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Hi folks

Trawling around the web I came across a company that sells GaAs diode
bridges, and Schottky diode bridges "for sampling applications". The url's
are and
.

I haven't contacted them, and I have no idea of prices. But if anyone has a
sampler with a dead front end, this may be one possibility for fixing it.

Craig

Hi Miroslav,

Thanks for the message

--- In TekScopes@y..., Miroslav Pokorni <mpokorni2000@y...> wrote:

That was quite a thing that you found, really something to be proud

of.

I am curious what was voltage drop across each of these two 130 Ohm

resistors.

If those two resistors were really overloaded, then circuitry

graduates from complex to a kluge. Please, let me know what was
voltage drop.

It was no kludge, just a faulty batch of 130 ohm resistors I suspect.
They are in series from the 11 volt supply to ground so each had 5.5
volts across them. That's less than 0.25 watts.

Morris

Hi Gang,

The 282 is an adapter that allows use of conventional X1 and X10 probes on a
sampling unit such as the 1S1, 3S1, 4S1, 4S2A and others. There is a good
picture and explanation of it on page 319 of the 1969 Tek Catalog. This item
requires power which is obtained from a connector on the front of the above
sampling units. The risetime (and bandwidth) of the a system using the 282
will be limited primarily by the probe you use with it. For example, a P6008
(X10, 10 meg Ohm input R) will have a risetime of 4 ns and P6011 (X1, 1 meg
Ohm input R) will have a risetime of 12 ns. New cost of a 282 in 1969 was
$95.

Stan
w7ni@...

Craig Sawyers wrote:

Hello Craig,
this thing is to connect a conventional high impedance probe to a 50 Ohm
input.
Sampling plug ins usually have 50 Ohm input impedance to match the RF. The
282
has a high impedance input to connect a normal probe and a 50 Ohm
GR output
to
match to 50 Ohm inputs of e.g sampling plug ins. It's an amplifier inside
and it needs
a DC power supply.
I mail you a scan out ot the 1968 Tek catalog to your e-mail adress

Thanks, Leo! A scan would be very welcome - thanks.

Cheers

Craig

Hello Craig,
this thing is to connect a conventional high impedance probe to a 50 Ohm
input.
Sampling plug ins usually have 50 Ohm input impedance to match the RF. The
282
has a high impedance input to connect a normal probe and a 50 Ohm GR output
to
match to 50 Ohm inputs of e.g sampling plug ins. It's an amplifier inside
and it needs
a DC power supply.
I mail you a scan out ot the 1968 Tek catalog to your e-mail adress
Leo
-----Ursprüngliche Nachricht-----
Von: Craig Sawyers [mailto:c.sawyers@...]
Gesendet: Freitag, 28. Dezember 2001 13:19
An: TekScopes@...
Betreff: [TekScopes] Odd item on eBay


Hi gang

Just seen a "Tektronix model 282 probe adaptor" on eBay. Anyone any
suggestion what this thing is? It is item number 1683252239.

Thanks

Craig


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Hello Morris,

That was quite a thing that you found, really something to be proud of.

I am curious what was voltage drop across each of these two 130 Ohm resistors. I have seen a number of resistors in Tek instruments that were discolored from overheating, because they were undersized. In an 1A1, the resistors would be probably carbon composition, a tough beast to kill, but they do not show discoloration either, so you would not have a visual indication that there is something wrong.

If those two resistors were really overloaded, then circuitry graduates from complex to a kluge. Please, let me know what was voltage drop.

Regards

Miroslav Pokorni

morriso2002 <morriso2002@...> wrote: Hi all,

Here's a tale of a diabolical fault I recently encountered in a piece
of classic Tek equipment. The experienced Tek people here might
say "I knew about that" but it was a great achievement for me!

The patient was my youngest 1A1 plugin, with FET inputs and lever
input switches. The symptoms - low gain on both channels on switching
on, with further gradual drop in gain as the unit warmed up over 5-10
minutes. DC balance was preserved.

For those of you not familiar with the 1A1 (what are you doing here?)
it's a standard 2 channel vertical amplifier for the 530 to 550
series. Early models had nuvistor inputs and later models have FET
inputs. Each channel has an amplifier board with the transistor
amplifiers following the input stage and there is a common output
card with the chop/alt/add circuitry and a hybrid cascode output
using nuvistors for the final grounded grid stages. Amplification is
differential throughout.

Since the fault was common to both channels I initially thought it
was in the output card and spent a lot of time swapping my small
stock of nuvistors and probing around, all to no avail. The clue to
the solution came when I substituted boards from a known good 1A1. I
found that swapping the channel 2 board cured the problem. Further
measurements with the original card showed that the 11 volt supply
was high at 12.25 volts. Because the fault seemed temperature
sensitive I tried using freeze spray and found that cooling
transistors Q253A&B (a pair of 2N3563s) temporarily restored
performance on channel 2. The base bias for these 2 was derived from
the +11 volt rail and was too high, causing excess collector current.

Where does the +11 volts come from? Tek designs of this era were
notorious for clever and tricky use of the power supplies. Plugins
are provided with the standard scope supplies at the connector and
one pin has to sink 150 mA at 75 volts. This is derived from the +100
volt supply in the scope dropped through a couple of 12.6 volt tube
heaters. In different plugins it is used for a series heater string
and miscellaneous DC supplies. My 1A1 has 2 tubes and this accounts
for 12.6 volts of the 75. The rest is dropped through a string of
resistors and provides +39, +11 and +5 volt rails. The 11 volt rail
supplies grid bias for the output tubes and is also the collector
supply for the transistors feeding Q253A&B from where it affects the
bias on all the following amplifiers.

Tracing through the divider, I found R496 and R497, both 130 ohms 5%
half watt and in series, had drifted high. Not by much, they were 140
and 147 ohms when cold but this was enough to increase the bias which
caused thermal runaway of Q253A&B. I checked this by temporarily
shunting them with 2.7K which I calculated would reduce the total
resistance to the proper value - this fixed the problem instantly! I
replaced them permanently with 1% half watt metal film resistors, the
11 volt supply is now at 11.4 volts and the plugin works perfectly.

Why did swapping the Ch 2 card cure the problem? The two resistors
are each on one of the input cards. Swapping one card reduced the
total resistance just enough to stop the problem and point me to what
was going on. Why was DC balance preserved? Because the fault was
common mode, and fortunately didn't upset the operating conditions of
the output tubes.

What a sneaky fault! Who would have imagined a problem in the output
tube heater supply would cause thermal runaway of a couple of pairs
of transistors a few stages back which would in turn upset
differential gain but not DC balance? It shows how carefully you have
to understand how this complex circuitry works. It also shows how
interlinked all the various parts of the circuit are - there's no
such thing as an isolated stage for troubleshooting purposes.

Since I was using a 556 (850 watts consumption) for simultaneously
supplying the 1A1 and troubleshooting it, it was a hot experience so
a cold beer was very welcome afterwards!!

Cheers,

Morris


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Hi gang

Just seen a "Tektronix model 282 probe adaptor" on eBay. Anyone any
suggestion what this thing is? It is item number 1683252239.

Thanks

Craig

Hi,

that story reminds me a bit about onother story were 2 identical parts in
separate circuits
failed at the same time in the same way. In my collection I have also a
Philips PM3230, a real
dual beam scope with tubes. After the scope hasn't been used for a while, I
wasn't able to
turn the brighness down. And that was the case for both beams. I spent hours
in
measuring in the HV supply circuits common for both electron guns, but
everything was OK.
Then I started looking at the voltages of one individual gun. What I found:
The Z-Axis modulation is done via the grid. A capacitor is connected between
the grid and
the Z-Axis input on the back. On the Z-Axis connector side of the capacitor
a 1 MOhm resistor
is shunted to GND. That's a common construction used in many scopes. When I
removed
the cap, the brightness control worked for that particular channel. I
measured across the
cap and found it had a resistance of several 100 Kohms. And that was exactly
also the case
in the 2nd channel. Both parts failed at the same time in the same way. The
leaking cap in series
with the 1MOhm resisitor was pulling up the grid voltage towards GND and was
overriding the
intensity control

Leo




-----Ursprüngliche Nachricht-----
Von: morriso2002 [mailto:morriso2002@...]
Gesendet: Donnerstag, 27. Dezember 2001 23:56
An: TekScopes@...
Betreff: [TekScopes] Fun with the 1A1


Hi all,

Here's a tale of a diabolical fault I recently encountered in a piece
of classic Tek equipment. The experienced Tek people here might
say "I knew about that" but it was a great achievement for me!

The patient was my youngest 1A1 plugin, with FET inputs and lever
input switches. The symptoms - low gain on both channels on switching
on, with further gradual drop in gain as the unit warmed up over 5-10
minutes. DC balance was preserved.

For those of you not familiar with the 1A1 (what are you doing here?)
it's a standard 2 channel vertical amplifier for the 530 to 550
series. Early models had nuvistor inputs and later models have FET
inputs. Each channel has an amplifier board with the transistor
amplifiers following the input stage and there is a common output
card with the chop/alt/add circuitry and a hybrid cascode output
using nuvistors for the final grounded grid stages. Amplification is
differential throughout.

Since the fault was common to both channels I initially thought it
was in the output card and spent a lot of time swapping my small
stock of nuvistors and probing around, all to no avail. The clue to
the solution came when I substituted boards from a known good 1A1. I
found that swapping the channel 2 board cured the problem. Further
measurements with the original card showed that the 11 volt supply
was high at 12.25 volts. Because the fault seemed temperature
sensitive I tried using freeze spray and found that cooling
transistors Q253A&B (a pair of 2N3563s) temporarily restored
performance on channel 2. The base bias for these 2 was derived from
the +11 volt rail and was too high, causing excess collector current.

Where does the +11 volts come from? Tek designs of this era were
notorious for clever and tricky use of the power supplies. Plugins
are provided with the standard scope supplies at the connector and
one pin has to sink 150 mA at 75 volts. This is derived from the +100
volt supply in the scope dropped through a couple of 12.6 volt tube
heaters. In different plugins it is used for a series heater string
and miscellaneous DC supplies. My 1A1 has 2 tubes and this accounts
for 12.6 volts of the 75. The rest is dropped through a string of
resistors and provides +39, +11 and +5 volt rails. The 11 volt rail
supplies grid bias for the output tubes and is also the collector
supply for the transistors feeding Q253A&B from where it affects the
bias on all the following amplifiers.

Tracing through the divider, I found R496 and R497, both 130 ohms 5%
half watt and in series, had drifted high. Not by much, they were 140
and 147 ohms when cold but this was enough to increase the bias which
caused thermal runaway of Q253A&B. I checked this by temporarily
shunting them with 2.7K which I calculated would reduce the total
resistance to the proper value - this fixed the problem instantly! I
replaced them permanently with 1% half watt metal film resistors, the
11 volt supply is now at 11.4 volts and the plugin works perfectly.

Why did swapping the Ch 2 card cure the problem? The two resistors
are each on one of the input cards. Swapping one card reduced the
total resistance just enough to stop the problem and point me to what
was going on. Why was DC balance preserved? Because the fault was
common mode, and fortunately didn't upset the operating conditions of
the output tubes.

What a sneaky fault! Who would have imagined a problem in the output
tube heater supply would cause thermal runaway of a couple of pairs
of transistors a few stages back which would in turn upset
differential gain but not DC balance? It shows how carefully you have
to understand how this complex circuitry works. It also shows how
interlinked all the various parts of the circuit are - there's no
such thing as an isolated stage for troubleshooting purposes.

Since I was using a 556 (850 watts consumption) for simultaneously
supplying the 1A1 and troubleshooting it, it was a hot experience so
a cold beer was very welcome afterwards!!

Cheers,

Morris


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That's a new one on me, Morris. Congratulations and thanks for sharing that
info.

Stan
w7ni@...

morriso2002 wrote:

I'll "second" that Jim. That one is worth printing (already done).

Nice work Morris and thanks for the details and explanation. I learned a lot from that post.

Phil

Morris

That's a keeper.

Jim Nunn

jimnunn0000@...

Hi all,

Here's a tale of a diabolical fault I recently encountered in a piece
of classic Tek equipment. The experienced Tek people here might
say "I knew about that" but it was a great achievement for me!

The patient was my youngest 1A1 plugin, with FET inputs and lever
input switches. The symptoms - low gain on both channels on switching
on, with further gradual drop in gain as the unit warmed up over 5-10
minutes. DC balance was preserved.

For those of you not familiar with the 1A1 (what are you doing here?)
it's a standard 2 channel vertical amplifier for the 530 to 550
series. Early models had nuvistor inputs and later models have FET
inputs. Each channel has an amplifier board with the transistor
amplifiers following the input stage and there is a common output
card with the chop/alt/add circuitry and a hybrid cascode output
using nuvistors for the final grounded grid stages. Amplification is
differential throughout.

Since the fault was common to both channels I initially thought it
was in the output card and spent a lot of time swapping my small
stock of nuvistors and probing around, all to no avail. The clue to
the solution came when I substituted boards from a known good 1A1. I
found that swapping the channel 2 board cured the problem. Further
measurements with the original card showed that the 11 volt supply
was high at 12.25 volts. Because the fault seemed temperature
sensitive I tried using freeze spray and found that cooling
transistors Q253A&B (a pair of 2N3563s) temporarily restored
performance on channel 2. The base bias for these 2 was derived from
the +11 volt rail and was too high, causing excess collector current.

Where does the +11 volts come from? Tek designs of this era were
notorious for clever and tricky use of the power supplies. Plugins
are provided with the standard scope supplies at the connector and
one pin has to sink 150 mA at 75 volts. This is derived from the +100
volt supply in the scope dropped through a couple of 12.6 volt tube
heaters. In different plugins it is used for a series heater string
and miscellaneous DC supplies. My 1A1 has 2 tubes and this accounts
for 12.6 volts of the 75. The rest is dropped through a string of
resistors and provides +39, +11 and +5 volt rails. The 11 volt rail
supplies grid bias for the output tubes and is also the collector
supply for the transistors feeding Q253A&B from where it affects the
bias on all the following amplifiers.

Tracing through the divider, I found R496 and R497, both 130 ohms 5%
half watt and in series, had drifted high. Not by much, they were 140
and 147 ohms when cold but this was enough to increase the bias which
caused thermal runaway of Q253A&B. I checked this by temporarily
shunting them with 2.7K which I calculated would reduce the total
resistance to the proper value - this fixed the problem instantly! I
replaced them permanently with 1% half watt metal film resistors, the
11 volt supply is now at 11.4 volts and the plugin works perfectly.

Why did swapping the Ch 2 card cure the problem? The two resistors
are each on one of the input cards. Swapping one card reduced the
total resistance just enough to stop the problem and point me to what
was going on. Why was DC balance preserved? Because the fault was
common mode, and fortunately didn't upset the operating conditions of
the output tubes.

What a sneaky fault! Who would have imagined a problem in the output
tube heater supply would cause thermal runaway of a couple of pairs
of transistors a few stages back which would in turn upset
differential gain but not DC balance? It shows how carefully you have
to understand how this complex circuitry works. It also shows how
interlinked all the various parts of the circuit are - there's no
such thing as an isolated stage for troubleshooting purposes.

Since I was using a 556 (850 watts consumption) for simultaneously
supplying the 1A1 and troubleshooting it, it was a hot experience so
a cold beer was very welcome afterwards!!

Cheers,

Morris

X10 Overlay: Help file

XTPRO .X20 Overlay: Help file

XTPRO .X30 Overlay: Help file

XTPRO .X40 Overlay: Help file

XTPRO .X50 Overlay: Help file







**** CUSTOMIZATION ****





XTreePro has several operational features that you can

customize according to your own preference. There are three

methods for customization:



1. Run XTPROCFG, the XTreePro configuration program. With

XTPROCFG you use menus to modify and save configuration options

and change the video attributes for XTreePro's displays.

Joseph,
I ordered my copy of book, though I did not get it yet, through some organization of used book retailers at: . I think they are B.C. based, your back yard. There was quite selection offered and variety of prices, too.
Regards
Miroslav

Stan or Patricia Griffiths <w7ni@...> wrote: Hello Joseph,

I don't have anymore copies of the Tek First 40 Years book available for sale at
this time. I find them around here in estate sales occasionally and put them
on eBay when I get spares. Keep searching eBay and you will probably find one.

Stan
w7ni@...

Joseph Orgnero wrote:

Hello stan,
If you still have a copy of the Tek anniversary book available, I would like
to order one. Let me know the cost of surface mailing to Canada.
Thanks

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Why such concern about accuracy? Even the crappiest crystal osc
or frequency counter will be 100 times more accurate than the best
possible with a scope!

Yeah, I know - you can only pull a crystal oscillator a tiny amount using
the parallel tuning capacitor. I just have this thing about getting things
adjusted accurately, and at least this gets me a bang-on accurate counter to
boot *very* easily.

Craig

Why such concern about accuracy? Even the crappiest crystal osc or frequency counter will be 100 times more accurate than the best possible with a scope!

I need a fixer-upper board for a Tek 2246. Bellieve money is not the
main issue. Many Thanks.
Paulo

Hello Craig,
If you can measure the colour oscillator frequency of a
colour TV while receiving a transmission it will be 4433618.75 Hz., use that to
check the frequency meter. The standard used to be +/- 5 Hz. but if you check
with the BBC I think they use an atomic standatd now and is extremely accurate
(even 5 Hz. is only 1 part per million).
In the US the frequency is 3.579545 MHz.
A very Merry Christmas and Happy New Year to all. I hope there's (another)
Tektronix in your future.
Cheers, Don Black.

Craig Sawyers wrote:

Hi list

One of the problems with living in the UK is that we are in the wilderness
for Tek gear. You only have to look at eBay UK and US and compare the two
to get the drift!

Faced with not being able to get a hold of a time mark generator on my side
of the pond (and since shipping costs for bulky gear from the US are
prohibitive), I tried to think of a way of generating accurate time marks so
I could calibrate my 545A and 7603/7B53A.

Now I have a counter/timer (HP 5328A - cost me all of ???22UK), whose
calibration accuracy is unknown, and I also have a signal generator whose
calibration is unknown. However, if the 5328A's calibration was on the
button, I would have a traceable method of generating time marks up to at
least 100MHz (<10ns spacing).

So what I have done is build a simple tuned RF receiver, made from a high-Q
honeycomb coil (built according to
). This measured 350uH on my
bridge. I then resonated it at 60kHz with two 10nF capacitors in parallel
and connected it in differential mode to my 7A22.

Why 60kHz? Well there is a time code transmission in the UK on 60kHz,
traceable to the NPL (equivalent to the NBS in the US) to an accuracy of 1
part in 10^11 (or 10 cycles at 60kHz per year). Much to my delight, the
signal from such a rudimentary arrangement was 500uV, just using the coil as
the antenna (and with the hf and lf filters on the 7A22 set correctly for
the frequency to reduce noise).

An alternative, not yet tried, is to use the Radio 4 long-wave transmission
at 180kHz (UK of course). This is Caesium clock referenced at 180kHz, and
is again set to an accuracy of better than 1 part in 10^11. Quite something
for a broadcast radio station!

I now need an easy op-amp based high-Q filter tuned to 60kHz (over the
holiday break) to reduce noise and boost the signal by a factor of 100 or
so. Then I have an absolute method of checking the calibration of my timer.
Now by tuning my signal generator to a particular frequency as registered by
the now-calibrated timer, I can generate time marks of any period for
calibrating my 'scopes!

I'll let you know how I get on....

Craig

The reason I am ignorant of the "inductance standardizer" is that
I have never
wanted to calibrate an S-30. I have just used them as they were
and trusted
that the 300 uH position on the switch was still OK. So far, so
good . . .

Hi Stan

If for some reason the 300uH has been tinkered with, I guess the other way
to do this *without* using the standardizer (which requires a 130LC in
*known* calibration) is to deliberately resonate the inductor in the S-30
with a value of capacitor large enough to swamp strays in the wiring and
winding capacitance in the inductor - say 10nF. That should resonate at
92kHz with a 300uH coil (even if the coil has a resistance of 1 ohm, the Q
will still be 27). So equipped with a signal generator, and ideally a
counter/timer to verify the frequency if should be possible to set the coil
absolutely without relying on transferring its value from another 130LC.

Craig