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Hi,

I am desperately looking for the instructions that Tek. used to attach to the P6042 probe transformer/hall assembly T1 replacement kit (050-0439-00/01).

Each kit came with three selected resistors (R10, R14 and R11 or R13) that were matched at the factory to the transformer/hall sensor in the kit,
as well as instructions on how to set the temperature compensation variable resistor R12, which is what I am after!

The P6042 service manual gives no clue, except saying that "...adjustment procedure for R12 supplied with T1. Order Tektronix Part No. 050-0439-00"

Thanks in advance,

Yeah I'm very curious about this too. My replacement kit's part number is 120-0464-01 however.

@snapdiode it is my understanding that 120-0464-00 and 120-0464-01 are the part numbers Tek. used for the T1 transformer/hall assembly alone, whereas the 050-0439-00 and 050-0439-01 are the kits including the matching selected resistors R10, R14 and R11 or R13. Since these resistors are matched by Tek. to the transformer assembly, I am surprised that Tek. ever sold the 120-0464-01, I always assumed that that was just an internal part number.

Do I understand that you once bought a 120-0464-01? Can you tell us more?

I couldn't tell you, it seems to be a fortuitous eBay find. It came in a VHS mailer with a printed label from 1987 in the sleeve. It is packed with resistors but no other useful info. There's a P6042 album you can look for in the photo albums.

Thanks, I looked at the picture and I must say it does not look like a Tektronix label on that bag. It definitely looks like some reseller-company repackaged this.

Yes, and there weren't 4 heads in there though.

On Wed, Feb 24, 2021 at 04:26 PM, benj3867 wrote:

I am desperately looking for the instructions that Tek. used to attach to the
P6042 probe transformer/hall assembly T1 replacement kit (050-0439-00/01).

Find it here: www.hakanh.com/dl/docs/kitinstructions/050-0439-01.pdf

/H?kan

@zenith5106 Thanks a lot!

Unfortunately, I do not see the information on how to calibrate R12 :-(
It looks like every manual promises the information will be in another manual. It is highly frustrating.

The P6042 service manual says "...adjustment procedure for R12 supplied with T1. Order Tektronix Part No. 050-0439-00"

The 050-0439-01 instructions you so kindly provided say: "If R11 was installed...adjust R12... to the CLOCKWISE extreme" and "If R13 was installed...adjust R12... to the COUNTERCLOCKWISE extreme", followed by "Refer to Manual Insert for recalibration"

And the manual insert (that you also kindly provided) totally ignores the issue :-( :-(

I can hardly believe that fully clockwise or fully counterclockwise is the final position of the adjustment. If that was the case why use a variable resistor?

Is this anything like the procedure for the A6302 current probe? I've
got a couple of those here and seem to remember that there is an
adjustment for the offset voltage of the hall effect sensor. In early
models it was a variable resistor, but later it was changed to be a
fixed resistor whose value was specified for the individual hall
effect/current transformer assembly.So if that assembly was replaced,
the resistor would probably need changing too.

Some hall sensors needed a positive offset, some negative, so
sometimes the resistor was connected with one end to the positive
supply rail and sometimes to the negative. In either case, the
existing variable resistor would need to be turned all the way to one
end because it's no longer in use, and presumably the fixed resistor's
value is determined based on the variable resistor being set this way.

Chris

On Mon, Mar 1, 2021 at 11:19 AM benj3867 via groups.io
<benj3867@...> wrote:

@zenith5106 Thanks a lot!

Unfortunately, I do not see the information on how to calibrate R12 :-(
It looks like every manual promises the information will be in another manual. It is highly frustrating.

The P6042 service manual says "...adjustment procedure for R12 supplied with T1. Order Tektronix Part No. 050-0439-00"

The 050-0439-01 instructions you so kindly provided say: "If R11 was installed...adjust R12... to the CLOCKWISE extreme" and "If R13 was installed...adjust R12... to the COUNTERCLOCKWISE extreme", followed by "Refer to Manual Insert for recalibration"

And the manual insert (that you also kindly provided) totally ignores the issue :-( :-(

I can hardly believe that fully clockwise or fully counterclockwise is the final position of the adjustment. If that was the case why use a variable resistor?

Actually it was the fixed resistor in the early ones and a potentiometer (wired as such) in the later ones...

David

@Chris, the probe kit for the P6402 comes with 3 selected resistors: R10, R14, and R11 or R13. The first two (R10, R14) are doing what you said: they are selected to bias the hall sensor correctly. The third resistor, together with the variable R12, are to minimize drift with temperature changes.

@David, looking at the circuit diagram, R12 is in series with R11 (or R13), with nothing else connected to their common junction. Thus, indeed, if one selects R11/R13 correctly, there is no need to also change the value of R12. This is assuming of course that the required value of R11+R12 (or R12+R13) depends only on the sensor and not on anything else in the circuit of the individual P6042 unit the replacement kit is installed in, which seems not unreasonable in this context.

The instructions H?kan shared with us mean that the circuit only sees R11 or R13, as R12 is set to add zero resistance in both cases.

Which begs the question: why did Tek. decided to have a *selected* resistor in series with another resistor (variable or fixed)?
It makes no sense.

The only explanation I can come up with, is that during manufacturing of a P6042 the selection of R11 and R13 was rough (say they were picked from one of a relatively few bins of values), and the final `selection' was done by adjusting R12. In contrast, the resistors in the replacement kit were selected using a more accurate and lengthy process and need no further tweaking by R12.
Is this plausible?