Date   
Re: My 2465B has arrived + A5 Board leaky caps cleanup

BryanByTheSea
 

That's a excellent tip for removing SMD caps, thanks for sharing.

Re: My 2465B has arrived + A5 Board leaky caps cleanup

Roger Evans
 

Alex,
There is a vast amount of information around about the A5 corrosion problem. The corrosion usually causes two 10k precision resistors to change their value. These set the voltage reference for the DAC that controls most of the operating points for the scope, including trigger levels (that causes the Test 5 failre) and also the brightness levels of trace and readout. There is a high probability that the screen will be OK after you replace the damaged components. Before I did my A5 repair I also had nothing visible on screen, I adjusted the Grid Bias pot before repairing the A5 board as a confidece measure to see that the rest of the scope was OK.
Roger

2465B leaky voltage

 

This morning, I was working with my scope, and I touched the CH1 BNC socket - ground side.
BZZZZ.

I thought I was dreaming.

I measured the voltage to AC Ground - 113VAC!!!

So something's leaking somewhere.

This is a 3 wire AC system - Live, Neutral, Ground.

I immediately checked my Signal Generator, on the same outlet - just fine, so it's definitely the scope.

Before I start poking around, does anyone have some fast pointers, to zero in on?

Menahem

Re: 2465B leaky voltage

ppppenguin
 

Are you sure the scope is properly grounded? Measure it rather than assuning it's OK because another peice of kit doesn't give any trouble. Just stray capacitance can cause an ungrounded chassis to feel a bit lively and measure at half mains voltage (I'm assuming you're in a 220V/230V/240V country). However there's little current available as you'll find if you try a lamp between the scope ground and actual ground.

As far as I can see, there aren't any "Y" capacitors between live or neutral and ground. But C1020 and C1051, both 2200p, are from ground to parts of the power supply that are ahead of the main isolating transformer.

Re: 2465B leaky voltage

 

Correct on the 230VAC assumption!

I've checked that it is "grounded" - there are Y capacitors in the sealed EMI-filter unit - right at the AC input, and I'm beginning to suspect those of failure.

All the caps are new, so those 2.2nF's are not suspect.

The 113VAC voltage exists, even if the machine is switched off.

Re: 2465B leaky voltage

ppppenguin
 

Shalom Menachem. I've just looked at your profile and note you're in Jerusalem.I've been amused when visiting Israel to find some high current applainces connected using our old British BS546 15 amp plugs and sockets.And landline phones using the same connector as in the UK, though with different pinout as I discovered the hard way.

I've certainly had a Schaffner mains inlet filter fail badly. It was on a Tek 1755A Vectorscope. It got hot enough to melt solder before an RCD tripped.

The question still remains, is the chassis just floating at half mains or is there real current available? Easily tested with a lamp or resistor to true ground or neutral. If there are Y caps in a mains input filter then loss of ground will definitely cause the chassis to float at half mains. Once you're sure that it's just floating rather than with real current available then I'm pretty certain you've got a missing ground. In the scope itself, in the mains lead or at your power outlet.

Re: My 2465B has arrived + A5 Board leaky caps cleanup

 

Alex,

The filter gets put back in after you put on the front panel. Just make sure the metal clip is installed on the front panel at the top of where the filter goes. You just slip the filter in starting at the top and the spring tension will allow it to snap into the side and bottom groves.

Manuel

Re: My 2465B has arrived + A5 Board leaky caps cleanup

Siggi
 

On Fri, 26 Oct 2018 at 01:13 <tekscopegroup@...> wrote:

Comments and suggestions very welcomed about any follow up tests to make
sure I have possibly not missed anything on the A5 cleanup, any know
suspect VIAs to check, or hidden traces to verify they have continuity to
another part, etc. Any other obvious possibilities besides the A5 mess on
why the screen is non-op?
A5 problems are a sufficient condition for no screen. On my 2467 a clamping
zener on the -1.25V reference had gone short, causing no display at all.

You've probably read up on this already, but the resistor network that sets
the DACs reference current is your prime suspect for the no display
condition. In your shoes, I'd buzz out all the traces and the resistors
involved there - this is everything connecting to pins 14 and 15 on the
DAC. Note that if you need to replace R2012/R2013 that they're precision,
low tempco resistors, so ideally you'd want to replace them with like -
especially if you intend to calibrate the scope. The little trimpot is a
frequent casualty of capacitor leakage, so give that a good look. I
wouldn't worry about jiggling it or replacing it, you'll have to go through
the DAC calibration procedure either way. It's a simple enough procedure,
and I think it's safe to assume that bringing the DAC into spec will bring
you nearer calibration than wrecking it.

There was a recent thread here discussing the +1.36, -1.25 reference
voltages and how they derive directly from the DACs reference current. I
don't think on your A5 board they will be brought to a test point, but if
you hunt them down, they allow you to assess the wellness of the DACs
reference, which is otherwise difficult to measure.

Re: 2465B leaky voltage

Chuck Harris
 

Let's gather some solid evidence:

The bond wire in the IEC style power cord goes
directly to the chassis by way of the mains power
line filter module.

It is a belt and suspenders system. The filter
module is in a metal can that has a metal mounting
flange that is screw mounted to the scope's chassis.

Inside of the can is a strap that goes from the bond
wire pin of the socket directly to a terminal on the
back of the can. The terminal is riveted to the
can.

The ground terminal on the back of the can has a green/
yellow wire soldered to it. The green/yellow wire has
a crimped on closed ring lug that is affixed with a nut
to a riveted threaded stud on the rear panel of the scope.

The rear panel of the scope is screwed to the chassis
using multiple screws.

The BNC connectors on the 2465 are directly (mechanically)
connected to the chassis at the front panel beneath the
bezel ring. Each has its own torx screw.

Assuming that the scope is the problem is a poor idea.
First do some measurements.

Connect a good low ohm meter to the offending BNC connector's
shield connection. Measure ohms to the front panel ground
banana socket. Measure ohms to the bond pin on the rear
IEC power connector.

If either of these measurements is not very near zero ohms,
you have a problem within your scope. Most likely inside of
the rear power filter... usually a burned out strap due to
a very, very high current path from the filter bond pin to
the filter hot mains lead... or possibly a manufacturing
defect.

By very near zero, I mean less than 1/4 ohm.

Next, unplug your power cord from the wall outlet, and
plug it into the IEC connector on the back of your scope.
Measure from the bond wire pin of the cord to the
front panel ground banana socket.

If it is not very near zero ohms, you have a bad power cord.

By very near zero, I mean less than 1/2 ohm.

If these grounds are correct, your problem is likely in your
bench power, or your house grounding system.

-Chuck Harris

M Yachad wrote:

Correct on the 230VAC assumption!

I've checked that it is "grounded" - there are Y capacitors in the sealed EMI-filter unit - right at the AC input, and I'm beginning to suspect those of failure.

All the caps are new, so those 2.2nF's are not suspect.

The 113VAC voltage exists, even if the machine is switched off.



Re: 2465B leaky voltage

ppppenguin
 

Chuck, thanks for laying out, step by step, what I was summarising.

The 113V reading is about what you would expect using a DVM with high (10M) input resistance with the scope's ground disconnected. It's simply the pair of Y caps in the filter acting as a potential divider. I don't know the value of the Y caps but from memory the maximum current that's allowed to flow from live to ground is about 250uA for a Class II (double insulated) appliance, somewhat more for a Class I (grounded) appliance. Even 250uA will give you a tingle, I've felt this many times when handling kit that isn't grounded.

If 1 of the Y caps in the filter was faulty I would expect the voltage reading to be either close to zero or close to full mains. The fact that it's close to half mains strongly suggests that the filter is OK and the scope's ground is missing. Also if one of the y caps was faulty I would expect a 30mA RCD (aka GFI) to trip. Assuming your lab is protected by one of these, and I really hope it is.

Re: Type G plugin versions

Dave Wise
 

Further study of the catalogs suggests that they never did retool. In 1967, some instruments with plastic trim went "limited demand" without pictures; others simply dropped the trim. As far as I can tell, the hole stayed the same size. It's possible that the BNC was switched from square four-screw mount to round flange and single large rear retention nut. If I remember to, I will study my plugins when I'm at home this weekend.

Dave Wise
________________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Dave Seiter <d.seiter@...>
Sent: Friday, October 26, 2018 12:17 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Type G plugin versions

Wow- my G is s/s 9934, so it's just after the change. Strange that they didn't change the sheet metal right away.
-Dave

From: Albert Otten <aodiversen@...>
To: TekScopes@groups.io
Sent: Thursday, October 25, 2018 12:44 PM
Subject: Re: [TekScopes] Type G plugin versions

According to the later manual Type G switched from UHF (131-012) to BNC (131-277) at S/N 9480. No idea in which year that was.
Albert

On Thu, Oct 25, 2018 at 08:17 PM, Dave Wise wrote:


I don't know the G serial number at which Tek switched from UHF to BNC*, but
the 1962 catalog shows UHF while 1963 is BNC**. I think I have a newer manual
at home, I'll try to remember to look.

There was a mod kit for converting instruments in the field. I have at least
one modded scope and plugin. Yours too, most likely, as Tek would not have
sold instruments with such an obvious bodge.

Dave Wise

* For what it's worth, the 535A mainframe switched at 31260.
** Some old models were not updated.

Re: 2465 CRT Smoke

dharwood1980@...
 

Gents,

Apologies for my delayed update. Unfortunately, work took me away for longer than expected.

As most of you expexted, it was just a power supply issue. I gave it the full work over this time with a good cleaning of the smoke residue near the CRT and the scope is right back in business.

Thank you all again for the helpful advice!

Re: TDS3032 Loosing its GPIB Address

David Kuhn
 

Hello again Hakan,

Hey, sorry to revisit this again. I just order one “brand new”, from China,
$38.29/shipping. I am supposed to have it sometime next month (Nov ‘18).
I’ll have to post if I’m successful . It looks like a lot of work to pull
the board out to replace the chip. Hopefully, I don’t break it. In
September, I did buy another used TDS3032, from Alltest, in NJ, for $1500
with a NIST cert, and a six month warranty. It works perfect and matches my
tired one perfectly.

I may just buy that Siglent I was thinking of for about $400/NIST cert to
play with and see if I can get a software work-around for the pulse width
measurement reference levels. It is probably fine for the rest of my data
collection work. It is so good looking and sexy for the price - lol.

Dave

On Thu, Sep 6, 2018 at 5:12 PM zenith5106 <hahi@...> wrote:


If you mean Tek P/N I have no idea, if you mean the Dallas number, yes it
is DS1742W-150

/Håkan



the blue filter slot on 244* scopes

John Ferguson
 

I have 2 2445B's and a 2465.  They have moulded-in grooves in the top of the bezel, but not slots. It appears that the only way I can put a blue filter on one of my scopes is to remove the bezel and install it from the inside.

What am I missing?


john

Re: 2465B leaky voltage

Chuck Harris
 

I have seen so many of the IEC type power cords, made in China,
with failed wires that I am immediately suspicious of them.

I have taken a few apart, and was appalled at how crappy the
hidden connections were. Not solder, not crimp, but wires pressed
into "V" shaped nocks in the stamped brass (?) that forms the
socket and plug pins...

I just found a #14ga stranded copper wire, with a couple of
funny capsule shaped bulges in it. It had no conductivity
from end to end... So, I cut open one of the bulges, and it
was entirely filled with a copper salt. Someone probably spattered
some acid (flux?) on the bulk wire reel of the wire coating machine...
The acid slowly etched away the copper metal, and the fuse was lit,
waiting to catch some future user.

I have never seen anything like that with USA built wire.

I have seen other IEC cords where the internal insulation
turned to goo. The first sign was green goo leaking out of
the socket side of IEC cords that I left hanging from my cord
storage comb.

There seems to be a feature of human nature to always look
for the most difficult and expensive to fix failure when
seeing symptoms of simple problems. I see it in others, and
I am constantly fighting it in myself.

-Chuck Harris

ppppenguin wrote:

Chuck, thanks for laying out, step by step, what I was summarising.

The 113V reading is about what you would expect using a DVM with high (10M) input resistance with the scope's ground disconnected. It's simply the pair of Y caps in the filter acting as a potential divider. I don't know the value of the Y caps but from memory the maximum current that's allowed to flow from live to ground is about 250uA for a Class II (double insulated) appliance, somewhat more for a Class I (grounded) appliance. Even 250uA will give you a tingle, I've felt this many times when handling kit that isn't grounded.

If 1 of the Y caps in the filter was faulty I would expect the voltage reading to be either close to zero or close to full mains. The fact that it's close to half mains strongly suggests that the filter is OK and the scope's ground is missing. Also if one of the y caps was faulty I would expect a 30mA RCD (aka GFI) to trip. Assuming your lab is protected by one of these, and I really hope it is.

Re: the blue filter slot on 244* scopes

Chuck Harris
 

The trick.

The filter goes inside of the bezel lips, right tight against the clear
plastic implosion protection screen.

It slides up into a slot and a waiting spring, inside of the top lip
of the bezel, and the combination of gravity and spring pressure holds
it into a shallow groove along the inside of the bottom lip, of the bezel.

To remove the filter, take your fingers, and put some big finger prints
on the center of the filter, as you use your finger's friction to slide
the filter up into the groove with the retaining spring.

While the filter is in the up position, slip a fingernail under the
bottom edge of the filter and pull it towards you... If you don't have
fingernails, stick a business card under the filter's bottom edge, and
then release it. Pull the business card out, and the filter will come
with it.

-Chuck Harris

John Ferguson via Groups.Io wrote:

I have 2 2445B's and a 2465. They have moulded-in grooves in the top of the bezel,
but not slots. It appears that the only way I can put a blue filter on one of my
scopes is to remove the bezel and install it from the inside.

What am I missing?


john

Re: the blue filter slot on 244* scopes

Craig Cramb
 

Installing requires removal of front and carefully installed so finger prints don’t make display dirty. I think Chuck is only talking about removal ,but why not remove the front and not take risk about cracking or scratches to plastic display.

Craig

On Oct 26, 2018, at 12:22 PM, John Ferguson via Groups.Io <jferg977=aol.com@groups.io> wrote:

What am I missing?


john

Re: the blue filter slot on 244* scopes

Chuck Harris
 

No, I am not only talking about removal.

Unless you are working with something way different than the
2465, 2465A, or 2465B, what I said applies to both removal and
installation of the blue filter.

The clear implosion filter is a whole different kettle of
fish, and its careless removal usually results in breaking the
knobs under the CRT when you remove them to remove the bezel...

-Chuck Harris

Craig Cramb wrote:

Installing requires removal of front and carefully installed so finger prints don’t make display dirty. I think Chuck is only talking about removal ,but why not remove the front and not take risk about cracking or scratches to plastic display.

Craig
On Oct 26, 2018, at 12:22 PM, John Ferguson via Groups.Io <jferg977=aol.com@groups.io> wrote:

What am I missing?


john


Re: the blue filter slot on 244* scopes

 

Chuck is 100% correct.  DO NOT REMOVE THE BEZEL to move the blue filter (installing or removing).  Bezel removal requires pulling the knob covers off the knobs below the screen.  This requires skill to do without breaking the tiny fingers that hold the knobs in place.  Besides, it is a nightmare to install the blue filter when the bezel is disassembled because the bezel spring cant be properly compressed when the bezel is removed.  Removing/installing the blue filter is trivial unless something is broken.  Here is the explanation again:
The blue filter is precisely as wide as the screen bezel opening and slightly taller.  There are slots at the top of the screen and the bottom.  The slot at the top has a small bent metal spring and the slot at the bottom is about 2-3 millimeters deep with nothing at the bottom.  To install the blue filter you simply place the top edge of the filter against the screen and slide it up against the spring.  A slight upward force with your finger tips is enough to compress the spring and let the filter slide upward.  Your fingers can then press the filter against the screen and it will drop into the slot at the bottom.  If this doesn't work there is dirt or something in the slots.  Find out why it doesn't work before setting out to "fix" anything.

On ‎Friday‎, ‎October‎ ‎26‎, ‎2018‎ ‎01‎:‎06‎:‎19‎ ‎PM‎ ‎CDT, Chuck Harris <cfharris@...> wrote:

No, I am not only talking about removal.

Unless you are working with something way different than the
2465, 2465A, or 2465B, what I said applies to both removal and
installation of the blue filter.

The clear implosion filter is a whole different kettle of
fish, and its careless removal usually results in breaking the
knobs under the CRT when you remove them to remove the bezel...

-Chuck Harris

Craig Cramb wrote:
Installing requires removal of front and carefully installed so finger prints don’t make display dirty. I think Chuck is only talking about removal ,but why not remove the front and not take risk about cracking or scratches to plastic display.

Craig
On Oct 26, 2018, at 12:22 PM, John Ferguson via Groups.Io <jferg977=aol.com@groups.io> wrote:

What am I missing?


john


Re: the blue filter slot on 244* scopes

 

IF you do need to remove the knobs, I have found that applying some heat from a hot air gun will allow you to pull the knobs off without breaking the internal tabs. I use a hot air rework gun with a small nozzle and set to 100 degrees C.

Regards,
Tom

----- Original Message -----
From: "machineguy59 via Groups.Io" <machineguy59=yahoo.com@groups.io>
To: <TekScopes@groups.io>
Sent: Friday, October 26, 2018 2:39 PM
Subject: Re: [TekScopes] the blue filter slot on 244* scopes


Chuck is 100% correct. DO NOT REMOVE THE BEZEL to move the blue filter (installing or removing). Bezel removal requires pulling the knob covers off the knobs below the screen. This requires skill to do without breaking the tiny fingers that hold the knobs in place. Besides, it is a nightmare to install the blue filter when the bezel is disassembled because the bezel spring cant be properly compressed when the bezel is removed. Removing/installing the blue filter is trivial unless something is broken. Here is the explanation again:
The blue filter is precisely as wide as the screen bezel opening and slightly taller. There are slots at the top of the screen and the bottom. The slot at the top has a small bent metal spring and the slot at the bottom is about 2-3 millimeters deep with nothing at the bottom. To install the blue filter you simply place the top edge of the filter against the screen and slide it up against the spring. A slight upward force with your finger tips is enough to compress the spring and let the filter slide upward. Your fingers can then press the filter against the screen and it will drop into the slot at the bottom. If this doesn't work there is dirt or something in the slots. Find out why it doesn't work before setting out to "fix" anything.

On ‎Friday‎, ‎October‎ ‎26‎, ‎2018‎ ‎01‎:‎06‎:‎19‎ ‎PM‎ ‎CDT, Chuck Harris <cfharris@...> wrote:

No, I am not only talking about removal.

Unless you are working with something way different than the
2465, 2465A, or 2465B, what I said applies to both removal and
installation of the blue filter.

The clear implosion filter is a whole different kettle of
fish, and its careless removal usually results in breaking the
knobs under the CRT when you remove them to remove the bezel...

-Chuck Harris

Craig Cramb wrote:
Installing requires removal of front and carefully installed so finger prints don’t make display dirty. I think Chuck is only talking about removal ,but why not remove the front and not take risk about cracking or scratches to plastic display.

Craig
On Oct 26, 2018, at 12:22 PM, John Ferguson via Groups.Io <jferg977=aol.com@groups.io> wrote:

What am I missing?


john