HMV soundbox no.4 - UK Vintage Radio Repair and Restoration Discussion Forum

Tractorfan · 5th Mar 2017, 6:52 pm

Hi,
I have an 1930 HMV 101 'suitcase' type gramophone with a no.4 soundbox which (I think) is the pot-metal version. As expected, the rubbers have hardened with age and it sounds even more tinny that I imagine it would have in days of yore.
Is it much of a job to renew said rubbers? And is there a risk of breaking something if I have a bash at replacing them myself? I'm a bit wary of snapping or stripping a screw thread or damaging the pot metal bit.
Cheers, Pete.

RojDW48 · 6th Mar 2017, 1:33 am

I re-rubbered a soundbox (might have been a Columbia) under Barry's (Audio1950) expert guidance, but I didn't get it quite right. It's not rocket science but you do need to get it dead right - and it does make a significant difference. I knew nothing at all about these things at the time - I thought the rubbers were made of some kind of ceramic material - they were that hard! Barry's the man to ask for help.

Audio1950 · 6th Mar 2017, 1:25 pm

First, determine whether is is pot-metal or brass. Scratch a tiny bit of the paint off the back, and it the underlying metal is silver coloured, then it's pot metal. If it's brass, it will be obvious. If it IS pot-metal, be very careful! Try to gently undo the four screws on the back, (heating with a soldering iron sometimes frees them). If that doesn't work, put the whole thing in the freezer overnight, then try again. If and when you do get the screws out, then you have to separate the front from the back, which again can be problematic, if the metal has swollen. If the back is jammed on, try gently tapping all round the gap between the two with a Stanley knife blade, but it may take some time before it gives. Having (hopefully!) got it apart, you then take out the tiny screw and its' washer from the centre of the diaphragm, drop it on the floor and spend the next hour searching for it. The diaphragm and the red gasket will now push out. Hopefully, the gasket will not be welded to the diaphragm, but if it is, as you remove the gasket, it will delaminate the diaphragm. and you'll have to get a new one, which is a good idea anyway. New gaskets and diaphragms are available from Holmfirth Antiques (Ken Priestley) Reassembly is straightforward, but before starting, make sure the stylus bar is swinging freely. A drop of oil on the pivots will usually help, but don't be tempted to take it to bits, they are the devils' own job to get right again. When you get the new diaphragm and gaskets in place, replace the screw in the centre, put a tiny blob of black wax on the centre of it, and hold a soldering iron onto the front of the bar, near the centre. The heat will quickly melt the wax, and seal the bar to the diaphragm. Finally, if the back was a tight fit, go round the raised section of the back with a fine file, until the back fits with no resistance. Sounds more complicated than it actually is, but just don't hurry, or you'll end up breaking the back, and will have to fork out for another soundbox!

Barry

ukvrshaun · 6th Mar 2017, 9:30 pm

I'll add that there's also an excellent visual description of the process here: http://www.restore-a-gram.co.uk/hmv-...urb/4589510399

But first you've got to get that pot-metal back off. (A 1930 HMV 101 will have a pot-metal No.4, if it's original). Plusgas (or equivalent) is good for getting the screws out safely. Don't force them, they shear quite easily.

Note also that there are may be two of those tiny washers to lose. One on either side.

Shaun

5th Mar 2017, 6:52 pm	#1
Tractorfan Dekatron Join Date: Mar 2008 Location: St. Frajou, l'Isle en Dodon, Haute Garonne, France.(Previously: Ellesmere Port, Cheshire, UK.) Posts: 3,184	HMV soundbox no.4 Hi, I have an 1930 HMV 101 'suitcase' type gramophone with a no.4 soundbox which (I think) is the pot-metal version. As expected, the rubbers have hardened with age and it sounds even more tinny that I imagine it would have in days of yore. Is it much of a job to renew said rubbers? And is there a risk of breaking something if I have a bash at replacing them myself? I'm a bit wary of snapping or stripping a screw thread or damaging the pot metal bit. Cheers, Pete. __________________ "Hello?, Yes, I'm on the train, I might lose the signal soon as we're just going into a tunn..."

6th Mar 2017, 1:33 am	#2
RojDW48 Nonode Join Date: Jun 2014 Location: Bristol, UK. Posts: 2,074	Re: HMV soundbox no.4 I re-rubbered a soundbox (might have been a Columbia) under Barry's (Audio1950) expert guidance, but I didn't get it quite right. It's not rocket science but you do need to get it dead right - and it does make a significant difference. I knew nothing at all about these things at the time - I thought the rubbers were made of some kind of ceramic material - they were that hard! Barry's the man to ask for help. __________________ '....don't go mistaking Paradise for that home across the road!' (Bob Dylan)

6th Mar 2017, 1:25 pm	#3
Audio1950 Dekatron Join Date: Nov 2008 Location: Whittlesey, near Peterborough, Cambridgeshire, UK. Posts: 3,763	Re: HMV soundbox no.4 First, determine whether is is pot-metal or brass. Scratch a tiny bit of the paint off the back, and it the underlying metal is silver coloured, then it's pot metal. If it's brass, it will be obvious. If it IS pot-metal, be very careful! Try to gently undo the four screws on the back, (heating with a soldering iron sometimes frees them). If that doesn't work, put the whole thing in the freezer overnight, then try again. If and when you do get the screws out, then you have to separate the front from the back, which again can be problematic, if the metal has swollen. If the back is jammed on, try gently tapping all round the gap between the two with a Stanley knife blade, but it may take some time before it gives. Having (hopefully!) got it apart, you then take out the tiny screw and its' washer from the centre of the diaphragm, drop it on the floor and spend the next hour searching for it. The diaphragm and the red gasket will now push out. Hopefully, the gasket will not be welded to the diaphragm, but if it is, as you remove the gasket, it will delaminate the diaphragm. and you'll have to get a new one, which is a good idea anyway. New gaskets and diaphragms are available from Holmfirth Antiques (Ken Priestley) Reassembly is straightforward, but before starting, make sure the stylus bar is swinging freely. A drop of oil on the pivots will usually help, but don't be tempted to take it to bits, they are the devils' own job to get right again. When you get the new diaphragm and gaskets in place, replace the screw in the centre, put a tiny blob of black wax on the centre of it, and hold a soldering iron onto the front of the bar, near the centre. The heat will quickly melt the wax, and seal the bar to the diaphragm. Finally, if the back was a tight fit, go round the raised section of the back with a fine file, until the back fits with no resistance. Sounds more complicated than it actually is, but just don't hurry, or you'll end up breaking the back, and will have to fork out for another soundbox! Barry

6th Mar 2017, 9:30 pm	#4
ukvrshaun Retired Dormant Member Join Date: Oct 2016 Location: Hitchin, Hertfordshire, UK. Posts: 33	Re: HMV soundbox no.4 I'll add that there's also an excellent visual description of the process here: http://www.restore-a-gram.co.uk/hmv-...urb/4589510399 But first you've got to get that pot-metal back off. (A 1930 HMV 101 will have a pot-metal No.4, if it's original). Plusgas (or equivalent) is good for getting the screws out safely. Don't force them, they shear quite easily. Note also that there are may be two of those tiny washers to lose. One on either side. Shaun