How to know if a HMV soundbox No. 4 needs to be repaired?

[gramophoneshane]

It's definately an all pot metal no.4 unfortunately. You can just see cracks begining to form around the outer edge of the bezzel. It looks as though a worm has been crawling around under the plating

As Steve recommended to Rasmus, your best bet would be to get an earlier all brass no.4 to restore and use.
Even if you did get this one apart, you'd find over time the rattle will return because the metal slowly continues to swell, which will throw out your needle bar adjustment & cause the front & back to clamp the gasket unevenly.
Brass HMV no.4's a really common & should only cost 1/10th of what a brass ortho would. Actually, if it were me, I'd get one in it's original box so I could store the pot metal no.4 in it, but I'd keep it with the machine, & the box would protect both the machine & soundbox from being damaged.
The gaskets in these can be deceiving. Some will be hard as rock, but others can look & feel as good as new. A lot depends on storage conditions, and with the absents of light, moisture & air circulation, they can look pretty good after 80 years, but it's highly unlikely they'll still perform the same as they did/should.

If you're not stuck on being totally original, you might want to think about replacing the original red one piece gasket with 2 separate gaskets the same as you'd use in an Exhibition. I haven't tried it myself yet, but I've heard several people say that using the ordinary gasket tubing will greatly improve performance. I wouldn't doubt it actually, as the split in the original type gasket where the mica sits seems a bit hit & miss IMO, and they dont seem to cushion the diaphragm quite as well as the old style tubing.
Apart from that, I've found the one piece gaskets can be a pain to install.
I dont know if there's a trick to it, but on a couple occasions I've damaged the edge of the mica putting the gasket on. Feeding the edge of the mica into the split is easy, until you get to the last section, where you have to pull & stretch the gasket enough to pass over the edge of the mica. It's easy to catch the mica while feeding it into the split, which can cause the layers to separate, as in the picture below (at the 7, 8 & 9 o'clock positions).

[Steve E.]

thank you very very much!!

[phonojim]

If you need a diaphragm, The Victrola #4 uses the same size as the one used in common Columbia Grafonola #6 reproducers. Ron Sitko stocks the Columbia diaphragms. I asked about gaskets some years ago and was advised to cut them from craft foam from Michaels (probably other stores as well). They turned out to be a little too thin, so I inserted an Orthophonic gasket between the backplate and the rear foam gasket. This does throw the needle angle off slightly, so I will probably cut 2 new spacers out of thinner material so I can use one on each side of the diaphragm. In spit of that, it does sound very good.
I do second the cautions about potmetal. I have had success with putting the reproducer in the freezer overnight which shrinks everything and loosens it up so you at least have a chance of getting it apart without damage. Work carefully; it may take several tries to work it apart. I did an Edison S reproducer this way. It took 4 or 5 times in and out of the freezer before I was able to get it apart but it worked and what was an unusable parts source is now a good, clean working reproducer.

Jim

[Steve E.]

I see no brass ones on Ebay. What is the going rate for these jobbies these days?