Paging hi-fi/electronics chaps

<puzzled>

er, contacts for what?

 

Of it's own accord

You said this elsewhere, but what 'contacts' are there inside?

 

(Switch)

To make a circuit, you need contacts, however, you'll find them not like a
switch, more like a circular dial type jobbie with a cam inside.

Easy way, open the case, find the inside of the volume, balance or power
button & blast the living **** out of it with said cleaner.

If you get stuck, send me a pic & I'll 'shop it where you need to infuse the
shit man!

--


Nige,

Honda VTR1000 SOLD!
BMW K1200S
Range Rover Vogue
Aprilia RSV Mille

 

You can't get to the contacts in the switches but you can spray it on
the switch
and hope some gets in, then flick the switch a few times to clear the
oxidization.

If the problem is before the tape loop, you could just plug the source
into the tape input and forget about it.

 

Two countries divided by a common language then...

 

No. They are different things.

A cold joint is one where solder has been applied but the components are
not heated suffciently. This is especially common on relays going
through wave soldering, as the thick tracks on the pcb & the relay
itself are good heat sinks

A dry joint is just that i,e, no solder was applied to the joint. This
could be due to contamination or oxidation. Dry joints are quite common
on surface mount assemblies where no solder paste is applied due to a
blocked hole in the screen.

 

I have to say that in 25 years of electronics that's the first time I've
heard that distinction. Not that I'm saying you're wrong, just that I've
never ever heard anyone use the term cold joint.

--
Malc

Rusted and ropy.
Dog-eared old copy.
Vintage and classic,
or just plain Jurassic:
all words to describe me.

 

A dry joint is one where the solder has not whetted the wire

It would be a cracked joint you'd be meaning

 

I'm beginning to regret my use of the word "simple" - the point is that
if you can find the problem it's a quick fix, but diagnosis can be
difficult, particularly if as in your case it would be a matter of
removing the PCB from the amp.

To be honest unless you know someone who is good with electronics that
you can get to have a look at it for the price of a pint I'd just buy a
new one.

If you really want to have the case off:

(Be careful, by the way: there are some hefty capacitors in a typical
amplifier which might give you a jolt.)[/QUOTE]

Really ?

Are you confusing microfarads with voltage there ?

 

I can have a look if you send it down

www.cetltd.com

 

The term cold joint became quite common after the introduction of surface
mount technology[1]. It might be that Mike is a merkin and I worked for a
merkin firm, and the term is less common in the UK. At the same time, we
started using the term to describe through hole components such as
described above.

[1] the solder paste[2] is applied to pcb pads using a screen; the
component is laid onto the pcb with its leads in the paste; the circuit
board is baked in an oven. Ideally the paste melts and forms the joint. If
the oven is the wrong temperature or the wrong paste is used then the paste
does not melt leaving you with a cold joint.
[2] a mixture of solder, flux and a volatile bulking agent

 

We have (or had, as recently as a couple of years ago, when we last had
cause to use them) an electronics mending shop within walking distance.
Indeed, I have in the past strolled round there with the amp under my arm.

Speakers - 20+ years
CD player - 15+ years
TV - 10+ years

The PC is probably about 6 years old.

 

Surface mount isn't difficult, just small. It's as easy to reflow a SM
joint as any other.

 

Really ?

Are you confusing microfarads with voltage there ?[/QUOTE]

Huh ?

I've had a jolt from a capacitor and it threw me bodily across the
room.

Mains is nothing compared to a charged electrolytic.

Paul.

 

In message

In an audio amp ?

We are specifically talking about an audio amp here

It depends on the voltage, doesn't it

a 1uF 16v electrolytic might piss off a goldfish

a 1uF 250v ceramic charged to mains voltage will give you a jolt

a 10000uF 16v electrolytic capacitor could melt a screwdriver but you
wouldn't really feel anything unless you put your tongue across the
contacts

a 1000uF 250v electrolytic is probably not a good device to wet your
fingers and put them across the contacts

 

Here, there still is, but they are rapidly disappearing.
I just took my telly in for repair - I'm holding off buying an LCD until
the Irish market settles down properly to the new HD standard, so it's
worthwhile repairing a steam set for another two years of use and by
then the LCD I want will be cheaper anyway.
Anyway, a small TV repair shop in my nearest small town is still doing a
thriving trade repairing older tellys for exactly that reason. The shop
also repairs amps, which is handy.

 

Can't remember the capacitance, (I think it was a polystyrene
capacitor) but I remember the voltage it had been charging up from. It
was up to about 20KV, thankfully only at a few mA. I'd been arsing
around with a negative ion generator, which had a diode-capacitor
ladder stepping up the mains.

I've always loved electronics, me ;-)

Paul.

 

In message

So not in an audio amp then ...

 

er, yes - I knew that much

Ah, hence the confusion - yes, it "does it on it's own" i.e. not after
me having switched anything anywhere. That's why I can't see that
it's anything to do with any contacts.

 

Ooh, ta. I'll prolly have the top off and give it a clean out and
have a look see, and if it still plays up I may well take you up on
that.