Date   
Re: Pot core disassembly and other topics like the 7704A

Merchison Burke
 

What about the pizza, is it ready yet?

I can bring over my "bake and salt-fish" and we can have a party.

On 2017-Jun-30 2:32 AM, edbreya@... [TekScopes] wrote:
Partial success so far. There were two different types cooking in this batch - two of one kind and about ten of another. The two came apart OK at about 140 deg C, while the others are still holding strong at 165, but at least showing some sign of goop deterioration. It's now set to about 175, and hopefully these holdouts will finally let go soon. It's them or me now, to see who craps out before it gets too late to keep going.

Ed




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Re: 475 Grid Bias problem

 

I picked up a HV probe to verify the -2450v and found that it's really -2218v versus the -2440v that my ancient Triplett meter read. Since it's so far out of spec I'm looking at the HV regulation logic to see why it's so much more positive (232v too positive).
-2218 volts is definitely low assuming that your high voltage probe
measurement is accurate (see the other posts about probe accuracy)
however because of the way the DC restorer works, the absolute cathode
voltage is not critical for proper functioning of the intensity. The
cathode voltage is closely regulated because it has a direct effect on
the horizontal and vertical deflection accuracy.

The sense and control resistors (4 of them, 2 for regulation and 2 for focus) are a thick film ceramic assembly so they aren't as easily checked while in-circuit. Since the regulator seems to be running fine (waveforms look symmetric and oscillator frequency appears okay) I suspect that either the resistor R1303B on the base of Q1306 has changed to too high in value or the sense resistor R1303A has changed to too low in value.
The thick film resistor network is usually pretty reliable unless
physically damaged.

If there were a leaky filter cap on the HV output then I think the regulator would compensate for it until it became excessive so I'm focusing on the regulator side. I'm trying to do minimal damage while troubleshooting so I'll try to electrically disconnect one end
of the thick film assembly to see if I can get an accurate reading on the resistors connected to the base of Q1306.
That is definitely the case; if the regulator's control loop is
working correctly, then it will regulate the output until leakage
becomes excessive and at that point, fuse F1318 will likely blow. The
base voltage of Q1308 indicates how hard the control loop is driving
the oscillator. It should be about +4.4 volts and if it is
significantly lower, then the regulator is driving the oscillator too
hard.

On the low voltage side, take a really close look C1302 and the C1304;
leakage there will directly affect the regulation. Make sure that the
voltage across C1304 is about 50.6 volts.

Also check C1318 which decouples the high current supply to the high
voltage oscillator. If it is worn out, then the oscillator power will
be limited.

Also, the schematic for the 475A more closely represents this 475 scope for this HV area but the component designations and placement are different so I'm working off both as I troubleshoot.
The high voltage schematics that I have for the 475 and 475A look
practically identical.

Re: 475 Grid Bias problem

 

When I picked up a high voltage probe to make cathode voltage
measurements, I first used the highest stable DC voltage that I could
measure normally using my multimeter and then measured it both with my
multimeter and the probe to confirm the probe's accuracy. As it ended
up, the probe was accurate however I had exactly the problem Dave
describes when I used my best bench multimeter because on its lower
voltage ranges, its input resistance was infinite instead of 10
megohms.

Also be careful about some lower quality multimeters which have a 9M
or 11M input resistance on some ranges.

On Wed, 28 Jun 2017 23:19:18 +0100, you wrote:

Don't be too sure that your HV probe and meter together are telling you the
truth. It very much depends on the HV probe, the meter to which it's
connected, and exactly how they are connected.

Most HV probes these days work on the assumption that the meter to which
they are connected has in input impedance of 10M-Ohm, and that you have them
connected precisely as described in the instructions.

If it doesn't then all sorts of strange results may be encountered. The
usual problem is using "good meters" on a low range which have a very high
(G-Ohms) input impedance which results in a high reading, but I've also seen
cases where you get a low reading (I think this was when the earthy end
connections were made incorrectly).

Dave

Re: Pot core disassembly and other topics like the 7704A

Ed Breya
 

Partial success so far. There were two different types cooking in this batch - two of one kind and about ten of another. The two came apart OK at about 140 deg C, while the others are still holding strong at 165, but at least showing some sign of goop deterioration. It's now set to about 175, and hopefully these holdouts will finally let go soon. It's them or me now, to see who craps out before it gets too late to keep going.

Ed

Re: Pot core disassembly and other topics like the 7704A

Ed Breya
 

I'm cooking some transformers tonight in my good old Blue-M lab oven that I haven't used in over twenty years. After nearly an hour at 125 deg C setpoint, no result - the goop on the core side joints isn't showing any sign of giving it up (not even soft). I cranked it up to about 140, and will see what happens after a while. I don't know how accurate the oven is, but it's definitely getting hot - I'll up it a little at a time if this new setting doesn't do it. I guess I could cook up a frozen pizza at least. Will report tomorrow on whether it's a success or a meltdown - the transformers, I mean.

Ed

Re: DM501A Can't find main board serial number

Rick
 

Dave, do you DM501A's have that same square wave on the +12v side of the R1405? Not to put you to work but if they're still on the bench that would be great to know.

Rick

Re: DM501A Can't find main board serial number

Rick
 

Because the display was stable showing -.0064 I was able to check the BCD for each digit. On my scope it showed D1 was 0040 and D2 was 0240. D3 & D4 were 0000. That all decodes to 0064. The sign symbol is receiving +2.5v. I think the display is valid.

So I went back to the diagnostic tree in the manual and went in the direction of verifying that relay K1408 was open and then checking R1511, R1408 and trimmer R1405. R1408 was good. R1511 is supposed to be 5% 2.7ohm . It was 25% off so replaced it. That didn't help zeroing out the display. No change.

The R1405 trimmer does trim full scale +12v to - 12v but the meter was not very stable towards +12v. The power supply procedures have you check only the -12v side which was fine but not the +12v. I decided to use the scope and while it is +12v it has a very clean 2vpp square wave on it. I wasn't expecting to see that. R1405 trims between +12v and -12v. So the square wave is bleeding onto the wiper. The square wave almost disappears when getting to the far -12v side.

I need to understand where the square wave is coming from. I suppose it could be coming from the wiper but then I would think it would bleed onto the -12v side and it doesn't. It only shows on the +12v side. The next thing to check in diag. tree is U1601, the analog section of A/D Converter. Among other branches, the trimmer is connected to the Hi-Q GND pin 2 on U1601. I don't really know how that works. I wish I knew what the hell I was doing!

Re: On-topic: HP 1743A portable oscilloscope having unique feature?

 

With the HP 1743A set in "B-runs-after delay" mode, both markers / cursors are
placed by hand (delay knobs), each by a small amount before subsequent rising edges
of a 1 KHz (exact) square wave. Let's say that the interval shows "0.837 ms" on the
numeric display.
>>
Exactly, just like any other delta delay timebase.
I was trying to give exact instructions on how to set the HP 1743A for this demo. I was hoping that was clear but I could have written it better. Sorry, Dutch, not native English.

I just tried a 2236 and a 2247A. Both indeed behave like the HP 1743A.
The 2236 was produced from 1984, the 2247A from 1989, according to TekWiki.
The HP 1743A was produced from 1977 / '78, preceding both Teks by at least 6 years.


Raymond

Re: On-topic: HP 1743A portable oscilloscope having unique feature?

 

On 29 Jun 2017 19:16:19 +0000, you wrote:

I am not sure what you mean here. All of the oscilloscopes which
support delayed sweep and delta delayed sweep graphically show what
measurement is being made.
I think that I still haven't been able to explain what I think is unique for a 'scope of its era and very useful.
I'll try and explain. I'll refer to the start of each B-sweep as the marker or cursor:

With the HP 1743A set in "B-runs-after delay" mode, both markers / cursors are placed by hand (delay knobs), each by a small amount before subsequent rising edges of a 1 KHz (exact) square wave. Let's say that the interval shows "0.837 ms" on the numeric display.
Exactly, just like any other delta delay timebase.

Now, when I switch to "B triggerable after delay" (on rising edge), not only do the cursors jump to the first rising edges of the waveform after their respective delay, but also the interval display now shows "1.000 ms". If I increase the Stop delay setting beyond the next falling edge, the Stop cursor jumps to the rising edge of the next period and the numeric display shows "2.000 ms". Furthermore, if I slightly change the signal period (depending on both delay settings) and I vary the input frequency, the cursors follow and *so does the numeric display value*.
Obviously, the standard 7000 time bases don't do that, not even the delta time setups, nor do the 2236, 2247A and others, to the best of my knowledge.
Right, the 7000's 7B85 and 7B15 timebases and the DM43 and DM44
measure the delay time and delta delay time using the voltage levels
of the sweep so trigger after delay has no effect on the delay time
measurement; only the b-sweep start points are measured. Tektronix
indicates this by placing a ">" symbol in front of the delay or delta
delay time on the readout to reflect that the actual delay is greater
than shown.

The 2236 and 2247A however measure the delta delay time using the
timer/counter and do exactly what you describe when set to trigger
after the delay because the timer/counter looks at the a-gate and
b-gate signals just like the HP 1743A; when set to trigger after
delay, they measure the time difference between the triggered edges.
The 2236 documentation distinguishes these two modes as nontriggered
measurement and triggered measurement on page 4-8 of its operating
manual. The 2247A documentation is obtuse.

Re: On-topic: HP 1743A portable oscilloscope having unique feature?

 

In theory two separate b-gate signals could have been generated during one sweep


Using dual B-sweeps on separate A-sweeps has the advantage of giving more freedom
in the choice of the B-sweeps as a fraction of the A-sweep. With both B-sweeps on one
A-sweep, overlapping B-sweeps (delta-time < B-sweep "speed") would be a bit awkward...
I made this remark because it would be a bit "awkward" to generate two B-sweeps during the same A-sweep using one B-sweep generator if the second B-sweep would have to start before the first would be finished. Obviously, this is not a problem with two B-sweep generators or if the "B-sweeps" would in fact be just cursors or markers. This latter configuration would allow interval measurement but would preclude combining the marker function with real B-sweeps of "arbitrary" length.

Raymond

Re: On-topic: HP 1743A portable oscilloscope having unique feature?

 

Hi Fabio,
I'm glad my description explained it for you. It really is a neat feature, so informative and intuitive in use.
Apparently, your 464 no longer is an adventure but a given! Don't you like its analog storage?

Raymond

Re: New member looking for a Tek 465

Fabio Trevisan
 

Hi Ricardo,
There is a couple of active Brazilian members here, myself and Samuel.
I think it's just fair to give you a reception and some advice on first
hand.

About the 465 on advertise...
At first look, it's not exactly a bargain.
To start with, it has a few cosmetic issues that one can spot right on.
1. The numbers on the CH1 voltage attenuator selector dial, that were
supposed to be painted on the transparent scale, are wiped out or very
faded.
2. Most (if not all) of the push button selectors lost their markings or
they're very faded.
3. It's missing the back-feet (which is rather important because those
scopes are big and very often you want to use it standing on their feet, on
the floor, instead of table-top).
4. It's missing the grid of the back fan exhaust port, which is shown
replaced by a foam pad!!! I'm not sure if whoever did that really knew what
he was doing, because this FAN is actually an EXHAUST fan, so there's no
point in filtering the air coming out of the fan and, besides, it blocks
the airflow to some extent and those fans are not very powerful (unless
they have changed it).

Other from cosmetic, at least the scope seems to be working, it's coming
with a pair of probes! Cheap ones though, not Tektronix probes, but they're
at least 100 reais value, and, deducting from the faded buttons and
modified FAN exhaust port, someone has performed some servicing on it or at
the very least tried to clean it (maybe too much).

The 465s are excellent scopes, (although the 465Bs are better) and they are
relatively easy to repair because they're mostly transistorized (they have
very few proprietary Tektronix Integrated circuits, which is good, because
they're not that easy to find).

I would ask the seller to post a video of the scope, showing it changing
vertical sensitivity (on both channels), and changing horizontal sweep
speeds, and increasing the CRT intensity (on the fastest sweep speeds), to
see if the CRT is in good shape or is worned out.

Anyway, you must consider that those scopes are - at least - 30 years old,
and there is a lot of things that can be worn-out. To start with, the big
electrolytic capacitors of the low voltage power supplies, if they haven't
been replaced yet, they're very likely to fail soon enough.

All in all, at that price or even a little bit cheaper, there's at least a
couple of other Tek scopes of the same family and age selling at
MercadoLivre. Some of which are selling for almost a year, so the seller
may feel tempted to accept an offer.

I bought mine about 1 year ago, also from ML, for about half of that
price... and to Brazilian standards, THAT was a bargain!... but I have
already spent about the same amount in parts, to put it fully in shape. I
must say that I`m almost there!

Welcome to the Tek lovers place!

Rgrds,

Fabio



2017-06-29 17:31 GMT-03:00 ric_rock@... [TekScopes] <
TekScopes@...>:



Hi!


My name is Ricardo, I am from Brasil (or Brazil) and I am looking for a
Tektronix 465 scope.


So I started to find informations about this model (by google) and I found
a post somewhere in internet that said this is the best place about
Tektronix scopes.


So here I am, and apreciate to get some infos about Tektronix 465 (what I
need to know to buy with confidence).


I am looking for this add:
http://produto.mercadolivre.com.br/MLB-882374651-
osciloscopio-tektronix-465-de-100-mhz-n-hp-minipa-heathkit-_JM
http://produto.mercadolivre.com.br/MLB-882374651-
osciloscopio-tektronix-465-de-100-mhz-n-hp-minipa-heathkit-_JM




I don´t know if it is in a good shape. The value is aprox. 300 US$.


There are some pictures in the link above.


I am looking for a scope to build (and repair) some áudio amplifiers (to
be honest, to buy some chinese kits).




Thanks for helping, and excuse my poor english.
Ricardo




Re: On-topic: HP 1743A portable oscilloscope having unique feature?

Fabio Trevisan
 

Hi Raymond,
I understood what you mean!
Having myself a Tek 464 with DM44 option, when I first learned what it was
capable of doing, I was amazed, most especially because it's all analog and
it didn't need to add pretty much anything to the already existing scope's
A& B sweep circuitry. Essentially, it's only an additional multi-turn DTP
pot alternatively engaged by a flip-flop, and the voltmeter being able to
measure the voltage difference between the 2 pots' wipers... So simple and
ingenious!.
But indeed, it relies fully on both DTP's wiper voltages and, although we
can change the scope from "B SWEEP STARTS AFTER DELAY" to a NORM, or CH1 or
CH2 or any EXT post-delay B trigger event, and thus have the delta-time
alternated B Sweeps post-triggered, and see the intensified portions jump
to immediate post trigger edges, at both different times, the delta-time
reading on the voltmeter will still reflect only the position of both DTPs'
postions, irrespective of the actual time when the B-sweep was triggered.
To make the same happen on the DM44 (still in the analog realm), perhaps
one could sample-and-hold the actual A sweep's ramp voltage, by the time of
the alternated B post-trigger events, and have the volt-meter to measure
the difference of voltages between the outputs of the sample-and-holds...
But as I write this, I realize that a sample-and-hold simply just doesn't
hold the voltage forever if you don't convert it to digital! (well... maybe
long-enough with a MOSFET buffer)... Rats... I was already thinking of ways
to implement this little upgrade!.

Upon consideration, it seems that HP was really in the lead in that realm.

Rgrds,

Fabio


2017-06-29 16:16 GMT-03:00 @Raymond [TekScopes] <
TekScopes@...>:



I am not sure what you mean here. All of the oscilloscopes which
support delayed sweep and delta delayed sweep graphically show what
measurement is being made.
I think that I still haven't been able to explain what I think is unique
for a 'scope of its era and very useful.
I'll try and explain. I'll refer to the start of each B-sweep as the
marker or cursor:

With the HP 1743A set in "B-runs-after delay" mode, both markers / cursors
are placed by hand (delay knobs), each by a small amount before subsequent
rising edges of a 1 KHz (exact) square wave. Let's say that the interval
shows "0.837 ms" on the numeric display.
Now, when I switch to "B triggerable after delay" (on rising edge), not
only do the cursors jump to the first rising edges of the waveform after
their respective delay, but also the interval display now shows "1.000 ms".
If I increase the Stop delay setting beyond the next falling edge, the Stop
cursor jumps to the rising edge of the next period and the numeric display
shows "2.000 ms". Furthermore, if I slightly change the signal period
(depending on both delay settings) and I vary the input frequency, the
cursors follow and *so does the numeric display value*.
Obviously, the standard 7000 time bases don't do that, not even the delta
time setups, nor do the 2236, 2247A and others, to the best of my
knowledge.
Mind you, I'm not saying I couldn't do the measurements that I'm doing
here with other 'scopes, just not in this way and not with a display like
this. Its simplicity and non-ambiguity immediately struck me once I saw it
first.

Raymond

[Non-text portions of this message have been removed]



[Non-text portions of this message have been removed]

New member looking for a Tek 465

Ricardo
 

Hi!


My name is Ricardo, I am from Brasil (or Brazil) and I am looking for a Tektronix 465 scope.


So I started to find informations about this model (by google) and I found a post somewhere in internet that said this is the best place about Tektronix scopes.


So here I am, and apreciate to get some infos about Tektronix 465 (what I need to know to buy with confidence).


I am looking for this add:
http://produto.mercadolivre.com.br/MLB-882374651-osciloscopio-tektronix-465-de-100-mhz-n-hp-minipa-heathkit-_JM http://produto.mercadolivre.com.br/MLB-882374651-osciloscopio-tektronix-465-de-100-mhz-n-hp-minipa-heathkit-_JM




I don´t know if it is in a good shape. The value is aprox. 300 US$.


There are some pictures in the link above.


I am looking for a scope to build (and repair) some áudio amplifiers (to be honest, to buy some chinese kits).




Thanks for helping, and excuse my poor english.
Ricardo

Re: On-topic: HP 1743A portable oscilloscope having unique feature?

 

I am not sure what you mean here. All of the oscilloscopes which
> support delayed sweep and delta delayed sweep graphically show what
> measurement is being made.
I think that I still haven't been able to explain what I think is unique for a 'scope of its era and very useful.
I'll try and explain. I'll refer to the start of each B-sweep as the marker or cursor:

With the HP 1743A set in "B-runs-after delay" mode, both markers / cursors are placed by hand (delay knobs), each by a small amount before subsequent rising edges of a 1 KHz (exact) square wave. Let's say that the interval shows "0.837 ms" on the numeric display.
Now, when I switch to "B triggerable after delay" (on rising edge), not only do the cursors jump to the first rising edges of the waveform after their respective delay, but also the interval display now shows "1.000 ms". If I increase the Stop delay setting beyond the next falling edge, the Stop cursor jumps to the rising edge of the next period and the numeric display shows "2.000 ms". Furthermore, if I slightly change the signal period (depending on both delay settings) and I vary the input frequency, the cursors follow and *so does the numeric display value*.
Obviously, the standard 7000 time bases don't do that, not even the delta time setups, nor do the 2236, 2247A and others, to the best of my knowledge.
Mind you, I'm not saying I couldn't do the measurements that I'm doing here with other 'scopes, just not in this way and not with a display like this. Its simplicity and non-ambiguity immediately struck me once I saw it first.

Raymond

Re: On-topic: HP 1743A portable oscilloscope having unique feature?

 

The 6R1 makes voltage measurements on the sweep ramp like the HP 1722A
and Tektronix 7B85 do but it lacks the delta delayed sweep capability
they have which increases accuracy. The delta delayed sweep
capability is basically used to make "slide-back" measurements in the
time domain on any part of the waveform and is especially useful to
take advantage of the increased accuracy available from a
timer/counter.

On Thu, 29 Jun 2017 19:53:37 +0200, you wrote:

Hi all,

I don't know if this the exact topic, but a TEK 567 with the 6R1 plugin
and the 3S76 and 3T77 was able to to time interval measurements, even
depending on the amplutude of the trace, not only the sweep position,
and it had picosecond resoluion.

A very versatile plugin, must have been a marvel when it came out in (my
guess) 1961. Awesome, using counters built with discrete transistors and
nixies of course.

Regards, Jochen DH6FAZ

Re: General advice on replacement of old decoupling tantalum capacitors (by new tants or alum. lytics).

Chuck Harris
 

Visually, other than reading the number, that is, the
150D style doesn't have an annular crimp ring around
the "+" end like an aluminum electrolytic has... it has
straight sides. It also has a glass seal, with a ball
where the lead meets the seal.

The 109D style came in two cases. The oldest has the
end with the seal much larger in diameter, and the seal
is usually white teflon. The newer style has an annular
crimp ring around the "+" end, like an aluminum electrolytic.
The newer style often leaks, even while in storage.

-Chuck Harris

David Wise david_wise@... [TekScopes] wrote:

Many of the hermetic-seal dry-slug caps used by HP were Sprague 150D series. You
can find catalog pages online here and there. They also used some 109D wet-slug
caps. Nasty when the seal fails, the acid can dissolve PCB traces. There's one
in every 8552 spectrum analyzer IF module.

Re: On-topic: HP 1743A portable oscilloscope having unique feature?

 

On 29 Jun 2017 17:31:41 +0000, you wrote:

The HP 1743A uses dual B-sweeps, subtracting the counts and averaging them before displaying them numerically. Each counter is started by the A-gate.
Using dual B-sweeps on separate A-sweeps has the advantage of giving more freedom in the choice of the B-sweeps as a fraction of the A-sweep. With both B-sweeps on one A-sweep, overlapping B-sweeps (delta-time < B-sweep "speed") would be a bit awkward...
The automatic measurement does not care about overlapping since it is
the starting edge of the a-sweep and b-sweeps which are used and this
is not a concern when the b-sweeps are being displayed which is what
is done for maximum accuracy. The article I linked shows the later in
figures 3b and 3c and this is what makes delta delayed mode so useful.

Technically, the HP 1743A's solution avoids the need to duplicate several circuits.
Everybody else did it the same way and I think it was simply because
it was so trivial to do like alternate sweep. I was just pointing out
that the time measurement could be made in one sweep with a simpler
timer/counter if the b-sweep trigger circuits were duplicated to
generate two b-sweep gates during one a-sweep.

As I mentioned before, triggering the - intensified - B-sweeps by the Start- and Stop-events results in the delta-time being shown numerically *and* graphically, without having to adjust cursors or markers, within limits. *That* I haven't seen in any 'scope of its era nor in slightly later Teks like the 2236, 2247A a.o.

Raymond
I am not sure what you mean here. All of the oscilloscopes which
support delayed sweep and delta delayed sweep graphically show what
measurement is being made. Their a-sweep shows the intensified
sections and of course they can display both b-sweeps. If you want to
use just the intensified sections to make the measurement you can do
that or you can display the b-sweeps with or without the a-sweep for
increased accuracy.

Oscilloscopes with timer/counters like the 2236 and 2247A are needed
to take advantage of triggers after measurements but these particular
oscilloscopes also support gated measurements which the older HP 1743A
does not.

Cursors replaced delta delayed sweep capability in DSOs and I agree
that in many cases, they are not as good but gated (windowed)
measurements make up for this. Oddly enough, the 2440 series of DSOs
have delta delayed sweep capability.

Re: On-topic: HP 1743A portable oscilloscope having unique feature?

Jokken Feldhaar
 

Hi all,

I don't know if this the exact topic, but a TEK 567 with the 6R1 plugin
and the 3S76 and 3T77 was able to to time interval measurements, even
depending on the amplutude of the trace, not only the sweep position,
and it had picosecond resoluion.

A very versatile plugin, must have been a marvel when it came out in (my
guess) 1961. Awesome, using counters built with discrete transistors and
nixies of course.

Regards, Jochen DH6FAZ


Am 28.06.2017 um 14:54 schrieb @Raymond [TekScopes]:

A few days ago, I acquired two HP 1743A's, both in need of some
repairs. These 'scopes basically are HP 1740A's with a numerical
(B-)delay readout, much like a DM44-equipped 465 or the like at first
view.
After taking care of repairs, I started playing with one of these and
found an interesting and useful consequence of its design that I'm not
aware of in Tek 'scopes from the same or even slightly later period
(1977 - '78), portable or mainframe. Am I mistaken?

These 'scopes allow delta-time measurements using dual markers. They
measure the time between sweep-start and the start of the marker by
counting elapsed time, not by measuring momentary sweep voltage. This
makes the measurement independent of sweep linearity.
The delta-time measurements use highlighting on two independent
alternating B-delayed sweeps.
The most intriguing consequence is the ability to digitally show the
time (3 - 5 digits resolution, floating point format) between e.g.
edges on waveforms without manually moving a cursor; by setting the
"Stop" marker in "triggerable after delay" mode, it follows the Stop
event (within limits) and indicates the time between Start and Stop
marker, even when that time changes. In essence, it's a time interval
counter with 'scope display... Unfortunately, there's only one common
trigger level adjustment for both B-sweeps...

Haven't seen this elsewhere in the period.
Any comments?

Raymond



[Non-text portions of this message have been removed]



[Non-text portions of this message have been removed]

Re: General advice on replacement of old decoupling tantalum capacitors (by new tants or alum. lytics).

Dave Wise
 

Many of the hermetic-seal dry-slug caps used by HP were Sprague 150D series. You can find catalog pages online here and there.
They also used some 109D wet-slug caps. Nasty when the seal fails, the acid can dissolve PCB traces. There's one in every 8552 spectrum analyzer IF module.

Dave Wise
________________________________________
From: TekScopes@... <TekScopes@...> on behalf of Chuck Harris cfharris@... [TekScopes] <TekScopes@...>
Sent: Thursday, June 29, 2017 9:29 AM
To: TekScopes@...
Subject: Re: [TekScopes] General advice on replacement of old decoupling tantalum capacitors (by new tants or alum. lytics).

[snip]

There are some premium, axially leaded, dry slug
capacitors available. They are in a steel case, and
have a glass seal on the "+" end. They always have
a prominent ball where the "+" lead is attached to
the glass seal. They last effectively forever, and
were once used in the space program. HP was quite
fond of them. They range from very small, about
3/32 inch diameter, through 1 inch diameter. Take
out a 2nd mortgage on your house if you want to buy
some new.

-Chuck Harris