Re: Tek 7904 help!
Thank you Raymond and Harvey. Will try your suggestions and see what happens. Checked all tants in the ps for shorts - no discolored resistors or smell! Will check them in the nether regions!toggle quoted messageShow quoted text
On Wednesday, July 8, 2020, 08:53:08 PM EDT, Harvey White <madyn@...> wrote:
When I used a variac, I looked at the current draw. If it turned out to
be excessive, I looked for a problem with the primary supply.
I don't remember that I spent too much time at lower voltages, and ran
it up to the 80 to 90 volt range if the current draw was excessive. I
used the variac to check if the main bulk supply was shorted. When it
wasn't, I ran it up higher.
It seemed to work without stressing the supply too much. Some supplies
draw excessive current because the switch doesn't come on (and off)
until a minimum voltage, that's the reason for being sneaky in this
case. You try to avoid that overcurrent draw due to the switching
circuit not working.
More of a turn it up and see what it draws, turn it right back down,
then figure out why.
think that'll work?
On 7/8/2020 8:39 PM, Raymond Domp Frank wrote:
On Thu, Jul 9, 2020 at 02:10 AM, Harvey White wrote:Since you have a variac, you might want to run the voltage up from zero- The 7904 has a primary switching power supply (PSU), so *no variac* allowed: You may overload (and damage) circuits while varying the input voltage.