Monday 7 August 2023

Classic Sennheiser HD480 Headphone earpads

I have a pair of Sennheiser HD480 headphones, back when new they were "good HiFi".  

But the foam inside the earpads has disintegrated over time, and spares are difficult to find.  Canford Audio will sell a pair of their own design, but unfortunately as Canford are primarily a business supplier, they have minimum order value, a postage charge, etc.. so, unless one is shopping for other things they carry, one set of ear pads ends up costing over £50!

Disintegrated foam from the earpads

However, there is a way to fix them....  and its very very cheap.... 

wadding, not the easiest thing to photograph!

Quilting wadding.   Available from shops which sells supplies for quilting, and one needs a small piece of offcut of approx 10mm thick (1/2 inch would be fine).   The material I have is a synthetic, very open weave.   

Dismantle the headphone - run a finger nail around the metal trim ring behind the earpiece, and the trim piece and earpad will pop off.  Brush or gently hoover the remains of the foam from the earphone, and remove it from the mesh fabric cover.   

Use the metal trim piece as a template, and use a pen to draw round its outer edge on the wadding.  Then cut out with scissors to make a circle.  Its not precision cutting, just near-enough.  

Earphone, trim ring, and earpad with new wadding inside.


Push the round piece of wadding into the earphone mesh, running finger around a few times so it seats neatly.   

Refit trim piece and earpad to earphones by gently clicking into place.  Probably need to work around the rim a few times to get it to seat.   

HD480's with newly repadded earpads

I'm very happy with the result.    And having seen how the earpads are constructed, a replacement cover fabric doesn't look that hard....  As I'm pushing 60 my hearing isn't what it was when the phones were new, but such repairs mean these have a continued life. 

Monday 20 February 2023

2mm conversion of NGS Hunslet

I've been looking at how to convert the N Gauge Society's Hunslet shunter to 2mm finescale for quite a while.  

Superficially it looked easy - same bearings in split frame as Bachmann have used in several of their smaller steam shunters, such as the Jinty and 57xx.    But, there were a few "gotchas" to catch those who might rush in.   The main one being the very tight clearance between a spur gear in the mechanism and one of the axles.  That meant the usual 2mm finescale parts for the Jinty conversion wouldn't fit without modification.  The muff connecting one axle needs to be thinned quite considerably, to less than 2mm O/D (when its got a 1.5mm hole inside it, that means a very thin wall).   Its possible if you have a lathe, and might be possible with care by holding a muff in a minidrill and filing/sanding the muff down to size (a sliding fit axle inside the muff stops it deforming).  In the photo below, the left side of the muff has been reduced from the nominal 2.3mm diameter of the right side: 

With that step out of the way, the rest is "normal conversion" - coupling rods to make (or reduce the hole size in the N gauge rods), and drop in the wheels.  

The other approach is to finescale the supplied wheels.  This is relatively simple to do for the lathe owner, the wheels are brass, so machine easily.  Reduce the flange height from 0.7mm to 0.5mm, and shave about 0.4mm off the back of the wheel, then gently round the edge of the flange with a file whilst the wheel spins in the lathe.  The hardeset part of this job is work-holding:  I made a tool which centred the wheel precisely, provided a drive pin, and had a shaft through the axle hole to a clamping domed washer and nut (sounds more complex than it really is!).  
The N wheels have a back-to-back of around 7.3mm.  For 2mm finescale it needs to be 8.5mm, an increase of 1.2mm.  The re-profiling gets 0.4mm per wheel, so 0.8mm, but a further 0.4mm is needed by sliding the wheels out on their axles.  This is OK, but I felt it was better if the bushes were replaced with slightly wider ones to reduce the amount of axle side-to-side float: for which the conversion bushes to use 2mm Scale Association wheels are suitable if drilled out to 3.0mm.  (I made my own, but that was because I hadn't got any conversion ones to hand and have enough machinery to make them quickly).  

So, neither method is quite "drop-in", but both fairly simple.  

Below is some video on YouTube of one loco running through a 2mm turnout.  This had the wheels turned down.  I'll get round to uploading some video of one using 2mm wheels later.