I DO NOT SUPPLY
At the outset I would not hold my hand up to being an expert at this and offer it here as I way I dealt with the problem of the No. 4 soundbox from an HMV 101 which had a hardened gasket and side movement in the pivot assembly. Unlike taking up watercolour painting, which I did in mid 2000's, where there was an abundance of information on how to do it, gramophone restoration seems to be at the other end of the information spectrum. Still if results are anything to go by what I have done seems to have worked so....
The HMV No 4 Soundbox Refurbishment
Let's start with a cross section of The No 4 Soundbox to be aware of just what's going on
The starting point - a prod with the point of a cocktail stick revealed a hardened gasket pivot left and right showed that there was play. This needs to be tight enough not to allow this but also free enough to allow movement of the arm back and forth to activate the diaphragm.
The back needs to be removed by undoing the 4 screws that fix it to the front ring. Beware with a pot metal back as there could be problems with breakages at this point. Pre 1928 backs were made of brass and do not have this problem. A useful tip - always give the screws a drop of Plusgas to assist. The heads of any screws on a soundbox can and will shear - play safe.
In this case the two parts separated without a hitch
Using a jewellers screwdriver and a steady hand remove the small screw that fixes the needle bar to the diaphragm. Take special care because two washers (one on the front and one on the back) will be in the old wax. NB Sometimes there is only one washer at the back.
The diaghragm with its old hardened gasket.
Remove the old gasket. It tends to break away fairly easily. The new gasket may than be fitted by carefully locating the edge of the diaphragm in the slot in the new gasket
With the body lying face down balance a washer on the fixing point of the needle bar.
Carefully position the diaphragm with its new gasket fitted into the recess of the body taking care not to dislodge the washer from the needle arm. Place the second washer onto the diaphragm over the hole. I now used a gramophone needle to align all the holes.
Soften a small wad of bees wax (experience will show you how much) between your fingers and press it gently onto the screw. A jewellers screwdriver or similar helps to mould it into position. (Wax not shown in picture but it's not rocket science where it goes.)
Insert screw that fixes diaphragm to needle arm.
GENTLY bring a soldering iron to the wax and screw. Watch for the flow of wax forming a circular seal. If you've applied too much or too little wax simply melt it, remove it and start again.
Repeat the above stage on the front where the needlebar fixes to the diaphragm. This time though try and make a miniature sausage of wax to wrap around the needle bar fixing point. Melt the wax by touching the needle bar at a point close to the wax.
I'm not sure whether this is the point at which the pivot assembly should be set but I decided to do it here. The notes on the photos explain how I did it.
A diagram detailing the pivot area is shown on HMV No 5 Refurb page.
Finally re assemble back and check movement of needle bar by gently rocking needle screw back and forth. Final test was then done on a good but not favourite record
In this instance I felt I had no need to disassemble the pivot bar but this could have been done to clean anything that might obstruct free movement. However proceed with caution as the pivot bar contains two minute steel bearings which are easily lost.
Click thumbnails for larger images