Mullard Type MUS217 No. 83330 Information wanted - UK Vintage Radio Repair and Restoration Discussion Forum

Mullard_Nut_74 · 5th Apr 2020, 8:49 am

Hi all,
I have been searching the interwebs for information about my Mullard radio and perhaps a circuit diagram.
Had no luck at all.
When I type in either serial number from the ID plate, all I get is a circuit for a 20W amplifier.

This is my first radio I am trying to repair but not the first one I have owned.
I have always had valve equipment and replaced tubes etc but never done a proper repair.
I want to repair this one properly as I really like the look and the style of it.
Photos of the unit can be found in my albums section.

I am off to a bad start as I cant even seem to get the chasis out of the pristine Bakelite housing.

cathoderay57 · 5th Apr 2020, 8:59 am

Agreed, I could only find the MUS219. Are you certain that you've read the label correctly? If so then if you list the valve numbers it should be possible to identify a similar circuit. Being MUS it sounds like a live chassis model. Cheers, Jerry

Cobaltblue · 5th Apr 2020, 9:01 am

Hi

I see its on Radiomuseum but no circuit

https://www.radiomuseum.org/r/mullard_mus217mus_21.html

Its almost certainly going to be the same as a Philips.

Worth rooting around the Radiomuseum

This Philips is similar but not an export model https://www.radiomuseum.org/r/philips_151u.html

Cheers

Mike T

Mullard_Nut_74 · 5th Apr 2020, 9:10 am

Quote:

Originally Posted by cathoderay57

Agreed, I could only find the MUS219. Are you certain that you've read the label correctly? If so then if you list the valve numbers it should be possible to identify a similar circuit. Being MUS it sounds like a live chassis model. Cheers, Jerry

They are all British made Mullard tubes in great condition.

UY41
UL4
UBC41
UCH42
UF41

Mullard_Nut_74 · 5th Apr 2020, 9:19 am

Looks like the one Mike.
Tube numbers match except I only see a UL4 in my unit and both radios say UL41.
This may just be down to the paint rubbing off the tube.
Someone has cut the speaker wires and they were rubbing against the tube.
I must say though that the Mullard export model is far better looking than the Philips.
I think my grill cloth even matches my unit so I might have a fairly untouched unit on my hands.
I remember plugging it in 14 years ago and it working for a short period of time before going silent.
Perhaps I cut the speaker wires in an attempt to remove the chasis.
I cant remember that long ago.

Edit: Sorry the grill cloth does not match.
Stupid me was looking at the picture I took myself.
Insert forehead slap here.

Mullard_Nut_74 · 9th Apr 2020, 4:50 pm

Im having trouble starting on my radio.
I am a bit terrified of cutting out a capacitor and replacing it.
Do the markings on these black lumps actually mean anything?
I cant match the numbers with anything on the circuit diagram and I cant find anything on Google when I type in the gold numbers and letters.

I THINK they say things like
S4K7P & L47KP & 2K2P but they are so badly aged that I cant be sure.
Any advice on how to read these?

dazzlevision · 9th Apr 2020, 5:14 pm

Markings decoder for Philips black wax dipped axial paper capacitors:

First Letter: working voltage =

L = 125 V
No letter = 400 V
H = 600 V
S = 800 V
T = 1000 V

Capacitance value in pF is (ie 56K = 56000pF)

Then tolerance code:

A = + - 10%
P = + - 20%

Example:

A capacitor with the inscription: "S 10 CP 5.1" = 10nF at 800V 20% tolerance.

This is followed by a production code (5.1 for example), which is not of interest.

Mullard_Nut_74 · 9th Apr 2020, 11:02 pm

Thanks for that.
Is there a table of these Philips codes somewhere?
I searched for one and couldnt find anything on the net.

Mullard_Nut_74 · 10th Apr 2020, 2:06 pm

I just came across another heap of issues.
The Schematic I am using for the Philips set lists a UCH41 but my Mullard radio has a UCH42.
The multi voltage selector just fell apart when I took it off to look at where the connections go and there is 3 possible ways to piece it back together.
There is a huge black wax capacitor with no markings on pin 4 of UY41 that runs straight to chasis ground but I can find no such capacitor on the schematic.
The output transformer has some kind of black tar like substance oozing out the top of it and looks like boiled over burnt varnish so I dont trust it will be working either.

I am not winning with this one. I am starting to think this radio is a basket case and way out of my league.
Perhaps I need to find and start with a nice simple unit with less electronics and less damage.

Simon Gittins · 10th Apr 2020, 8:15 pm

You could certainly find an easier radio as a first restoration project but you don't need to give up on this one yet.

The UCH42 is a later version of the UCH41.

Voltage selector falling apart, yes, they do that! Perhaps you could just rewire the mains input to the relevant connections for your voltage.

Is the capacitor definitely on pin 4 of the UY41 and are there any other connections to this pin? Pin 4 is shown as internally connected and should not really have been used as a junction point (although they often were).

The output transformer may or may not be ok, it's worth doing a continuity check on the primary first.

5th Apr 2020, 8:49 am	#1
Mullard_Nut_74 Tetrode Join Date: Mar 2020 Location: Sydney, New South Wales, Australia. Posts: 65	Mullard Type MUS217 No. 83330 Information wanted Hi all, I have been searching the interwebs for information about my Mullard radio and perhaps a circuit diagram. Had no luck at all. When I type in either serial number from the ID plate, all I get is a circuit for a 20W amplifier. This is my first radio I am trying to repair but not the first one I have owned. I have always had valve equipment and replaced tubes etc but never done a proper repair. I want to repair this one properly as I really like the look and the style of it. Photos of the unit can be found in my albums section. I am off to a bad start as I cant even seem to get the chasis out of the pristine Bakelite housing.

5th Apr 2020, 8:59 am	#2
cathoderay57 Nonode Join Date: Oct 2017 Location: Bristol, UK. Posts: 2,386	Re: Mullard Type MUS217 No. 83330 Information wanted Agreed, I could only find the MUS219. Are you certain that you've read the label correctly? If so then if you list the valve numbers it should be possible to identify a similar circuit. Being MUS it sounds like a live chassis model. Cheers, Jerry

5th Apr 2020, 9:01 am	#3
Cobaltblue Moderator Join Date: Dec 2010 Location: Exeter, Devon and Poole, Dorset UK. Posts: 6,875	Re: Mullard Type MUS217 No. 83330 Information wanted Hi I see its on Radiomuseum but no circuit https://www.radiomuseum.org/r/mullard_mus217mus_21.html Its almost certainly going to be the same as a Philips. Worth rooting around the Radiomuseum This Philips is similar but not an export model https://www.radiomuseum.org/r/philips_151u.html Cheers Mike T __________________ Invisible airwaves crackle with life or at least they used to Mike T BVWS member. www.cossor.co.uk

5th Apr 2020, 9:19 am	#5
Mullard_Nut_74 Tetrode Join Date: Mar 2020 Location: Sydney, New South Wales, Australia. Posts: 65	Re: Mullard Type MUS217 No. 83330 Information wanted Looks like the one Mike. Tube numbers match except I only see a UL4 in my unit and both radios say UL41. This may just be down to the paint rubbing off the tube. Someone has cut the speaker wires and they were rubbing against the tube. I must say though that the Mullard export model is far better looking than the Philips. I think my grill cloth even matches my unit so I might have a fairly untouched unit on my hands. I remember plugging it in 14 years ago and it working for a short period of time before going silent. Perhaps I cut the speaker wires in an attempt to remove the chasis. I cant remember that long ago. Edit: Sorry the grill cloth does not match. Stupid me was looking at the picture I took myself. Insert forehead slap here. Last edited by Mullard_Nut_74; 5th Apr 2020 at 9:22 am. Reason: Correction of information

9th Apr 2020, 4:50 pm	#6
Mullard_Nut_74 Tetrode Join Date: Mar 2020 Location: Sydney, New South Wales, Australia. Posts: 65	Re: Mullard Type MUS217 No. 83330 Information wanted Im having trouble starting on my radio. I am a bit terrified of cutting out a capacitor and replacing it. Do the markings on these black lumps actually mean anything? I cant match the numbers with anything on the circuit diagram and I cant find anything on Google when I type in the gold numbers and letters. I THINK they say things like S4K7P & L47KP & 2K2P but they are so badly aged that I cant be sure. Any advice on how to read these? Attached Thumbnails

9th Apr 2020, 5:14 pm	#7
dazzlevision Dekatron Join Date: Sep 2003 Location: Near Swindon, North Wiltshire, UK. Posts: 3,621	Re: Mullard Type MUS217 No. 83330 Information wanted Markings decoder for Philips black wax dipped axial paper capacitors: First Letter: working voltage = L = 125 V No letter = 400 V H = 600 V S = 800 V T = 1000 V Capacitance value in pF is (ie 56K = 56000pF) Then tolerance code: A = + - 10% P = + - 20% Example: A capacitor with the inscription: "S 10 CP 5.1" = 10nF at 800V 20% tolerance. This is followed by a production code (5.1 for example), which is not of interest.

9th Apr 2020, 11:02 pm	#8
Mullard_Nut_74 Tetrode Join Date: Mar 2020 Location: Sydney, New South Wales, Australia. Posts: 65	Re: Mullard Type MUS217 No. 83330 Information wanted Thanks for that. Is there a table of these Philips codes somewhere? I searched for one and couldnt find anything on the net.

10th Apr 2020, 2:06 pm	#9
Mullard_Nut_74 Tetrode Join Date: Mar 2020 Location: Sydney, New South Wales, Australia. Posts: 65	Re: Mullard Type MUS217 No. 83330 Information wanted I just came across another heap of issues. The Schematic I am using for the Philips set lists a UCH41 but my Mullard radio has a UCH42. The multi voltage selector just fell apart when I took it off to look at where the connections go and there is 3 possible ways to piece it back together. There is a huge black wax capacitor with no markings on pin 4 of UY41 that runs straight to chasis ground but I can find no such capacitor on the schematic. The output transformer has some kind of black tar like substance oozing out the top of it and looks like boiled over burnt varnish so I dont trust it will be working either. I am not winning with this one. I am starting to think this radio is a basket case and way out of my league. Perhaps I need to find and start with a nice simple unit with less electronics and less damage. Attached Thumbnails

10th Apr 2020, 8:15 pm	#10
Simon Gittins Heptode Join Date: Jan 2006 Location: Cornwall, UK. Posts: 506	Re: Mullard Type MUS217 No. 83330 Information wanted You could certainly find an easier radio as a first restoration project but you don't need to give up on this one yet. The UCH42 is a later version of the UCH41. Voltage selector falling apart, yes, they do that! Perhaps you could just rewire the mains input to the relevant connections for your voltage. Is the capacitor definitely on pin 4 of the UY41 and are there any other connections to this pin? Pin 4 is shown as internally connected and should not really have been used as a junction point (although they often were). The output transformer may or may not be ok, it's worth doing a continuity check on the primary first.