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Left channel dies in multiple units

Donato808

Donato808

New Member
This issue is making my head hurt. I have acquired a few vintage receivers over the years and cleaned them up with deoxit which has helped dramatically but I am by no means an expert on repairing things.

I have a little audio setup on my back patio where I run a few crappy Sony speakers that are getting beat up by the elements and also two minimus 7s mounted under the overhang of my roof. I've been using a rotation of literally three different vintage receivers to power this setup and while they all start out fine, after a short period of time the left channel goes out. In ALL THREE of them. I use different audio sources (TV, CD player and wireless transmitter from vinyl setup inside the house) and while at first it sounds like the left channel kinda shorts out, I have to wiggle the volume or balance knob (more specifically if i turn the volume knob up louder sometimes that will kick on the left channel again and it will stay on for a bit, but i prefer lower volume listening so i turn the volume back down and after some time the left channel will have cut out again) so now yet again the left channel is out and I am tired of switching out receivers.

My initial thoughts are that something is overloading that left channel and causes something in the receivers to shut off but not break permanently, because somehow after some rest the channel is back working again.

Does this make any sense to anyone? Any ideas on what I can try to get to the bottom of this issue? For reference the receivers I'm using are a Technics SA-303, Vector Research VR-2000 and Lafayette LR-5555-a.
 
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avionic said:
Maybe your left channel speaker(s) are bad.

Fouled protect relay contacts will do this.
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Thank you! I will definitely look into this. I am wondering though, I have A and B speaker selector switch each routed to different speakers - my A speakers are going to the Sony speakers and my B speakers are the minimus 7s, and when the left side goes out BOTH the Sonys and minimus 7s go out so I don't think it would be BOTH the relay contacts or speakers being bad?? I will do some investigating tomorrow though, thank you for the reply!
 
Donato808 said:
so I don't think it would be BOTH the relay contacts
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For both A & B there is only one set of contacts for the left channel and one set for the right channel. unless you have more than one protect relay. Most Receivers only have one relay. Look at the schematic.. The relay is usually before the speaker select switches.. So.. Yes it could be the relay.
 
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On the three receivers or whatever they are. Have you tried swapping the speakers around ? Left to right and right to left ?
 
I'd be checking both of the left channel speakers. If one is shorted -- That's all it takes.
 
I would suspect the A/B switch box. It is the only thing that is always there when it fails. A bad or dirty contact in it can cause failure at low voltage/volume that goes away when you crank it up. Easy to check. Just take it out of the loop and see if the problem goes away.
 
avionic said:
For both A & B there is only one set of contacts for the left channel and one set for the right channel. unless you have more than one protect relay. Most Receivers only have one relay. Look at the schematic.. The relay is usually before the speaker select switches.. So.. Yes it could be the relay.
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Thank you for the replies!! I guess I wasn't aware of exactly what the relay contacts are and where to find them. I don't have access to a schematic, but perhaps one of you could identify it by looking at the insides?? I will attach a picture of the inside of my VR-2000. Can you tell what I should be cleaning/checking in here???
 

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In your photo . Top of photo on the main circuit board. Black rectangular plastic box... Close to the pins with the brown and white wire connected.
 
avionic said:
In your photo . Top of photo on the main circuit board. Black rectangular plastic box... Close to the pins with the brown and white wire connected.
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Awesome thank you! I thought that's what it was! So what should I do?? Make sure the wires are connected well? Take off plastic box and spray deoxit inside?? Forgive me, it will be my first time doing such work.
 
I find it very unlikely to be the receivers if 3 different ones all have the same issue. I'd be looking at the parts that did not change, namely the speakers and the wiring.
 
gadget73 said:
I find it very unlikely to be the receivers if 3 different ones all have the same issue. I'd be looking at the parts that did not change, namely the speakers and the wiring.
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I agree, I will be checking the wiring and changing out the speakers today and see how that goes. Thank you!
 
Donato808 said:
...
I have a little audio setup on my back patio where I run a few crappy Sony speakers that are getting beat up by the elements and also two minimus 7s mounted under the overhang of my roof...
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The first thing to clarify is exactly how many speakers you have and how you have them wired. "A few crappy Sonys plus Minimus 7's" sounds like a lot of speakers, you absolutely have to be careful how you wire them from an impedance standpoint. Having several speakers wired in parallel, for example will result in VERY low impedance that will shut down an amp.

It would be best to list the number and model number of each speaker, then measure each with an ohmmeter (making sure the speaker wires are disconnected when measuring). Write down the reading for each and compare it against the impedance spec for that specific brand/model speaker.

Based upon the "few" comment, I suspect you have several speakers in parallel (low impedance will kill an amp), and they aren't balanced (e.g. more speakers in parallel on the left than the right), which would explain the left only being taken out.

The other possibility is that one of the speakers has an issue (which could also explain "left only" failure), which you should be able to identify with the ohmmeter readings.
 
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Donato808 said:
I agree, I will be checking the wiring and changing out the speakers today and see how that goes. Thank you!
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I would definitely not change out the speakers without first determining exactly what is wrong. It's much better to understand the cause instead of just changing things. See my post above -- it's either a wiring problem (too many speakers in parallel) or an individual speaker problem (should be easy to isolate the bad speaker with an ohmmeter). If it's a wiring problem (too many in parallel), changing speakers almost certainly won't help and might be worse if the new speakers have lower impedance.

It's very possible to damage an amp with very low impedance -- fortunately the protection circuits have prevented that, but it's not something you want to keep putting the amp(s) through.
 
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Donato808 said:
Awesome thank you! I thought that's what it was! So what should I do?? Make sure the wires are connected well? Take off plastic box and spray deoxit inside?? Forgive me, it will be my first time doing such work.
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Tap on the relay with something that won't cause any more problems to see if the speakers come in.
 
Yeah, my wording may have been misleading. When I said a "few" I only meant two speakers. My receiver has A and B speaker selector buttons, and for my A speakers I am using the Sonys (one on the left and one on the right) and for my B speakers I am using two minimus 7s. So I don't think the amp is overloading with a bunch of speakers, but I appreciate you clarifying that. The Sony speakers are SS-MF315 tower speakers.

I opened up the relay and cleaned it the best I could with some Deoxit and checked to see if anything major was wrong. I closed it back up and as of now both channels are working. It seems to come and go, but for now all is well! Thank you for all your thoughtful responses. I will continue to look into speaker issues and test for weirdness before I experience the same issue again.
 
Donato808 said:
Yeah, my wording may have been misleading. When I said a "few" I only meant two speakers. My receiver has A and B speaker selector buttons, and for my A speakers I am using the Sonys (one on the left and one on the right) and for my B speakers I am using two minimus 7s. So I don't think the amp is overloading with a bunch of speakers, but I appreciate you clarifying that. The Sony speakers are SS-MF315 tower speakers.

I opened up the relay and cleaned it the best I could with some Deoxit and checked to see if anything major was wrong. I closed it back up and as of now both channels are working. It seems to come and go, but for now all is well! Thank you for all your thoughtful responses. I will continue to look into speaker issues and test for weirdness before I experience the same issue again.
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If you have an ohmmeter, definitely measure each speaker individually. I agree with @gadget73 , with 3 amps displaying this issue, in one channel only, it's extremely unlikely to be an amp issue and very likely to be an individual speaker issue.

The Minimus 7's are 8 ohms. If the Sony speakers are 4 ohms, then it would be 2.7 ohms in parallel (which might be too low). If the Sony's are 8 ohms, then that would be 4 ohms in parallel which should typically be ok. Fixing the relay is fixing a symptom of the problem. It's far more likely one of the speakers has low impedance for some reason.
 
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