First thing is to check the power supply test points. After adjusting the sweep span you can check accuracy using a 5 or 10 mhz TCXO or equiv. Some counters have a rear panel output or find one on e-bay.
Bill, KB3DKS

groups.io not group.io

Dave

I've created two new groups on Groups.io Solartron_Schlumberger_Equipment
and Datron-Wavetek for discussion of Solartron/Schlumberger and
Datron/Wavetek T&M equipment respectively.




All welcome

Cheers

Dave Partridge

Stefan,


I do have the very good manual. There is no details on the circuits. I fear I will be doing a recap on the controller. If I have to troubleshoot I plan on jacking the rear wheel up so I can use a scope in place.


Jerry Massengale

Sounds like one of the Tek scopes is going on a road trip ;-).

You have the manual, right? It shows the pinout for the speed sensor
but no schematics.

ST

On Sun, Apr 17, 2016 at 4:01 PM, jerry massengale j_massengale@aol.com
[TekScopes] <TekScopes@yahoogroups.com> wrote:

Hi,


My BadBoy Buggy has developed a fault that causes the buggy to creep along at a crawl. The controller flashes a * *** status that indicates that the controller is not seeing speed pulses from the speed sensor on the motor. This occurs after a minute or two of operation but will work again after cool off.


I have ordered a speed sensor kit on the advice of the manufacture but have my doubts about a heat sensitive sensor. When I disconnected the old one a lot of dust fell out.


I am hoping a group member may have some advice. These 48V systems are common on golf carts. The sensor may consist of a hall device and an NPN transistor run on 15V from the controller.



Jerry Massengale




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



------------------------------------
Posted by: jerry massengale <j_massengale@aol.com>
------------------------------------


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

Yahoo Groups Links

My question is can I do it with the time bases I have?

Isn't that what I said?

yes, pick your best and make it your standard


Jerry Massengale

thanks


Jerry Massengale

Hi Jerry,
Posting there has been disabled until the trigger is pulled.

On Sun, Apr 17, 2016 at 7:55 AM, jerry massengale j_massengale@aol.com
[TekScopes] <TekScopes@yahoogroups.com> wrote:

my msgs bounce

Jerry Massengale

Hi,


My BadBoy Buggy has developed a fault that causes the buggy to creep along at a crawl. The controller flashes a * *** status that indicates that the controller is not seeing speed pulses from the speed sensor on the motor. This occurs after a minute or two of operation but will work again after cool off.


I have ordered a speed sensor kit on the advice of the manufacture but have my doubts about a heat sensitive sensor. When I disconnected the old one a lot of dust fell out.


I am hoping a group member may have some advice. These 48V systems are common on golf carts. The sensor may consist of a hall device and an NPN transistor run on 15V from the controller.



Jerry Massengale

I believe it was mentioned that, for now, posting is disabled as it's just a backup in case something happens to Yahoo. That wasn't mentioned in the welcome email I got from Groups.io, though, so that could cause some confusion.

John

To: tekscopes@yahoogroups.com
From: TekScopes@yahoogroups.com
Date: Sun, 17 Apr 2016 09:55:43 -0400
Subject: [TekScopes] cannot msg group.io


























my msgs bounce



Jerry Massengale























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

my msgs bounce


Jerry Massengale

Thanks for the replies. I have neither a standardiser nor a calibrator nor the 7B71 mentioned in the manual. My question is can I do it with the time bases I have?

If you have a Good standardizer you can set the Horizontal sweep on the mainframe and then adjust your timebases to your Time standard generator(TG 501). This is more an in-house concern and not necessary if you are not sharing time bases.


Jerry Massengale

7704A actually (does it make a difference?) and yes I have the manual, that's where I got the
procedure from.

Yup. The 7704 was a first generation instrument (1969) and there quite a lot of differences between
that and the 7704A (1973 onwards).

Anyway, if you have three timebases which all vote that the horizontal gain of the mainframe is out
of calibration *by the same factor*, I'd tend to adjust the mainframe horizontal gain on that basis.
The official way of doing this is with the calibration fixture - in the mode described it puts up
vertical stripes across the CRT, and you adjust so that they coincide with the graticule lines.

7704A actually (does it make a difference?) and yes I have the manual, that's where I got the procedure from.

7704 or 7704A? And whichever, do you have the manual?

My 7704 is about .75 of a horizontal division out with all timebases, by which I mean a 7B80, 7B85, and 7B92A. I conclude it is the 7704 itself that needs horinzontal calibration. The manual specifies a procedure involving a calibration fixture as a horizontal plugin and a 7B71 as a vertical plugin, neither of which I have. Is there a way involving what
I do have that won't blow it up? I can see that logically most any timebase would do as a vertical plugin, and any other fixture as a horizontal plugin that would produce the same centred vertical line: my question is as to the practicability.


TIA


EJP

Hi Dennis,
I can confirm your suspicion that I haven't read the section in the PG502 manual describing the power supply. :)

This Sunday morning at breakfast I took the pleasure to read it and found myself stated in
the assumption that the 12V is the most important voltage before everything else can happen. Sure, the +5V comes right after that and is then important for the rest to work.

I will now do measurements on all Zeners (especially VR616) and will also check R615 (1.1 Ohms)


--
Christoph

On 17 Apr 2016, at 08:11, Tom Gardner tggzzz@gmail.com [TekScopes] <TekScopes@yahoogroups.com> wrote:

For reference, this is the output of the frequency generator on the
Gratten GA1042CAL: https://goo.gl/photos/ehgMShwBNJADPqfw7 <https://goo.gl/photos/ehgMShwBNJADPqfw7>

This is Channel 1 on the 475, AC coupled:
https://goo.gl/photos/KBMdeGE8tjfVs72u5 <https://goo.gl/photos/KBMdeGE8tjfVs72u5>

This is Channel 2 on the 475, AC coupled:
https://goo.gl/photos/bQ35QgFkUjpwYd9W6 <https://goo.gl/photos/bQ35QgFkUjpwYd9W6>

This is Channel 1 on the 475, DC coupled:
https://goo.gl/photos/mfHQWHazjLktXQKp8 <https://goo.gl/photos/mfHQWHazjLktXQKp8>

This is Channel 2 on the 475, DC coupled:
https://goo.gl/photos/dapEDZRzWcyNZ7F68 <https://goo.gl/photos/dapEDZRzWcyNZ7F68>

All are shown with BW limit turned on (set to 20mhz on the 475; on the
Gratten it's just on/off), including on the Gratten, to limit noise
emitted by the Arduino that otherwise makes the traces hairy.

Note that the slow rise of the leading edge of the squarewave plateau is
still present. This is the 475 on Channel 2 at 5 microseconds per
division, demonstrating roughly 20 to 25 microseconds to reach the
nominal plateau: https://goo.gl/photos/oxUYm3ETvwcVJBxBA <https://goo.gl/photos/oxUYm3ETvwcVJBxBA>

I wouldn't call that a slow risetime since it looks like <1us.

The squarewave risetime is fine. Sorry, I probably shouldn’t have written “leading edge”. I think that’s caused confusion, and I probably should have clarified that the “slow rise” is not the squarewave risetime, but the slow increase in voltage on the plateau of the waveform.

My concern here is the slow rise on the plateau of the squarewave after the initial risetime, on the leading side, from just below the full voltage to the full voltage, over a period of roughly 20 to 25 microseconds.

There does appear to be a little plateau effect.

Exactly. That’s my concern.

The risetime is usually measured between 10% and 90% points.

And I'm sure you realise that the risetime of a 20MHz bandlimited
signal will be vaguely around 20ns.

Yes.

I believe that slow rise accounts for the obviously rounded leading edge
of the square wave when displayed at .2 milliseconds per division.

It would help if you would note the X and Y sensitivity near
to the URL to each picture; I'm not sure which pictures you are
referring to. If it is the earlier pictures in this post, then the
millisecond plateau slope on AC coupling is normal.

The vertical attenuation in all pictures in this post is 2mv/div, which should mean the attenuators are out of circuit.

Viewing the output of the Channel 2 vertical amplifer on the Gratten --
via the BNC connector on the back panel of the 475 -- demonstrates what
appears to be the same slow rise, though it's perhaps not as obvious due
to the graininess of the Gratten display. I presume this localises the
problem to the vertical amplifier rather than the vertical deflection
circuitry?

I'm not sure what to tackle next. Any suggestions?

I would look at the service manual to discover these modules:
1) input attenuator stages
2) separate front-end preamp-stages before the two channels
are multiplexed onto the beam
3) common amplifier stages after the switching
Then write down a list of which are "active" for each gain setting.

Yes, I’m generally aware of the stages and their overall effect. I was hoping (perhaps over-optimistically!) that the symptoms might narrow this down to something recognised and specific, such as dirty attenuator switches, incorrect bias on both channel's 2nd vertical amplifier stages, or some other “oh yeah, I’ve had that, it’s the <x>”, etc.

That will enable you to work out the "simplest" configuration
with fewest twiddleable pots/caps in the entire chain;

Whilst it’s possible that I’m dealing with a unit where the previous owner corrupted calibration by arbitrarily twiddling screws, it was used in a commercial industrial setting where this is unlikely. I suspect component failure or contact oxidation over miscalibration, at least until I can definitively determine otherwise.

I echo the suggestion to divide down the square wave to ~20mVp-p
Choose resistors that are low enough that the 20pF input capacitance
isn't a factor, and high enough that they don't change the signal source.

That’s hopefully what I’ve done, and that’s what the images I’ve linked show.

At high frequencies/fast sweep rates, don't expect the arduino
output to be a good square wave,

Up to about 1mhz it’s quite good, and declines significantly in quality thereafter.

and do realise that probing techniques
become very important. When observing <10ns signals, it is best to
couple a signal source directly to the input; if not then use 50ohm
coax and a 50ohm termination.

I’m using 50ohm coax with 50ohm termination.



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