Ron(UK) wrote in message
...
N_Cook wrote:
This is the amp in question
http://home.graffiti.net/diverse:gra...net/peavey.jpg
Yellow ring stands in for the 4 inch fan removed (position marked with
Fs )along with metal sheet that encloses the heatsink. The view of this
amp
is upside down as the fan is at the base. So drawing air horizonatally
theough a "designed" 5/8 inch space under the amp. Air then goes through
the
1 in of fan vertically and then has to sharply divert horizontally to
flow
either way through the 3 ducts in each direction. The central duct
contains
no active ducts and as far as I can see only interferes with air flow as
they are right up against the fan housing. Air then vents mainly at
either
end when the metal closure in place with not enough space to add a fan
or 2
at those points and nowhere near the mains transformer and main air
outlet
vent . A lot of venting must go up and out the mixer pannel slider holes
etc
as well. The 2 TO3 mounted thermal switches are marked S and restrict
the
air flow through the uppermost duct in the pic, the leads and spades as
much
as the switch body


I think that the worst part of that desgn IIRC is that the board is
mounted inverted with the sinks beneath, thus any heat which tried to
escape by convection has to pass through the pcb, heating the other
components. Am I correct in that assumption?

Ron


The heatsink is fitted onto the pcb that caries nothing on that area but
holds a lot of ceramic W/W seen either side on the pic, usefully, I suppose,
in the airflow.


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/