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475A with High +110 rail

 

I have searched for a previous thread that was referred to in a post about a "high" 110 voltage rail on a 475 from back in 2012. I failed to find that post or any other applicable answer, perhaps I am not searching for the correct words? So I will ask for some help. I have a 475A with DM44 s/n B012228. After a thorough cleaning, I turned it on and find that for the most part it works great, no triggering issues, bright trace, all controls respond as expected, just dirty pots and switches. I supply various signals to the A and B channels and the scope displays a good trace with with amplitude matching the output of my signal generator, so calibration seems to be close enough for hobby work. The scope simply does not act as if there is anything wrong. For safety sake, I pulled the case and tested the various system voltages on the A9 interface voltage test points. I found everything to be spot on, except the +110 volt rail, Voltages as follows:
-15V = -14.998
-8V = -8.005
5V = 5.005
15V = 15.002
50V = 50.035
Unregulated 50V = 63.35
110V = 134.66

Line Voltage is 120V and the voltage calibrator on the transformer is set to the proper voltage. I pulled and tested Q1490, Q1494, Q1496 and Q1497. These all tested "good" with a transistor tester. I also replaced Q1490 and Q1494 with "Known Good" components, with no change noted in the +110V rail. I did not have exact replacements for Q1497 or Q1496, but they did both test good. I did go through to check and seat all the transistors that I could reach on all the boards. I checked the various resistors in LV +110 Supply regulator circuit (the ones I could reach) and found then to be very close to correct. I do not want to start un-soldering components without some idea of what to check next. I do not know if CR1489 has anything to do with the voltage regulation or not, but that component appears to be part of the +110 regulation system. Other than the "too high" +110 rail, the scope demonstrates no other issues, nothing smells "Hot" and no "magic smoke", The boards inside the scope are perfect, no signs of repairs, heat or damage. I just want to sort this out before I use the scope very much. Collector voltage on Q1497 is 134.5 and Q1496 at about 133.8. Almost everything agrees with the schematic EXCEPT that pesky +110V rail. Any ideas where to check next?


--
Michael Lynch
Dardanelle, AR


Re: 2465B Parametric Freq Measurement Error

 

Is my Tektronix 2465 DMS using the same part number or do I need a
different one?
Where would I find more information how to perform the replacement?
Thanks.
Tony

On Sun, Apr 28, 2019 at 8:43 PM Chuck Harris <cfharris@...> wrote:

The parametric measurements use the trigger hybrid extensively,
and their performance is directly related to how well that hybrid
performs. Some are better than others.

-Chuck Harris

joe@... wrote:
After successfully calibrating my 2465B, it reports "All tests passed"
on start up. The question marks are all gone! My issue is with the
parametric measurement of frequency. When I attempt to measure the
frequency of a sine wave at frequencies higher than 10 MHz, the scope
reports the frequency as 35.62 kHz. Any test frequency above 10 MHz gets
the exact same report, 35.62 kHz. Below 10 MHz, it reports various
incorrect values (i.e. a 4.89 MHz signal is reported as 6.35 MHz). At
about 500 kHz and lower frequencies, the scope reports the correct
frequency. I have replaced the PAL at U975 - no change. Any suggestions?






Re: 2465B Parametric Freq Measurement Error

 

If I replace the trigger hybrid, do I have to do the whole calibration again? Joseph Suste


Re: 2465B Parametric Freq Measurement Error

Chuck Harris
 

The parametric measurements use the trigger hybrid extensively,
and their performance is directly related to how well that hybrid
performs. Some are better than others.

-Chuck Harris

joe@... wrote:

After successfully calibrating my 2465B, it reports "All tests passed" on start up. The question marks are all gone! My issue is with the parametric measurement of frequency. When I attempt to measure the frequency of a sine wave at frequencies higher than 10 MHz, the scope reports the frequency as 35.62 kHz. Any test frequency above 10 MHz gets the exact same report, 35.62 kHz. Below 10 MHz, it reports various incorrect values (i.e. a 4.89 MHz signal is reported as 6.35 MHz). At about 500 kHz and lower frequencies, the scope reports the correct frequency. I have replaced the PAL at U975 - no change. Any suggestions?




Re: 2246 no display/odd behavior

 

Take note of where the grid bias R2719 is currently set by following the setup in the manual. You will do this in XY mode. See if you can get a dot displayed.

I agree that all the power supply rails look good.

The battery can be any 3.6 volt lithium cell with leads just for a test.

Good luck and regards


2465B Parametric Freq Measurement Error

 

After successfully calibrating my 2465B, it reports "All tests passed" on start up. The question marks are all gone! My issue is with the parametric measurement of frequency. When I attempt to measure the frequency of a sine wave at frequencies higher than 10 MHz, the scope reports the frequency as 35.62 kHz. Any test frequency above 10 MHz gets the exact same report, 35.62 kHz. Below 10 MHz, it reports various incorrect values (i.e. a 4.89 MHz signal is reported as 6.35 MHz). At about 500 kHz and lower frequencies, the scope reports the correct frequency. I have replaced the PAL at U975 - no change. Any suggestions?


My TDR Evaluation of the SG503 012-0482-00 Cable has been uploaded

 

I uploaded the results of my testing the SG503 012-0482-00 cable. In
addition I compared it to two other similar cables: a Tektronix 012-0057-00
50¦¸ cable, and a Pomona Electronics 50¦¸ cable.



It is located at:

/g/TekScopes/files/Evaluation%20of%20the%20Tektronix%20012-
0482-00%20cable%20for%20the%20SG503.pdf



Dennis Tillman W7PF


New file uploaded to [email protected]

[email protected] Notification
 

Hello,

This email message is a notification to let you know that a file has been uploaded to the Files area of the [email protected] group.

File: Evaluation of the Tektronix 012-0482-00 cable for the SG503.pdf

Uploaded By: Dennis Tillman W7PF

Description:
Detailed TDR examination of the SG503 012-0482-00 cable with a comparison to three other similar cables.

You can access this file at the URL:
/g/TekScopes/files/Evaluation%20of%20the%20Tektronix%20012-0482-00%20cable%20for%20the%20SG503.pdf

Cheers,
The Groups.io Team


2246 no display/odd behavior

 

Ok. I've removed the battery - have a new one on order. When reassembling I found that J2208 was installed backwards initially. Corrected but no change in behavior. All further testing is done with the battery removed:

Exact voltages:
+131.34
+58.201
+15.052
+7.4913
+5.2186
-5.2245
-7.5541
-16.005

These all seem to be in spec.

I have a 6kV probe on order - should be here in a few days. I will probe the HV line at that point.

Beam finder does nothing. There is no display at all - no text, no beam. No change whether the front panel is powered up or not.


Re: SG504 or 503 cable

 

Ok, compared the RG-58 Tektronix cable to an RG-400 I built of similar length.
At 200Mhz and 4Vpp (x1 amplitude) we have ....

The OEM Tektronix cable clocked in at 0.20 dBm low.

DIY RG-400 cable was only 0.01 dBm low!!

Now B4 you guys roast me over the Boonton 4210 microwattmeter with the 4210-4B sensor....
I make no claims, infer from the results what you will (expect 1.5% accuracy from the Boonton).

But...I feel pleased that the SG 503 combined with a RG-400 cable and the Boonton show what could be a nearly perfect output.
I must mention that I recently serviced the SG 503 using liquid de-oxit on the rotary frequency selector contacts and polished the brass nut and seat contact point on the variable tuning capacitor.

~A


Re: 2246 no display/odd behavior

 

How can you edit a post on this system?
Anyway-
Have you replaced the battery yet? Should do that first and reboot the scope several times to get the ram initialized.

Pay attention to the adjustments section, especially the power supply and beam (grid bias) adjustments.

What are the _exact_ low voltage measurements?

The ripples shown on your pictures all look good.

Can you measure the -2.7 kV line safely? That can be accessed by looking at the cathode or filaments on the CRT.

Does the Beam finder button do anything?

Regards


2246 no display/odd behavior

 

Ok so some updates:

I haven't found any previous posts that address my issues.

All voltages on the low side are in spec. Looking back at the ripple measurements in my first post I think they are all OK but a second set of eyes would be helpful. The p-p measurements seem high but there are very few points. The bulk of the points seem within the specs but there's some pronounced waveforms there that I don't know about being allowable.

I checked the ESR for all the electros on the power supply board - everything looks good (I used the Blue meter and tested in-situ).

Under the board I found a broken (lifted?) trace between C2244 and R2231. See here: I ran a jumper and re-assembled and no change in behavior. Still not display apart from a brief flash at power off and still the off behavior from the front LEDs where they don't power on unless I fiddle with the buttons.

There is a RIFA cap C2217 that looks a bit rough but not blown. I'm open to further suggestions or testing approaches. Still not sure if the two problems may be related or which I should focus on first. FWIW I can now get that PSU in and out in about 10 minutes flat... practice :D


Re: Powering up a 577 for the first time

 

The 577 used one of the Tek custom potted SMPS transformers if my memory is correct. Next to a tube failure, that is your biggest worry.
I agree with others.
Clean, repair power cord, fuse, power, debug any failure.
There are quite a few threads here on fixing a577.
Keep us up to date.

Sent from kjo iPhone


Re: Powering up a 577 for the first time

 

I think a good visual inspection followed by the use of an ohm meter would be my first plan. Then repair the cord and install the correct fuse. If you have an ESR meter, check the bulk capacitors and replace as necessary.

Power it up directly and measure the power rails next. I usually follow the performance section of the service manual as it will show you what works.

Calibration would be your next step and lead you to any troubleshooting that might still be needed.

Good luck and nice find with the cover still there.

Regards

On 4/27/2019 6:35 PM, groups@... wrote:
All,

While I was searching eBay for a transistor adaptor for my 576, I came across a parts 577 in good condition with both the adaptor and an original safety cover for a low price... and ended up snagging it, too.

It was advertised as not powering up - and on closer inspection, the power cable's strain relief is loose, and there's no fuse present. I can obviously fix both, but I'm wary of powering it up given that perhaps there's a reason the fuse is absent (although I'm comfortable checking rail voltages with suitable precautions once it's up). Any advice? Would a variac help?

Thanks,

Neil



Re: Powering up a 577 for the first time

 

If you use the correct fuse then the fuse will protect the equipment. If the fuse blows then you need to go into troubleshooting mode.

On April 27, 2019 4:35:59 PM MDT, groups@... wrote:
All,

While I was searching eBay for a transistor adaptor for my 576, I came
across a parts 577 in good condition with both the adaptor and an
original safety cover for a low price... and ended up snagging it, too.

It was advertised as not powering up - and on closer inspection, the
power cable's strain relief is loose, and there's no fuse present. I
can obviously fix both, but I'm wary of powering it up given that
perhaps there's a reason the fuse is absent (although I'm comfortable
checking rail voltages with suitable precautions once it's up). Any
advice? Would a variac help?

Thanks,

Neil

--
Sent from my Android device with K-9 Mail. Please excuse my brevity.


Re: Wanted: Earth leads with croc-clip for P6139A

 

I'm still wanting these if anyone can help.

Thanks
David

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of David C. Partridge
Sent: 04 April 2019 18:55
To: [email protected]
Subject: Re: [TekScopes] Wanted: Earth leads with croc-clip for P6139A

Yes I'm in the UK. You may be able to send them quite cheaply (about ten dollars for up to 8oz) if you use a pre-paid padded envelope 1st class international mailer.

Anyone closer?

David

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Stephen Hanselman
Sent: 04 April 2019 17:34
To: [email protected]
Subject: Re: [TekScopes] Wanted: Earth leads with croc-clip for P6139A

OK, I do have a bag of 6 inch long "ring" mount style and have verified them on my P6139. They have an alligator clip on the end.

Are you in the UK? Shipping will be more than the cost of the clips I'm afraid

steve

-----Original Message-----
From: [email protected] <[email protected]> On Behalf Of Stephen Hanselman
Sent: Thursday, April 4, 2019 8:35 AM
To: [email protected]
Subject: Re: [TekScopes] Wanted: Earth leads with croc-clip for P6139A

I¡¯m pretty sure I have a bundle of those I¡¯ll check when I get to the office

Regards,

Stephen Hanselman
Datagate Systems, LLC
3107 North Deer Run Road #24
Carson City, Nevada, 89701
(775) 882-5117 office
(775) 720-6020 mobile
s.hanselman@...
www.datagatesystems.com
a Service Disabled, Veteran Owned Small Business
DISCLAIMER:
This e-mail and any attachments are intended only for use by the addressee(s) named herein and may contain legally privileged and/or proprietary information. If you are not the intended recipient, any dissemination, distribution or copying of this e-mail and any attachments is strictly prohibited. If you have received this e-mail in error, please immediately notify me and permanently delete the original and all copies and printouts of this e-mail and any attachments.
On Apr 4, 2019, at 06:22, David C. Partridge <david.partridge@...> wrote:

No, those are the older ones the ones I'm looking for look like this:

<>

Dave

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of
Colin Herbert via Groups.Io
Sent: 04 April 2019 13:13
To: [email protected]
Subject: Re: [TekScopes] Wanted: Earth leads with croc-clip for P6139A

Would these do?


eads-w
ith-Alligator-Clip-Tektronix-HP/222659358233?ssPageName=STRK%3AMEBIDX%
3AIT&_
trksid=p2060353.m1438.l2649

They have a length of 7 inches (17.5 cm). I bought some a while ago
and they are fine, if possibly not genuine Tek. He also has the "witches hat"
grabbers for P6139, etc. probes. Be careful, though, as while he will
offer combined postage, eBay doesn't seem to go along with that. It
took me some time to get combined postage when I bought three items
from him. Of course, this might have improved, now.

Colin.

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of David C.
Partridge
Sent: 04 April 2019 12:03
To: TekScopes
Subject: [TekScopes] Wanted: Earth leads with croc-clip for P6139A

I'm looking for the earth leads with crocodile clip to fit the P6139A
and similar probes.

I have the ones that connect to mini-grabbers, but lack the croc-clip
versions.

Does anyone have these available?

Cheers, David











Powering up a 577 for the first time

 

All,

While I was searching eBay for a transistor adaptor for my 576, I came across a parts 577 in good condition with both the adaptor and an original safety cover for a low price... and ended up snagging it, too.

It was advertised as not powering up - and on closer inspection, the power cable's strain relief is loose, and there's no fuse present. I can obviously fix both, but I'm wary of powering it up given that perhaps there's a reason the fuse is absent (although I'm comfortable checking rail voltages with suitable precautions once it's up). Any advice? Would a variac help?

Thanks,

Neil


Re: A Probing Question

 

Hello Everyone,

Thank all of you who responded to this query and Raymond in particular.? I hope that there are a few other people in the group who benefited from this discussion.? I certainly did.? My aha moment came when I saw Raymond's mention of the 25 ohm output impedance for the DUT (confirmed by the ABC's).? To summarize what I think I have learned:? Obviously capacitive loading of higher z circuits at high frequencies would be a problem with any sort of mechanical probe.? In order to be able to sell and have people be able to compare the performance of higher frequency probes, the industry(Tek) had to draw a line in the sand for comparison purposes and that was done at 25 ohms.? The typical probe impedances at rated frequency of about 500 ohms then make perfect sense as that represents somewhere around an additional 5% load on the circuit being measured.? If the user is bent on trying to measure higher impedance circuits at high frequencies, then as the younger generation says, It is what it is!

Thank you for your time and bandwidth,

Jack Reynolds

On 4/27/2019 12:16 AM, Raymond Domp Frank wrote:
On Sat, Apr 27, 2019 at 05:59 AM, Raymond Domp Frank wrote:

If you want to do measurements on high-frequency signals or signals with
high-frequency content, always consider using Lo-Z probes like 1:1 50 Ohm,
1:10 500 Ohm or even 1:100 5 kOhm probes. These have relatively constant
impedance and many can be made at home. Search for that on the Internet.
You may want to look for an old-fashioned Lo-Z probe like a P6056 (500 Ohm) or P6057 (5000 Ohm). Even with their standard BNC connection, they work well with your more modern digital 'scope and can be bought for little money.

Raymond



11801 10x rise time measurement error

 

I just got bit by this yet again. Does anyone know if it was fixed and what ROM version fixes it?

Doing an "autoset" fixes it, but as I have not been able to identify what triggers it, it's hard to tell when I need to do an autoset again.

It is *really* annoying.

Thanks,
Reg


Re: [Test-Equipment] Suggestions for going through Tek2465DVS/DMM?

 

Thank you Siggi for your email and information.
I'll work on the scope today, despite needing to assemble few computers for
my customers.....
I was working way to hard and sometimes I need to "recharge my capacitors"
with some troubleshooting I don't know anything about!
It is great to get something old working again, so it has a chance to live
for a long time - I hope.
The capacitors you are talking about are my next project, I'll test and
look over all of them, not just the "square once".
Several people had suggestions, including couple that mentioned the stuck
Beam Switch, so that is my first goal today.
You have a GREAT Weekend!
Tony

On Fri, Apr 26, 2019 at 4:22 PM Siggi <siggi@...> wrote:

Good luck,

the RIFA caps are worth replacing, especially if you're in 240V land. Make
sure you replace them with properly specified X or Y class capacitors, as
required. You can find plenty of info about what that means on the
interwebs, but I wouldn't buy those from any but reputable sources.

Those old scopes are a work of art, and the service manuals are an
education - you're in for a treat :).

Good luck,
Siggi

On Fri, Apr 26, 2019 at 12:34 PM Tony Fleming <czecht@...> wrote:

Thank you very much for comprehensive email, that is pointing me to the
right direction!
It seems to me that the Beam Switch is sticking for sure and could cause
most of my problems.
I'll try to update the videos as soon as I make some progress.
Should I also replace some of the square caps that are something like
0.006xx nF? Many people do this ASAP, since these caps are not a good
quality - despite most of the parts are very good quality.
Where should I buy the caps and other parts, if I'll need them?
I'm sure, China and eBay should not be on my list for caps - right?
Anyway, Have a great day and I'll post videos so you can see what I did
and
the results that happen.
Have a great day and weekend!
Tony

On Fri, Apr 26, 2019 at 9:05 AM Siggi <siggi@...> wrote:

Hey Tony,

welcome to the group. I watched the videos you posted in another thread
detailing your 2465 CTS troubles <
>.
Here's my advice for how to proceed:

1. Get a service manual for your scope. You can download one from
here <
>, or if you're not satisfied with
the
scan quality you can buy a very good quality scan from Artek
Manuals <
>.
2. Get familiar with the controls of your scope. Alan Wolke has a
bunch
of tutorial-like videos on coupling and trigger setup and such,
there's
a
list of his YouTube videos here <
>.
3. Read this document <
>
on
how to troubleshoot oscilloscopes.

Now looking through your videos, I think you one problem for sure, and
possibly one more.

1. Your beam finder button sticks or glitches.
2. Something else, possibly more than one other problem.

It's very hard to reason about what the CRT is displaying while the
beam
finder is bad, but it's easy to fix. You can probably get by with
isopropyl
alcohol - just squirt some into the switch and work it several times.
If
that doesn't do it, get yourself some kind of contact cleaner (Deoxit
D5
is
what I use), and clean the switch with that.

What makes me think that you may have a second problem is the fact that
the
readout would sometimes shrink only in the horizontal, but it's
possible
that this is simply due to a high-resistance beam finder switch, so fix
that first.

Once the beam finder switch is good, it's possible to move forward to
diagnose whatever else is wrong, if anything. A key question I found
myself
asking while watching your videos was whether the intermittent
shrinking
affects only the readout, or whether it also affects the traces.
Unfortunately I didn't see the shrinkage occur while traces and readout
were both displayed.

Note that for the traces to be displayed, your triggering controls have
to
be set up right. If you set the trigger to AUTO & CH1, then set the CH1
coupling switch to GND coupling, you should be able to display all
traces
reliably.

Siggi

On Fri, Apr 26, 2019 at 1:12 AM Tony Fleming <czecht@...> wrote:

I have the same oscilloscope. It is also listed under (at least that
is
what I found today) as Tektronix 2465CTS (or 2465 CTS) .
Mine has some problems, sometimes I loose the text on top and bottom
of
the display and also the FIND BEAM gets stuck, so I don't know
exactly
where to find the solution.
Anyway, I hope your scope is working.

Tony Fleming