HMV 157 with Sound Box no. 5A (Adjustment)

[Inigo]

Frankly, don't touch it, or it will not close properly anymore. The problem is common, a little ovalization of the barrel wall which makes the mouth non circular, so the lid doesn't fit. Be patient and with three hands, try to fit the lid while pressing the sides of the barrel until it eventually fits in. Maybe you'll need to give some kicks on the lid with a soft blunt mallet, to force it until it frees the small channel around the inner border of the barrel, where the white clip ring must enter and close the lid in place. If you fix the barrel on s work bench vise, probably it will be easier. I don't have a work bench and do all this on the floor on an old towel...
Prior to that, you must give kicks with the mallet through a wooden block or alike, on the spring coils, to be sure the spring is down into the barrel and the lid and circlip can fit properly.
Dear chap! You almost have it! I would clean the grease from the barrel and lid outer sides first, to be able to grip the barrel properly.

[phyi9530]

Hi Inigo,

Many thanks for your reply - really appreciate that. I tried with my father to push the lid into the barrel but unfortunately it just did not work. The barrel has deformed to an extent that one side of the lid will sit the circumference wall of the barrel. At the end we have no choice but to shave slightly the lid. I have put in plenty of the white Lucas lithium grease to both the springs but after playing for a day or so, the effect is not good. The lithium grease may have been too thin and we can hear the spring bumping and even the "steel-ly" sound when spring rubs against the barrel wall while winding the springs up - there is however no more bumping sound when the springs uncoil. But being afraid that the springs will suffer damage, I have no choice but to buy another auto mobile blue colour high performance grease which is thicker than the lithium grease. As we were so reluctant to remove the springs again, we used small syringe to pump the grease in especially for the spring at the bottom of the barrel. We had the motor reinstalled and so far the springs seem to be able to be wound up smoothly, without the bumping sound (Thank God). Hope it will last long and will continue to observe.

As to the indented needle bar of the sound box, I have also unsoldered the connection of the needle bar to the diaphragm, removed the needle bar, tried to straighten the needle bar (yes it does look like it has suffered some form of strike before), and re-solder the connection. While I still feel that the needle bar remains somehow indented slightly, but it is much better than it was before. The sound is good except that it seems to be lacking in bass (which it had when the needle bar was indented). I loosened the two screws at both ends to make the needle bar more flexible and it seems better with some bass vaguely heard - will need to study / experiment further to see how to improve the bass.

Any way, I am really grateful for your and others' responses here! This is my first project with gramophone and hope to have more hands-on opportunity in future. Have also enclosed herewith photo of the blue grease I newly bought and the adjusted sound box for reference.

Thanks and regards,
Robert

[JerryVan]

It appears that you've done an excellent job with the needle bar. Loss of bass can be due to an air leak in the reproducer diaphragm. If you blow gently into the back of the reproducer and sense that there is air flow, (a leak), it may explain your loss of bass. Leaks can be caused by bad diaphragm gaskets, or a punctured diaphragm. Areas of corrosion on the diaphragm can also cause a perforation in the very thin aluminum. Even the very tiniest of holes can kill the bass response. Small holes can be patched by placing a tiny drop of shellac, or silicone sealant, over the hole. Wetting the tip of a toothpick with the shellac, and placing a small drop over the hole, is all that's needed.

Also, now that you have the needle bar straight, be sure that the needle bar is not touching the metal "tongue" that lies beneath it. The tongue is meant to be a safety stop that prevents the needle bar from being jammed into the diaphragm. (Oddly, you had the opposite problem, with the needle bar having been pulled away from the diaphragm.) If it's now touching the needle bar it will ruin the sound reproduction.

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[Inigo]

The lack of bass can be due to the diaphragm being broken, or having a small hole that leaks the air pressure, or the edges or the gaskets. Some air leak behind the diaphragm, even being very small, is noticed immediately as lack of bass.
It can also be that the needlebar is too tight and doesn't move freely. It can be that the manipulation has detached the spider from the diaphragm.
Of course it can be any other air leak in the tonearm or the horn.
The whole sound path from behind the diaphragm to the horn mouth must be completely airtight. You must check and grease every junction.

[phyi9530]

Thank you both for your reply. The diaphragm does have some minor punctured area as I had accidentally knocked on it when trying to straighten the needle bar. Guess I will have to just learn to live with it without the bass.

The speed indicator does not move freely as it should be. Have attached a photo of the mechanism of it. I tried check online and noted that the Victor counterpart does have a small spring there to push the speed indicator pad to continuously touch the speed regulator pad. I have 2 motor no. 32 here but both of them do not have the small spring. Would like to double check if the HMV version should also have that spring? Or it's of a different mechanism? If the spring is missing, will have to figure out a way to find a substitute spring I guess to make it work again.

On a side note, I am looking for a book that details the various models sold by HMV, and found this book "His Master's Gramophone: A Guide to the Acoustic Instruments Sold by the Gramophone Company in Great Britain 1897-1960" by Brian Oakley and Christopher Proudfoot. Could not however get a copy online as it seems to be out of stock on all the websites (not even 2nd hand book!). Does anyone know where/ how to buy a copy of it (physical or softcopy is fine)? Or is there any other recommended book?

Many thanks.

Regards,
Robert

[Inigo]

The punctured diaphragm. If you can retouch the holes with white vynil glue (the sort of white acrylic glue sold for paperwork in the school, for varnishing painting works of children etc, that is soluble in water) you can cover and seal the holes, and the diaphragm will recover its good sound. A photo of the broken diaphragm would help to give you better advice.
Others cover the holes with shellac.
The speed indicator mechanism should have a small wire spring; I've seen two different models, one with a straight L spring, steel wire very thin and elastic, and other way is a thin small coil spring like the ones in the wrist watches tic-toc mechanism, coiled around the small axis.
I've repaired one of mine using a thin nylon thread tied to the pad lever, and with a nut tied at the other side to provide a small weight. If you hang the thread with the nut at the correct side when the motor is in its normal position, you'll have a solid unbreakable weight spring substitute. You'll have to investigate a bit for finding the correct thread length and the nut weight. Too heavy and the pad will press too much on the governor disc, too light and it will have not enough force to maintain the pad against the disc. The ideal is the minimum weight that causes but a light pressure on the pad.

[JerryVan]

The punctured diaphragm should be an easy fix by the methods idicated by Inigo and by myself.