On 29 Dic, 04:43, Jim Yanik wrote:
"DaveM" wrote :





"David Wright" wrote in message
...
If you get some money send it in for repair and calibration. *Cost on
good test equipment is out of site.

"giannibo" wrote in message

...
HELP! Someone know the mainframe oscilloscope Tektronix 7000 series?
I have some 7704 with power supply broken,with same defect: don't
start the oscillator.
Some suggestion??

You can download the manual for the 7704 from
http://bama.edebris.com/manuals/tek/7704/. *It should help you figure
out the problem.
The usual suspects are aging electrolytic capacitors.

both in the power supply and the mainframe itself.



just make sure you have a 7704 and not a 7704A. There's a big difference.

although both have complex series-resonant switching power supplies.

usually,you hear a clicking or "chirping" from the PS;it's trying to
start,but something is loading a supply,or a diode is shorted.
Some failures blow a lot of parts....and then the line fuse afterwards.

--
Jim Yanik
jyanik
at
kua.net- Nascondi testo tra virgolette -

- Mostra testo tra virgolette -

Thanks for answer.The model is 7704A. I replace the fast diode.The
defect remaining is that try to start the oscillator,but isn't
stable.After several test, I found that disconnecting the transistor
TO5 on parallel to base-emitter of power transistor, the oscillator
start, but isn't stabilized.May be is the small SCR. I checked all
components, only the SCR remain... Further the semiconductor indicated
on circuit as a element with 2 emitter, what is?This machine remain on
stock for several years, so some components are gone.Is a pity ,
because this instrument is made on beautifull mode, and I try to save.
Thanking for help!!
Gianni