Date   

Re: Beware of old AntiStatic foam

Ken, WA2LBI
 

That old foam is awful stuff. I’ve had headphone head bands and ear pads
crumble to dust. I’ve also lost ICs that were pressed into the foam.
Foam-lined storage cases have damaged or destroyed stored items. Old
microphone inserts become dust. There are many other examples...

A few years ago, after many leaking batteries - some still new in the
package, I removed every Duracell battery from every device I own. I’ve
lost a number of flashlights, kid’s toys, remote controls, etc. The worst
is the damage done to my electronic test gear. I switched to Energizer and,
since then, have not had a single device device damaged by battery leakage.

The other item to check is the stick on feet used on so much equipment. As
we know, they turn to a slimy, sticky mess that also gets on the adjacent
surface and is difficult to remove. At the very least, over time, they
“migrate” from their original position and leave a slimy trail.

<rant off>

Ken
WA2LBI


On Sun, Mar 21, 2021 at 12:01 Harvey White <madyn@dragonworks.info> wrote:

As I've mentioned previously, the latest run of Duracell (guaranteed not
to leak before 10 years) does exactly that, and often in the package.

The good news is that they will often give you money to replace the
damaged item if you call them. Their warranty is "repair or replace",
but you do have to call.

I've had the foam in probe cases crumble, (both HP and Tek), anti static
foam corrode and crumble, etc...

Harvey


On 3/21/2021 9:50 AM, David Slipper wrote:
Nasty!! I wonder what other time-bombs are awaiting us!?

I'll certainly be checking my stock of bits and spares.

I always assumed that a famous brand of NiMh batteries were supposed
to be leak proof - Hah! I nearly lost a pair of nice walky-talkies and
a multimeter that way, so now cells get removed from rarely used items
and I make a point of checking torches and the like regularly.

Sadly not surprised at anything these days,
Dave


On 21/03/2021 13:07, - wrote:
Well, this thread just showed up on EEVBlog. This is exactly the
kind of
damage that I used to see happen to IC and to TE accessories that were
stored in the old antistatic foam.

<
https://www.eevblog.com/forum/chat/beware-of-old-antistatic-foam/?topicseen
--
Ken
WA2LBI

Sent from one of my mobile devices


Re: Beware of old AntiStatic foam

Harvey White
 

As I've mentioned previously, the latest run of Duracell (guaranteed not to leak before 10 years) does exactly that, and often in the package.

The good news is that they will often give you money to replace the damaged item if you call them.  Their warranty is "repair or replace", but you do have to call.

I've had the foam in probe cases crumble, (both HP and Tek), anti static foam corrode and crumble, etc...

Harvey

On 3/21/2021 9:50 AM, David Slipper wrote:
Nasty!! I wonder what other time-bombs are awaiting us!?

I'll certainly be checking my stock of bits and spares.

I always assumed that a famous brand of NiMh batteries were supposed to be leak proof - Hah! I nearly lost a pair of nice walky-talkies and a multimeter that way, so now cells get removed from rarely used items and I make a point of checking torches and the like regularly.

Sadly not surprised at anything these days,
Dave


On 21/03/2021 13:07, - wrote:
Well, this thread just showed up on EEVBlog.  This is exactly the kind of
damage that I used to see happen to IC and to TE accessories that were
stored in the old antistatic foam.

<https://www.eevblog.com/forum/chat/beware-of-old-antistatic-foam/?topicseen







Re: More fun with avalanche pulsers

 

Thanks for the tip!
It turns out that paint color is not useful as a guide to the material's specs though. I had expected a color-coding standard but there does not seem to be one. I have found some tables validating my assumption that yellow is low permeability and green is high, although not to be relied on.

Anyhow, I found that using a 33 ohm emitter load instead of 50 for the avalanche transistor (adding another 100 ohm in parallel) minimized the reflection and other distortion of the falling edge, although at the cost of some amplitude. 8 volts is still more than enough into 50 ohms.

Now to figure out the smallest Minibox I can cram it all into. I can't believe how expensive they have become! Price of aluminum, or price of labor? I think I may use a 10-turn pot to adjust the avalanche bias supply rather than an internal trimmer.


Photo Notifications #photo-notice

TekScopes@groups.io Notification <noreply@...>
 

The following photos have been updated in the FG502 doesn't start at some specific settings album of the TekScopes@groups.io group.

By: durechenew@...


The following photos have been updated in the FG502 doesn't start at some specific settings album of the TekScopes@groups.io group.

By: durechenew@...


FG502 doesn't start at some specific settings

durechenew@...
 

The following post was initially in tek500 group; it seems that group is not as active as this one and I thought it may help if it's posted here (I see other posts for 500):

Have an FG502 for while; repaired some issues (if someone interested, I can provide details). For the specific item I have the issue is it doesn't start right away (triangular form generator) on rages 10^2, 10^3, 10^4 with the dial set at 7 and above (to 11); that happens when device is cold. It starts after 40 to 90 seconds (I believe it's about how cold it is). If worm, starts normal. In all other settings starts normal.
Digging around I found that the triangular generator stays in a state where is happy (I can provide all voltages in significant points of the schematic) until it decides to start working. I'm attaching two pictures of a normal start and the delayed one. In the second one (4018-1) note the Ch4 (blue) baseline is at the top of the display screen.
Question: has someone encountered this behavior (and a solution; or suggestions)?

P.S. it may be that the issue is larger (doesn't start rightaway above 10^2 in any condition when very cold); hope someone can suggest something, as I exhausted all (first) thoughts about how to deal with it. Two pictures in album with same name.


Added album FG502 doesn&#39;t start at some specific settings #photo-notice

TekScopes@groups.io Notification <noreply@...>
 

durechenew@... added the album FG502 doesn't start at some specific settings


Re: Beware of old AntiStatic foam

David Slipper
 

Nasty!!  I wonder what other time-bombs are awaiting us!?

I'll certainly be checking my stock of bits and spares.

I always assumed that a famous brand of NiMh batteries were supposed to be leak proof - Hah! I nearly lost a pair of nice walky-talkies and a multimeter that way, so now cells get removed from rarely used items and I make a point of checking torches and the like regularly.

Sadly not surprised at anything these days,
Dave

On 21/03/2021 13:07, - wrote:
Well, this thread just showed up on EEVBlog. This is exactly the kind of
damage that I used to see happen to IC and to TE accessories that were
stored in the old antistatic foam.

<https://www.eevblog.com/forum/chat/beware-of-old-antistatic-foam/?topicseen



Re: OT: MC12080 prescaler chip weirdness

tekscopegroup@...
 

Perhaps this item might be of use, or at least a good guide as there is a schematic posted as well. No relation to listing.

https://www.ebay.com/itm/153648250450


Beware of old AntiStatic foam

-
 

Well, this thread just showed up on EEVBlog. This is exactly the kind of
damage that I used to see happen to IC and to TE accessories that were
stored in the old antistatic foam.

<https://www.eevblog.com/forum/chat/beware-of-old-antistatic-foam/?topicseen


Re: PS 5010 troubleshooting (no negative, erratical display)

 

Hi Steve,

interesting... I like this supply and use it quite often. You can even use it to drive and control a transistor's base!

When I first used these PS5004 I thought the display was digitally controlled, but since it was able to show a negative voltage or a bit above 20V I began to doubt. And indeed.

For the alignment I was referring to the fact that alignment of the same 3 pots (zero, fine and coarse) is done several times in different chapters.

FIRST: §2 "Full Scale (R2043) and Fine Span (R2044) Presets"
This comes right after §1 coarse reference adjust (the switch).
A note says this should only be done when the reference IC has been changed. It consists of aligning the pots for a voltage of 6,550 volts.

SECOND: §4 "Zero Output Adjust (R3062)"
There is an instruction of how to connect the PS5004 to the voltmeter that I did not really understand. It says
"Connect the PS 5004 OUTPUT to the digital voltmeter input using a bnc cable and a pair of bnc-to-banana plug adapters. The shield side of the bnc is connected to the PS 5004 OUTPUT terminal, and the voltmeter Low input. The voltmeter guard is driven by the Low input. Connect the patch cable from the PS 5004 OUTPUT terminal to the ground post connector."
Anyone else who finds that substandard in terms of clarity? It looks like a cut&paste mess to me, but did Tektronix already have text processing these days?

THIRD: §§5&6: "Full Scale Adjust (R2043) & Fine Span Adjust (R2044)"
This time you align the same pots as in §2 with reference to the real output (in CAL mode). The pots had to be turned quite a bit (plusminus 2 revolutions) to get the right voltage here. But that means that the preset alginment in §2 was useles... No?

FOURTH: §7 "Full Scale (R2043), Fine Span (R2044), and Zero Output (R3062) Final Adjusts"

This time all three pots are re-aligned with reference to the real output, with the unit in normal RUN mode (not CAL mode). Again, I wonder what the alignments in §§2, 4, 5 & 6 were good for. I could have started the whole alignment right here, skipping the previous steps, couldn't I?
Perhaps not because these alignments interact somewhat, so you would have to repeat the steps in §7 several times if the previous steps haven't been done.

The next steps are for alignment of the DMM and current output. I always end up with a quite precise power supply, the DMM usually shows -0,0001 when at minimum. But thats well within specs...

cheers
Martin


Re: chinese witches hats for old probes help

Stephen
 

While I was looking for hook tips for a pair of P6105, I’d read a few reports on these Chinese probe tips. Some sais they worked fine and are good, while some stated the exact opposite... They said they were very fragile and broke easily.
Please let us know what you think when you get them.

Cheers


Re: 7A16A high frequency compensation.

Albert Otten
 

Yeah, it's that aberration "up" in the 10 ns point I can not eliminate. I
didn't think it was the cable. I generally observe the "dribble up"
phenomenon. Do you think is the cable ?
I also have a 7A16 (not A) but I don't think it has that reflection. Maybe
because of the smaller bandwidth?
The 7A16A input causes reflection anyway. When the cable impedance doesn't match the PG506
output impedance then the reflection from there can be observed at the CRT after twice the cable travel time.
I wouldn't bother too much about not perfectly flat, in my opinion the step response is very nice.
(How did you calibrate the PG506?)

What do you think about the trim pot not shown in the schematics? May it be
the very latest revision? I did not find more recent schematics.
That must by R436 in the LF filter leg between pins 2 and 3 of U450. Has always been there according to parts list.
Is present in my 1973 unit.

Albert


Re: chinese witches hats for old probes help

dave G8SFU
 

They were slip on hook tips I was looking for.

Thanks to all who replied about the Chinese witches hats.
I ordered a pack of six so will report back in a few weeks, if they come, if they fit, and if they actually work.
Dave   g8sfu

⁣Sent from BlueMail ​

On 11 Mar 2021, 15:11, at 15:11, Torch <tekscopes@verhey.org> wrote:
Are these the screw-on tips, or the slip-on tips?



Re: More fun with avalanche pulsers

Chuck Harris <cfharris@...>
 

A rule of thumb:

If a toroid is painted all over, it is powdered iron.
If a toroid is black, but not painted, it is ferrite.
If a toroid is covered with a form fitting plastic case,
it is a ribbon steel.

-Chuck Harris

Charles wrote:
...An unknown green one saturated too soon and required very few turns - must be an
iron powder one with high permeability. Finally a 3/4" yellow core (72 turns to get
to 250 uH, that was tedious) worked at the original frequency and didn't cause
trouble unshielded :)


Photo Avalanche pulser breadboard 2. Output at 5 ns/div, 2 v/div. updated #photo-notice

TekScopes@groups.io Notification <noreply@...>
 

The following photos have been updated in the Sampling with 3S2 album of the TekScopes@groups.io group.

By: Charles <charlesmorris800@...>


More fun with avalanche pulsers

 

I rebuilt the pretrigger and avalanche pulser onto one tightly packed board, and added SMA connectors for the output and the charge line to allow fast change. BNC for the ~65 volts from the power supply.
I'd discovered a GR 874 shorted termination in my bag of adapters, so I spent some time playing with shorted lines and reflections. Then I wanted to make a smaller toroid for the power supply - the junkbox one was (relatively) huge and wouldn't fit in a compact box. The Tek 130 LC meter got a workout figuring out AL for various cores. I was able to make a half-inch core work (think it was a T50-43) but the clock frequency required was high enough that it was getting into the unshielded pulser sitting next to it. An unknown green one saturated too soon and required very few turns - must be an iron powder one with high permeability. Finally a 3/4" yellow core (72 turns to get to 250 uH, that was tedious) worked at the original frequency and didn't cause trouble unshielded :)

A better RG-58 cable (SMA to BNC) worked well as a charge line, whereas a similar RG-174 cable was a droopy disaster. Putting the cheap BNC RG-58 cables on the end (with a barrel adapter) was also unsuitable. The "better" cable is too short by itself to be useful for risetime measurements on slower scopes, since the flat top is only about 3.5-4 ns long. As mentioned in the "3T77A tunnel diodes (again)" thread, I will try RG-402 (.141 semirigid) before calling it good enough. I doubt I have the skill or patience to build a really fast pulser to push the S-2(72 ps) or especially the S-4 (25 ps) to its limits.

Added a couple pics to the Sampling with 3S2 album of the breadboard so far and the pulse output.


Re: How to troubleshoot a faulty 7B92A?

Dan G
 

On Sat, Mar 20, 2021 at 04:19 PM, Thierry Delaitre wrote:

Regarding pin 7 and the TRIG'D light, the light is off when the scope gets
switched-on (with AUTO, AC, INT). The TRIG'D light switches on if i change the
mode to NORM. The light stays on if I revert the mode back to INT.
This is definitely abnormal. When switching from AUTO to NORM, the TRIG'D
light should flash briefly, but then go out. This suggests that the sweep timing
capacitors did not charge, or that sweep end detection circuits are not working.
It also explains why the hold-off and auto ramps are stuck low.

As Mark suggested, if you have not already done so, make sure all mechanical
switches, especially S490, operate correctly.

I would also look at pins AV (Aux Gate signal) and AR (Main Gate signal)
to see whether the plug-in thinks it has started a sweep or not. These
are normally square pulses, but yours are probably stuck. Whether they
are stuck high or low may provide a clue as to what is wrong.

Pin 10 remains at a constant DC high voltage and Pin 8 remains at a constant
DC low voltage. both pin 10 and 8 do not show any visible waveform
This now makes sense given your TRIG'D explanation above.
While this is not what these signals should look like, I think it is the result
of problems earlier in the sequence of events. They may be ok once
the plug-in is able to complete the sweep ramp.

I use a scope probe on the same scope to troubleshoot.
Sounds good.


dan


Re: 1S1 on ebay

Sean Turner
 

I received it...seller did a great job packing it. It appears to be functional, certainly moreso than my prototype one. I think it will need some caps done as well, but having a mostly working one will be a massive help troubleshooting!

Sean

On Sun, Mar 14, 2021 at 06:35 PM, Sean Turner wrote:


Guilty as charged. LOL! I need another one so I can hopefully have a reference
to compare things I find in my prototype 1S1 to.

Sean
Hide quoted text ( #quoted-182801618 )

On Sun, Mar 14, 2021 at 04:17 PM, Charles wrote:



So who got the 1S1... there were 8 bids and it went for $104!


Re: PS 5010 troubleshooting (no negative, erratical display)

ditter2
 

Hello Martin,

On the PS5010, my reference to the voltage and current ramping is the programming that takes place in the current and voltage limit DACs on a user request through front panel ON/OFF switch, or through remote control. This action takes place in both ON > OFF and OFF > ON operations. If you are monitoring the DAC outputs with a scope when the Output is toggled, you will see this programming action. It is to protect the output relay. Because the supply will normally go into CC mode during this transition, the software does not monitor the loop status during this time, to prevent reporting of the mode change.

If you need to draw a small amount of current to get regulation, then the minimum load is not sufficient to keep the output regulated. This could be either in the supply itself, or possibly (??) C-E leakage around the pass transistor in the mainframe. That would explain different amounts of the effect in different mainframe slots.

For the PS5004 – I designed all of it. For some fun, get a schematic and quickly try to find the precision 16 bit DAC needed to support the output resolution. If you are looking for a large “brick”, you won’t find it. 16 bit DACs were available at the time, but cost about 2.5 times the proposed manufacturing cost target for the entire built and tested instrument. The DAC I designed is a gated charge pump, using simple digital counter logic to set the duty factor of the current gate clock. BTW, Sony independently came up with the same idea for the 16 bit DACs needed in CD players about the same time.

I believe the part of the cal procedure you are referring to asks you to set output V to max, then back down one count (If my memory is correct – that was designed 40 years ago.) What you are doing is setting the full scale of the fine span of the DAC. Rather than take the full 16 bit resolution in one span, there are two charge pumps, scaled – I believe 200 counts (Each is 8 bits, the fine is 1/200th the coarse. They don’t map 1:1 with the digital pot coarse-fine range). Since calibration requires use of the digital knobs to set ranges, and the display is a volt meter measuring the measured output (not the programmed value as in the PS5010), the only way to set known values with the knob is at the extremes. So “0” is easy to set – turn both knobs to the left several turns and you can calibrate out the offsets in the system. Turn either or both knobs to the right several turns and you are at full scale – it is now possible to set the full span gain of the coarse current pump. Turning only the fine control down one “click” reduces the coarse stage DAC count by 1, and sets the fine DAC to is max scale. Now the user can calibrate the full scale of the fine . The order might not be the same as what I wrote in the cal procedure 40 years ago, but the process is the same.
Steve


Re: 7A16A high frequency compensation.

unclebanjoman
 

Hi Albert,
thanks!
Yeah, it's that aberration "up" in the 10 ns point I can not eliminate. I didn't think it was the cable. I generally observe the "dribble up" phenomenon. Do you think is the cable ?
I also have a 7A16 (not A) but I don't think it has that reflection. Maybe because of the smaller bandwidth?

Anyway, now the response of my 7A16A is much better than before. Initially was horrible. I think the previous owner tried to calibrate it but then gave up.
Really a tour de force: more than 4 hours fiddling the pots!

What do you think about the trim pot not shown in the schematics? May it be the very latest revision? I did not find more recent schematics.

Max

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