Philips 10 watt Novosonic amplifier repair - UK Vintage Radio Repair and Restoration Discussion Forum

KeithEllis · 19th Apr 2009, 11:39 pm

Hello everyone.

I've finally got around to repairing (or attempting to repair at least) a Philips 10 watt Novosonic amplifier. This has been cluttering my shed for the last eighteen months or so, and consists of two matching wooden cabinets (each 3 feet high and 15 inches square), one containing the amp and a Philips record deck, the other a 12" bass speaker and a 7" treble unit. I have a curry's brochure from 1957 and this was the most expensive item listed, and is detailed in their hI-fI section. The whole thing seems extremely well made.

Basically I want to get this working to see if the sound quality warrants the effort I'd have to put in to bring the cabinets back up to scratch, as they're both in fairly poor cosmetic condition. It was powered up by the previous owner prior to me collecting it, so when I got it home I did switch it on (not as cautious as I am now!) but with little effect - although with the volume up to max there was a faint, poor quality sound from the speaker. I've not powered it up since.

I've purchased the service data, which is quite extensive at seven pages, and have decided to replace the coupling caps and all the Dubliner electrolytics (see attachments), plus a few out-of-spec resistors. The first thing I want to do though is bring the mains wiring up to requirements. I was very surprised by how flimsy this is considering how much the unit cost. The on/off switch is also defective as it tested live with a neon screwdriver - luckily I was cautious enough to have some rubber between my finger and the switch!

So my first question is this: should I replace the mains lead with two core flex or do I need three core so the chassis can be earthed? Also (and I hope this isn't too silly a question), which lead is which? Does the live connect to the voltage selector, or mains transformer? The current lead looks like speaker cable. I've tried to capture this area in one of the attached images.

Any help would be much appriciated.

Thanks
Keith

KeithEllis · 19th Apr 2009, 11:46 pm

Just thought I should mention the valve line-up: EF86; ECC83; EL84x2; EZ81.

Cheers
Keith

PJL · 20th Apr 2009, 7:44 am

The live should connect to the mains switch. You should earth the chassis so use 3-core cable. If you want it safer then you need to replace the switch with a 2 way one and switch both live and neutral, and add a fuse into the live wire...Peter

Station X · 20th Apr 2009, 9:11 am

When you say the mains switch tests live presumably you mean the BODY of the switch rather than the contacts which should be live? That being the case the whole chassis will be live because the body of the switch is electrically connected to it.

BE VERY CAREFUL.

julie_m · 20th Apr 2009, 9:49 am

The valve numbers begin with E, which usually (except in a few, rare cases, distinguible by a power transformer which is barely any bigger than the speaker transformer -- so not like yours) means a non-live chassis. It would definitely be worth fitting a 3-core mains lead and earthing the chassis.

By the way, in the UK, where all plugs are non-reversible, double-pole power switches are really no safer than single-pole, and may be less safe under fault conditions (if the live contact welds up, but the neutral contact is still functional, the appliance seems to be off but is still live; this can happen in cases of live-earth short, and I've seen it with my own eyes).

Steve_P · 20th Apr 2009, 11:03 am

Always switch Live. A double pole switch is a good idea, as is a fuse on the Live end after the switch. And a 3A fuse in the plug.

Caps need changing as do out of spec resistors. This is probably in Push-Pull by the way.

Sockets and Plugs can also be a problem here. And meter out the transformers just to be sure. You do not need a matched pair of EL84's by the way. They match themselves very quickly.

Cheers,

Steve P.

Tim · 20th Apr 2009, 12:47 pm

Quote:

By the way, in the UK, where all plugs are non-reversible, double-pole power switches are really no safer than single-pole, and may be less safe under fault conditions (if the live contact welds up, but the neutral contact is still functional, the appliance seems to be off but is still live

Provided the socket one is plugging into is not wired backwards. Probably more common than welded switches!
I would rather use a double pole switch, and risk the live contacts welding than the rather more common "backwards mains syndrome".
Of course it's impossible to eliminate EVERY risk.

KeithEllis · 20th Apr 2009, 11:53 pm

Thanks for your quick responses, guys. Much appreciated.

I think I'm a little confused with this whole switch thing. When I say the switch tests live, I mean the toggle part itself rather than the body of the switch, which was behind the fascia panel - this has only been powered up whilst all the parts were in situe, not with the amp removed. So that being the case, is the switch at fault as no part of the wiring is connected to the chassis? And as you say AJS, this is not a live chassis design.

I think I'm confused with this because on all the stuff I've worked on so far, the colour coding of the mains cable made it obvious what was live and neutral; also the terminals on this switch are not marked + or -.

Another thing that I'm confused by is the rectifier valve. The service data shows this to be an EZ81, but the one I removed was an EZ80. Judging by the dust build-up it doesn't look like it’s been touched for decades, so I'm not sure if this was a mistake or not. And would it still work with an EZ80?

Cheers
Keith

Station X · 21st Apr 2009, 7:39 am

The only parts of that switch which should be live are the two solder tags on it. In fact with the switch in the OFF position only one of the tags should be live.

A suggested by several posts in this thread fit a three core flex with the earth wire connected to the chassis and the switch in the live wire. For additional safety fit a double pole switch. Switch weld ups are unlikely. If you're worried about reversed wired mains sockets, then get one of those plug in socket testers from your local DIY store and test all your sockets.

LATER EDIT.

Having re-read the post I see that it's the actual toggle of the switch which is live. That being the case it definitely needs changing. It would appear that the toggle is electrically insulated from the body of the switch, so anyone touching the earthed chassis and the live toggle at the same time will get a shock. In a correctly wired installation this should trip the RCD.

Sideband · 21st Apr 2009, 8:24 am

Quote:

Originally Posted by KeithEllis

Another thing that I'm confused by is the rectifier valve. The service data shows this to be an EZ81, but the one I removed was an EZ80. Judging by the dust build-up it doesn't look like it’s been touched for decades, so I'm not sure if this was a mistake or not. And would it still work with an EZ80?

Cheers
Keith

An EZ80 would probably be OK if the total HT current did not exceed 90mA (for reliability, 75mA would be better). The EZ81 is rated at 120mA so has more 'margin'. The heater current of the EZ81 is also higher at 1 amp whereas the EZ80 heater is 600mA.

Personally I think with push-pull EL84, the EZ80 is running near it's limit.

Rich.

KeithEllis · 22nd Apr 2009, 11:47 pm

Thanks Graham, I don’t think I made it clear at the start that the toggle was live, but now I’ve read the posts a few times it’s much clearer what I need to do.

I've also discovered that a 2 amp fuse exists in the body of the voltage selector, although finding a replacement wouldn't be easy as it doesn't appear to be a standard size - I've read a few posts here about how Philips gear isn't always very easy to work on, as they weren’t very conventional with their designs.

Regarding the rectifier valve, I've found an EZ81 that I removed from an old tape recorder, so when the time comes I'll use that - thanks Rich.

So far I've replaced all the caps, and am about to rewire the mains and fit a new switch with a view to testing it at the weekend (when I've dug out the two units from the back of the shed!). I'll let you know how I get on.

Keith

PJL · 23rd Apr 2009, 7:44 am

There may be a terminology problem here. I would describe the toggle part of the switch as the metal lever arm that you touch to operate the switch. If this is live then the switch is most definitely faulty and needs replacing...Peter

AlanBeckett · 23rd Apr 2009, 9:22 am

Peter,
Strickyly speaking that's the dolly.
I don't think I've ever come across one that was live, although it might be if the chassis onto which it's mounted is. That would be a lethal combination.
Alan

PJL · 23rd Apr 2009, 11:11 pm

Interesting, from what I can make out, 'toggle' appears to describe the mechanical sprung action that holds the switch in the on or off state.

AlanBeckett · 23rd Apr 2009, 11:23 pm

Peter,
That sounds plausible, although I'm still not clear which part of Keith's switch is live.
Keith, be careful.
Alan

KeithEllis · 24th Apr 2009, 1:55 am

Yes, it was definitely the toggle/dolly that tested live. I must admit I found it strange at the time, as the body of the switch is mounted on a wooden fascia panel that's at least 10cm away from the chassis.

I will be careful Alan - I've been extra cautious since receiving a nasty shock from the deck of a so called 'restored' Dansette some time ago. I'll post some photos of the whole thing when I retrieve the two units from the shed at the weekend. Hopefully it'll make it easier to see what I mean.

Keith

dseymo1 · 24th Apr 2009, 8:05 am

I have a number of these Bulgin switches in stock.
Firstly, I must remember to check them for leakage before use

Secondly, Keith, if you'd like to keep your amp original, you'd be welcome to one of them (assuming that they're not all leaky).

KeithEllis · 24th Apr 2009, 11:08 pm

That would be great, thanks.

I'll send you a PM to arrange.

Thanks
Keith

dseymo1 · 25th Apr 2009, 12:01 pm

Interestingly, I've checked my switches, and they measure about 50 Megs between the dolly and any of the terminals. Not enough to do any harm, but may well give a tingle if not earthed. Not what I'd have expected from a Bulgin component, I have to say - perhaps the insulation degrades over time?

jjl · 25th Apr 2009, 12:19 pm

Keith

In equipment using mains transformers where the chassis is not earthed as in your amp. it is very common for sufficient leakage and / or capacitive coupling to exist between mains live and chassis to light a neon screwdriver. Only a few microamps are required.
See here for a recent post on this subject

http://vintage-radio.net/forum/showt...t=leakage+neon

So your switch may not be faulty. The best way to test the switch would be to use a Megger or similar to perform an insulation test on it.

Hope this helps.

John

19th Apr 2009, 11:39 pm	#1
KeithEllis Retired Dormant Member Join Date: Nov 2006 Location: Nottingham, Notts. UK. Posts: 113	Philips 10 watt Novosonic amplifier repair Hello everyone. I've finally got around to repairing (or attempting to repair at least) a Philips 10 watt Novosonic amplifier. This has been cluttering my shed for the last eighteen months or so, and consists of two matching wooden cabinets (each 3 feet high and 15 inches square), one containing the amp and a Philips record deck, the other a 12" bass speaker and a 7" treble unit. I have a curry's brochure from 1957 and this was the most expensive item listed, and is detailed in their hI-fI section. The whole thing seems extremely well made. Basically I want to get this working to see if the sound quality warrants the effort I'd have to put in to bring the cabinets back up to scratch, as they're both in fairly poor cosmetic condition. It was powered up by the previous owner prior to me collecting it, so when I got it home I did switch it on (not as cautious as I am now!) but with little effect - although with the volume up to max there was a faint, poor quality sound from the speaker. I've not powered it up since. I've purchased the service data, which is quite extensive at seven pages, and have decided to replace the coupling caps and all the Dubliner electrolytics (see attachments), plus a few out-of-spec resistors. The first thing I want to do though is bring the mains wiring up to requirements. I was very surprised by how flimsy this is considering how much the unit cost. The on/off switch is also defective as it tested live with a neon screwdriver - luckily I was cautious enough to have some rubber between my finger and the switch! So my first question is this: should I replace the mains lead with two core flex or do I need three core so the chassis can be earthed? Also (and I hope this isn't too silly a question), which lead is which? Does the live connect to the voltage selector, or mains transformer? The current lead looks like speaker cable. I've tried to capture this area in one of the attached images. Any help would be much appriciated. Thanks Keith Attached Thumbnails

19th Apr 2009, 11:46 pm	#2
KeithEllis Retired Dormant Member Join Date: Nov 2006 Location: Nottingham, Notts. UK. Posts: 113	Re: Philips 10 watt Novosonic amplifier repair Just thought I should mention the valve line-up: EF86; ECC83; EL84x2; EZ81. Cheers Keith

20th Apr 2009, 7:44 am	#3
PJL Dekatron Join Date: Sep 2005 Location: Seaford, East Sussex, UK. Posts: 5,997	Re: Philips 10 watt Novosonic amplifier repair The live should connect to the mains switch. You should earth the chassis so use 3-core cable. If you want it safer then you need to replace the switch with a 2 way one and switch both live and neutral, and add a fuse into the live wire...Peter

20th Apr 2009, 9:11 am	#4
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,289	Re: Philips 10 watt Novosonic amplifier repair When you say the mains switch tests live presumably you mean the BODY of the switch rather than the contacts which should be live? That being the case the whole chassis will be live because the body of the switch is electrically connected to it. BE VERY CAREFUL. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

20th Apr 2009, 9:49 am	#5
julie_m Dekatron Join Date: May 2008 Location: Derby, UK. Posts: 7,735	Re: Philips 10 watt Novosonic amplifier repair The valve numbers begin with E, which usually (except in a few, rare cases, distinguible by a power transformer which is barely any bigger than the speaker transformer -- so not like yours) means a non-live chassis. It would definitely be worth fitting a 3-core mains lead and earthing the chassis. By the way, in the UK, where all plugs are non-reversible, double-pole power switches are really no safer than single-pole, and may be less safe under fault conditions (if the live contact welds up, but the neutral contact is still functional, the appliance seems to be off but is still live; this can happen in cases of live-earth short, and I've seen it with my own eyes). __________________ If I have seen further than others, it is because I was standing on a pile of failed experiments.

20th Apr 2009, 11:03 am	#6
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: Philips 10 watt Novosonic amplifier repair Always switch Live. A double pole switch is a good idea, as is a fuse on the Live end after the switch. And a 3A fuse in the plug. Caps need changing as do out of spec resistors. This is probably in Push-Pull by the way. Sockets and Plugs can also be a problem here. And meter out the transformers just to be sure. You do not need a matched pair of EL84's by the way. They match themselves very quickly. Cheers, Steve P. __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?

20th Apr 2009, 11:53 pm	#8
KeithEllis Retired Dormant Member Join Date: Nov 2006 Location: Nottingham, Notts. UK. Posts: 113	Re: Philips 10 watt Novosonic amplifier repair Thanks for your quick responses, guys. Much appreciated. I think I'm a little confused with this whole switch thing. When I say the switch tests live, I mean the toggle part itself rather than the body of the switch, which was behind the fascia panel - this has only been powered up whilst all the parts were in situe, not with the amp removed. So that being the case, is the switch at fault as no part of the wiring is connected to the chassis? And as you say AJS, this is not a live chassis design. I think I'm confused with this because on all the stuff I've worked on so far, the colour coding of the mains cable made it obvious what was live and neutral; also the terminals on this switch are not marked + or -. Another thing that I'm confused by is the rectifier valve. The service data shows this to be an EZ81, but the one I removed was an EZ80. Judging by the dust build-up it doesn't look like it’s been touched for decades, so I'm not sure if this was a mistake or not. And would it still work with an EZ80? Cheers Keith

21st Apr 2009, 7:39 am	#9
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,289	Re: Philips 10 watt Novosonic amplifier repair The only parts of that switch which should be live are the two solder tags on it. In fact with the switch in the OFF position only one of the tags should be live. A suggested by several posts in this thread fit a three core flex with the earth wire connected to the chassis and the switch in the live wire. For additional safety fit a double pole switch. Switch weld ups are unlikely. If you're worried about reversed wired mains sockets, then get one of those plug in socket testers from your local DIY store and test all your sockets. LATER EDIT. Having re-read the post I see that it's the actual toggle of the switch which is live. That being the case it definitely needs changing. It would appear that the toggle is electrically insulated from the body of the switch, so anyone touching the earthed chassis and the live toggle at the same time will get a shock. In a correctly wired installation this should trip the RCD. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

22nd Apr 2009, 11:47 pm	#11
KeithEllis Retired Dormant Member Join Date: Nov 2006 Location: Nottingham, Notts. UK. Posts: 113	Re: Philips 10 watt Novosonic amplifier repair Thanks Graham, I don’t think I made it clear at the start that the toggle was live, but now I’ve read the posts a few times it’s much clearer what I need to do. I've also discovered that a 2 amp fuse exists in the body of the voltage selector, although finding a replacement wouldn't be easy as it doesn't appear to be a standard size - I've read a few posts here about how Philips gear isn't always very easy to work on, as they weren’t very conventional with their designs. Regarding the rectifier valve, I've found an EZ81 that I removed from an old tape recorder, so when the time comes I'll use that - thanks Rich. So far I've replaced all the caps, and am about to rewire the mains and fit a new switch with a view to testing it at the weekend (when I've dug out the two units from the back of the shed!). I'll let you know how I get on. Keith

23rd Apr 2009, 7:44 am	#12
PJL Dekatron Join Date: Sep 2005 Location: Seaford, East Sussex, UK. Posts: 5,997	Re: Philips 10 watt Novosonic amplifier repair There may be a terminology problem here. I would describe the toggle part of the switch as the metal lever arm that you touch to operate the switch. If this is live then the switch is most definitely faulty and needs replacing...Peter

23rd Apr 2009, 9:22 am	#13
AlanBeckett Rest in Peace Join Date: Dec 2008 Location: Burton upon Trent, East Staffordshire, UK. Posts: 1,686	Re: Philips 10 watt Novosonic amplifier repair Peter, Strickyly speaking that's the dolly. I don't think I've ever come across one that was live, although it might be if the chassis onto which it's mounted is. That would be a lethal combination. Alan

23rd Apr 2009, 11:11 pm	#14
PJL Dekatron Join Date: Sep 2005 Location: Seaford, East Sussex, UK. Posts: 5,997	Re: Philips 10 watt Novosonic amplifier repair Interesting, from what I can make out, 'toggle' appears to describe the mechanical sprung action that holds the switch in the on or off state.

23rd Apr 2009, 11:23 pm	#15
AlanBeckett Rest in Peace Join Date: Dec 2008 Location: Burton upon Trent, East Staffordshire, UK. Posts: 1,686	Re: Philips 10 watt Novosonic amplifier repair Peter, That sounds plausible, although I'm still not clear which part of Keith's switch is live. Keith, be careful. Alan

24th Apr 2009, 1:55 am	#16
KeithEllis Retired Dormant Member Join Date: Nov 2006 Location: Nottingham, Notts. UK. Posts: 113	Re: Philips 10 watt Novosonic amplifier repair Yes, it was definitely the toggle/dolly that tested live. I must admit I found it strange at the time, as the body of the switch is mounted on a wooden fascia panel that's at least 10cm away from the chassis. I will be careful Alan - I've been extra cautious since receiving a nasty shock from the deck of a so called 'restored' Dansette some time ago. I'll post some photos of the whole thing when I retrieve the two units from the shed at the weekend. Hopefully it'll make it easier to see what I mean. Keith

24th Apr 2009, 8:05 am	#17
dseymo1 Retired Dormant Member Join Date: Dec 2007 Location: Shropshire, UK. Posts: 3,051	Re: Philips 10 watt Novosonic amplifier repair I have a number of these Bulgin switches in stock. Firstly, I must remember to check them for leakage before use Secondly, Keith, if you'd like to keep your amp original, you'd be welcome to one of them (assuming that they're not all leaky).

24th Apr 2009, 11:08 pm	#18
KeithEllis Retired Dormant Member Join Date: Nov 2006 Location: Nottingham, Notts. UK. Posts: 113	Re: Philips 10 watt Novosonic amplifier repair That would be great, thanks. I'll send you a PM to arrange. Thanks Keith

25th Apr 2009, 12:01 pm	#19
dseymo1 Retired Dormant Member Join Date: Dec 2007 Location: Shropshire, UK. Posts: 3,051	Re: Philips 10 watt Novosonic amplifier repair Interestingly, I've checked my switches, and they measure about 50 Megs between the dolly and any of the terminals. Not enough to do any harm, but may well give a tingle if not earthed. Not what I'd have expected from a Bulgin component, I have to say - perhaps the insulation degrades over time?

25th Apr 2009, 12:19 pm	#20
jjl Octode Join Date: Jan 2003 Location: Ware, Herts. UK. Posts: 1,082	Re: Philips 10 watt Novosonic amplifier repair Keith In equipment using mains transformers where the chassis is not earthed as in your amp. it is very common for sufficient leakage and / or capacitive coupling to exist between mains live and chassis to light a neon screwdriver. Only a few microamps are required. See here for a recent post on this subject http://vintage-radio.net/forum/showt...t=leakage+neon So your switch may not be faulty. The best way to test the switch would be to use a Megger or similar to perform an insulation test on it. Hope this helps. John