Belton micalex tube sockets any experience ?

[richwalters]

ANyone in DIYaudio had any experience of using these composite mica ceramic sockets ? Other forum sites, the opinion is mixed. YOur views ?

richy

[Ty_Bower]

I've used a couple of their different styles. I like them all, but like anything you need to be aware of a few things. They all appear to be very well constructed. The machining and tolerances are excellent. They do a great job of gripping the tube pins. Now, here's my minor nit picks. The noval sockets mount on top of the chassis plate, which might be awkward if you've got a thick top plate. The chassis mount octals are just a little too big in diameter for rebuilding old amps from yesteryear. You'd have to drill the chassis holes a little larger. This is a non-issue for new construction. The PC mount octal socket has some odd pin spacing that renders it incompatible with most "normal" PCB applications.

Overall I like them, and I will use them again in the future.


http://i69.photobucket.com/albums/i4...E/P1140836.jpg
http://i69.photobucket.com/albums/i4...o/P1120109.jpg
http://i69.photobucket.com/albums/i4...tGo/Belton.jpg

[richwalters]

The problems mount up; I discovered the original IO socket pins suffering from metal fatigue and easily broken, so ripped all the old Chinese ones out. I decided to examine the tube sockets around.
The top row in photo with the Beltron in the middle picture and the lower undesirable types. The traditional phenolic McMurdo I thought of using and the ceramic amphenol but the body wasn't quite strong as the new micalex.
The lower lot, the first with skeleton base clamp was from the amp; the middle chinese ceramic is totally useless with so much wobble. No good without tube Jock straps. The nylon, no chance with the heat.
Revamping and upgrading an old amp chassis I made some 40 yrs ago from 2 x 50W to 2 x 200W per channel, isn't quite so surgically easy especially when amp has to keep to the original 19" rack width dimensions. The mains transformer a custom design (with especially low Bmax) is the biggest change, some fat 30 Lbs weight requires a reinforced chassis.
I decided to use pencil EH KT90's instead of fat glass KT88's. The KT90's will provide approx 20% more power than KT88's in similiar operating conditions and will last longer.
B+ raised from 460V to 575V and upped heater current. The raft of changes is considerable with the power supply. SO a winters work ahead.

SOme might question the proximity of all transformers: From other amps I made in similar designs, hum isn't an issue. a -80dB figure or better is regulary obtained.

richy

[richwalters]

Here's another shot; by luck had a woodworking borer exactly 30mm; put in a pillar drill (no-one should ever attempt this with a hand drill) and holes nicely enlarged.

The other refurbishment question is by how much to gut out the previous components or leave most in if they are in good condition. Modern components are easily damaged, esp caps and film resistors by chassis reworking, there is the added risk that any fine aluminium swarf must be hunted down before the space gets complex.

The parallel copper busbar in pic is the high current heater line.

richy