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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment. |
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3rd Jun 2018, 11:55 am | #1 |
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Murphy A855G- no sound.
Hi,
I was using the above record player which was working perfectly. I had had it on for about four hours non stop and it started to overheat. All of the functions still appear to work perfectly with the exception of the sound, there is none at all . From memory, it's a 1969 model. Any help will be fully appreciated. Thanks, Steve. |
3rd Jun 2018, 12:46 pm | #2 |
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Re: Murphy A855G- no sound.
Service data is here: https://www.service-data.com/section.php/5164/1/a855g.
The overheating points to the output stage, or just possibly power supply. Unfortunately, there aren't any fuses to blow! Time to get your meter out I think. |
3rd Jun 2018, 3:33 pm | #3 |
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Re: Murphy A855G- no sound.
Hi Bill,
Thanks for the reply. I will purchase the data. Do you have any pointers as to possible / probable fault? Thanks Stephen |
3rd Jun 2018, 4:03 pm | #4 |
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Re: Murphy A855G- no sound.
Not without a clue or two, except to say that there are only a couple of things that can draw enough current to cause overheating. Why they're doing that remains to be seen. What exactly gets hot?
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4th Jun 2018, 11:21 am | #5 |
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Re: Murphy A855G- no sound.
It was the front left corner that was overheating, sorry I can't be more specific as I know that is where the workings are. I have left it on for a couple of hours now and nothing is warming up. The deck appears to function normally. Thanks, Stephen.
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4th Jun 2018, 12:08 pm | #6 |
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Re: Murphy A855G- no sound.
When you say the "Deck" is functioning normally, do you mean that the Autochanger (= Deck) or the amplifier is now running again and the player is now all OK?
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4th Jun 2018, 2:39 pm | #7 |
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Re: Murphy A855G- no sound.
Sorry, the auto changer and the speed settings are all performing normally.
There is no hum from anywhere. |
4th Jun 2018, 5:16 pm | #8 |
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Re: Murphy A855G- no sound.
Do you have any means of measuring voltages?
Can you post a photograph with the part that did get hot marked in some way. |
5th Jun 2018, 4:38 pm | #9 |
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Re: Murphy A855G- no sound.
Hi, I have tried to attach a picture of the relevant parts.
I don't currently posses a test meter but will buy one. I am competent and mechanically minded, but I am at a loss when it comes to the clever part of diagnosing the fault |
5th Jun 2018, 4:55 pm | #10 |
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Re: Murphy A855G- no sound.
To aid any member offering assistance.
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Graham. Forum Moderator Reach for your meter before you reach for your soldering iron. |
5th Jun 2018, 7:20 pm | #11 |
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Re: Murphy A855G- no sound.
So the area of the apparent overheating is where the mains transformer sits.
The first thing that we would want to know, and you haven't said, is does the indicator lamp still light up? This lamp is fed from its own winding on the transformer and if it's lit then it may indicate that the transformer is OK. If the lamp isn't lit, did it work before the overheating? The other secondary winding shown in the circuit feeding the rectifier diodes could be faulty, so the first thing is to measure the AC voltage across the ends of this winding, and if OK, then the DC across that first smoothing capacitor just shown in the picture. That's a start. Hope the transformer isn't burnt out. |
5th Jun 2018, 8:09 pm | #12 |
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Re: Murphy A855G- no sound.
... and a diode test on both the BY126s?
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6th Jun 2018, 12:19 pm | #13 |
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Re: Murphy A855G- no sound.
Hi,
Thanks for the r plies. I will buy a new multimeter, learn how to use it, and try and do the suggested checks. The lamp worked intermittently and on trying it today, one of the wires has been / has become detached. Regards Stephen |
11th Jun 2018, 11:05 am | #14 |
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Re: Murphy A855G- no sound.
Hi,
I have bought a multimeter and would really appreciate knowing what setting to use and how to do the suggested tests. Thanks Stephen |
11th Jun 2018, 1:05 pm | #15 |
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Re: Murphy A855G- no sound.
The make and model of your new meter plus a photo, they all do a similar job but with slight differences.
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11th Jun 2018, 1:49 pm | #16 |
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Re: Murphy A855G- no sound.
Hi,
It's a B &Q digital multimeter model number MS8233A. Many thanks Stephen |
11th Jun 2018, 3:43 pm | #17 |
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Re: Murphy A855G- no sound.
This web page will show you the basics of using the meter, may as well know how to use it before testing the record player.
When testing the voltage I recommend a small battery to begin with, an AA and an PP3 would be fine and you probably have those to hand. https://www.ifixit.com/Guide/How+To+...ltimeter/25632
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11th Jun 2018, 3:47 pm | #18 |
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Re: Murphy A855G- no sound.
Thanks Frank,
I will give it a go. Stephen |
11th Jun 2018, 6:25 pm | #19 |
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Re: Murphy A855G- no sound.
Hi,
I have viewed the link and is a good beginners guide, which seems attainable. However I have uploaded a couple of new pictures. It has the power cable in from the plug and a feed for the turntable. I am unable to identify anything else. The second picture seems to show that the windings are burnt. Thanks Stephen |
11th Jun 2018, 7:19 pm | #20 |
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Re: Murphy A855G- no sound.
The transformer does not very good.
The secondary windings are probably underneath the transformer, the transformer is probably hiding them from view. It’s also possible that the chassis had a cut out under the transformer to allow it to drop through. Make sure the player is unplugged from the mains power and you will need to release the chassis from the cabinet, all the component for the PSU are likely underneath out of sight.
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