Marconiphone 4816 - UK Vintage Radio Repair and Restoration Discussion Forum

sexton_mallard · 8th May 2016, 10:13 am

I picked up a nice little 12 inch Marconiphone 4816 at Golborne mainly as a reminder of a childhood memory. It powers up fine with a nice bright picture. The tuner push-buttons will not latch but I get a reasonable picture from my RF modulator when holding a button in. I will try the repair I have seen elsewhere on this forum on other Thorn sets.

I see at least 1 component on the main board that looks like a black Callins cap. Are there any potential stock faults to be aware of or mods I should carry out while I have the back off fixiing the tuner? Thanks in advance as always.

slidertogrid · 8th May 2016, 11:47 am

Hi These are great little sets. It wasn't unusual to see them slogging on for 20 years or so.
While you have the tuner out I would remove clean and re-tension slightly the tuning vanes earth springs. They are often covered in a brown grease that causes poor connection.
You need a fairly big iron to release them from the tuner body.
I would check that there isn't a capacitor on the DC side of the EHT rectifier it was only fitted to early models and the 14" version I think. It goes short and can damage the stick and lopt.
I have a poor unfortunate example in the loft somewhere that has had mains put up it's 12V socket... I haven't looked inside it, apparently it went pop...!
Rich.

KeithsTV · 8th May 2016, 5:04 pm

I have the Ferguson version of this set, bought new in 1976, which is still going. I feed it from the RF output of a PVR box. I haven't have many problems with it, a dry joint on one of the rectifier diodes being one that I remember. I also have the service manual for it and there was an Les Lawry Johns service article which I also have. I posted them here.

https://www.vintage-radio.net/forum/...ad.php?t=35588

Keith

Heatercathodeshort · 10th May 2016, 6:59 pm

One item needs to be checked to maintain reliable operation.
Many 1590/91 series were destroyed due to the L.T. rail rising over a long period. By the time the customer notices the hum bars on the picture due to the voltage rising to over 15V, the CRT has been overrun to the point that it will no longer give a reasonable picture at it's correct 11.5V.
The cause of all this mayhem is simply the 220 ohm LT adjust pot rising to over 2K. I used to replace this on site with a high quality ceramic type that would not fail in this disastrous way. Well worth a check. Adjust for a fraction under 12v on the test point. John.

Restoration73 · 10th May 2016, 7:43 pm

Severe DC ripple is often caused by the 4700uF smoother; when I repaired a new one
in 1972 it was down to defective rivets on the capacitor.
Poor tuning reset is down to the soldered joints at each end of the tuning bar. I
recommend the use of 40/60 high melting point solder and a large iron here.

FERNSEH · 10th May 2016, 8:01 pm

The 1590 chassis was introduced late 1972 and I was selling the Marconi and Alba versions in 1973. One the earliest faults encountered was failure of the two diodes in the full wave rectifier, the original diodes were not up to the job.
Fortunately, 3amp diodes of the 1N5401 type were becoming readily available.
The set supply volts control is a dodgy thing and should be always checked whenever one of these sets comes in for servicing. Apart from these simple to fix faults these are absolutely suburb little sets. After forty years those lockfit transistors might start to be giving trouble.
There's a Marconi 4816 upstairs, if any forum member fancies it I can take it with me down to Mikey's bash on Saturday.

DFWB.

Philips210 · 10th May 2016, 10:54 pm

Quote:

Originally Posted by FERNSEH

these are absolutely suburb little sets.

Hi.

Agreed, I repaired quite a few of these sets back in the 1980's and always found them to be easy to repair. The early ones had germanium series regulator and line output transistors, both were eventually replaced with silicon devices.
Thanks for the tip on the Set output volts preset, I had forgotten about that problem. I too have one in the loft which I must get up and running again. I picked up another one from our local car boot sale for only £3 but it's CRT was badly scratched. I stripped it for spares and the tuner knobs and aluminium caps were a perfect match for my little 17" Marconiphone (BRC 1500 chassis).
My only gripe on the 1590 is the cabinet back has the mains lead passing through it so the mains plug has to be removed if you don't want the back cover on the bench or generally in the way when servicing.
I seem to remember the LOPTx is quite reliable not like the later 1690. Also on the 1590, the e.h.t. stick rectifier is easily replaceable. Great little sets, easy to work on, fairly compact and not too heavy to move around and they produce quite a decent picture.

Regards
Symon.

FERNSEH · 10th May 2016, 11:08 pm

Don't forget the 14" versions of this chassis. Marketed as an Alba in a maroon cabinet and also as HMV and Ultra in different presentations. All have the same cabinet shape. There was a posh HMV model in a wooden cabinet, looked like a miniature table set.

DFWB.

Philips210 · 10th May 2016, 11:21 pm

Hi.

Yes, the 14" version uses the 1591 chassis. I didn't come across too many of these. There must have been many more 1590 sets in circulation compared to the 1591 sets.

Regards
Symon.

Welsh Anorak · 11th May 2016, 2:34 pm

The main problem with the pretty 14" was the poor tube which didn't last long. As long as the HT was OK the 12" tubes lasted forever, only failing when some ham-fisted loon (hello!) broke the neck.
Glyn

Heatercathodeshort · 11th May 2016, 7:35 pm

I'm surprised at your experience with the 14" tube Glyn. I found them just as good as the smaller 12" version except of course when the LT pot plays up!
Unlike the 20" versions of the Philips KT3 that went flat in 12 months.
Pictures here of the Ultra 6818, very stylish, Teddy Rosen would have been delighted.
The other picture could be a 1500 at first glance but is in fact the HMV version in the wooden cabinet. Now this is style! This example in my collection is the only one I have ever seen and I must have serviced hundreds of 1590/91 chassis and the valve version [ Yes there was a mains only valve version of the 12" 3816 the 3805] Good old Thorn. Regards, John.

FERNSEH · 11th May 2016, 8:06 pm

Hi John,
Customers loved the woodie HMV 1591, does model 2841 sound right?
Worth remembering the almost identical cabinet of the 12" models 4816 and the white Ultra 6816 was first used in the valve Ferguson 3805 which was made in 1971. Called the Ferguson Courier, is that right?

DFWB.

sexton_mallard · 10th Dec 2016, 7:13 pm

I finally found some time to sort out the tuner that had the seemingly common problem affecting Thorn tuners with broken plastic pieces on each of the push button rods. After looking at some other repairs on this forum, I used some No.10 cup washers – the type used for countersunk screws set into a flat surface. Not pretty, but does the job. The selector was cleaned, reassembled and treated to a drop of oil before being replaced onto the tuner unit. It now has a nice 'clickety clack' tactile feeling again.

A check of the supply voltage showed it to be at 9.7v. Now tweaked up to 11.5v and measured again after a couple of hours, the set produces a nice bright picture. Now to enjoy this little telly.

8th May 2016, 10:13 am	#1
sexton_mallard Heptode Join Date: Sep 2013 Location: Ellesmere, Shropshire, UK & Co. Cork, Ireland. Posts: 502	Marconiphone 4816 I picked up a nice little 12 inch Marconiphone 4816 at Golborne mainly as a reminder of a childhood memory. It powers up fine with a nice bright picture. The tuner push-buttons will not latch but I get a reasonable picture from my RF modulator when holding a button in. I will try the repair I have seen elsewhere on this forum on other Thorn sets. I see at least 1 component on the main board that looks like a black Callins cap. Are there any potential stock faults to be aware of or mods I should carry out while I have the back off fixiing the tuner? Thanks in advance as always. Attached Thumbnails __________________ Dom Less snakes...more ladders! Last edited by sexton_mallard; 8th May 2016 at 10:19 am.

8th May 2016, 11:47 am	#2
slidertogrid Octode Join Date: Apr 2005 Location: Peterborough, Cambridgeshire, UK. Posts: 1,898	Re: Marconiphone 4816 Hi These are great little sets. It wasn't unusual to see them slogging on for 20 years or so. While you have the tuner out I would remove clean and re-tension slightly the tuning vanes earth springs. They are often covered in a brown grease that causes poor connection. You need a fairly big iron to release them from the tuner body. I would check that there isn't a capacitor on the DC side of the EHT rectifier it was only fitted to early models and the 14" version I think. It goes short and can damage the stick and lopt. I have a poor unfortunate example in the loft somewhere that has had mains put up it's 12V socket... I haven't looked inside it, apparently it went pop...! Rich. __________________ The rotation of the earth really makes my day...

8th May 2016, 5:04 pm	#3
KeithsTV Nonode Join Date: Aug 2007 Location: South Bradford, West Yorkshire, UK. Posts: 2,573	Re: Marconiphone 4816 I have the Ferguson version of this set, bought new in 1976, which is still going. I feed it from the RF output of a PVR box. I haven't have many problems with it, a dry joint on one of the rectifier diodes being one that I remember. I also have the service manual for it and there was an Les Lawry Johns service article which I also have. I posted them here. https://www.vintage-radio.net/forum/...ad.php?t=35588 Keith

10th May 2016, 6:59 pm	#4
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: Marconiphone 4816 One item needs to be checked to maintain reliable operation. Many 1590/91 series were destroyed due to the L.T. rail rising over a long period. By the time the customer notices the hum bars on the picture due to the voltage rising to over 15V, the CRT has been overrun to the point that it will no longer give a reasonable picture at it's correct 11.5V. The cause of all this mayhem is simply the 220 ohm LT adjust pot rising to over 2K. I used to replace this on site with a high quality ceramic type that would not fail in this disastrous way. Well worth a check. Adjust for a fraction under 12v on the test point. John.

10th May 2016, 7:43 pm	#5
Restoration73 Nonode Join Date: Jun 2013 Location: Surbiton, SW London, UK. Posts: 2,801	Re: Marconiphone 4816 Severe DC ripple is often caused by the 4700uF smoother; when I repaired a new one in 1972 it was down to defective rivets on the capacitor. Poor tuning reset is down to the soldered joints at each end of the tuning bar. I recommend the use of 40/60 high melting point solder and a large iron here.

10th May 2016, 8:01 pm	#6
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: Marconiphone 4816 The 1590 chassis was introduced late 1972 and I was selling the Marconi and Alba versions in 1973. One the earliest faults encountered was failure of the two diodes in the full wave rectifier, the original diodes were not up to the job. Fortunately, 3amp diodes of the 1N5401 type were becoming readily available. The set supply volts control is a dodgy thing and should be always checked whenever one of these sets comes in for servicing. Apart from these simple to fix faults these are absolutely suburb little sets. After forty years those lockfit transistors might start to be giving trouble. There's a Marconi 4816 upstairs, if any forum member fancies it I can take it with me down to Mikey's bash on Saturday. DFWB.

10th May 2016, 11:08 pm	#8
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: Marconiphone 4816 Don't forget the 14" versions of this chassis. Marketed as an Alba in a maroon cabinet and also as HMV and Ultra in different presentations. All have the same cabinet shape. There was a posh HMV model in a wooden cabinet, looked like a miniature table set. DFWB.

10th May 2016, 11:21 pm	#9
Philips210 Nonode Join Date: May 2007 Location: Redruth, Cornwall, UK. Posts: 2,580	Re: Marconiphone 4816 Hi. Yes, the 14" version uses the 1591 chassis. I didn't come across too many of these. There must have been many more 1590 sets in circulation compared to the 1591 sets. Regards Symon.

11th May 2016, 2:34 pm	#10
Welsh Anorak Dekatron Join Date: Apr 2005 Location: North Wales, UK. Posts: 6,927	Re: Marconiphone 4816 The main problem with the pretty 14" was the poor tube which didn't last long. As long as the HT was OK the 12" tubes lasted forever, only failing when some ham-fisted loon (hello!) broke the neck. Glyn

11th May 2016, 7:35 pm	#11
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: Marconiphone 4816 I'm surprised at your experience with the 14" tube Glyn. I found them just as good as the smaller 12" version except of course when the LT pot plays up! Unlike the 20" versions of the Philips KT3 that went flat in 12 months. Pictures here of the Ultra 6818, very stylish, Teddy Rosen would have been delighted. The other picture could be a 1500 at first glance but is in fact the HMV version in the wooden cabinet. Now this is style! This example in my collection is the only one I have ever seen and I must have serviced hundreds of 1590/91 chassis and the valve version [ Yes there was a mains only valve version of the 12" 3816 the 3805] Good old Thorn. Regards, John. Attached Thumbnails

11th May 2016, 8:06 pm	#12
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: Marconiphone 4816 Hi John, Customers loved the woodie HMV 1591, does model 2841 sound right? Worth remembering the almost identical cabinet of the 12" models 4816 and the white Ultra 6816 was first used in the valve Ferguson 3805 which was made in 1971. Called the Ferguson Courier, is that right? DFWB.

10th Dec 2016, 7:13 pm	#13
sexton_mallard Heptode Join Date: Sep 2013 Location: Ellesmere, Shropshire, UK & Co. Cork, Ireland. Posts: 502	Re: Marconiphone 4816 I finally found some time to sort out the tuner that had the seemingly common problem affecting Thorn tuners with broken plastic pieces on each of the push button rods. After looking at some other repairs on this forum, I used some No.10 cup washers – the type used for countersunk screws set into a flat surface. Not pretty, but does the job. The selector was cleaned, reassembled and treated to a drop of oil before being replaced onto the tuner unit. It now has a nice 'clickety clack' tactile feeling again. A check of the supply voltage showed it to be at 9.7v. Now tweaked up to 11.5v and measured again after a couple of hours, the set produces a nice bright picture. Now to enjoy this little telly. Attached Thumbnails __________________ Dom Less snakes...more ladders!