HK Audio Actor / Lucas power amps , generic problem?

[N_Cook]

Gareth Magennis <sound.service@btconnect.com> wrote in message
news:Af61n.20179$AV4.16792@newsfe04.ams2...

"Ron" <ron@lunevalleyaudio.com> wrote in message
news:FMWdnar5p5rYhd7WnZ2dnUVZ8nGdnZ2d@bt.com...
On 05/01/2010 09:59, Arfa Daily wrote:
"N_Cook"<diverse@tcp.co.uk> wrote in message
news:hhv006$kqa$1@news.eternal-september.org...
They have an otherwise original assembly method of the final contact
to
the
pins of TO3 power transistors by 2 zero ohm "resistor" links, so 2
current
paths to the pcb traces. Anyone else observed bad solder joints to
these
links on the pcb? and cause? believed conventional solder not PbF





I repair many of these, and can honestly say that I have *never*
observed
any bad joints at the place you mention. By far the commonest problem
is
failed output transistors. This occurs because the heatsinks are only
just
about adequate with proper cooling. As soon as the fan air intake vents
start to clog up with fluff, the outputs start to run too hot. Over a
period
of time, this dries out the heatsink paste to a powder, leading
ultimately
to transistor failure.

Whenever I get one, I always remove the other pair of transistors as
well,
clean down their heatsinks, and re-paste them, not forgetting the
flatpak
transistor that's in contact with the underside of one heatsink on each
channel.

The manufacturers recommend that when the outputs are replaced, two of
the
BC546Bs nearby are replaced as well (T7 / 8 on one channel, 10 / 11 on
the
other). Check also C3 and C21 to make sure that they are not bulging.

Other than this, these amps are very well behaved, and new outputs and
fuses
will, in 99.9% of cases, effect a complete cure. Note, however, that
they
have proper differential inputs, so are not that easy to drive
correctly,
unless you have a proper balanced XLR source, and that they don't like
earthed test equipment connected to their outputs / inputs
simultaneously. I
usually hook a completely isolated speaker to them for final check, as
the
music shop which sends these to me for repair, often remove the amp
chassis
from the cab, to ease the transport, and save me having to strip it all
out.
He now tells customers when they collect the repaired unit, that they
should
brush out the air vents at three monthly intervals.

I agree with Arfa, I`ve repaired dozens of these and always found the
solderwork to be excellent. Perhaps someone else has been in there
before
you. There was a mod for early units, different output transistors and
the
addition of a couple of 1N7007 on the print side of the board.

Ron(UK)


Well, I agree with Arfa and Ron. I've repaired lots too, since the
cooling
is also IMHO inadequate, which is quickly made worse by fluff around the
fan
vents.
Never had any dry joints, but seen plenty of the bulging caps Ron
mentioned.
I replace them with 105 degree types regardless of apparent condition.

One warning - it is easy to accidentally short the solder tags the big
diodes are soldered to, to the zero ohm links as you tighten the nuts. If
you power up fully in this condition with 4 amp fuses you will blow the
Darlingtons again.
You have probably noticed both speaker output tags have amplifiers on
them,
there is no grounded speaker connection, though each output is referenced
to
ground.



Gareth.

I see no circuitwise reason for those repeated cap failures. The Darlington
heatsinks are elevated off the pcb (trackside) with spacers and although
the minor component side of the pa pcb is un-fanned I would not have thought
pcb and working caps would get to 85 deg C
Will make airflow mods and RTV-stick non-resettable thermochromic dots
around various items , for if it bounces back.

 

[Gareth Magennis]

"N_Cook" <diverse@tcp.co.uk> wrote in message
news:hi4kpm$5dr$1@news.eternal-september.org...

Gareth Magennis <sound.service@btconnect.com> wrote in message
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"Gareth Magennis" <sound.service@btconnect.com> wrote in message
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"Arfa Daily" <arfa.daily@ntlworld.com> wrote in message
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"N_Cook" <diverse@tcp.co.uk> wrote in message
news:hi1o7d$fic$1@news.eternal-september.org...

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

Oh, BTW, can you confirm which way the fans run? Sucking air out the
cabinet or blowing it in?



Gareth.


This one is outwards
4,000 sq mm of purpose built inlet holes and 3,300 sq mm through fan vent
I
would have thought was quite adequate if the air was directed over the
heatsinks and not wind-breaked. This one permanent mounted high up away
from
floor dust.
Compared with Laney CD850 , totally inadequate constriction on outlet over
fan .
3 of those I've cut away the "vent" holes over the fan, fared off and
covered with a wire grille and they've not bounced back (each was cutting
out thermally after extended but normal use)
As the Laney original design just 14 small slots with a combined area of
only 1.5 sq
inches, let alone vortexing, so overloading the 3 inch diameter fan
with through ducted area of about 6 sq ins , ridiculous aerodynamics

Thought so.
I did once think about reversing the fan, blowing air into the amplifier,
but there is too much risk of the impeller being fouled by a blow to the
casing around the vents. Surely this would mean more internal turbulence,
thus better cooling?
It must have been designed this way round for a reason, though, (?) so I
gave up on that idea.



Gareth.

 

[N_Cook]

Gareth Magennis <sound.service@btconnect.com> wrote in message
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"N_Cook" <diverse@tcp.co.uk> wrote in message
news:hi4kpm$5dr$1@news.eternal-september.org...
Gareth Magennis <sound.service@btconnect.com> wrote in message
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"Gareth Magennis" <sound.service@btconnect.com> wrote in message
news:E7i1n.3069$2F5.2098@newsfe07.ams2...


"Arfa Daily" <arfa.daily@ntlworld.com> wrote in message
newsWb1n.11179$mQ.2517@newsfe01.ams2...

"N_Cook" <diverse@tcp.co.uk> wrote in message
news:hi1o7d$fic$1@news.eternal-september.org...




Thought so.
I did once think about reversing the fan, blowing air into the amplifier,
but there is too much risk of the impeller being fouled by a blow to the
casing around the vents. Surely this would mean more internal turbulence,
thus better cooling?
It must have been designed this way round for a reason, though, (?) so I
gave up on that idea.



Gareth.

The main disadvantage that way round is all internal stuff gets heated up to
some intermediary temperature, between ambient and heatsink temp

 

[Gareth Magennis]

"N_Cook" <diverse@tcp.co.uk> wrote in message
news:hi4t13$q18$1@news.eternal-september.org...

Gareth Magennis <sound.service@btconnect.com> wrote in message
news:Af61n.20179$AV4.16792@newsfe04.ams2...


"Ron" <ron@lunevalleyaudio.com> wrote in message
news:FMWdnar5p5rYhd7WnZ2dnUVZ8nGdnZ2d@bt.com...
On 05/01/2010 09:59, Arfa Daily wrote:
"N_Cook"<diverse@tcp.co.uk> wrote in message
news:hhv006$kqa$1@news.eternal-september.org...
They have an otherwise original assembly method of the final contact
to
the
pins of TO3 power transistors by 2 zero ohm "resistor" links, so 2
current
paths to the pcb traces. Anyone else observed bad solder joints to
these
links on the pcb? and cause? believed conventional solder not PbF





I repair many of these, and can honestly say that I have *never*
observed
any bad joints at the place you mention. By far the commonest problem
is
failed output transistors. This occurs because the heatsinks are only
just
about adequate with proper cooling. As soon as the fan air intake
vents
start to clog up with fluff, the outputs start to run too hot. Over a
period
of time, this dries out the heatsink paste to a powder, leading
ultimately
to transistor failure.

Whenever I get one, I always remove the other pair of transistors as
well,
clean down their heatsinks, and re-paste them, not forgetting the
flatpak
transistor that's in contact with the underside of one heatsink on
each
channel.

The manufacturers recommend that when the outputs are replaced, two of
the
BC546Bs nearby are replaced as well (T7 / 8 on one channel, 10 / 11 on
the
other). Check also C3 and C21 to make sure that they are not bulging.

Other than this, these amps are very well behaved, and new outputs and
fuses
will, in 99.9% of cases, effect a complete cure. Note, however, that
they
have proper differential inputs, so are not that easy to drive
correctly,
unless you have a proper balanced XLR source, and that they don't like
earthed test equipment connected to their outputs / inputs
simultaneously. I
usually hook a completely isolated speaker to them for final check, as
the
music shop which sends these to me for repair, often remove the amp
chassis
from the cab, to ease the transport, and save me having to strip it
all
out.
He now tells customers when they collect the repaired unit, that they
should
brush out the air vents at three monthly intervals.

I agree with Arfa, I`ve repaired dozens of these and always found the
solderwork to be excellent. Perhaps someone else has been in there
before
you. There was a mod for early units, different output transistors and
the
addition of a couple of 1N7007 on the print side of the board.

Ron(UK)


Well, I agree with Arfa and Ron. I've repaired lots too, since the
cooling
is also IMHO inadequate, which is quickly made worse by fluff around the
fan
vents.
Never had any dry joints, but seen plenty of the bulging caps Ron
mentioned.
I replace them with 105 degree types regardless of apparent condition.

One warning - it is easy to accidentally short the solder tags the big
diodes are soldered to, to the zero ohm links as you tighten the nuts.
If
you power up fully in this condition with 4 amp fuses you will blow the
Darlingtons again.
You have probably noticed both speaker output tags have amplifiers on
them,
there is no grounded speaker connection, though each output is referenced
to
ground.



Gareth.


I see no circuitwise reason for those repeated cap failures. The
Darlington
heatsinks are elevated off the pcb (trackside) with spacers and although
the minor component side of the pa pcb is un-fanned I would not have
thought
pcb and working caps would get to 85 deg C
Will make airflow mods and RTV-stick non-resettable thermochromic dots
around various items , for if it bounces back.

Maybe a batch of dodgy caps, along with the dodgy Darlingtons?!

100v 105C caps are not exactly expensive or physically large, so a bit of a
no brainer for bullet proofing this application.




Gareth.

 

[N_Cook]

Maybe a batch of dodgy caps, along with the dodgy Darlingtons?!

100v 105C caps are not exactly expensive or physically large, so a bit of
a
no brainer for bullet proofing this application.




Gareth.

no room for that size, unless put on track side of the pcb . As it happens
space there and as the temp sensing TO220 s and fan air flow/temp sensor
that side already I will solder replacements on that side I think

 

[Arfa Daily]

That was my definition of inadequate. The fact that 3 of us here have
seen large quantities of the same units with the exact same problems bear
this out.
I'm sure we've all seen plenty of amplifiers with a whole ton of dust
inside that have been working hard for years.

I had a theory that because once repaired they tend not to come back,
this may point to either a manufacturing issue or dodgy batch of
Darlingtons (?)



Gareth.




Oh, BTW, can you confirm which way the fans run? Sucking air out the
cabinet or blowing it in?



Gareth.

I'd never really considered a dodgy batch of transistors. I'd always put it
down to the cooling becoming poor when the fan grille got clogged, leading
to the paste frying to dust, and the transistors then overheating with
little or no compensation from the flatpak transistor in contact with the
underside of the heatsink. I have always obtained my transistors for these
from Farnell, but I noticed last time I ordered a few weeks back, that the
price of them seems to have gone up quite a bit from what I remember them
being last time ...

You know, off the top of my head, I really can't remember if the fan sucks
or blows. I should have been able to tell you today, as the shop that I do a
lot of these for, primed me earlier in the week for one that was coming in
as an urgent repair, as the band had a gig Saturday night. It hasn't
arrived, so if it does turn up tomorrow (ha! - today now!), the repair cost
has doubled ...

I seem to think that the fan sucks air into the cab, which is what causes
the clog at the grille, but could be wrong. Oh to be young again, with a
head that stores things with total recall :-\

Arfa

 

[Arfa Daily]

"Ron" <ron@lunevalleyaudio.com> wrote in message
news:v_OdnWRuW6c3JtjWnZ2dnUVZ7oednZ2d@bt.com...

On 07/01/2010 02:46, Arfa Daily wrote:
"N_Cook"<diverse@tcp.co.uk> wrote in message
news:hi1o7d$fic$1@news.eternal-september.org...

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 ...

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.

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.

Arfa

 

[Ron]

On 09/01/2010 02:14, Arfa Daily wrote:

"Ron"<ron@lunevalleyaudio.com> wrote in message
news:v_OdnWRuW6c3JtjWnZ2dnUVZ7oednZ2d@bt.com...
On 07/01/2010 02:46, Arfa Daily wrote:
"N_Cook"<diverse@tcp.co.uk> wrote in message
news:hi1o7d$fic$1@news.eternal-september.org...

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