agree that the turntable has nothing to do with this. I still think it was the fault of a faulty refurbishment.

pivot
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Re: Need some input - unusual receiver overheating issue

Post by pivot » 08 Jul 2019 22:42

I certainly would not rule out the refurb but we are dealing with a unit that is 40 years old. A part not normally part of a rebuild, say a diode in the biasing circuit may have gone out of spec. A competent tech, other than the one who did the rebuild perhaps, might be able to tell.

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Re: Need some input - unusual receiver overheating issue

Post by Adamo0926 » 08 Jul 2019 22:47

Well obviously I have to believe it was the very loud hum/buzz that damaged the drivers. So how could the receiver send such a sound to the speaker with nothing playing ? Are you saying that some failure in the Yamaha would send a very loud signal to the speaker so that it could be heard 2 floors up ? The whole thing seems bizarre to me. I have yet to get an update on the receiver or speakers from the tech. I will probably hear something tomorrow.

lenjack
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Re: Need some input - unusual receiver overheating issue

Post by lenjack » 08 Jul 2019 23:05

A bad filter cap could easily do that if the volume control was way up.

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Re: Need some input - unusual receiver overheating issue

Post by pivot » 08 Jul 2019 23:28

Adamo0926 wrote:
08 Jul 2019 22:47
Are you saying that some failure in the Yamaha would send a very loud signal to the speaker so....
If a power supply cap failed, if the bias went out of spec, if for some other reason the output stage goes unstable, the amplifier may oscillate with the full output of the amp until it fails thermally (over heats) or the protection circuits shut it down. It will be as loud as the amp can get. Not weird at all. Early solid state amps were infamous for instability. Odd for the Yamaha to go wacky like that but if something when way out of spec.

vanakaru
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Re: Need some input - unusual receiver overheating issue

Post by vanakaru » 09 Jul 2019 08:36

I have heard this noise/loud hum and fried a speaker or two. If you measure the output voltage on faulty line like this it is 10 times of the normal. Then it either melts the thin wires on sound coil or causes deformation of the speaker cone and coil cylinder.
So for me it sounds that the amp failed and took speaker with it.

circularvibes
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Re: Need some input - unusual receiver overheating issue

Post by circularvibes » 09 Jul 2019 11:16

When your filter capacitors fail, you are sending AC directly to the speakers. At least that is how my tech explained it to me. The loud raucous hum is 60 cycle hum.

Adamo0926
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Re: Need some input - unusual receiver overheating issue

Post by Adamo0926 » 09 Jul 2019 15:07

vanakaru wrote:
09 Jul 2019 08:36
I have heard this noise/loud hum and fried a speaker or two. If you measure the output voltage on faulty line like this it is 10 times of the normal. Then it either melts the thin wires on sound coil or causes deformation of the speaker cone and coil cylinder.
So for me it sounds that the amp failed and took speaker with it.
Well my theory was wrong, but I think what vanakaru just posted is what happened.

Just got word that the receiver is basically fried and we already knew the drivers in one of the speakers are blown.

The only condition out of the norm with this failure is that the receiver was mistakenly left powered on for about a week. So I have read tons of stuff regarding leaving equipment powered on or not. I can tell you this, I will never leave my receiver on 24/7.

I'm just going to use common sense here. Some of these receivers are 40+ years old. I would think that leaving it on
constantly would increase the chance of some internal component failing. And that could lead to a catastrophic failure as in this case. I'm not going to play Russian Roulette with equipment this old. That's just how I feel about it, if others feel differently then that's cool.

But what I just did in order to get an expert opinion on this, was to email Dr John Chandy who is the head of the Electrical Engineering Department at the University of Connecticut. I asked him his opinion about this debate. As soon as I hear from him I will post it here. But being Summer and the University not in session, I might not hear from him for a bit.

So all I have to go by now is personal experience with my friend's receiver. It was left on for a week straight. It fried itself and took a speaker out with it. For me, no matter what anyone else says, it's case closed....

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Re: Need some input - unusual receiver overheating issue

Post by Tinkaroo » 09 Jul 2019 15:38

I'm sorry to hear about your friends receiver, but hope it can be repaired.

If you ever get more detail on the components that failed please post it here for the benefit of those who like to be better educated about this failure.

I own a lot of vintage amps and receivers and agree with you it's not a good idea to leave them on 24-7.

Adamo0926
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Re: Need some input - unusual receiver overheating issue

Post by Adamo0926 » 09 Jul 2019 18:06

Tink.....I have been listening to my Yamaha CR-2020 this morning. But just as an experiment I turned it off, let it cool down completely, then just powered it on without listening to it. Volume down all the way. After just leaving it like that for maybe 30 minutes, the top was already decently warm. So I'm sorry but leaving a 40 year old receiver on 24/7/365 just seems like insanity to me.

If these receivers were meant to be left powered on constantly then why is there even a power on/off button ? Wouldn't the manual tell you that to extend the life of your receiver you should keep it powered on ? I have never read a manual for any piece of audio equipment that I have say that it should be powered on all the time. All I know is that I have just seen the results of one of these receivers being left on for a week, and the result was not pretty. One fried receiver and at least one blown ADS L810 speaker. So leaving my stuff on 24/7 ? Thanks but no thanks.

As for my friend's receiver.....getting it repaired now is out of the question because the thing is becoming a money pit. I think he will try to sell as being for parts or repair, or maybe work a deal with tech who has it where the tech will buy it from him so the tech will then part the thing out.

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Re: Need some input - unusual receiver overheating issue

Post by Tinkaroo » 09 Jul 2019 18:21

That is very sad to hear, and I'm sure your friend is upset about losing their receiver.

I have. CR-1000, CR-820 and a CT-600 tuner and like them a lot.The biggest one the CR-1000 which was their earlier top of the line, fortunately does not get very hot.

Good advice to not leave any receiver turned on for such a long time. I know you will take good care of yours.