Murphy A855G- no sound. - UK Vintage Radio Repair and Restoration Discussion Forum

Steve Erskine · 3rd Jun 2018, 11:55 am

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.

AC/HL · 3rd Jun 2018, 12:46 pm

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.

Steve Erskine · 3rd Jun 2018, 3:33 pm

Hi Bill,
Thanks for the reply.
I will purchase the data.
Do you have any pointers as to possible / probable fault?
Thanks
Stephen

AC/HL · 3rd Jun 2018, 4:03 pm

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?

Steve Erskine · 4th Jun 2018, 11:21 am

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.

Edward Huggins · 4th Jun 2018, 12:08 pm

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?

Steve Erskine · 4th Jun 2018, 2:39 pm

Sorry, the auto changer and the speed settings are all performing normally.
There is no hum from anywhere.

AC/HL · 4th Jun 2018, 5:16 pm

Do you have any means of measuring voltages?
Can you post a photograph with the part that did get hot marked in some way.

Steve Erskine · 5th Jun 2018, 4:38 pm

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

Station X · 5th Jun 2018, 4:55 pm

To aid any member offering assistance.

Techman · 5th Jun 2018, 7:20 pm

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.

buggies · 5th Jun 2018, 8:09 pm

... and a diode test on both the BY126s?

Steve Erskine · 6th Jun 2018, 12:19 pm

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

Steve Erskine · 11th Jun 2018, 11:05 am

Hi,
I have bought a multimeter and would really appreciate knowing what setting to use and how to do the suggested tests.
Thanks
Stephen

Nuvistor · 11th Jun 2018, 1:05 pm

The make and model of your new meter plus a photo, they all do a similar job but with slight differences.

Steve Erskine · 11th Jun 2018, 1:49 pm

Hi,
It's a B &Q digital multimeter model number MS8233A.
Many thanks
Stephen

Nuvistor · 11th Jun 2018, 3:43 pm

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

Steve Erskine · 11th Jun 2018, 3:47 pm

Thanks Frank,
I will give it a go.
Stephen

Steve Erskine · 11th Jun 2018, 6:25 pm

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

Nuvistor · 11th Jun 2018, 7:19 pm

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.

3rd Jun 2018, 11:55 am	#1
Steve Erskine Retired Dormant Member Join Date: Jan 2017 Location: Glasgow, Scotland, UK. Posts: 32	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
AC/HL Dekatron Join Date: Nov 2003 Location: Heckmondwike, West Yorkshire, UK. Posts: 9,642	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
Steve Erskine Retired Dormant Member Join Date: Jan 2017 Location: Glasgow, Scotland, UK. Posts: 32	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
AC/HL Dekatron Join Date: Nov 2003 Location: Heckmondwike, West Yorkshire, UK. Posts: 9,642	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?

4th Jun 2018, 11:21 am	#5
Steve Erskine Retired Dormant Member Join Date: Jan 2017 Location: Glasgow, Scotland, UK. Posts: 32	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.

4th Jun 2018, 12:08 pm	#6
Edward Huggins Dekatron Join Date: Sep 2015 Location: Southwold, Suffolk, UK. Posts: 8,325	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? __________________ Edward.

4th Jun 2018, 2:39 pm	#7
Steve Erskine Retired Dormant Member Join Date: Jan 2017 Location: Glasgow, Scotland, UK. Posts: 32	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
AC/HL Dekatron Join Date: Nov 2003 Location: Heckmondwike, West Yorkshire, UK. Posts: 9,642	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
Steve Erskine Retired Dormant Member Join Date: Jan 2017 Location: Glasgow, Scotland, UK. Posts: 32	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 Attached Thumbnails

5th Jun 2018, 4:55 pm	#10
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,286	Re: Murphy A855G- no sound. To aid any member offering assistance. Attached Thumbnails __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

5th Jun 2018, 7:20 pm	#11
Techman Dekatron Join Date: Nov 2009 Location: Lincolnshire, UK. Posts: 5,000	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
buggies Heptode Join Date: Jan 2009 Location: West Lothian, UK. Posts: 761	Re: Murphy A855G- no sound. ... and a diode test on both the BY126s? __________________ George

6th Jun 2018, 12:19 pm	#13
Steve Erskine Retired Dormant Member Join Date: Jan 2017 Location: Glasgow, Scotland, UK. Posts: 32	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
Steve Erskine Retired Dormant Member Join Date: Jan 2017 Location: Glasgow, Scotland, UK. Posts: 32	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
Nuvistor Dekatron Join Date: Aug 2013 Location: Wigan, Greater Manchester, UK. Posts: 9,431	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. __________________ Frank

11th Jun 2018, 1:49 pm	#16
Steve Erskine Retired Dormant Member Join Date: Jan 2017 Location: Glasgow, Scotland, UK. Posts: 32	Re: Murphy A855G- no sound. Hi, It's a B &Q digital multimeter model number MS8233A. Many thanks Stephen Attached Thumbnails

11th Jun 2018, 3:43 pm	#17
Nuvistor Dekatron Join Date: Aug 2013 Location: Wigan, Greater Manchester, UK. Posts: 9,431	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 __________________ Frank

11th Jun 2018, 3:47 pm	#18
Steve Erskine Retired Dormant Member Join Date: Jan 2017 Location: Glasgow, Scotland, UK. Posts: 32	Re: Murphy A855G- no sound. Thanks Frank, I will give it a go. Stephen

11th Jun 2018, 6:25 pm	#19
Steve Erskine Retired Dormant Member Join Date: Jan 2017 Location: Glasgow, Scotland, UK. Posts: 32	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 Attached Thumbnails

11th Jun 2018, 7:19 pm	#20
Nuvistor Dekatron Join Date: Aug 2013 Location: Wigan, Greater Manchester, UK. Posts: 9,431	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. __________________ Frank