Date   

Re: What's a chat.. and why?

Michael W. Lynch
 

I did not realize that we could chat, silly me. I just I never paid attention to the menu, skipped right over that part.. Kind of like the "POLL" feature; not used much in this group, but part of the "groups.io" package. I can see the occasional benefit of chat, but chat is not the best way to share to the broader audience on this forum.

--
Michael Lynch
Dardanelle, AR


Re: PG506 Repair - I had a Great Day today/

Mark Vincent
 

Rene,

I see you said you recapped the unit. For the caps in the primary power section, they should be a low ESR high temp type, e.g. Nichicon ULD, UCY, etc.

Mark. You may have used this type already. The one for the 120V supply should be 200V. The heat will reduce with low ESR types provided the rated voltage on the caps are high enough. If the voltage is lower than the peaks of the unfiltered ac, it heats the caps up and causes higher power to be dissipated in the driver transistors and transformer. For square wave oscillation, the minimum rated voltage for caps is 1,5x the rated ac voltage from a winding. It is possible the additional heat is from a ,1mfd that is leaking that is on the -72V line.

Check VR210. If that is bad, the AMPL VAR, R225A, will not work right. Michael Lynch is right about checking the diodes.

Mark


Re: Challenging 2465 PS repair

-
 

I do the same but I have an amp meter attached to my Variac and I start
out at about 1 VAC and watch for excessive current. If the device under
test is rated to draw say 5 amps at 115 VAC and I apply say 3 VAC and it's
already drawing 3 Amps then there's probably a short somewhere. But the
low amount of power (9 Watts) isn't as likely to cause damage as applying
115 VAC and 20 Amps (the normal limit of 115 VAC circuits) would.

On Mon, May 3, 2021 at 11:46 AM Milan Trcka <milan.v.trcka@gmail.com> wrote:


In an attempt to keep in as much smoke as possible when powering up
suspect or failed PS, I use an adjustable transformer (Variac) to slowly
bring up mains voltage while monitoring for vital signs. Use isolation
transformer or battery powered isolated scope when monitoring waveforms.

M






Re: Transporting a 500-Series Scope without Breaking the CRT

stevenhorii
 

In the UPS facility I used to ship items from (Gardena, CA) they had a sign
on the wall saying “pack for a four-foot drop onto concrete”. I took them
at their word. I had a rare Mercury spacecraft horizon scanner, so I used
mil-spec packing for it. In it’s own fiberglass shipping box and that into
a cube-shaped box with about four inches of foam around all sides. At the
UPS facility, they put it on the scale and said there was a surcharge
because the item was “too large for the weight”. I pointed to the sign and
told them it was packed to meet that requirement. They didn’t care - that
was their policy. I understand this - their thinking is that it takes up
more space than it is “worth” in an air cargo container or truck so their
surcharge is to offset that “opportunity cost”. Some pencil-pusher probably
figured out that it costs them less to pay the (rare) claim rather than the
opportunity cost of not packing more boxes in the shipping container or
vehicle.

I also had a Spacelab computer in its transit case (high-density
polyethylene with plenty of fitted fairly stiff foam inside). When I
received it, the plate with the handles and all the connectors was dented
in. It must have been dropped far enough that the computer banged into the
inside of the container. UPS said “inadequately packed” and would not back
down despite photos. Fortunately, the guy who sold me the computer had
spare parts from one he parted out and he sent me a replacement end plate.
The internal electronics had not been damaged.

If I do have Tek scopes shipped, if they are plug-in types (7000-series,
etc) I always tell the shipper to remove any plug-ins and pack them
separately. I offer to pay extra shipping and packing costs if necessary. I
also tell them to put a layer of styrofoam or polyethylene foam over the
face of the scope to protect the knobs on the front. The best sellers have
done this and more. One wrapped the scope (a 7854) with about six inches of
bubble on all sides plus an additional two inches over the front and then
put two crossed-layers of corrugated cardboard in front of that. It went
into a double-wall box. It was shipped to me cross country and was handled
by FedEx Ground. The scope arrived in fine condition and worked when
powered up. I also always check for loose parts (rattles, etc) before
applying power.

On Mon, May 3, 2021 at 10:56 Greg Muir via groups.io <big_sky_explorer=
yahoo.com@groups.io> wrote:

Back in the late 90’s I had a small piece of equipment that was captured
in a military shipping container consisting of 2” closed cell stiff foam
shock absorbers around each corner of the unit faced with an aluminum layer
on each one. The transit container consisted of .062” aluminum walls both
inside and outside with a 3/8” layer of plywood sandwiched in between the
aluminum. The unit itself weighed around 20 pounds with the container
coming in a close second.

When received from UPS Ground the knobs (or at least the parts of them
with the control shafts) were sticking out through the exterior aluminum.
Needless to say the unit was toast. The UPS inspector tried to tell me
that the unit was “inadequately packed.” I told him that my impression
was that the container must have been dropped from at least a 10 foot
height onto a concrete floor.

UPS begrudgingly reimbursed the cost of the unit but would not refund the
shipping charges.

Greg






Re: Challenging 2465 PS repair

Siggi
 

On Mon, May 3, 2021 at 3:54 AM satbeginner <castellcorunas@gmail.com> wrote:

After studying the schematic of this power supply, it is vaguely similar
to the 22xx power supplies, but with at least one major difference.

Similar is, it has a Primary switcher, and it has a secondary switcher,
but, were in the 22xx PS the secondary switcher runs at it's own frequency,
in this 246x PS the secondary switcher uses the same frequency as generated
by the primary switcher.
This makes it a bit more of a challenge to separate the Primary and the
Secondary to test them one at the time.
Switchers will run just fine on DC input, and if you have a suitable bench
supply to run it from, that gives you two big benefits:
1. Limited energy input, the current limit could be set low enough that
nothing blows up.
2. Mains isolation, so you can now peek around anywhere with your scope.

Unfortunately the DC bus on this scope runs at 2-300V (I see a 264V
annotation on the schematic), using an AC voltage doubler when on 115V
input, and not many bench supplies have that sort of voltage output. I do
find that switchers will often start way below their supposed minimum input
voltage, which may work just fine for diagnosis. You really don't want to
load them - as others have mentioned - with a low input voltage.


Re: Tektronix Probe Replacement Parts and Accessories

Rogerio O
 

Thank you very much for sharing your work.
I had spent a lot of time trying to figure out the correct Tek part number of the probe parts I was willing to buy....
Roger


Re: What's a chat.. and why?

Ondrej Pavelka
 

I believe it allows people to join online for instant messaging, could be
very helpful for some brain storming or troubleshooting session.

On Mon, 3 May 2021, 01:27 Roy Thistle, <roy.thistle@mail.utoronto.ca> wrote:

Hi:
I saw the post on the 2430A was as a chat?
Do we do that on TekScopes?
And why would someone want to? ... What's the advantage of that over
starting/participating in a thread?
It appears that chats are in the sub-basement of TekScopes.
--
Roy Thistle






Re: Challenging 2465 PS repair

 

The 2465 PSU is a switcher, so a variac is strongly counter indicated as this will typically cause the PSU to draw excess current at low voltages (below the nominal range of say 100-120V, or 200-240V over here).

D.

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Milan Trcka
Sent: 03 May 2021 16:46
To: TekScopes@groups.io
Subject: Re: [TekScopes] Challenging 2465 PS repair


In an attempt to keep in as much smoke as possible when powering up suspect or failed PS, I use an adjustable transformer (Variac) to slowly bring up mains voltage while monitoring for vital signs. Use isolation transformer or battery powered isolated scope when monitoring waveforms.

M


Re: Challenging 2465 PS repair

Tom Gardner
 

Since a *switching* PSU will attempt to deliver a constant output
power, a low input voltage means a high input current flowing through
transistors, diodes and some capacitors.

An abnormally high current might cause damage.

On 03/05/2021, Milan Trcka <milan.v.trcka@gmail.com> wrote:

In an attempt to keep in as much smoke as possible when powering up suspect
or failed PS, I use an adjustable transformer (Variac) to slowly bring up
mains voltage while monitoring for vital signs. Use isolation transformer or
battery powered isolated scope when monitoring waveforms.

M






Re: Challenging 2465 PS repair

Milan Trcka
 

In an attempt to keep in as much smoke as possible when powering up suspect or failed PS, I use an adjustable transformer (Variac) to slowly bring up mains voltage while monitoring for vital signs. Use isolation transformer or battery powered isolated scope when monitoring waveforms.

M


Tek 465 - help is needed...

Dr. Manfred K. Zeller
 

Channel 1 Beam with the Beam Finder cannot regulated down over the whole screen with the position knob - it is only on the upper side of the screen.
Only a little - two or three scales.

Result: no Beam in channel 1

Channel 2 is working.

Voltage: ok
Manual: there

Thanks!
Regards
Manfred


Re: Transporting a 500-Series Scope without Breaking the CRT

Greg Muir
 

Inspectors have a tendency to come out of the woodwork when the insurance value equals several months or more of a mid-level managers income.

Greg


Re: Transporting a 500-Series Scope without Breaking the CRT

-
 

Greg,

I'm surprised to hear you say that UPS even sent an inspector out to look
at the item. I've never even heard of a UPS inspector and UPS has never
sent anyone to look at any of my damaged packages. They just automatically
say that the package wasn't packed properly.

UPS inspectors probably sub as Tooth Fairies or Unicorns when they're
not busy (sarcasm intended) inspecting packages for UPS.

On Mon, May 3, 2021 at 10:56 AM Greg Muir via groups.io <big_sky_explorer=
yahoo.com@groups.io> wrote:

Back in the late 90’s I had a small piece of equipment that was captured
in a military shipping container consisting of 2” closed cell stiff foam
shock absorbers around each corner of the unit faced with an aluminum layer
on each one. The transit container consisted of .062” aluminum walls both
inside and outside with a 3/8” layer of plywood sandwiched in between the
aluminum. The unit itself weighed around 20 pounds with the container
coming in a close second.

When received from UPS Ground the knobs (or at least the parts of them
with the control shafts) were sticking out through the exterior aluminum.
Needless to say the unit was toast. The UPS inspector tried to tell me
that the unit was “inadequately packed.” I told him that my impression
was that the container must have been dropped from at least a 10 foot
height onto a concrete floor.

UPS begrudgingly reimbursed the cost of the unit but would not refund the
shipping charges.

Greg






Re: Transporting a 500-Series Scope without Breaking the CRT

Greg Muir
 

Back in the late 90’s I had a small piece of equipment that was captured in a military shipping container consisting of 2” closed cell stiff foam shock absorbers around each corner of the unit faced with an aluminum layer on each one. The transit container consisted of .062” aluminum walls both inside and outside with a 3/8” layer of plywood sandwiched in between the aluminum. The unit itself weighed around 20 pounds with the container coming in a close second.

When received from UPS Ground the knobs (or at least the parts of them with the control shafts) were sticking out through the exterior aluminum. Needless to say the unit was toast. The UPS inspector tried to tell me that the unit was “inadequately packed.” I told him that my impression was that the container must have been dropped from at least a 10 foot height onto a concrete floor.

UPS begrudgingly reimbursed the cost of the unit but would not refund the shipping charges.

Greg


Re: PG506 Repair - I had a Great Day today/

tek_547
 

Thanks Albert and Michael for the information. Looks like T130 in my PG506 is a bit warmer then yours Albert, so maybe something is consuming extra current somewhere...
And next days I investigate the 4N27 and the 7400 Michael, so when I know more I report it here.
Rene


Re: Challenging 2465 PS repair

satbeginner
 

Hi all,

I am determined to repair this PS, so I removed all broken, damaged or suspicious parts and ordered new ones.
For the time being, I removed all the burned fiberglas parts of the PCB, leaving me with a nice, clean 8mm hole in the PCB and many open spaces were new parts will be placed.

After studying the schematic of this power supply, it is vaguely similar to the 22xx power supplies, but with at least one major difference.

Similar is, it has a Primary switcher, and it has a secondary switcher, but, were in the 22xx PS the secondary switcher runs at it's own frequency, in this 246x PS the secondary switcher uses the same frequency as generated by the primary switcher.
This makes it a bit more of a challenge to separate the Primary and the Secondary to test them one at the time.

The good news is, the service Manual has a procedure to do this, but extra dummy loads are needed.
I ordered these parts as well, and when they arrive I will continue this repair.

To be continued, stay safe,

Leo


Re: New Chat: 2430A scope problem #chat-notice

Szabolcs Szigeti
 

Hi,

First of all, get the service manual and do the performance validation
checks and if necessary do the adjustment (calibration) for the 2430A
calibration is fairly simple, you don't really need much special equipment.
Also, check the power supply values and ripple, as the PSU in these units
are prone to cap leaking, and failure. So you can pretty much expect
recapping, and I say this even though I'm very much against indiscriminate
recapping of stuff as a general cure for everything. But so far I had three
24XX DSOs, out of these all three had to be recapped.


Szabolcs


TekScopes@groups.io Notification <noreply@groups.io> ezt írta (időpont:
2021. máj. 2., V, 15:28):

A new chat has been created:
New

I have bought a 2430A tek scope. the rising edge of the waveform is very
wobbly not just plain jittery, even on save mode. Looking for advice on how
to fix it. Also on how to fine tune this scope.
Thanks
kanwal

*By:* kanwal.jawanda@gmail.com

View/Join This Chat <https://groups.io/g/TekScopes/chat/8087>

Do not reply to this message to post to the chat. You can participate in
chats only through the group's website.




Re: Save this 533A from the trash in Arlington Virgina #photo-notice

 

It is sitting in my garage right now, awaiting space in the lab for a full intake inspection. It's a damn nice looking scope, and should be days of fun fixing up.

-- Jeff Dutky


Re: Save this 533A from the trash in Arlington Virgina #photo-notice

Glydeck
 

This is good news!

On May 2, 2021, at 10:18 AM, Reddy via groups.io <wpost2=verizon.net@groups.io> wrote:

Jeff Dutky picked up the scope today (Sunday).





Re: PG506 Repair - I had a Great Day today/

Michael W. Lynch
 

On Sun, May 2, 2021 at 07:44 AM, tek_547 wrote:


If you have the possibility pls check the 5V1 at the collector from Q70, mine
is 4,75V. For TTL logic (U670, 671, 673 & 675) this is the absolute minimum.
Maybe this is the reason of the problem so I am interested in the value from
your PG506.

And also look that if inside your PG506 T130 in the power supply is about
70°C when the STD AMP switch is activated. So almost not possible to you put
your finger on the windings of it. Is this on yours the same?
Thanks so far and hopefully you have some suggestions, Rene
Rene,

I will take another look at mine tomorrow. I will give you as much as I can as far has how mine acts. I will pay special attention to T130, including some temperature measurements. Your U400 measurements that you are describing do not sound correct.

Glad you included your control settings as we always need to standardize our panel settings when making measurements and observations, so that we can be on the same page. I believe that you can check the opto-couplers using a diode test. I had one bad 4N27 on my unit, one side checked as an NPN and the other side checked open, it should have checked as a diode.

One thing that you may find helpful and what helped me diagnose the issue with mine was actually diagramming the inputs, outputs and cross connections on U400. It is an SN74LS00N Quad 2 input Positive NAND gate, so sorting out what goes in and what comes out is important and helpful. This is how I finally isolated and found my problems, since U400 is sort of the "doorkeeper" to the rest of the circuit. .

--
Michael Lynch
Dardanelle, AR

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