Date   

Re: 2235 power supply noise

mikepickwell@...
 

Thank you Ed.


I'll fill the hole with silicone and experiment with different values at R919.


Cheers, Mike


Re: 2235 power supply noise

Ed Breya
 

See message #76038. Ed


Re: 2235 power supply noise

Tom Jobe <tomjobe@...>
 

Thank you Hakan!
This kind of good information is very rare to see, and hopefully it will
help the current 2235 problem being worked on.
This information will help many folks in the future!
tom jobe...

On 10/20/2017 6:30 AM, hahi@telia.com [TekScopes] wrote:

I'm completely at a loss as to how to proceed now. Is the problem
elsewhere? Is my replacement
T906 faulty?
Please help!
This was a known problem at the time.
See these articles from the internal Service Info from 85 and 87:

//
RE: Mod #54681

Implemented in Manufacturing:

2213A B016090
22I5A B013550
2235 B015626
2236 B014885

The preregulator and DC-DC converter
frequencies may be harmonically close
enough to produce an audible beat.
This anomaly will only occur after
changing some major power supply
frequency determining part, e.g. T944.
Engineering, changed R919 to a
selectable part, allowing a Technician
to alter the preregulator frequency a
small, but sufficient amount, thereby,
stopping the audible beat.

R919 Nominal value 10Kohm 315-0103-00
Alternate value #1 11Kohm 315-0113-00
Alternate value #2 9.1Kohm 315-0912-00

AND:

2213/2215A /2235/2236 AUDIBLE NOISE
FROM POWER SUPPLY

REF: Mod #61544

S/N: Not available

There have been three "speakers"
identified in the 2200 Series which
emit high-frequency audible sound from
the power supply. Due to the urgency
of this change to the field, only two
of these components have been changed
on this mod. These components and new
Tektronix part numbers are as follows:

T906: Tektronix P/N 120-1439-01
C907: Tektronix P/N 285-1177-01

In a very few instruments T948 was
found to be the third culprit. Chang­ing
this part number will require UL
testing and recertification, so some
testing and evaluation need to be
conducted before the part can be modi­fied.

If an instrument comes into the Ser­vice
Center with this problem try changing
C907 first. If this does not eliminate the
sound, change T905.
//


/Håkan






[Non-text portions of this message have been removed]


Re: 2235 power supply noise

mikepickwell@...
 

Many thanks for the helpful replies folks.


I just removed R919 and it measured as almost exactly 10K. I don't have any 9.1K or 11K resistors so a put back in a 10K paralleled with a 1M making 9.09K. This didn't change anything.


I don't know what damping substance Tektronix used but I would think that high temperature RTV sealant would be suitable. Do you think I should give this a try?


Holding the probe near T906 I get a very clear waveform with a period of about 48uS which I believe gives a frequency of about 20.8kHz. Obviously that's not the loud audible frequency I can hear though as 20K is too high. However, half that (i.e. about 10,000Hz) would make sense. I just tried playing about with a test tone generator and I estimate the noise the scope is making is indeed about 10,000Hz


I have a frequency counter on my multimeter. Please can someone tell me where best to connect the leads of the multimeter to measure the frequency the HVO.


Thanks, Mike


Re: 2235 power supply noise

 

T906 / T905? Is that a typo?
I just saw that. OCR program error, sorry.
Should be T906.

/Håkan


Re: 2235 power supply noise

n4buq
 

2213/2215A /2235/2236 AUDIBLE NOISE
FROM POWER SUPPLY

REF: Mod #61544

S/N: Not available

There have been three "speakers"
identified in the 2200 Series which
emit high-frequency audible sound from
the power supply. Due to the urgency
of this change to the field, only two
of these components have been changed
on this mod. These components and new
Tektronix part numbers are as follows:

T906: Tektronix P/N 120-1439-01
C907: Tektronix P/N 285-1177-01

In a very few instruments T948 was
found to be the third culprit. Chang­ing
this part number will require UL
testing and recertification, so some
testing and evaluation need to be
conducted before the part can be modi­fied.

If an instrument comes into the Ser­vice
Center with this problem try changing
C907 first. If this does not eliminate the
sound, change T905.
//


/Håkan
T906 / T905? Is that a typo?

Barry - N4BUQ


Re: 2235 power supply noise

 

I'm completely at a loss as to how to proceed now. Is the problem elsewhere? Is my replacement
T906 faulty?
Please help!
This was a known problem at the time.
See these articles from the internal Service Info from 85 and 87:

//
RE: Mod #54681

Implemented in Manufacturing:

2213A B016090
22I5A B013550
2235 B015626
2236 B014885

The preregulator and DC-DC converter
frequencies may be harmonically close
enough to produce an audible beat.
This anomaly will only occur after
changing some major power supply
frequency determining part, e.g. T944.
Engineering, changed R919 to a
selectable part, allowing a Technician
to alter the preregulator frequency a
small, but sufficient amount, thereby,
stopping the audible beat.

R919 Nominal value 10Kohm 315-0103-00
Alternate value #1 11Kohm 315-0113-00
Alternate value #2 9.1Kohm 315-0912-00

AND:

2213/2215A /2235/2236 AUDIBLE NOISE
FROM POWER SUPPLY

REF: Mod #61544

S/N: Not available

There have been three "speakers"
identified in the 2200 Series which
emit high-frequency audible sound from
the power supply. Due to the urgency
of this change to the field, only two
of these components have been changed
on this mod. These components and new
Tektronix part numbers are as follows:

T906: Tektronix P/N 120-1439-01
C907: Tektronix P/N 285-1177-01

In a very few instruments T948 was
found to be the third culprit. Chang­ing
this part number will require UL
testing and recertification, so some
testing and evaluation need to be
conducted before the part can be modi­fied.

If an instrument comes into the Ser­vice
Center with this problem try changing
C907 first. If this does not eliminate the
sound, change T905.
//


/Håkan


Re: 2235 power supply noise

Bert Haskins
 

On 10/20/2017 7:24 AM, mikepickwell@hotmail.com [TekScopes] wrote:

Time for another update:


My replacement T906 arrived from Canada this morning. Annoyingly I had
to pay the post office £15 for import duty and handling making the
final cost for the part about £60.


I've just installed it and I was gutted to find that the high pitched
squealing noise coming from the power supply section is just as bad as
ever. Aargh!


The good news is that the recap has obviously done the scope some good
as the trace is now cleaner and sharper than I have ever seen it.


So just to summarise:


I've replaced all of the electrolytic capacitors apart from a few
small 22uF in awkward positions. All of the electrolytics around the
power supply have been changed.


I've also replaced T906 and CR907.


The scope seems to function perfectly as far as I can tell but it
makes a god awful high pitch squealing noise which drives you crazy
after a few minutes.


I'm completely at a loss as to how to proceed now. Is the problem
elsewhere? Is my replacement T906 faulty?


Please help!
Are you sure that the HVO is not running at too low frequency?
It should be running well above the human hearing range.
I would expect it to be about 60Khz.
I would think that you could read the frequency right from the 2235 just
by having the probe near the xformer.
If not just make up a small loop at the end of the probe.
-Bert


[Non-text portions of this message have been removed]


Re: 2235 power supply noise

chipbee40
 

T906 is the usual cause of squeal from the power supply. Later versions had the center hole filled with a white goop. I seem to remember a discussion on here about how to do it/ what to use. I had some success with coating the transformer with transformer lacquer. Put it in a poly bag and squish it into all orifices. Did your replacement have the hole filled?
The other possibility is too much current draw. Maybe something else is failing. how hot does the side of the scope get?


Re: 2235 power supply noise

mikepickwell@...
 

Time for another update:


My replacement T906 arrived from Canada this morning. Annoyingly I had to pay the post office £15 for import duty and handling making the final cost for the part about £60.


I've just installed it and I was gutted to find that the high pitched squealing noise coming from the power supply section is just as bad as ever. Aargh!


The good news is that the recap has obviously done the scope some good as the trace is now cleaner and sharper than I have ever seen it.


So just to summarise:


I've replaced all of the electrolytic capacitors apart from a few small 22uF in awkward positions. All of the electrolytics around the power supply have been changed.


I've also replaced T906 and CR907.


The scope seems to function perfectly as far as I can tell but it makes a god awful high pitch squealing noise which drives you crazy after a few minutes.


I'm completely at a loss as to how to proceed now. Is the problem elsewhere? Is my replacement T906 faulty?


Please help!


Re: Fast Rise/Fall Time Pulser

Adrian Nicol
 

I had a quick look at that same 'scope at the show yesterday - very, very nice but on price I got the impression it is one of those "If you have to ask you can't afford it" bits of kit!


On Thursday, October 19, 2017 10:34 PM, "'Craig Sawyers' c.sawyers@tech-enterprise.com [TekScopes]" <TekScopes@yahoogroups.com> wrote:


  > I wonder how long we will wait until these show up on ebay :).

I'll almost certainly be in my box before that 33GHz real-time beast becomes affordable!

Craig

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Re: Restoring a type 547 and 422 scopes (also my introduction to the group=

The Guy
 

Hi all,
Been trying to continue fixing this wonderful scope (it has a problem with the time base B triggering system), and it is developing some further problems, it is and old grandpa this scope.
 It was working pretty well until now besides the channel B triggering issue, but it just started doing some weird stuff... like right after start up the intensity remains maxed up while the intensity knob doesn´t do crap. If I fiddle with the TIME/CM knob a little, suddenly the trace deflects up disappearing actually for a while. When it comes back down the intensity magically appears to be right (dimmed down) and the intensity control starts working again as well. Weird.
After a while the trace also starts to deflect down and back to the center of the screen, it sorts of "faints" down, some sort of weird quick voltage variation happening somewhere. Could be a leaky cap?
Any ideas? This thing seems to be heading south real quick...
Thank you.

On Thursday, September 7, 2017 9:35 AM, "Kevin Wood mailinglists@the-wood-family.com [TekScopes]" <TekScopes@yahoogroups.com> wrote:


Well, this prompted me to fire up my 546 to check and.. you're
absolutely right. Not sure where I got the feeling that the filament
glowed visibly. I'm sure I've seen a delay element that does light up..
Then again, I remembered it being on the central bulkhead of the 'scope
and not down with the rest of the PSU components so I clearly confused
it with something else.

Anyway, apologies for the bum steer.

Kevin
G7BCS

On 06/09/17 16:59, David Wise david_wise@phoenix.com [TekScopes] wrote:
K600's heating element does not heat to visible temperature.  The only sign that it is warm is its contacts closing. 

------------------------------------

------------------------------------


------------------------------------

Yahoo Groups Links


Re: OT my 22xx plotter belt is gone how to repair?

Harvey White
 

On Thu, 19 Oct 2017 16:55:18 -0400, you wrote:

The little pen plotter that I sometimes use with my 2230 and 2232 scopes
has a cog belt that has rotted.
Several chunks have just come off.
This is a new one for me.
Any ideas on what I can do to replace the belt?
I actually have some belts that are much longer so the trick might be
how to shorten one of them.
From the markings on the belt and measurements you can determine the
type of belt. McMaster-Carr (www.mcmaster.com) has a good stock of
belts, as well as a very good catalog with lots of belt information.

Harvey



Thanks,
Bert


Re: OT my 22xx plotter belt is gone how to repair?

Ed Breya
 

Did you look around for info on the plotter to see if it can be found? Also, maybe the belt has some ID markings. Or, maybe the pulleys are marked. These sorts of things are somewhat standardized, so maybe possible to get exact replacements.

If you can't ID it, you can search among standard ones by the dimensions, including drive lug size and pitch.

Ed


Re: OT my 22xx plotter belt is gone how to repair?

Ted Rook
 

You could give these people a try

http://www.sdp-si.com/products/Timing-Belts-and-Cables/index.php

also McMaster-Carr has a small selection of belts

both these firms do small orders with credit card payment.

Ted

On 19 Oct 2017 at 16:55, Bert Haskins bhaskins@chartermi.net [TekSc[TekScopes] OT my
22xx plotter belt is gone how t wrote:


The little pen plotter that I sometimes use with my 2230 and 2232 scopes
has a cog belt that has rotted.
Several chunks have just come off.
This is a new one for me.
Any ideas on what I can do to replace the belt?
I actually have some belts that are much longer so the trick might be
how to shorten one of them.

Thanks,
Bert


Re: AN/USN-425(V)1 465M practically dead.

dmb06851@...
 

I will look into that tomorrow, thank you Barry.


Re: AN/USN-425(V)1 465M practically dead.

n4buq
 

From: "dmb06851@yahoo.com [TekScopes]" <TekScopes@yahoogroups.com>
To: TekScopes@yahoogroups.com
Sent: Thursday, October 19, 2017 4:04:45 PM
Subject: Re: [TekScopes] AN/USN-425(V)1 465M practically dead.

No Barry. Nothing lights except the screen graticule illumination.
Have you checked the low-voltage power supply values? There are a few test points that are labeled with their appropriate values located near F558.

Thanks,
Barry - N4BUQ


Re: Fast Rise/Fall Time Pulser

Ed Breya
 

Fabio, when you wrote:

"Wow!
That's fast!
I wonder what's the input capacitance of this 33GHz beast."

I assume you were talking about the scope. Ideally, there is no input capacitance - just 50 ohms.

Ed


Re: Fast Rise/Fall Time Pulser

Craig Sawyers <c.sawyers@...>
 

I wonder how long we will wait until these show up on ebay :).
I'll almost certainly be in my box before that 33GHz real-time beast becomes affordable!

Craig


Re: Fast Rise/Fall Time Pulser

 

I wonder how long we will wait until these show up on ebay :).

----- Original Message -----
From: Fabio Trevisan fabio.tr3visan@gmail.com [TekScopes]
To: TekScopes@yahoogroups.com
Sent: Thursday, October 19, 2017 11:24 AM
Subject: Re: [TekScopes] Re: Fast Rise/Fall Time Pulser



Wow!
That's fast!
I wonder what's the input capacitance of this 33GHz beast.

Brgrds,

Fabio

On Oct 18, 2017 7:35 PM, "groups1234567890@yahoo.com [TekScopes]" <
TekScopes@yahoogroups.com> wrote:

Earlier today I had an opportunity to ask Tek engineers to test the pulser
on 33GHz bandwidth realtime DPO73304SX scope. It is an impressive
instrument because it is a realtime (not a sampling) scope and triggers
from the input signal itself. Here are some pictures. I hope LCD Tek
equipment is still (barely) within bounds here.
Leo

http://leobodnar.com/balloons/NTP/Tektronix-1.jpg
http://leobodnar.com/balloons/NTP/Tektronix-1.jpg
http://leobodnar.com/balloons/NTP/Tektronix-2.jpg
http://leobodnar.com/balloons/NTP/Tektronix-2.jpg

http://leobodnar.com/balloons/NTP/Tektronix-3.jpg
http://leobodnar.com/balloons/NTP/Tektronix-3.jpg

http://leobodnar.com/balloons/NTP/DPO73304SX-1.png
http://leobodnar.com/balloons/NTP/DPO73304SX-1.png



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