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Still looking.

Anyone have any experience of the TLA622 logic analyser, trying to sort display issues on one I have aquired

On Wed, May 8, 2024 at 6:29?AM Ed Breya via groups.io
<edbreya@...> wrote:

When one object dumps charge to another with enough energy to make a spark, then you don't need any sophisticated instruments to tell the polarity. A couple of anti-parallel-connected LEDs will suffice. Electrostatics was pretty well figured out by brilliant minds long ago, with comparatively crude instruments, way before tubes and transistors and ICs. Except for scientific curiosity, there's no need to recreate it (aka reinvent the wheel) to answer the question.

Any DMM in its voltage mode can sense the currents flowing in an electrostatic situation, so just bring a handheld DMM in its lowest VDC range, clamped with those anti-paralleled LEDs or regular diodes, and have at it. Use a simple, cheap DMM, like a Harbor Freight one, in case you accidentally discharge into a bad spot. Or, just leave out the DMM and use the LEDs. Don't forget the clipboard, paper, and pen to record the results, and try to look cool while doing it. Don't use a phone - keep it well away from all this activity.

One thing that may help is to look at the various HBM (human body model) electrostatic specifications, to get an idea of magnitudes involved. You can only store so much energy in practical conditions.

Ed

the led idea is pretty good. i was considering something like that for
a moment, but then i thought maybe the voltages involved would just
burn through a silicone junction.

my phone's been in my pocket during each esd event in that store, and
it still works. those things are really well made nowadays.

Hi everyone, I'm searching for some Tektronix 500 series plugins and wondered if anyone on here may have one for sale. They don't need to be working, but do need to be in good cosmetic condition and complete. I'm trying to find :

1l5, 1l10, 1l30, 1l40, 1l60
S type
Q type
1S2

If you have anything, please let me know!

Julian

This is probably familiar to most people who have ever tried to replace an old electrolytic capacitor.
It is very easy to make an adapter, at no cost.
It is enough to cut off the edge of the old electrolyte, approximately 3 millimeters from the edge.
You will get an outer ring that fits perfectly back to where it was, and the bakelite center will serve perfectly to place a modern electrolyte on it.

Here are pictures of how I usually do it:

/g/TekScopes/album?id=294954

@Beros <radiobero.bb@...> added the photo album can electrolytic adapter ( /g/TekScopes/album?id=294954 )

On Tue, May 7, 2024 at 05:12 PM, Dale H. Cook wrote:

On 5/7/2024 4:43 PM, cheater cheater wrote:

also why buy aluminium leaf? why not use alu foil?

Aluminum foil is far too thick. An electroscope needs minimum mass, and that
means leaf, not foil. The repulsive force in an electroscope is far too low
for foil to work.

I believe it's the stiffness, more than the mass, that's important, but the problem remains that the electroscope needs to be sensitive to extremely small forces.

For detecting direction of current flow you want a sensitive galvanometer, of
the type used as a detector for instruments such as a Leeds & Northrop Type
K-3 Universal Potentiometer. You would probably need an adjustable current
limiter of fairly high resistance to avoid damaging the galvo.

A galvanometer will tell you the direction of current flow, but it won't tell you which side got the built-up charge. He might be able to discern this by taking an electroscope around the store and touching it to various things, the cart: his finger, something "grounded." It should be possible to eventually pick out which item is different. Even this may be difficult, because I'm not sure what effect charge on the electroscope housing may have. It might be necessary to ground the housing with a wire that's long enough reach "ground" and also allow the electroscope to move around to reach everything he wants to check. (The problem here is that electroscopes traditionally have two glass windows, so the interior is not a completely field free region.)

--
Jim Adney
Madison, WI USA

Mark,

I checked those and one of them is well within tolerance. The other one is just at the high end of its tolerance. I may replace one or both of them but they should be okay for now.

Thanks!
Barry - N4BUQ

Barry,

These are a bleeder for the cathode circuit and partial divider for high voltage and focus circuit. I replaced mine with 1W 1% types and spaced them off the board. The 1W types I use are about 1cm in length, not 3,68 x 8,74mm types.

You will find the two 22meg resistors to be well out of tolerance. Use VR37 Vishay types.

Mark

Without looking, that sounds like the typical "focus string" divider that probably includes the focus pot somewhere, to get the right operating voltage for the function, and it possibly does other things too. Carbon composition resistors are often used for this, and they tend to drift upwards over time. Your idea to mount the replacements with more board clearance is sound.

It's also possible that strings of resistors are used for feedback in high voltage regulator circuits, but if so, they would be better grade metal film resistors. Tek hardly ever did this for CRT HV regulation - they used instead a carbon or metal film resistor network on a ceramic substrate. You can usually spot this part easily in the circuit.

Ed

Hi All,
I've a TM504 with 4 modules for sale.
Also a Scopemobile Type 204. The TM504 tucks nicely into the 204.
Both can be seen here:


Local sale & PU only.

Please respond privately off group. I will not respond here, to preserve the bandwidth/protocol of the group.

Thank you - Bob

In my latest 7704A, I noticed the chain of nine 300K resistors (R4261 - R4277 and, possibly, R4279) in the CRT circuit have drifted significantly high (~20%) making what should be a total of 2.7M about 3.2M. It's rather obvious they've been running quite warm (discoloring on the PCB) and I'm going to replace them with some breathing room between the new resistors and the board but it got me to wondering what function those provide. I looked over the circuit description and didn't see those mentioned so it made me curious and, perhaps, someone could enlighten me. I presume they're probably a more-or-less standard part of a CRT circuit and that's why they're not called out in the circuit description but not sure.

Thanks,
Barry - N4BUQ

I'm doing some work with interfaces & doing some research on the test equipment & interfacing.

I'm interested in both serial & parallel & the various types of test equipment, breakout boxes, line monitors & "Smart Cable" interface aids.
I haven't managed to find a manual for a Parallel Breakout Box even though I've seen photos of them.

Breakout boxes & line monitors are available on ePay etc but most do not have the manuals with them.

I am sure that there are members with lots of experience & that may even have manuals laying around.
I'd appreciate if members could look to see if they do have manuals & contact me if they have specific hints on interfacing.
I have seen the occasional comment about equipment that will damage test equipment or is particularly difficult to interface but haven't found a single repository so I'm starting to put it together for myself.

I'm also interested in the link between the Wavetek & Beckman Industrial brands for their breakout boxes.
The products appear to be the same although Beckman uses the "Easy Bob" terminology.
One breakout box I've seen is Beckman but the manual with it is Wavetek.

Many thanks,
Brian Symons.

Should have mentioned, these are Tek scopes.

I should have mentioned - if you use a simple LED deal, use a different color for each direction. The signal will be brief, and it's easier to discern which color flashed, than which of two same ones close together did.

Ed

When one object dumps charge to another with enough energy to make a spark, then you don't need any sophisticated instruments to tell the polarity. A couple of anti-parallel-connected LEDs will suffice. Electrostatics was pretty well figured out by brilliant minds long ago, with comparatively crude instruments, way before tubes and transistors and ICs. Except for scientific curiosity, there's no need to recreate it (aka reinvent the wheel) to answer the question.

Any DMM in its voltage mode can sense the currents flowing in an electrostatic situation, so just bring a handheld DMM in its lowest VDC range, clamped with those anti-paralleled LEDs or regular diodes, and have at it. Use a simple, cheap DMM, like a Harbor Freight one, in case you accidentally discharge into a bad spot. Or, just leave out the DMM and use the LEDs. Don't forget the clipboard, paper, and pen to record the results, and try to look cool while doing it. Don't use a phone - keep it well away from all this activity.

One thing that may help is to look at the various HBM (human body model) electrostatic specifications, to get an idea of magnitudes involved. You can only store so much energy in practical conditions.

Ed

On 5/7/2024 7:35 PM, cheater cheater wrote:

Hmm... anything less rare? Anything I could take with me on the go?

Gold leaf is the standard for electroscopes because it can be beaten far thinner than other metals. It has been the standard for leaf electroscopes since British physicist Abrahm Bennett used it in 1787. There are pith ball electroscopes which are less sensitive than gold leaf electroscopes.

As I said upstream, if you need to detect the direction of the current you need a sensitive galvanometer.

--
Dale H. Cook, Member, NEHGS, AGS, MA Soc. of Mayflower Descendants;
Massachusetts State Coordinator for the USGenWeb? Project;
Administrator of

Hello,

I and a friend changed out the batteries in my newly purchased 2712 today. The GPIB battery was totally dead on an unloaded meter... The other battery had 3.xx left. Both batteries were swapped with new ones. They fit perfectly on the board! Thanks to all that answered and suggested batteries here! Also, thanks to whoever told me to hurry once you put in the GPIB board battery, the 2712 got powered up maybe 3 to 5 minutes after the GPIB battery was soldered in place.

When I run the self normalization all seems good until I get:

Amplitude Normalization Failed

The scope appears to be working well, I hang an antenna off it, and transmit with an HT on 146.52, and see a waveform, the right width, etc...

My God Tek builds nice equipment... There is not even any dust in the unit, save a tiny amount near the end of the CRT HV. All the boards look brand new, nothing has leaked, and it was even calibrated in 2015 by Tek...

So what does the Amplitude Normalization failed mean in terms of repair, and/or operation? Do I need to worry? Is there something else I should do, and try again?

--
73, and thanks,
Dave (NK7Z)

ARRL Volunteer Examiner
ARRL Technical Specialist, RFI
ARRL Asst. Director, NW Division, Technical Resources

Hmm... anything less rare? Anything I could take with me on the go?

On Wed, May 8, 2024 at 12:12?AM Dale H. Cook via groups.io
<bridgewaterma@...> wrote:

On 5/7/2024 4:43 PM, cheater cheater wrote:

also why buy aluminium leaf? why not use alu foil?

Aluminum foil is far too thick. An electroscope needs minimum mass, and
that means leaf, not foil. The repulsive force in an electroscope is far
too low for foil to work.

For detecting direction of current flow you want a sensitive
galvanometer, of the type used as a detector for instruments such as a
Leeds & Northrop Type K-3 Universal Potentiometer. You would probably
need an adjustable current limiter of fairly high resistance to avoid
damaging the galvo.
--
Dale H. Cook, GR/HP/Tek Collector, Roanoke/Lynchburg, VA

On 5/7/2024 4:43 PM, cheater cheater wrote:

also why buy aluminium leaf? why not use alu foil?

Aluminum foil is far too thick. An electroscope needs minimum mass, and that means leaf, not foil. The repulsive force in an electroscope is far too low for foil to work.

For detecting direction of current flow you want a sensitive galvanometer, of the type used as a detector for instruments such as a Leeds & Northrop Type K-3 Universal Potentiometer. You would probably need an adjustable current limiter of fairly high resistance to avoid damaging the galvo.
--
Dale H. Cook, GR/HP/Tek Collector, Roanoke/Lynchburg, VA