advertisement


How many hi-fi buffs does it take to change a light bulb?

B

bugbear

pfm Member
Not actually a joke.

I don't remember the last time the power switch light worked on my Sugden.

https://www.ukaudiomart.com/details...-au51p-paab-astereo-amplifier/images/1332442/

(that's not mine)

Can anyone tell me

a) how to source and fit a new bulb (assuming these things are standardised)
b) how to dim it down a bit (I recall it was too bright)

EDIT; the first image of the first post of this thread shows the wiring and switch pretty well.

https://www.pinkfishmedia.net/forum/threads/sugden-au51p-regulated-front-ends-and-lesw.190754/

BugBear
 
It looks the same switch as fitted to the MF A370 and if so the front kinda pulls off with a small screwdriver or two in just the right place to disengage the plastic tabs. It is awkward. It's a small filament bulb. You'll need to add a resistor to dim it. Can't help with which resistor without more info and it will be a bit "suck it and see" to get it to your preferred brightness.
 
Arkless Electronics said:
It looks the same switch as fitted to the MF A370 and if so the front kinda pulls off with a small screwdriver or two in just the right place to disengage the plastic tabs. It is awkward. It's a small filament bulb. You'll need to add a resistor to dim it. Can't help with which resistor without more info and it will be a bit "suck it and see" to get it to your preferred brightness.
Click to expand...
From my previous tracing of various parts, that light is being driven by 52V DC!!

BugBear
 
bugbear said:
Before I start prodding randomly at a 20 year (probably fragile) switch cover, how would you rate my chances of actually finding a replacement bulb? :oops:

BugBear
Click to expand...

Good. As to the chances of getting the cover off without breaking it... better than 50:50...
 
bugbear said:
I want better odds! I've lived without that light for at least 10 years, but I'm not sure how well I'd react to a broken switch cover...

BugBear
Click to expand...

Your risk.... If it's the switch I think it is (and I'm pretty sure it is) we used to break maybe 1 in 10 of the plastic covers when replacing the bulbs at MF back then.
 
Here's two pictures of the switch, first from above, second from below (via a mirror I should have cleaned :oops:).

switch by plybench, on Flickr

Does this match your memory? There definitely appears to be a screwdriver size slot on the top and bottom edges.

BugBear
 
It's an EAO switch of some series.

The coloured lens is actually a separate piece from the white opaque holder.

Different series use different types of bulb but they're all replaceable from the front.

It looks like it might well be a 31 series. Data sheet showing how it all fits together here.

https://uk.farnell.com/eao/31-261-0252/switch-1no-1nc-maintained/dp/3112100#

There is a trick to getting it off which is to not try to remove the orange cover first.

There is a special tool but you can do it by slipping a fairly stiff feeler gauge in and disengaging one of the tangs which holds the lens assembly in.

An experienced instrumentation engineer will just flick it out by clawing on the bottom when disengaged and lifting it slightly.
 
[ somewhere this thread missed the obvs joke about preferring the new 'inky black background..'
I have my coat, am leaving pronto...]
 
colasblue said:
showing how it all fits together here.

https://uk.farnell.com/eao/31-261-0252/switch-1no-1nc-maintained/dp/3112100#

There is a trick to getting it off which is to not try to remove the orange cover first.

There is a special tool but you can do it by slipping a fairly stiff feeler gauge in and disengaging one of the tangs which holds the lens assembly in.
Click to expand...
I am richly supplied with feeler gauges. Any hints as to required thickness (fairly stiff(*) sounds like 10-15 thou), and where/how to stick (*) it would be much appreciated.

BugBear

(*) ooh-er missus
 
Last edited:
I'd say thin enough to go between the switch button and switch bezel uncomfortably and thick enough to exert a bit of leverage when in place.

If you go for the top edge you slide it in above one of those slots, but don't actually try to prise the orange cover off, stick it in about 25 degrees above horizontally about half an inch and lever down slightly. Then rotate the lens forward around the bottom edge and hopefully out. It should be obvious when the tang has disengaged and the thing will come apart easily.

You can do similarly by going in at the bottom edge, levering up and rotating up and out around the top edge.

If you try to take the orange cover off first which would make the job appear easier you're likely to break the thin plastic strip on the far side of the slot, which will mean that the orange cover won't re-attach properly.

If you do happen to break it the whole lens cover is only a few quid.

This is what it looks like when its out and your job is to disengage one of those tangs to get it out (Assuming I've correctly identified it as 31 series, which hopefully somebody might confirm).

http://rover.ebay.com/rover/1/710-5...0001&campid=5338728743&icep_item=143006054287

Needles to say I'm sure - do it with the amp unplugged just in case!
 
This site contains affiliate links for which pink fish media may be compensated.
Actually hold fire - it looks more like a Schweitzer 10 series switch.


http://www.google.co.uk/url?sa=t&rc..._06_2010.pdf&usg=AOvVaw1eDjRF8JRJOwUfefvdNFW7


They work a bit differently and you do have to remove the orange plastic cover to gain access. You need to put a small screwdriver or some such into the slot at the top or bottom and release the tang which holds the lens cover on.

Bloody awkward and as Jezz said you do have a decent chance of breaking it.

They also aren't quite so readily available as EAO lenses.

This is yer boy I think but no longer stocked at Farnell so possibly made of unobtanium

https://uk.farnell.com/schweitzer/0854-0584/lens-rectangular-clear-yellow/dp/1148241

They also currently don't have them in green but will do in February.

https://uk.farnell.com/schweitzer/0854-0583/lens-rectangular-clear-green/dp/1148243?st=schweitzer lens

I'd let it alone until you have a spare lens in your hand, and actually if you can get one get a few since it looks like a thing in danger of imminent extinction.
 
I''ll have a look around the switch with a torch and a magnifier (and/or macro lens) tomorrow. Thanks very much for your advice.

BugBear
 
You could just change the switch for a more modern one with LED which will fit the same panel cut-out of course if having a "ON" light is that important to you... or drill a small hole and fit an "ON" LED.
 
Actually you probably couldn't.

This seems to me a to be a bit of stylistic modding for effect on the part of the manufacturer.

The switch is actually a surface mount one but has been recessed to look flush with the casework by mounting it on a panel behind the fascia.

You'd never get anything else to fit in that space perfectly (but obviously you could mod the bracketry to make something fit since the size of the button is pretty standard).

Actually come to think of it buy a whole switch actuator in case you ever need one! Ten years from now you probably won't be able to get one but you can get them now!

If you buy 100 you could become one of those eBay guys selling CB Naim switches for 65 quid a pop.

Trouble is they don't break very often.
 
You must log in or register to reply here.


advertisement


Back
Top