HiFi Subjectivist ¦ Audio Forum ¦ NVA User Group

It is to do with potential power in the fusing / explosion. Internal fuses are on low(ish) DC rails or on signal paths / speaker outputs. The potential is relatively low compared with mains potential, just a little pop when they blow. They have been known to break the glass on fusing, but it is rare and probably a cheap badly made fuse, but it is inside a case, nothing gets out. Where as a unfilled mains plug fuse can blow the plug out of the socket when it fuses, it can badly damage the wall socket so it needs replacing as it will be unsafe after the damage or just shows horrible burn marks. The sand damps the explosion which is why it is legally required, and a proper in spec plug fuse very very rarely breaks the glass or ceramic case.

When a fuse blows the filament vaporises and deposits itself on the inside of the tube. If the fuse gets hot enough this will conduct and render the fuse unfit. Ceramic fuses are therefore filled with quartz sand or similar to prevent this happening and are referred to as HRC fuses ( high rupturing capacity) These HRC fuses have the ability to break high currents into the thousands of amps if required. Glass fuses aren't expected to break high currents or get hot enough for the vapour deposits to compromise the fuse so filling is not necessary. These fuses are sometimes referred to as LRC fuses ( low rupturing capacity)
5 X 20 ceramic fuses are readily available for higher current protection.

Back in the dark old days of the late 70's to early 80's, one or two low mass stabilisers came along which were a pain to use on the springy LP12 but did seem to help a bit. the Michell clamp we all know I think, but Monitor Audio has a nifty plastic three-point thing (I forget the name - Pod?) which you placed on the record and then pushed down on the central part, locking it to the spindle. To release, lift the lock and it pops up so you can remove the thing.

The Revolver 'Pig' used to work sometimes on generally dished records played convex, but mine has crazed and no longer grips the spindle properly. I'm sure it's used to cover the ends of support sticks used in gardening, but I must admit I haven't looked hard to try to find a replacement.

Much later, I discovered the joys of the Notts Analogue Spacemat, which removed the need for clamps or weights I thought and also at high expense, the Ringmat, which despite the sideways thinking regarding the way the discs are supported, really did seem to work. I now feel that support at the disc centre is possibly more important then edge support, which is what many turntable manufacturers did, especially on my beloved 1970's Duals!

Yep it was called the 'POD'. Looked simular to the old Pickering Three legged jobbie. MA also did an arm lift 'STYLIFT' & ofc a Direct Drive Turntable 'ET500'..

I remember all of them, sad git I am.... The turntable had the ubiquitous cheap Matsushita OEM motor unit I recall and all of them had dynamic wow which the top Technics models didn't even before quartz locking!

Dr Bunsen Honeydew wrote: ↑Sat May 05, 2018 11:32 pm It is to do with potential power in the fusing / explosion. Internal fuses are on low(ish) DC rails or on signal paths / speaker outputs. The potential is relatively low compared with mains potential, just a little pop when they blow. They have been known to break the glass on fusing, but it is rare and probably a cheap badly made fuse, but it is inside a case, nothing gets out. Where as a unfilled mains plug fuse can blow the plug out of the socket when it fuses, it can badly damage the wall socket so it needs replacing as it will be unsafe after the damage or just shows horrible burn marks. The sand damps the explosion which is why it is legally required, and a proper in spec plug fuse very very rarely breaks the glass or ceramic case.

I found a video on Youtube showing one of those blowouts happening, bloody scary stuff! Thanks for the explanation, I understand now.

_D_S_J_R_ wrote: ↑Sun May 06, 2018 2:24 pm I remember all of them, sad git I am.... The turntable had the ubiquitous cheap Matsushita OEM motor unit I recall and all of them had dynamic wow which the top Technics models didn't even before quartz locking!

Not half as sad as me

I think the platter was the same used on the Rotel 'RP3000', Mine used to virtually wave when it spun at 45rpm. All said thought i thought it was a loverly little turntable, These days the technical issues could easily be sorted. They still sell well on the used market when they come up..

I use one occasionally on bendy records, the lightweight Clever Clamp being my weapon of choice usually (or always on a suspended TT). I have a few weights that I've tried, nothing fancy, but I find the best way to a flat record and good platter contact is sensible storage YMMV. I find if I'm cleaning 7" or 10" records on my cleaning machine a weight comes in handy as they can get sucked off the platter, not that I have many that size.