On 09/01/2010 02:14, Arfa Daily wrote:
wrote in message
...
On 07/01/2010 02:46, Arfa Daily wrote:
wrote in message
...

20 degrees is about the most or you block off access to the TO3s. Maybe
only
tinkering at the heat build up problem. Most air must go through the
25mm
or
so wide gap in the ps direction (over the tips of the vanes), rather
than
the 2 off 5mm gaps to the duct let alone through all those vanes. I
would
have thought there should be some shuttering to block off most of that
large
gap along the ps side , to force most air round and through the
heatsinks.

They were assembled with enough white goo to keep a goth happy for a
week.
So much that she filled the B& E holes so pins pushed through it, not
cleaned off, and some white goo actually under the solder joints (not
actually failures there). Those failed caps 47uF, 63V - in similar HK
amp
they were rated 40V 47uF , what is the problem in that area of the
circuit?




On reflection, I don't think that these are actually designed with
'forced
air' cooling in mind. Rather, I think that that type of heatsink is
intended
to suck the heat off the transistors, and then radiate it to free air,
and
that the purpose of the fan is to shift new cool air through the chassis
/
cabinet, to help the radiation take place. When the air intakes get
clogged,
the internal ambient temperature goes up, stopping the radiation from
taking
place efficiently, with a consequent large rise in the case temperature
of
the transistor, made worse by the dried out thermal paste.

I don't quite agree with Gareth that the heatsinking is inadequate. I
think
it is just about adequate, as long as the designed level of airflow
around
the chassis can be maintained. If it can't by virtue of the intakes being
clogged, then it becomes very marginal.

However, I suppose it could be argued that it is 'inadequate' in that
there
is little or no margin built in for compromised airflow.

Arfa


I suspect usage has a bit to do with it also. The Eliot/Lucas were never
intended for 'Heavy Metal' or bass heavy dance music. Prolonged thrashing
is probably what heats them up.
Another thing, they don't like having the satellite speaker plugged and
unplugged while drive is applied, I`ve fixed more than one where the owner
admitted that`s what happened.

Ron


Yes, they are a little odd around the output stages in terms of what can be
connected. They get very upset if you connect a dummy load with a ground
common to your scope ground, and the ground of the signal generator ...

Could that be because each pair of amps might run in opposing
polarities, the bass speaker is driven by two amps in bridge mode?

I do have a cd of service data, if you're interested I can pop it in my
Dropbox


I'd never considered that hot-plugging the sats might be an issue, but I
will mention that to the shop as something to tell punters not to do, as he
has quite a few of these rigs that he uses for rental.

Another thing which might contribute to amplifier failure is users
hooking dodgy speakers into the monitor output. I did see one case where
guy had managed to run a cable from the monitor output, out to a floor
monitor, then back to the satellite box. That went bang!



On a different subject, you know a bit about bingo don't you ? Know anything
of the maths or concept behind the RNG that used for producing the numbers.
I've found a number of patterns appearing, which seem to make the
'randomness' a lot less than you might have believed. Can't seem to find
anything much relevant about this, on t'net.

I have no idea how modern all electronic bingo machines work, in my day
it was either rolling wooden balls down a wooden chute, into
compartmentalised 'crate' (easily fiddled) or ping pong balls blown up a
tube by a blower - also easily fiddled. Either way a good caller can
'steer' the game.

Ron