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Re: 7704a repair adventure

Craig Sawyers <c.sawyers@...>
 

Based on the suggestions I've found a pair of 151-0127-00 <-> 2n2369.
Would be close enough for the time being?


Windsor Chan
I'd be tempted to just shove them in and see what happens - but don't blame
me if there is a puff of smoke from somewhere! They have lower Ft = 500MHz
and higher Coe = 4pF, and it may be that they oscillate, and you'll soon see
that in the trace ;-)

There are a lot of junker 7704A's out there, so try Sphere or Deane Kidd for
the real part. I picked up two non-working 7704A's with PI's (including a
couple of 7A13 diff comparators!) at a hamfest a couple of months ago for
�90UK, but they were easily fixed and I'll be listing them on eBay as
functional units in due course.

Craig


Re: 7704a repair adventure

Windsor Chan
 

Hi

Based on the suggestions I've found a pair of 151-0127-00 <-> 2n2369.
Would be close enough for the time being?


Windsor Chan


Re: 7704a repair adventure

Craig Sawyers <c.sawyers@...>
 

Thank you for the advice.
The device in question is in round plastic case.
Looks like a UFO :)
Windsor Chan
I know the sort of case you're talking about - it is called TO105 or TO107,
circular with a shiney domed top. My 7704A has T092 style case ones -
shaped like a letter D.

Craig


Re: 7704a repair adventure

Windsor Chan
 

Thank you for the advice.
The device in question is in round plastic case.
Looks like a UFO :)

Regarding the pairing up, that is a good idea
because if one tranny starts to run out of steam
before the other, there would be an imbalance.



Windsor Chan


Re: Book Ideas

Craig Sawyers <c.sawyers@...>
 

After suggesting to Scientific American Book Club that they need
some good electronics books in their club, I was contacted by the
Senior Editor of the club, asking if I have any suggestions.
Anyone read any good books lately?
Handbook of Analog Circuit Design, Feucht (ex Tek designer). Out of print.
The Art of Electronics, Horowitz and Hill. Very much in print.
From an earlier era, The Radiotron Designer's Handbook, preferably edition
4. Out of print.
Op-amp Cookbook, Jung. In print.

Craig


Re: Book Ideas

Scott Newell <newell@...>
 

At 10:05 PM 4/27/2004 -0700, Darrin Conniff wrote:
Hello Everyone,
After suggesting to Scientific American Book Club that they need some good
electronics books in their club, I was contacted by the Senior Editor of
the club, asking if I have any suggestions.

All the Tek concept series.
The two Jim Williams edited analog design books.
The Bob Pease book.
AoE.
Analysis and Design of Analog Integrated Circuits (Gray and Meyer).


newell


Book Ideas

Darrin Conniff <djconniff@...>
 

Hello Everyone,
After suggesting to Scientific American Book Club that they need some good electronics books in their club, I was contacted by the Senior Editor of the club, asking if I have any suggestions.
Anyone read any good books lately?
Let me know, and we'll see if we can help them get some quality electronics books, maybe help interest some future engineers...
I won't mention any names to the editor, just that the suggestions came from members of this list.
Thanks,
Darrin


647A Calibrator Squeel

Howard Matthews
 

Folks - any information appreciated.

I have 5 647A scopes in various states from almost calibrated to
(one) parts unit. All the working scopes have an audible high
frequency squeel that comes from the calibator unit. Turn the
calibrator off, or to 100v DC, and there is no squeel. In all
positions that output the square wave, there is an annoying squeel.

OK, a lot of people my age cannot hear it - but my hi frequency
hearing is still pretty good. It sounds like maybe 10kHz, which is
strange since the calibrator outputs a 1 kHz square wave. Well,
maybe not completely strange if you count the harmonics of 1 kHz.

Questions:
1. Was this normal in new scopes, i.e. a design flaw?
2. Is this caused by a transformer in an oscillator circuit aging?
3. Is there any known cure?

TNX, Howard


Re: 7904 readout 'jitter'

Craig Sawyers <c.sawyers@...>
 

I have a 7904 where the on-screen readout vertical position is
slightly depending on the vertical trace position.

On a steady beam this is not a problem but if you put the horizotal
time base in alt, the readout becomes bouncy. I think the problem is
in the unbalance of the vertical amp, but would like to hear some
other people about this 'problem'
Well, Fred - my 7904 is the same. The same thing happens slightly with my
7704A, and not at all with the 7834 and 7104. I've done a complete recal on
the 7904, and all offsets in y and t are absolutely on the button.

I suspect that it may have to do with the horizontal amplifier - there were
(at least) three different circuits that were used (B21000 and up, B080000 -
B209999, B010100 - B079999). The very earliest range of S/No.s had a
thermal balance control that was set to reduce readout jitter to less than
0.1 div, but this control does not exist on later units.

FWIW mine is in the middle range, with S/No B113428.

Any other information greatfully received....

Craig


Re: 7704a repair adventure

Craig Sawyers <c.sawyers@...>
 

You could try a PN2369A this is the to92 version of the 2N2369A
this is one of the fastest transistor around and readily
available. Since the 7704A is a 200 or 250 Mhz scope it will
probably be fast enough. Certainly worth a try until you can find
something else.
David diGiacomo replied off-list, thinking that I was the guy with the
problem - but he made a good suggestion for monteen (whoever he is...).
That is the 2N5770 - FT of 900MHz, Coe of 1.7pF and the same case style and
lead order. Made by Fairchild, in current production.

In fact, there are 100 for sale on eBay at the moment for $5.50 buy-it-now,
item 3812272299

Craig


7904 readout 'jitter'

pe1fbo <sh331182@...>
 

Hi All,

I have a 7904 where the on-screen readout vertical position is
slightly depending on the vertical trace position.

On a steady beam this is not a problem but if you put the horizotal
time base in alt, the readout becomes bouncy. I think the problem is
in the unbalance of the vertical amp, but would like to hear some
other people about this 'problem'

Thanks,

Fred de Vries


Re: 7704a repair adventure

pe1fbo <sh331182@...>
 

Hi there,

I would try the BFR90, BFR91 or the BFR96. It is probable part of an
differential amp, so the 'otherside' of the amp is best fitted with
the same type.

If you want to have an plastic TO92, you can take the 2N3563, it has
an Ft of 800 MHz, and will do the job I think.

alternatives are MPS911, MPS571, MPS901, ( Motorola )

Fred de Vries




--- In TekScopes@yahoogroups.com, "Craig Sawyers" <c.sawyers@t...>
wrote:
here are the characteristics:
151-0269-00 - Small signal high speed FMT5092

ft min: 1 GHz @ 5 V/10 mA (Vce/Ic)
hfe: min 30/max 300 @ 10 V/20 mA (Vce/Ic)
Breakdown voltages: Vceo: 15 V, Vcbo: 30 V, Vebo: 4 V
Icbo: 10 nA
Ccb: 1.5 pf
Vce sat: 150 mV/20 mA
Ic max: 80 mA
Case: TO-92
/Zenith
I've just had a browse around, and anything of that spec in a TO92
package
is *very* difficult to find! There is plenty of stuff in surface
mount, and
in those little pill-like packages with three or four leads
sticking out
radially - but getting that BW out of a discrete TO92 package is
very
difficult; it is clearly a very small device, with low Vceo of
only 15V and
Ccb of only 1.5pF (presumably including leads).

Try some of the Agilent stuff.

Craig


Re: 7704a repair adventure

gettingalongwouldbenice
 

Back in the day...the -269 was a cut above anything else
in it's class. Compared to most any other transistor
you could find, it had lower C, faster transient response,
low saturation, very linear gain vs current vs voltage
curves. And it really liked to amplify without oscillating.
And it was cheap.
Because of all that, it was a very popular transistor at TEK.

Remember that there are a bunch of time constants in the vertical
to compensate thermal time constants in the devices.

If you can find a pair anywhere else in the scope, or in
some less critical application in a plugin, I suggest you use real
-269s in the vertical and sub the other application that
doesn't show up directly on the screen as vertical deflection.
YMMV,
mike

--- In TekScopes@yahoogroups.com, "Craig Sawyers" <c.sawyers@t...> wrote:
here are the characteristics:
151-0269-00 - Small signal high speed FMT5092

ft min: 1 GHz @ 5 V/10 mA (Vce/Ic)
hfe: min 30/max 300 @ 10 V/20 mA (Vce/Ic)
Breakdown voltages: Vceo: 15 V, Vcbo: 30 V, Vebo: 4 V
Icbo: 10 nA
Ccb: 1.5 pf
Vce sat: 150 mV/20 mA
Ic max: 80 mA
Case: TO-92
/Zenith
I've just had a browse around, and anything of that spec in a TO92 package
is *very* difficult to find! There is plenty of stuff in surface mount, and
in those little pill-like packages with three or four leads sticking out
radially - but getting that BW out of a discrete TO92 package is very
difficult; it is clearly a very small device, with low Vceo of only 15V and
Ccb of only 1.5pF (presumably including leads).

Try some of the Agilent stuff.

Craig


Re: 7704a repair adventure

eboytoronto
 

Hi,

You could try a PN2369A this is the to92 version of the 2N2369A this is one of the fastest transistor around and readily available. Since the 7704A is a 200 or 250 Mhz scope it will probably be fast enough. Certainly worth a try until you can find something else.

Regards,

John Barnes

I've just had a browse around, and anything of that spec in a TO92 package
is *very* difficult to find! There is plenty of stuff in surface mount, and
in those little pill-like packages with three or four leads sticking out
radially - but getting that BW out of a discrete TO92 package is very
difficult; it is clearly a very small device, with low Vceo of only 15V and
Ccb of only 1.5pF (presumably including leads).

Try some of the Agilent stuff.

Craig



Re: 7704a repair adventure

Craig Sawyers <c.sawyers@...>
 

here are the characteristics:
151-0269-00 - Small signal high speed FMT5092

ft min: 1 GHz @ 5 V/10 mA (Vce/Ic)
hfe: min 30/max 300 @ 10 V/20 mA (Vce/Ic)
Breakdown voltages: Vceo: 15 V, Vcbo: 30 V, Vebo: 4 V
Icbo: 10 nA
Ccb: 1.5 pf
Vce sat: 150 mV/20 mA
Ic max: 80 mA
Case: TO-92
/Zenith
I've just had a browse around, and anything of that spec in a TO92 package
is *very* difficult to find! There is plenty of stuff in surface mount, and
in those little pill-like packages with three or four leads sticking out
radially - but getting that BW out of a discrete TO92 package is very
difficult; it is clearly a very small device, with low Vceo of only 15V and
Ccb of only 1.5pF (presumably including leads).

Try some of the Agilent stuff.

Craig


Re: 7704a repair adventure

Windsor Chan
 

Thank you Zenith,

I suspected that the value of ft would be in the GHz
range.

I'll take a look in my junk box to see if I've anything close.

My reference says 151-0269-00 = FMT5092 or 41632BD

here are the characteristics:
151-0269-00 - Small signal high speed FMT5092

ft min: 1 GHz @ 5 V/10 mA (Vce/Ic)
hfe: min 30/max 300 @ 10 V/20 mA (Vce/Ic)
Breakdown voltages: Vceo: 15 V, Vcbo: 30 V, Vebo: 4 V
Icbo: 10 nA
Ccb: 1.5 pf
Vce sat: 150 mV/20 mA
Ic max: 80 mA
Case: TO-92
/Zenith


Re: 500 series test gear

Dave Henderson <nr1dx@...>
 

Craig

Your right on the money

I suspect it was targeted at a "different market" than the 7000's though, i.e lower price

Dave

At 01:06 PM 4/9/2004, Craig Sawyers wrote:
I'm going to say something controvertial.

I'm pretty disappoined with the 500 series of test gear. Not the tubed
scopes - I mean the test modules that fit into the power units.

I've been building up a small collection - a PG502, TG501, PG506, SG503,
AA501 and a couple of power units.

Circuitry, performance and functionality is fine - but the mechanics is far
below the mainframe scopes of the same generation (7xxx series and
associated plug-ins). They are flimsy - because the top and bottom rails
aren't tied at the rear of the unit, they just folded tabs that screw to the
circuit boards. The front plastic trim loses the corners - because the
fixing screws that hold it in place are counterunk heads, too close to the
corner - so they stress the plastic, it cracks and the corner falls off.

Then there is servicing. They are nearly impossible to conveniently
dismantle to board level. With the 7xxx series plug-ins, the only board
that is hard to deal with is the mother board that links through to the edge
connector - but you just unplug the piggy back boards and have immediate
access. With the 5xx series units, there is a wild assortment of spacers
that fall out, self tapping screws of umpteen lengths, and boards trapped
behind the folded tabs on the top and bottom rails. Fortunately I've only
had to fix the TG501 ane the PG506, and I've been more than happy that I
don't have to fix these things for a living.

They really do look like they have been *mechanically* designed by Tek's "B"
team.

Flame suit on....

Craig





Yahoo! Groups Links




Re: 7704a repair adventure

 

--- In TekScopes@yahoogroups.com, "mongteen" <mongteen@h...> wrote:
Hello gang,

Today I aquired a 7704a from a surplus store. I inserted a 7a26
and a
7b80 and found that the vertical was deflected way off the top, only
visisble when beam finded was on. Fortunately I had a reasonably
good
working 7704a. The nice thing about the 7704a is that the "head" is
removable. So I did a head swap. On the new 7704a the problem
remained and the old 7704a still worked with the new display
section.
So without the manual I thought what could go wrong? I pulled the
readout board to no effect. Then I look at other 7xxx family
manuals
for inspiration.
Then I swaped the pair of delay line driving transistors and
BINGO! :)
Now the vertical deflection is operating good. Then I looked up
Stan
and Bill reference site and found that 151-0269-00 = FMT1061 .

Then I looked at my ECG semiconductor replacement guide, no matches.
Then googled FMT1061. No matches.

The question I have is what are the characteristics of the
151-0269-00 ?


Thanks
-----------
My reference says 151-0269-00 = FMT5092 or 41632BD

here are the characteristics:
151-0269-00 - Small signal high speed FMT5092

ft min: 1 GHz @ 5 V/10 mA (Vce/Ic)
hfe: min 30/max 300 @ 10 V/20 mA (Vce/Ic)
Breakdown voltages: Vceo: 15 V, Vcbo: 30 V, Vebo: 4 V
Icbo: 10 nA
Ccb: 1.5 pf
Vce sat: 150 mV/20 mA
Ic max: 80 mA
Case: TO-92
/Zenith


7704a repair adventure

Windsor Chan
 

Hello gang,

Today I aquired a 7704a from a surplus store. I inserted a 7a26 and a
7b80 and found that the vertical was deflected way off the top, only
visisble when beam finded was on. Fortunately I had a reasonably good
working 7704a. The nice thing about the 7704a is that the "head" is
removable. So I did a head swap. On the new 7704a the problem
remained and the old 7704a still worked with the new display section.
So without the manual I thought what could go wrong? I pulled the
readout board to no effect. Then I look at other 7xxx family manuals
for inspiration.
Then I swaped the pair of delay line driving transistors and BINGO! :)
Now the vertical deflection is operating good. Then I looked up Stan
and Bill reference site and found that 151-0269-00 = FMT1061 .

Then I looked at my ECG semiconductor replacement guide, no matches.
Then googled FMT1061. No matches.

The question I have is what are the characteristics of the
151-0269-00 ?


Thanks


SC504

regman10
 

I just got an SC504 and it's blowing the .3A fuse. Presumably this goes to
the HV circuit as the vertical attenuator, trigger (based on perfromancs of
the trigger and power indicator LED) and calibrator work just fine. I have
no way to test the horizontal amp. I have a bad feeling about the HV
supply. I found a calibration procedure and parts list on Logsa, but no
service manual. Does anyone have a schematic of the HV supply?

178681 - 178700 of 186252