Philips B4S51A/15 Valve Radio - UK Vintage Radio Repair and Restoration Discussion Forum

Mach One · 4th Jul 2018, 3:34 pm

I have one of these. It is actually the second one that I have had - the first one was bought in a charity shop in Brighton in around 1990 and I was immediately drawn to the fact that it was obviously a very modern / young valve set. It appears that it may have been one of the last ever made? The one in question was bought because it had all its knobs intact and would either make a good donating set for the original one or be the one to get up-to-scratch as it were. It is in fact the latter and I have had it around ten years awaiting refurbishment. Now is finally the time to get down to this very slow job-in-progress! All of mine are...

It works on AM, although I have the impression that it might be a little deaf. FM does not seem to work although I had that with the original one after several years of good service. All this on the internal antennae and I know that these sets are not that sensitive. I have started with powering it up and letting it warm up and then making an attempt to measure the voltages against the ones in the Service Manual. I was wondering if anyone would be interested in passing comment on the values? I have attached a picture of the voltages obtained which I entered into an Excel spreadsheet. Bearing in mind that the voltmeter is a Fluke 73III which has no loading effect on the circuit at all I am aware that the values would be generally higher than they would have been in the days of the trusty Avo Meter!

One further question: There is a lot of crackling and hissing - at least compared with what I know that there should be - coming out of the loudspeaker which is able to go quite high in audio level if the volume is turned up. This crackling is independent of the volume control and so I would assume part of the output valve circuitry somewhere. Any suggestions what would be causing it and how I might measure with my Fluke any possible rogue components if at all possible? I do not have a scope..

paulsherwin · 4th Jul 2018, 3:54 pm

These were made by Philips Sweden. I think that division was one of the last ones to make valve sets.

The crackling may be from a bad EBC81 - if you have two sets you can just sub it and see if it makes any difference.

Herald1360 · 4th Jul 2018, 8:29 pm

Quote:

Originally Posted by Mach One

Bearing in mind that the voltmeter is a Fluke 73III which has no loading effect on the circuit at all I am aware that the values would be generally higher than they would have been in the days of the trusty Avo Meter!
..

10megohms (Fluke load) is not negligible compared with the impedances at quite a few points in a valve set. Results will be higher than Avo but only if the Avo is set to 250v or less FSD. At 500v they'll be the same. Neither will indicate the true operating voltages except for psu direct outputs where the difference will be negligible.

Mach One · 7th Jul 2018, 10:55 am

Thank you, both, for your replies. Back this morning at a couple of hours of work on the set.

I have swapped both V4 (EBC81) and V5 (EL86) and there is no improvement in the crackle. It's not high level but it is noticeable and annoying.

I thought that I'd measure the resistors. All measured with the receiver completely cold and in situ - I am aware of the potential issues here. There are several that are significantly higher than the value that they should be, most notably:

R8 - should be 47k, measures 153k. (explains why V2 pin 1 reads low)
R9 - should be 33k, measures 146k. (explains why V2 pin 8 reads so low)
R15 - should be 47k, measures 80k. (I would expect V3 pin 8 to read even lower?)
R27 - should be 560k, measures 997k. (V6 pin 7/9 low...)
R28 - should be 220k, measures 870k. (I would expect V4 pin 1 lower...)
R45 - should be 560k, measures 1.3M. (what effect would that have?)

Other ones are higher but although I would only replace them if I had to.

Comments, please...

Mach One · 14th Jul 2018, 11:15 am

For those of you who are interested:

Having measured what appeared to be several resistors with much higher values than the circuit stated I ordered some replacements from CPC. I tried to order some which would not only be the correct value but which would look right in the set, meaning perhaps 2W versions. I was able to order most of them in either 1W or 2W sizes and have carefully replaced the rogue resistors this morning.

The most noticeable thing having switched on is that the crackling and slight loudspeaker mains hum is gone! That was a surprise. Also, the magic eye seems brighter and closes more on the signals available on the internal ferrite rod, so at the end of what is actually my first proper valve set repair in years I am very happy!

I did go round and measured all the voltages again and while many have changed, the changes were not as appreciable as I had expected. I was expecting to have to replace some capacitors but I can see none that look worse for wear and have not measured any voltage horrors that might indicate a short, for example. As I have no way of measuring them I think that I will leave well alone. Next is to make the set look as cosmetically good as possible and align for best reception.

Maarten · 14th Jul 2018, 11:24 am

The capacitors are generally polyester foil (but watch out, chances are there is one paper capacitor present in the primary circuit and possibly one on each output transformer - I don't have a schematic to verify right now). The unreliable resistors will be carbon composite types, known to go high over the years.

1965 was a year that most Philips factories still produced at least some valve models, phasing out started soon after that. In Europe, the 1967 model year was mostly valve-less, selling off some old stock chassis in partially new models and 1968 saw some bought in Italian low end valve sets. I think the last valve sets were from exotic places. Philips Chili came out with a new luxury valve set in 1969.

Ed_Dinning · 14th Jul 2018, 8:09 pm

Hi, the Philips caps are not the best in the world, so it could also be worthwhile replacing the critical ones in stressed positions as well as on the AVC line.
These may test OK on a DVM, but could be leaking at operating voltages.

Ed

Mach One · 16th Jul 2018, 10:02 am

Thank you for the suggestion.

Stressed positions? Ones which are dealing with a "high voltage"? And as far as the AGC on this set - there appear to be at least two of relatively small value across what looks like the AGC line. I guess that I shall just replace both anyway...

Boater Sam · 16th Jul 2018, 1:12 pm

Normally suspect any caps over 0.001 in value.
Audio coupling cap/s, all decoupling caps fro HT, tone correctors across output transformer, anti modulation cap across mains, AGC cap, output cathode cap.

4th Jul 2018, 3:34 pm	#1
Mach One Heptode Join Date: Sep 2005 Location: Shoreham-by-Sea, West Sussex, UK. Posts: 611	Philips B4S51A/15 Valve Radio I have one of these. It is actually the second one that I have had - the first one was bought in a charity shop in Brighton in around 1990 and I was immediately drawn to the fact that it was obviously a very modern / young valve set. It appears that it may have been one of the last ever made? The one in question was bought because it had all its knobs intact and would either make a good donating set for the original one or be the one to get up-to-scratch as it were. It is in fact the latter and I have had it around ten years awaiting refurbishment. Now is finally the time to get down to this very slow job-in-progress! All of mine are... It works on AM, although I have the impression that it might be a little deaf. FM does not seem to work although I had that with the original one after several years of good service. All this on the internal antennae and I know that these sets are not that sensitive. I have started with powering it up and letting it warm up and then making an attempt to measure the voltages against the ones in the Service Manual. I was wondering if anyone would be interested in passing comment on the values? I have attached a picture of the voltages obtained which I entered into an Excel spreadsheet. Bearing in mind that the voltmeter is a Fluke 73III which has no loading effect on the circuit at all I am aware that the values would be generally higher than they would have been in the days of the trusty Avo Meter! One further question: There is a lot of crackling and hissing - at least compared with what I know that there should be - coming out of the loudspeaker which is able to go quite high in audio level if the volume is turned up. This crackling is independent of the volume control and so I would assume part of the output valve circuitry somewhere. Any suggestions what would be causing it and how I might measure with my Fluke any possible rogue components if at all possible? I do not have a scope.. Attached Thumbnails

4th Jul 2018, 3:54 pm	#2
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,941	Re: Philips B4S51A/15 Valve Radio These were made by Philips Sweden. I think that division was one of the last ones to make valve sets. The crackling may be from a bad EBC81 - if you have two sets you can just sub it and see if it makes any difference.

7th Jul 2018, 10:55 am	#4
Mach One Heptode Join Date: Sep 2005 Location: Shoreham-by-Sea, West Sussex, UK. Posts: 611	Re: Philips B4S51A/15 Valve Radio Thank you, both, for your replies. Back this morning at a couple of hours of work on the set. I have swapped both V4 (EBC81) and V5 (EL86) and there is no improvement in the crackle. It's not high level but it is noticeable and annoying. I thought that I'd measure the resistors. All measured with the receiver completely cold and in situ - I am aware of the potential issues here. There are several that are significantly higher than the value that they should be, most notably: R8 - should be 47k, measures 153k. (explains why V2 pin 1 reads low) R9 - should be 33k, measures 146k. (explains why V2 pin 8 reads so low) R15 - should be 47k, measures 80k. (I would expect V3 pin 8 to read even lower?) R27 - should be 560k, measures 997k. (V6 pin 7/9 low...) R28 - should be 220k, measures 870k. (I would expect V4 pin 1 lower...) R45 - should be 560k, measures 1.3M. (what effect would that have?) Other ones are higher but although I would only replace them if I had to. Comments, please...

14th Jul 2018, 11:15 am	#5
Mach One Heptode Join Date: Sep 2005 Location: Shoreham-by-Sea, West Sussex, UK. Posts: 611	Re: Philips B4S51A/15 Valve Radio For those of you who are interested: Having measured what appeared to be several resistors with much higher values than the circuit stated I ordered some replacements from CPC. I tried to order some which would not only be the correct value but which would look right in the set, meaning perhaps 2W versions. I was able to order most of them in either 1W or 2W sizes and have carefully replaced the rogue resistors this morning. The most noticeable thing having switched on is that the crackling and slight loudspeaker mains hum is gone! That was a surprise. Also, the magic eye seems brighter and closes more on the signals available on the internal ferrite rod, so at the end of what is actually my first proper valve set repair in years I am very happy! I did go round and measured all the voltages again and while many have changed, the changes were not as appreciable as I had expected. I was expecting to have to replace some capacitors but I can see none that look worse for wear and have not measured any voltage horrors that might indicate a short, for example. As I have no way of measuring them I think that I will leave well alone. Next is to make the set look as cosmetically good as possible and align for best reception.

14th Jul 2018, 11:24 am	#6
Maarten Dekatron Join Date: Dec 2007 Location: Haarlem, Netherlands Posts: 4,199	Re: Philips B4S51A/15 Valve Radio The capacitors are generally polyester foil (but watch out, chances are there is one paper capacitor present in the primary circuit and possibly one on each output transformer - I don't have a schematic to verify right now). The unreliable resistors will be carbon composite types, known to go high over the years. 1965 was a year that most Philips factories still produced at least some valve models, phasing out started soon after that. In Europe, the 1967 model year was mostly valve-less, selling off some old stock chassis in partially new models and 1968 saw some bought in Italian low end valve sets. I think the last valve sets were from exotic places. Philips Chili came out with a new luxury valve set in 1969. Last edited by Maarten; 14th Jul 2018 at 11:31 am.

14th Jul 2018, 8:09 pm	#7
Ed_Dinning Dekatron Join Date: Jan 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 8,194	Re: Philips B4S51A/15 Valve Radio Hi, the Philips caps are not the best in the world, so it could also be worthwhile replacing the critical ones in stressed positions as well as on the AVC line. These may test OK on a DVM, but could be leaking at operating voltages. Ed

16th Jul 2018, 10:02 am	#8
Mach One Heptode Join Date: Sep 2005 Location: Shoreham-by-Sea, West Sussex, UK. Posts: 611	Re: Philips B4S51A/15 Valve Radio Thank you for the suggestion. Stressed positions? Ones which are dealing with a "high voltage"? And as far as the AGC on this set - there appear to be at least two of relatively small value across what looks like the AGC line. I guess that I shall just replace both anyway...

16th Jul 2018, 1:12 pm	#9
Boater Sam Banned Join Date: Dec 2013 Location: Middlewich, Cheshire, UK. & Winter in the Philippines. Posts: 3,897	Re: Philips B4S51A/15 Valve Radio Normally suspect any caps over 0.001 in value. Audio coupling cap/s, all decoupling caps fro HT, tone correctors across output transformer, anti modulation cap across mains, AGC cap, output cathode cap.