Date   

Re: Cleaning push button switches on 7603, 7B53, 7CT1N Etc.

 

The following only applies to the large marked pushbutton switches. It
does *not* apply to the small unmarked transparent switches found on
plug-ins like the timebases and early vertical plug-ins.

These switches can be cleaned with any safe solvent like alcohol or
naphtha however because they use sliding contacts, they must also be
lubricated or the contact surfaces will abrade and destroy themselves.
Naphtha is a very common "plastic safe" cleaner. Common lubricants
are silicon or poly phenyl ether oil. Silicon oil is kind of annoying
because it tends to creep over surfaces so I prefer the later.

I have been using this for both switches and potentiometers but there
are lots of options:

https://www.mgchemicals.com/products/cleaning-products-for-electronics/cleaners/contact-cleaners/super-contact-cleaner-with-ppe-801b

I spray the contact cleaner and lubricant into a needle oiler so I can
drip it into the switch without making a mess.

On Mon, 29 Jan 2018 10:01:09 -0800, you wrote:

Hello the group. This is my first post here. Nice group, improved forum workability!

Just repaired a 7603 I had in storage. Still, the push button switches are intermittent and even slow (sticky?). Just the same as the push button switches on a 7B53 and my 7CT1N.

1) Were these kind of switches lubricated?
2) Then, is this dried out lubricant?
3) What is the best way to both clean these switch contacts and remove the sluggishness?

Thanks for any assistance,
Stan


Re: 7603 PSU failure - got a screw loose?

 

Those are great pictures, thanks. I have not seen the PS503 service
manual or internal photographs of the PS503 before which predates the
PS503A.

The A version supports a 1 amp output current when used in a high
power slot and instead of a TO-3 packaged regulator, uses a TO-220
packaged regulator mounted up against the inside of the plug-in
chassis for a heat sink. Now I know that the board layout for the
PS503A was completely changed from the PS503 as shown below:

https://groups.io/g/TekScopes/album?id=21134

This is the unit which I ran through my ultrasonic cleaner
inadvertently removing the markings on the ICs and some other parts. I
changed all of the icky Texas Instruments IC sockets, replaced the
input and output capacitors, and replaced one bad bridge rectifier
with a unit from a defunct ATX power supply. In the lower right
corner, you can see the LED I added across the +5 volt output to show
that power is applied.

On Mon, 29 Jan 2018 01:23:37 -0800, you wrote:

Hi,

in my PS503 they used one of these sockets too for the 5V TO-3 regulator.
Here some pics: https://groups.io/g/TekScopes/album?id=21086

Leo


Cleaning push button switches on 7603, 7B53, 7CT1N Etc.

brasscat
 

Hello the group. This is my first post here. Nice group, improved forum workability!

Just repaired a 7603 I had in storage. Still, the push button switches are intermittent and even slow (sticky?). Just the same as the push button switches on a 7B53 and my 7CT1N.

1) Were these kind of switches lubricated?
2) Then, is this dried out lubricant?
3) What is the best way to both clean these switch contacts and remove the sluggishness?

Thanks for any assistance,
Stan


Re: Tektronix 454

Roger Evans
 

Erik,

I am about to go on holiday so here is something of a long list.

Make sure the Ch2 V/div switch is cleaned with IPA and rotated back and fore a few times.

It is just possible that one of the C149A - J trimmer capacitors has developed a short circuit, perhaps with some foreign object.

Read the theory of operation section of the manual, it shows how the V/div switch has three separate functions, input attenuator, and two sets of gain switching. There is a table showing which parts are switched in at each V/div setting so it helps to narrow down the source of the problem.

Make sure the CH1 preamp and the main Y amplifier are close to being correct. With the input set to GND the trace should be centred on the screen with the vertical position control around midway for all V/div setings. You should be able setup the Ch1 step attenuator balance according to the instructions in the manual. Also the V/div setiings should be close to correct. This is to make sure that the Ch2 preamp is the only source of major imbalance.

If you are following the schematics in a scanned version of the manual beware that the original has blue lines showing where components are located on particular circuit boards. These scan in as black lines and even have (oversized) dots where they cross real interconnections.

Set Ch2 input to GND and at least to begin with choose a V/div setting where the beam is on screen. If you can, centre the trace vertically else go as close as possible to centre. Measure the voltages at the grid of V113, cathode of V113 and collector of Q24 and compare with the manual.

Measure the voltage at R137 and see how it varies with the vertical position control.

Measure the following: collector Q124, collector Q134, emitter Q134, collector Q144, emitter Q144 and compare with the manual. How do they change when you rotate the V/div switch? Is there an obvious correlation of the voltages that disagree with the manual with which segments of gain switching are in use?

If you are suspicious of any of the transistors then swap them, one at a time with the corresponding part in Ch1. Maybe clean the legs while they are out. If you are not sure of the significance of any of the measurements then repeat them on Ch1.

If you get this far and all is well then refer to my previous e-mail for probing around Q164, Q174, Q184 and Q194.

Regards,

Roger


New file uploaded to TekScopes@groups.io

TekScopes@groups.io Notification <TekScopes+notification@...>
 

Hello,

This email message is a notification to let you know that a file has been uploaded to the Files area of the TekScopes@groups.io group.

File: Dynamic Load v2.DSN

Uploaded By: NigelP

Description:
Corrected Schematics with notes added

You can access this file at the URL:
https://groups.io/g/TekScopes/files/Dynamic%20Load%20v2.DSN

Cheers,
The Groups.io Team


New file uploaded to TekScopes@groups.io

TekScopes@groups.io Notification <TekScopes+notification@...>
 

Hello,

This email message is a notification to let you know that a file has been uploaded to the Files area of the TekScopes@groups.io group.

File: Dynamic Load Schematic v2.PDF

Uploaded By: NigelP

Description:
Corrected Schematics with notes added

You can access this file at the URL:
https://groups.io/g/TekScopes/files/Dynamic%20Load%20Schematic%20v2.PDF

Cheers,
The Groups.io Team


Re: Any experience with ELECTRONIC LOADS would be appreciated

NigelP
 

Whoops! Thanks for spotting that; I'll correct it but you can all assume the "normal" way of connecting a bridge is what is supposed to be done!

And now I've spotted more errors...... C1&2 should be much bigger.... 1000uF each, and R1/2/3/4 should be 2R2 each! Looks like I failed to fully edit the default values in all those positions. Too much haste and not enough speed :(; too excited about catching up on all the old stuff again and also finding that some of the old pencil&paper schematics weren't entirely in line with the actual hardware!

I'll correct and re-issue, apologies for any misleading issues. I've also added some useful notes.

Regards

Nigel


Tek Model 305 problem

wallace.gibbons
 

Greetings,
I have a 305 scope on the bench with a small problem. There's a small pulse
type waveform riding on top of any waveforms being displayed. It can be
seen with another scope by probing the vertical output amplifier outputs to
the CRT, and the vertical outputs from the main board.

If I disconnect the input to the vertical output amp board the trace is a
nice flat line. Good focus, very sharp line.

I assume from this that the errant signal is coupling into the vertical
channels on the main board. Probing the power supply outputs with another
scope has proved that only one supply was "noisy". I saw the pulse type
noise on the +150 volt power supply. I changed the two 10uf filter caps to
no avail. The +150 volts really isn't used in the signal chain but I
thought I'd eliminate it as a source.

The plus and minus 3 volt supplies look clean.

Has anyone seen this on a Model 305?

I know it's not a top of the line scope, not worth a whole lot, but it's a
friends and it's good enough for him to work on guitar amps and such.

Thanks,

Wally Gibbons
North Logan, Utah


Re: Focus on 475 scope

 

One issue I have seen on the 465 and 475 is the accumulation of black soot on many HV parts. I ran into exactly your problem more than once, and found that carefully cleaning all the soot with Q-tips and water or alcohol, and removing every bit of the (conductive) soot fixed my "insoluble" focus problem. it provides a sneak path for HV leakage, and disturbs the electron gun bias. the older the scope is, the more likely this problem becomes, you have to remove the aluminum HV protective cover to see it!

at the end of the day, keep in mind, this mesh style tube does not ever look really sharp in terms of focus.

this is really worth a try if nothing else seem to be wrong.
all the best,
walter
sphere research corp.


Re: Focus on 475 scope

donald collie
 

Looked at the photos - yes, that`s about as sharp as mine goes.
Cheers!...............................................................................................................................Don
C.

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On Mon, Jan 29, 2018 at 5:24 PM, Chuck Harris <cfharris@erols.com> wrote:

Usually, a pretty safe way is to force it to be out of focus
by turning the focus control fully one way, or the other.

-Chuck Harris

David Hess wrote:
My 7603 which spent considerable time in storage had its brightness
and sharpness improve after operating for days. if you do this, then
leave the beam intensity low but not off and for safety, only leave
the oscilloscope operating under supervision in case something goes
wrong.

On Fri, 26 Jan 2018 09:21:10 -0500, you wrote:

If your scope intensity double peaks, it could mean
that it is gassy, or it could mean that it has low
emission. Running the CRT will help get the gas
absorbed by the getter, so it may improve.

-Chuck Harris





Re: 7603 working .... then blank

Adrian Nicol
 

So there is a concurrent thread running on 7603 PSU failure (mine!!), which originated from the same symptoms:

All working, then a few seconds of 100Hz 'wiggling' then cold and dark, that thread might be worth a read?

PSU related so start there. Dead easy to check all the rails by removing the rear plastic cover (four screws) drop out the PSU LV Regulator PCB (four more screws) and all voltages both in and out, are easily accessible for probing on the assorted ribbon cables.

Take care 'unfolding' the board as the ribbons are stiff and in my case anyway, were snagged round stuff so it is easy to bend the SIL connector pins.  See  the SM schematic for details and yes, input voltages are on load, noticeably higher when things are not running!

Good luck,

Adrian

On 1/29/2018 10:09 AM, tinkera123 wrote:
Hi all,

Some background before questions:-

I picked up another 7603 Scope with 2 x 7A15A Vertical Plugins and a 7B53A Time Base ….. Beaverton B338,855 …. with Tek trolley, several basic probes, original Tektronix manuals and a few other bits and pieces …. very cheap as not many offered for sale in Australia that I know of.

So …. the common question is …. do I turn it on?? ……. or do a lot of testing first?? Usually, no …. all my old radios have been full of old electrolytics, wax, paper caps …. rat/mouse eaten …. used as a toilet etc.. But this Scope came to me as “Good operational condition” and I had photos of it working before I purchased and the guy was a retired telecommunications techo …

So yes, I gave it the once over …. power cord, correct voltage, Jumper in correct position, nice and clean, no burnt components, no burnt smells etc etc.. My intention was to turn it on …. side covers off … Safety goggles on … then check voltages at P1171 with Scope running.

I found the following issues:-

1. The display (no signal) was a bit fuzzy with some interference through it. This disappeared as the Scope warmed up.
2. The display completely disappeared for a second or two before re-appearing as normal. This decreased as the Scope warmed up.
3. Vertical Plug-in 2 Screen readout showed a “u” instead of a “V”. This slowly corrected to a “V”.

Calibrator functioned as I expected. All knobs functioned as expected. I was starting to relax …..

4. Then the Scope completely shut down ….. no Display (it transitioned from a normal looking square wave to squiggling lines to blank over 1 to 2 secs) …. Power light out …. Not sure about the Fan.

Waited for 10 mins and tried again …. The Fan operated, nothing else …. Same next morning. I will never know if these issues were already 'known' or occurred during transporting.
Currently, I am going through the circuit diagrams to work out what the possible causes could be …. making sure I can identify all the Boards, connectors, Tek terminology etc..

Questions:-
1. I would appreciate some expert opinions as to the probable cause(s)??
2. Am I correct I assuming that the voltages at P1171 are under operating conditions??

Cheers,
Ian


Re: 7603 working .... then blank

cmjones01
 

On Mon, Jan 29, 2018 at 02:09 am, tinkera123 wrote:
4. Then the Scope completely shut down ….. no Display (it transitioned from
a normal looking square wave to squiggling lines to blank over 1 to 2 secs)
…. Power light out …. Not sure about the Fan.
This is likely to be a failed tantalum bead capacitor, quite possibly in one of the plugins. To find it, take the plugins out one by one and try switching the scope on. If it comes out, you've found out which plugin has the problem. If it doesn't work even with all the plugins removed, the fault is in the mainframe.

To find the culprit in plugins, I just go round with my meter on continuity test range checking across all the likely-looking components. One failed short-circuit will typically make all the others on that power supply rail appear short-circuit too, so unless you have a ToneOhm or other means of isolating faults, desolder or cut one leg of any capacitor that appears shorted and check again. When I think I've found the problem, I try out the plugin with the offending capacitor removed. It may not meet its performance specs but it'll certainly tell you whether it's basically working or not.

Chris


Re: Help with CG5001AP/CG551AP calibration generators

 

Mod JB just adds GPIB to the 506

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of walter shawlee
Sent: 29 January 2018 01:05
To: TekScopes@groups.io
Subject: [TekScopes] Help with CG5001AP/CG551AP calibration generators

Tekwiki says that a TM506 modded JB is required to run it, but I have no idea what that mod does


7603 working .... then blank

tinkera123
 

Hi all,

Some background before questions:-

I picked up another 7603 Scope with 2 x 7A15A Vertical Plugins and a 7B53A Time Base ….. Beaverton B338,855 …. with Tek trolley, several basic probes, original Tektronix manuals and a few other bits and pieces …. very cheap as not many offered for sale in Australia that I know of.

So …. the common question is …. do I turn it on?? ……. or do a lot of testing first?? Usually, no …. all my old radios have been full of old electrolytics, wax, paper caps …. rat/mouse eaten …. used as a toilet etc.. But this Scope came to me as “Good operational condition” and I had photos of it working before I purchased and the guy was a retired telecommunications techo …

So yes, I gave it the once over …. power cord, correct voltage, Jumper in correct position, nice and clean, no burnt components, no burnt smells etc etc.. My intention was to turn it on …. side covers off … Safety goggles on … then check voltages at P1171 with Scope running.

I found the following issues:-

1. The display (no signal) was a bit fuzzy with some interference through it. This disappeared as the Scope warmed up.
2. The display completely disappeared for a second or two before re-appearing as normal. This decreased as the Scope warmed up.
3. Vertical Plug-in 2 Screen readout showed a “u” instead of a “V”. This slowly corrected to a “V”.

Calibrator functioned as I expected. All knobs functioned as expected. I was starting to relax …..

4. Then the Scope completely shut down ….. no Display (it transitioned from a normal looking square wave to squiggling lines to blank over 1 to 2 secs) …. Power light out …. Not sure about the Fan.

Waited for 10 mins and tried again …. The Fan operated, nothing else …. Same next morning. I will never know if these issues were already 'known' or occurred during transporting.
Currently, I am going through the circuit diagrams to work out what the possible causes could be …. making sure I can identify all the Boards, connectors, Tek terminology etc..

Questions:-
1. I would appreciate some expert opinions as to the probable cause(s)??
2. Am I correct I assuming that the voltages at P1171 are under operating conditions??

Cheers,
Ian


Re: 7603 PSU failure - got a screw loose?

satbeginner
 

Hi,

in my PS503 they used one of these sockets too for the 5V TO-3 regulator.
Here some pics: https://groups.io/g/TekScopes/album?id=21086

Leo


Re: NVRAM 2465 /2467 replacement

ADas
 

Hi John,
Yes I saw a few people had toyed with the idea of somehow getting a readout of the NVRAM, thats how i got my idea. Tek Scopes is an amazing community with a wealth of expertise.
The copy process turned out to be pretty simple really, mainly for three reasons, firstly the firmware eprom is socketed on the a5 board, so easy to take out. Secondly since the new nvram can be used to load the copy program into it, additional chips are not required. Thirdly the 27c011 eprom used for firmware is pin compatible with the DS1225, so the nvram can be placed in the eprom socket. I only had to learn the 6802 instructions, reset vector start address etc. The whole program to copy is only around 50 bytes. If any one else is interested i will post it.
cheers
ADAS


Re: Focus on 475 scope

Chuck Harris <cfharris@...>
 

Usually, a pretty safe way is to force it to be out of focus
by turning the focus control fully one way, or the other.

-Chuck Harris

David Hess wrote:

My 7603 which spent considerable time in storage had its brightness
and sharpness improve after operating for days. if you do this, then
leave the beam intensity low but not off and for safety, only leave
the oscilloscope operating under supervision in case something goes
wrong.

On Fri, 26 Jan 2018 09:21:10 -0500, you wrote:

If your scope intensity double peaks, it could mean
that it is gassy, or it could mean that it has low
emission. Running the CRT will help get the gas
absorbed by the getter, so it may improve.

-Chuck Harris



Re: Focus on 475 scope

 

It may be just a difference between the 475 and 475A oscilloscopes.
Someone else may know.

The power supply rejection of the vertical amplifier chain is not
infinite so excessive power supply noise might end up being displayed.
This could be caused by worn out or bad decoupling capacitors.

As a test to determine if the problem is with the circuits or the CRT,
I would short the vertical deflection pins together to see how this
affects the trace thickness. DO NOT short the vertical CRT pins to
ground or any other points as this will likely destroy the vertical
CRT amplifier; only short them together.

I had considerable trouble with Microsoft's sharing service. If I
thought someone could make something worse than Google Drive or Yahoo
Groups, then I was wrong.

On Wed, 24 Jan 2018 06:49:08 -0800, you wrote:

Hi everyone, i have 2. scope 475. I had recap both and now full working. But the line on the second one isn't sharper than first one. I check high voltage. 2.72kv for the first and 2.6k for the second one. So fucus and asting are working but i cant adjust the line more than that. Someone know what will be the problem ?

Thank you :)

Look picture here
https://1drv.ms/f/s!AnKLPDy3pII_gkwm-YPX7azSL7Y2


Re: Focus on 475 scope

 

My 7603 which spent considerable time in storage had its brightness
and sharpness improve after operating for days. if you do this, then
leave the beam intensity low but not off and for safety, only leave
the oscilloscope operating under supervision in case something goes
wrong.

On Fri, 26 Jan 2018 09:21:10 -0500, you wrote:

If your scope intensity double peaks, it could mean
that it is gassy, or it could mean that it has low
emission. Running the CRT will help get the gas
absorbed by the getter, so it may improve.

-Chuck Harris


Re: Focus on 475 scope

 

And the expansion mesh also creates a ghost from secondary emission
which follows and then proceeds the beam spot across the CRT. The
ghosting has the effect of reducing display contrast.

On Thu, 25 Jan 2018 11:22:06 -0800, you wrote:

The mesh itself also makes the beam fuzzier - even it is perfect on the way in. Like looking through a screen door. Ed

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