[Scott Dorsey]

Dave Plowman (News) wrote:
I've got a Shortcut 99 which has problems switching on. Leave it powered
up and it usually does after a couple of minutes, then works normally. But
not too reassuring, given the tasks it's sometimes needed for. ;-)

It would appear to be a PS fault - but all the caps etc check out ok and
I've re-flowed the entire board. As do the voltages when it's working.
Anyone come across this and got an educated guess?

Something has gone wrong with the kickstart circuit on the power supply.
On simple switching supplies, this will be just an RC constant that supplies
power to the pwm oscillator for long enough to get some voltage out of the
secondary.

Get the datasheet for the PWM chip that the power supply uses, look at the
sample circuits. Look for the kickstart circuit which almost certainly will
be identical to the sample circuits on the datasheet. Check the value of the
resistors and replace the small capacitor.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."