I DO NOT SUPPLY
Restoring the No. 5 series soundboxes is a little simpler than the No.4 in that the gaskets, being made of a felt material do not suffer in the same way as the No.4. This means that if the diaphragm and needlebar connection are in good shape there is no reason to remove the back, a blessing indeed as being made of pot metal they are very fragile, the 5b back less so than the 5a.
Should it be necessary to remove the back take care with the 4 screws that hold it in position as they are small and brass which means they could shear when being removed. A soak in Plusgas prior to attempting removal will help. Also remember that the pot metal back will have inevitably swollen making it grip tight onto the outer nickel or chrome ring. In fact in some cases, especially on the 5a it can cause the outer ring to crack. ( See photo). Should the back completely give up the ghost replacement backs for the 4, 5a and 5b can be obtained. Click the link in the left hand panel
As far as I am aware replacement diaphragms are not available so if damaged possibilty of repair is dependent upon the extent of the damage. Also note the needlebar is soldered to the diaphragm which may present additional difficulties.
The 2 areas of refurbishment that are usually needed relate to:
Cleaning and Adjustment of the Pivot Assembly
The diagram and photographs in the panel provide information on adjustment and construction of the 5a and 5b soundboxes. The adjustment is exactly the same as on the No.4 soundbox and so that has been repeated here from the No. 4 refurbishment page of the site. Cleaning is simply a matter of fully dismantling and removing any dirt etc from the components. Be very careful though being small, in particular the bearings they can easily be lost.
IMPORTANT: The needlebar must be held between the pivots at a point where lateral movement has been taken up AND NO MORE.
The last three photographs show a box that was in a bad way with splits and a barrel that was broken away. It now works but isn't pretty! I hadn't got a torch that could get the various areas hot enough to take the silver solder well. I was able however to get the barrel back despite obvious alignment problems encountered.
HMV No. 5 Series Refurbishment
Replacing the Insulator
Should the insulator that fits in the back of the soundbox need replacing there are currently two options. A note first of all. Most of the insulators will have hardened and despite this the soundbox may function in a satisfactory manner. However it's pretty obvious that it was designed to isolate the tonearm from the sound wave vibrations in the soundbox and being now hardened over time is not going to fulful that function. In my opinion this alone does not necessitate replacement and I notice that the new, replacement backs do not accomodate an insulator and yet are said to perform satisfactorily.
New replacement insulators for the 5 series as well as other soundboxes are available from Hong Kong (See eBay). I preferred to make one using Sugru, a self hardening rubber compound that I've used elsewhere. There is a link in the left panel to the manufacturer and it is usually available in DIY stores. B & Q I know stock it. The photos are self explanatory. except to say that once the Sugru has been "loaded" onto the brass collar it must be left for at least 24 hours to self cure.