Hello
First thing I should mention is that I think it is a crazy idea to
try to retrofit a PC power supply to repair your (or anyone else's)
machine. It is not impossible, but for starters, the thing is too
big physically, secondly, you have no -12v rail (you wold need to
generate this with a little switcher or charge pump etc), and most
importantly, the +12v to the hard drive needs to be well decoupled
from the analogue 12v rail. I have not had much experience servicing
any Vestax products, but from a quick look at the power supply (I
only have a partial schematic) for a HDR10, it is fairly
straightforward, and should be repairable by a technician or
enthusiast with moderate skills. I do not have a full circuit (the
ramp circuit is missing) but a quick explanation may help you or
others. Power comes in from the transformer to a bridge rectifier to
form a split rail supply of probably about +/- 18v. The +12v and -
12v for the analoge circuitry is formed with a 7812 and 7912 (3
terminal) voltage regulator. The 12v for the hard drive and pre-
regulation for the 5v logic supply is derrived from a pair of
switchmode PWM buck converters. These circuits are almost identical.
They operate synchronously from a ramp generator that is probably
synchronized to the audio clocking frequency or someting like that
(I don't have that part of the circuit) which is input on connector
P9 (on my HDR10 PSU). Now to check the thing, first, check to base
of all the large electro's to make sure they are not blowing their
vents, then see that you have about 16 to 18v on the positive and
negative of the bridge rectifier, if all is good then see if you
have +12v and -12v on the 3 terminal regulators (U1,7812 and U2,7912
respectively). If that is ok, now check the voltage accross C7 and
C8, and you should have approx 12V across each. Now if you don't get
any voltage - or wrong voltage on C7 and C8 but you do have the
previously mentioned voltages, I can see a few reasons why this
power supply can go astray. First thing I notice is a total lack of
bypass capacitors to U1, U2 and U4. These should all have a 100nf
ceramic and 10uf electrolytic as close as possible to their output
pins and ground and I would suggest you add them even if your
machine is working, else one day they will hickup and do something
nasty. If that doesn't fix it, you will need an oscilloscope to
check the ramp sync - I won't bother going into too much detail from
here on, because you will need to understand the schematic to be
able to use the scope - and vice versa. Hope this may be of help.
BTW moderator, I'm not trying to get a free ad here, but I just
wrecked a HDR10 and I will be putting the parts (including a working
PSU) up for grabs on Ebay (member name is meldavia).
Regards Dave
Hello David again, you will note that I have misled you on the
voltages below, of couse you should measure 5v across C7 and 12v
across C8, my apologies for the mistake.
Dave