My HMV 5A has LESS bass than my 5B - EDIT, FIXED! (Sticky bearings).

[EdgarFB]

That said, you can get away with taking the front off and throughly cleaning the diaphragm and then sorting the pivot bars.

Yes, thats just what I did. Then vary careful cleaning with a cotton bud. Its definitely sounding like a correctly functioning soundbox, I might have just had high hopes of it having more bass. The sound is almost as good as the 5B but not quite, but this can probably now just be put down to the immaculate condition of my 5B.

I might get it back on the bench later and see what the back is like for tightness, I'm quite hopeful as the pot metal looks really fresh. The whole thing looks very good now the dirt is off!

[poodling around]

It looks as in need of a complete overhaul. These can sound very well, indistinguishable from the 5B, but need to be in perfect condition, flexibility, cleanliness, soft gaskets, soft back neck collar, etc. Everything contributes to the sound, and it can be as good as any of the praised EMG or Expert soundboxes, but when it is in perfect condition. The diaphragm must also be cleaned from dirt and oxide, and any pores sealed with lacquer or a tiny drop of glue. Better if renovated (spares can be found). If you don't dare to do it yourself, there are specialists here that can overhaul it for you, as Wyatt, named MicaMonster herein.

Extremely interesting observations and advice Inigo.

[Orchorsol]

Be aware when adjusting the pivots that they are not quite as simple as they look - as these two images will explain.

APOLOGIES to whoever on this forum posted the useful hand-drawn one some years ago, I have long forgotten who that was (and thanks again).

[EdgarFB]

Be aware when adjusting the pivots that they are not quite as simple as they look - as these two images will explain.

APOLOGIES to whoever on this forum posted the useful hand-drawn one some years ago, I have long forgotten who that was (and thanks again).

Those are great! Just got it on the bench now as I'm wondering if the bearings are dirty/seized leaving it all a bit to rigid.

[EdgarFB]

Sorted! It was as I suspected the lack of movement in the arm. I've managed to lubricate the bearings now as I suspect they had seized a little, and generally lubricated and fiddled with everything until it felt just a little more free.

Now has a nice bit of thump to the double bass, on the whole I think I prefer my 5B as it has a bit more warmth in the higher register than this one but I might well keep picking them up to see how much they vary!

(Double-click the video above or click this link to go to the video on YouTube.)

...I wish I'd recorded it before, it sounded more like a No4

[leels1]

Be aware when adjusting the pivots that they are not quite as simple as they look - as these two images will explain.

APOLOGIES to whoever on this forum posted the useful hand-drawn one some years ago, I have long forgotten who that was (and thanks again).

Good advice!

Also worth noting that the little brass tube things that the pivots sit within are soldered to the front of the soundbox with very little solder. It’s really easy to put too much force into unscrewing them and breaking the mount off. It’s a real pain to get them back on and re solder but can be done, carefully!

[Inigo]

Also, any small misalignment among the two side cylinders may cause the pivots to get jammed. I've seen that, caused by a slightly non perfect front ring seat on the back, a warped back, etc. When adjusting the pivots, they don't behave the same at any rotation angle, but better in one position than in other, what makes one think that they both are not part of the same straight line anymore, like they should. Same with soundbox no 4, which has the same pivot system. This makes things a bit more difficult, although eventually you can find the sweet spot... That's because the pivot prongs which enter into the needlebar housings are a bit too long, and get jammed easily when not perfectly aligned. A slight design drawback..
Nevertheless, they can be adjusted, and when that sweet spot is found, they sound incredibly well.
A slight improvement can be found when adjusting the pressure of the back on the diaphragm edge, relaxing a bit the back screws. This adjustment I've done in some of my 5a/5b and improves the bass, the overall performance. I then fill the gap and the front ring with Elmer's glue ( white PVC glue) or a thin rubber ring, and fix the screws in their relaxed positions with glue. Some soundboxes I found sounded too compressed were improved this way. This has a double effect, which is to allow more diaphragm movement, and to increase the back air chamber behind the diaphragm.
Other refinements can also be done... They can sound marvelously!

[Marco Gilardetti]

Be aware when adjusting the pivots that they are not quite as simple as they look - as these two images will explain.

Thanks for posting, pal! It's curious how they made it so uselessly complicated when all they needed to do was to thread the receptacles; surely some patent issue involved.

I also have a 5A that sounds horribly; I've always blamed the felts (and could never find the time to replace them...) but now I wonder if it could be worth re-adjusting the ball/pivots first and forget about the felts.

[Inigo]

The felts usually don't suffer, unless someone has tinkered with them... I've seen others where the felts have been replaced by thin flat rubber rings.. but these tend to get stuck on the diaphragm edge. Thin cardboard or thick paper gaskets would also work, I wonder...

[GavinM]

You might struggle getting the back off the 5a as they seem to be a poorer quality pot metal than later 5bs.

That said, you can get away with taking the front off and throughly cleaning the diaphragm and then sorting the pivot bars. They can be very tight and it’s easy to snap the outer screw if it’s rusted into the collar, so some penetrating oil may help, but just be very careful.

What do you recommend for cleaning the diaphragms on these? I have a 5A which seems to be working fine but I've fought shy of trying to service it for fear of damaging the diaphragm.