Tektronix 7704A power supply question

[Fred Abse]

On Mon, 02 Mar 2009 15:56:34 -0700, Jim Thompson wrote:

I'm down to can't hear the wife unless she's right in my face ;-)

Is that patentable?

(Almost totally deaf in the left ear... you know... the one I damaged
while designing a hearing aid chip ;-)

That'll larn ye!

--
"Electricity is of two kinds, positive and negative. The difference
is, I presume, that one comes a little more expensive, but is more
durable; the other is a cheaper thing, but the moths get into it."
(Stephen Leacock)

 

[tekamn]

On 24 Feb., 23:11, Jim Yanik <jya...@abuse.gov> wrote:

"DaveM" <masondg4...@comcast99.net> wrote innews:KZ-dnYGRzOqFrTnUnZ2dnUVZ_tmWnZ2d@giganews.com:





"Joerg" <notthisjoerg...@removethispacbell.net> wrote in message
news:%SUol.23432$ZP4.7265@nlpi067.nbdc.sbc.com...
Robert Baer wrote:
Joerg wrote:

So, besides some other things theTektronix7704A had croaked.
T'was the switcher. No schematics available, the usual. Looks like
someone really "jammed it together" which is strange since this
unit has always had top-notch service at calibration places.
Anyhow, got it fixed now but there is something weird on there and
I'd like to know if it is normal:

A little neon lamp like the ones found in older illuminated light
switches flashes at sub-second intervals and the switcher does
slight ticking noises every time it flashes. The neon lamp looks
old, pretty black inside, but I dare not to swap it (don't touch a
running system ...). Other than that the whole scope works fine
again.

Is this normal? Is that neon lamp used as a "predecessor" of a
TL431?

  Hmm..the schematic i have shows only 3 neons, one between the 115V
  and the
230V switch terminls, one in oscillator configurationacross the
output of the FWB, and the third from the 115V switch terminal to
some ?reference? line.
  In certain applications, neon bulbs were purposly burned in (for
  looong
periods), turning them black inside, in order to gain voltage
stability.
  I understand the technique is both an art and a science.

That's what I was afraid they did. I've seen them used as references
as well, a quite horrid method because when it fails you are up the
creek. If I had the schematic I could try to replace it with
something more durable. Did you find the 7704A schematic online
somewhere? BAMA and Bitsavers didn't have it. Only the 7704 non-A and
that's way different, mostly discrete while the 7704A has those
new-fangled Tek custom chips :-(

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

Joerg,
You can download the complete manual set for the 7704 and 7704A scopes
from
http://www.ko4bb.com/cgi-bin/manuals.pl?dir=Tektronix/Tektronix_-_7704..
 Not the best quality, but very readable.

Cheers!

you do know there's a huge difference between the 7704 and 7704A?

--
Jim Yanik
jyanik
at
kua.net- Zitierten Text ausblenden -

Joerg will be soon able to notice that there is ,-)

 

[Joerg]

tekamn wrote:

On 24 Feb., 23:11, Jim Yanik <jya...@abuse.gov> wrote:
"DaveM" <masondg4...@comcast99.net> wrote innews:KZ-dnYGRzOqFrTnUnZ2dnUVZ_tmWnZ2d@giganews.com:





"Joerg" <notthisjoerg...@removethispacbell.net> wrote in message
news:%SUol.23432$ZP4.7265@nlpi067.nbdc.sbc.com...
Robert Baer wrote:
Joerg wrote:
So, besides some other things theTektronix7704A had croaked.
T'was the switcher. No schematics available, the usual. Looks like
someone really "jammed it together" which is strange since this
unit has always had top-notch service at calibration places.
Anyhow, got it fixed now but there is something weird on there and
I'd like to know if it is normal:
A little neon lamp like the ones found in older illuminated light
switches flashes at sub-second intervals and the switcher does
slight ticking noises every time it flashes. The neon lamp looks
old, pretty black inside, but I dare not to swap it (don't touch a
running system ...). Other than that the whole scope works fine
again.
Is this normal? Is that neon lamp used as a "predecessor" of a
TL431?
Hmm..the schematic i have shows only 3 neons, one between the 115V
and the
230V switch terminls, one in oscillator configurationacross the
output of the FWB, and the third from the 115V switch terminal to
some ?reference? line.
In certain applications, neon bulbs were purposly burned in (for
looong
periods), turning them black inside, in order to gain voltage
stability.
I understand the technique is both an art and a science.
That's what I was afraid they did. I've seen them used as references
as well, a quite horrid method because when it fails you are up the
creek. If I had the schematic I could try to replace it with
something more durable. Did you find the 7704A schematic online
somewhere? BAMA and Bitsavers didn't have it. Only the 7704 non-A and
that's way different, mostly discrete while the 7704A has those
new-fangled Tek custom chips :-(
--
Regards, Joerg
http://www.analogconsultants.com/
"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
Joerg,
You can download the complete manual set for the 7704 and 7704A scopes
from
http://www.ko4bb.com/cgi-bin/manuals.pl?dir=Tektronix/Tektronix_-_7704.
Not the best quality, but very readable.
Cheers!
you do know there's a huge difference between the 7704 and 7704A?

--
Jim Yanik
jyanik
at
kua.net- Zitierten Text ausblenden -

Joerg will be soon able to notice that there is ,-)

Schematic is for the 7704A, scope is a 7704A. What would be the problem?
Anyhow, it's fixed, works again

Since you are a Tek expert, do you know how easy it is to replace the
first mixer in a 7L12 or 7L13 with something off the shelf like
Mini-Circuits? It would be nice to add that module to this chassis but
many of them had their inputs fried and the sensitivity is shot.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.