Anybody out there also building the hybrid audio amplifier kit described
in the March 2004 issue of "Electronics World"? If so, I'd like to
compare notes.

(I'm unsure about how to mount a transistor in physical contact with an
output stage Vfet for thermal feedback, and then both onto the heatsink
using a standard thermal mounting kit. I haven't been able to contact
the kit designer yet.)

David

"David Holgate" wrote in message
...
Anybody out there also building the hybrid audio amplifier kit described
in the March 2004 issue of "Electronics World"? If so, I'd like to
compare notes.

(I'm unsure about how to mount a transistor in physical contact with an
output stage Vfet for thermal feedback, and then both onto the heatsink
using a standard thermal mounting kit. I haven't been able to contact
the kit designer yet.)

David

The usual method to mount a TO92 plastic transistor is to drill a suitably
sized hole in the heatsink, push the transistor into the hole so that it is
in bodily contact with the metal, and plug the rest of the hole with
Araldite.

Work OK on the Lindsey-Hood amp of the 1970's

....and I presume you mean Electronics and Wireless World?


--

Woody

The message
from "Woody" contains these words:

The usual method to mount a TO92 plastic transistor is to drill a suitably
sized hole in the heatsink, push the transistor into the hole so that it is
in bodily contact with the metal, and plug the rest of the hole with
Araldite.

Work OK on the Lindsey-Hood amp of the 1970's

...and I presume you mean Electronics and Wireless World?

It's now just called Electronics World. Not sure of its history, beyond
the fact that this is volume 110!

The case style of the transistor to be mounted directly onto the Vfet is
TO126. The Vfet itself is screwed onto the heatsink.

In article ,
Woody wrote:
The usual method to mount a TO92 plastic transistor is to drill a suitably
sized hole in the heatsink, push the transistor into the hole so that it is
in bodily contact with the metal, and plug the rest of the hole with
Araldite.

Work OK on the Lindsey-Hood amp of the 1970's

I used ally 'P' clips and glued them into those. Still working and
sounding good. ;-)

--
*The most wasted day of all is one in which we have not laughed.*

Dave Plowman London SW 12
RIP Acorn

The message
from Dave Plowman contains these words:

In article ,
Woody wrote:
The usual method to mount a TO92 plastic transistor is to drill a suitably
sized hole in the heatsink, push the transistor into the hole so
that it is
in bodily contact with the metal, and plug the rest of the hole with
Araldite.

Work OK on the Lindsey-Hood amp of the 1970's

I used ally 'P' clips and glued them into those. Still working and
sounding good. ;-)

--
*The most wasted day of all is one in which we have not laughed.*

Dave Plowman London SW 12
RIP Acorn

Thanks to those who offered advice. The designer has now been in touch
and explains that the active devices (one or two when placed in contact
with one another) should be secured via a mounting screw inserted from
the outside, through a mounting bush and then the heatsink (with a
suitable thermal pad on the other side. This gives the right insulation
and thermal transfer. Now I just need to replace the transistors that
overheated first time round...

David

In article ,
David Holgate wrote:
Thanks to those who offered advice. The designer has now been in touch
and explains that the active devices (one or two when placed in contact
with one another) should be secured via a mounting screw inserted from
the outside, through a mounting bush and then the heatsink (with a
suitable thermal pad on the other side. This gives the right insulation
and thermal transfer.

But isn't this the standard way of mounting a device with a 'live' tab?

--
*A closed mouth gathers no feet.

Dave Plowman London SW 12
RIP Acorn

*A closed mouth gathers no feet.

Sounds to me like being gobby is the way to go, then, as long
as one's surrounded by cute women!

666

The message
from Dave Plowman contains these words:

In article ,
David Holgate wrote:
Thanks to those who offered advice. The designer has now been in touch
and explains that the active devices (one or two when placed in contact
with one another) should be secured via a mounting screw inserted from
the outside, through a mounting bush and then the heatsink (with a
suitable thermal pad on the other side. This gives the right insulation
and thermal transfer.

But isn't this the standard way of mounting a device with a 'live' tab?

Probably is--this is the first time I've assembled such a kit, so I'm
learning as I go along. :-) The kit just said in the standard way, with
no further details given.

In article ,
David Holgate wrote:
But isn't this the standard way of mounting a device with a 'live' tab?

Probably is--this is the first time I've assembled such a kit, so I'm
learning as I go along. :-) The kit just said in the standard way, with
no further details given.

Ah - right. I thought when you mentioned standard mounting kit in your
first post, you'd got one to hand.

Maplin in the days when they did their own kits enclosed a Constructor's
Guide with every one, which gives clear instructions and diagrams for all
this sort of thing. If you send me your address, I'll post you one - being
a good Aberdonian I throw nothing out. ;-) It's a very useful booklet.

--
*My designated driver drove me to drink

Dave Plowman London SW 12
RIP Acorn

The message
from Dave Plowman contains these words:

In article ,
David Holgate wrote:
But isn't this the standard way of mounting a device with a 'live' tab?

Maplin in the days when they did their own kits enclosed a Constructor's
Guide with every one, which gives clear instructions and diagrams for all
this sort of thing. If you send me your address, I'll post you one - being
a good Aberdonian I throw nothing out. ;-) It's a very useful booklet.

Thanks Dave.