TDS540 scope is dead

[pirotte pascal]

Hi,

my Tektronix TDS540 scope is dead...
The switch mode power supply doesn't work anymore. The shopper
transistors (IRFP450) are alive, the fuse is OK, the main power
components (diodes, res,...) have been tested.

Any suggestion is welcome

Pascal

 

[Jim Yanik]

pirotte pascal <pascal.pirotte@swing.be> wrote in
news:bpsdqo$38u$1@snic.vub.ac.be:

Hi,

my Tektronix TDS540 scope is dead...
The switch mode power supply doesn't work anymore. The shopper
transistors (IRFP450) are alive, the fuse is OK, the main power
components (diodes, res,...) have been tested.

Any suggestion is welcome

Pascal

Bad electrolytics(too-high ESR) in the secondaries?
A Dick Smith ESR meter would help here.

does the PS make any noises,like a chirping or clicking?

--
Jim Yanik,NRA member
jyanik-at-kua.net

 

[pirotte pascal]

Jim Yanik wrote:

pirotte pascal <pascal.pirotte@swing.be> wrote in
news:bpsdqo$38u$1@snic.vub.ac.be:


Hi,

my Tektronix TDS540 scope is dead...
The switch mode power supply doesn't work anymore. The shopper
transistors (IRFP450) are alive, the fuse is OK, the main power
components (diodes, res,...) have been tested.

Any suggestion is welcome

Pascal




Bad electrolytics(too-high ESR) in the secondaries?
A Dick Smith ESR meter would help here.

does the PS make any noises,like a chirping or clicking?

Thank you for the answer, Jim


The power supply doesn't make any noise. The main diode bridge and its
(big) electrolytic capacitor are OK (DC voltage is OK when supply is
powered)



Pascal

 

[TekMan]

pirotte pascal <pascal.pirotte@swing.be> wrote in message news:<bpuv2n$h9m$1@snic.vub.ac.be>...

Jim Yanik wrote:
pirotte pascal <pascal.pirotte@swing.be> wrote in
news:bpsdqo$38u$1@snic.vub.ac.be:


Hi,

my Tektronix TDS540 scope is dead...
The switch mode power supply doesn't work anymore. The shopper
transistors (IRFP450) are alive, the fuse is OK, the main power
components (diodes, res,...) have been tested.

Any suggestion is welcome

Pascal




Bad electrolytics(too-high ESR) in the secondaries?
A Dick Smith ESR meter would help here.

does the PS make any noises,like a chirping or clicking?


Thank you for the answer, Jim


The power supply doesn't make any noise. The main diode bridge and its
(big) electrolytic capacitor are OK (DC voltage is OK when supply is
powered)



Pascal

as Jim proposed: chk the ESR.
There should be a kind of start-up circuit (resistor,
transistor-resistor combination) -- looks like this is the part of the
circuit that does not work.

AFAIK the tds540 has no real power switch on the front, it is a kind
of "start switch" like the more modern PC ATX style) power supplies)
have. If this auxiluary voltage supply is defectice, the main supply
will not start.

well, and besides this: check the front switch too.

HTH,
Andreas

 

[GPG]

Dont know this psu, but some iv'e seen have a startup supply from the
mains filter capacitor via acouple of high value resistors. check them for o/c.
Also check any small value electros on primary side. have you got a cct.