giannibo wrote in
:

On 4 Gen, 11:51, Andreas Tekman wrote:
On 1 Jan., 17:09, giannibo wrote:





On 31 Dic 2007, 23:35, Jim Yanik wrote:

giannibo wrote
innews:dca6ef88-f731-49ca
:

On 29 Dic, 04:43, Jim Yanik wrote:
"DaveM" wrote
innews:gcOdnekazMCkC-janZ2dnUVZ_
:

"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

roup
s.c
om
...
HELP! Someone know the mainframe oscilloscopeTektronix7000
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 t
o
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 transis
tor
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 indicat
ed
on circuit as a element with 2 emitter, what is?

A Diac;it triggers at ~33V IIRC.

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 sav
e.
Thanking for help!!
Gianni

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

- Mostra testo tra virgolette -

Thanks! I will replace it! In the meantime I foun that R120 and
*R122 ( 1,8 Kohm) *of Z axis board A41 are burning, with smoke.
Many defect all togheter!! Tomorrow i will check why these resistor
are smoking.Anyway I am bidding on *ebay a 7704 so I can compare
some situations.
Thanks. I wil post when I found all defect!
Gianni
IK4EWH- Zitierten Text ausblenden -

- Zitierten Text anzeigen -

Remember what Jim already said about 7704 and 7704A: Both models are
a lot different.

So if you plan to compare circuits and repair faults, go for the same
models at least.

hth,
Andreas- Nascondi testo tra virgolette -

- Mostra testo tra virgolette -

The model is 7704A and I got diagram. Now is working but isn't active
the automatic control. I must replace the DIAC. But rhey are others
defects... very hard competition!


read the service manual's circuit description;
it's VERY valuable in understanding how the PS works.
Make notes on a printout of the schematic.

--
Jim Yanik
jyanik
at
kua.net