N Cook wrote in message
...
jakdedert wrote in message
. ..
N Cook wrote:
Been looked at by one supposed repairman and returned in a sorry
state.

SMPS problem initially , but now could be more than that.
I don't suppose anyone has a schematic for this kit, may not be
necessary
but just in case.
Local recording studio's favoured piece of kit , with no full modern
day
replacement it would seem


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


Millions of them made, superseded by the SPX 900. All the programs
within also contained in the much more capable REV-7.

The 90's and many other Yamaha devices of the mid-80's suffered from a
potting compound which often turns conductive with age....

jak

Cold checking , have found 2 things wrong with the ps so not powered up
yet
No SMPS controller IC on the ps board , a TOP66 switcher driver and 3
small
transistors.
Raw + and -18V go to main board +/-15V regulators , raw 5V , ie rectifier
off the switching transformer followed by one L and one C goes straight to
the 5V TTL rail. Not even an obvious fat 5V zener across it.
No SMPS controller IC , that I can see on the main board and the 2 lines
from the main board marked PE and PC that go to the mains side of the ps
via
opto isolator , I'm assuming is go / no-go for the moment.

5V regulation via the whole ps unit ?
very strange

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




There are 15 assorted wirewound resistors on this ps , again rather odd.
If I get it working , a ventillation hole and grill cut in the top cover
would help.