"N_Cook" wrote in message
...
Gareth Magennis wrote in message
...

"N_Cook" wrote in message
...
Mains fuse blew in the middle of normal use.
No mention of PbF anywhere but it is. Unlikely the problem though.
Seems
bad
thermal design as audio-out vaned heatsink has cooling air through it
but
the non-vaned SMPS one does not have, as that intended? air will go
through
the path of least resistance over the uncluttered preamp . I can see a
baffle going in here to direct air over this plain block heatsink.
Anyone
experience of these little amps?
Both SMPS powerFETs s/c all round. Each has a discoloured patch on the
mounting-plate where the die overlies. No burning/blow-holes of these
powerFET encapsulations or 10R SMD gate droppers or anything else found
suspect from cold testing/close inspection, nor suspect looking PbF.
The
SMPS supervisor IC ident is ground off and a schematic for a similar
amp
has no ident. I could find details of any 8 pin 0.1 inch pitch package
with
push/pull drive in 1991 DATA linear colated listing- any suggestions
for
this sort of search?
p1 supply low side
p3 probably Enable
p4 Vcc
p5 and p7 hi/lo outputs
p6 mid connection to both output powerFET
Does not seem to be any thermal shutdown for the SMPS section




I've got one of those here I gave up on. Life's too short and doesn't
pay
enough for this kind of palaver.

Good luck!


Gareth.




So what was the failure on your one?




Both Power amp and Power supply.
Couldn't get a replacement for a blown PSU Mosfet, (Farnell had a one year
waiting list) so subbed in the highest spec one I could find, but it still
didn't power up, (amp disconnected) so I gave up.

If I come across something like this where schematics and parts are not
available, I am not about to spend 6 difficult hours on it, and only be able
to charge 3, so I now cut my losses and refuse.
This, together with muting all TV adverts the past 5 years, has improved my
life immeasurably.


Gareth.