It should be 9 Meg ohms. Then 90% of the signal is dropped across the probes 9 Meg and 10% across the scope's 1 Meg input impedance, giving 10:1 ratio.
The compensating capacitors across them are adjusted for the same division at high frequencies to maintain the flat response, that's hat you're setting when you adjust for flat square wave with the trimmer.

Don Black.

On 20-Feb-13 12:18 PM, David wrote:

?

On Wed, 20 Feb 2013 00:24:09 -0000, "Philip" ndpmcintosh@...>
wrote:

>The publication on scope probes mentioned earlier is good and I am working my way through it. I already had it in my document collection and it was on my reading list.
>
>If I ohm out a 10x 10Mohm probe in the same way, I get about 10 MOhms. I'll keep reading though...

I get almost exactly 9.00 MOhms on each of several different x10
probes within reach.

Dave,

I got it now.

Thanks,

Stan



--- In TekScopes@..., David wrote:

That is why I said in an earlier post, "Do not let the equipment
requirements or setup dissuade you as you can certainly complete it if
you can generate sine or triangle waveforms from 0.35 to 2 divisions."

All you need to do is connect the signal or function generator to the
channel 1 or channel 2 input with a short BNC patch cable and produce
a 50 kHz to 350 kHz sine or triangle wave with a CRT deflection of
0.35 divisions to 2 or 3 divisions. The vertical volts/div settings
are relatively unimportant because the internal trigger circuits see
exactly what is displayed on the CRT.

I would not worry about the external trigger calibration until you
verify that the internal trigger is working correctly and even then,
all that is really needed is a BNC T-connector to use as a splitter
and maybe an attenuator.

On Thu, 31 Jan 2013 00:23:28 -0000, "stan_katz"
wrote:

I can study the manual. What I can't do is figure out what cabling and interface devices I need. What's a 50ohm 5ns GR cable (GR stands for General Radio?). What's a 50ohm signal pickoff unit, GR to BNC adapter, X10 attenuator (a standalone cabled inline attenuator??). Sorry I'm so dense here, but I need help to cobble together whatever is alluded to here. All I have is a signal generator, and a bunch of 50ohm cables. I have a feeling if I were a ham radio guy, the above stuff would be obvious. Maybe someone can post Ebay links to whatever it is I should order. In the meantime, I'll continue to do my homework reading the manual.

Stan

--- In TekScopes@..., "Max Mazza" wrote:

If you finally have a good and decent copy of the manual, you can finally do the work in a right manner.
The page relevant to you should be 5-40 and followings.
However I recommend to pause and read carefully the manual first, then proceed calmly.

The best sensitivity when adjusting R565 should be checked with the trigger level position to 0, not full clockwise, anyway. Fully clockwise implies that you raises the trigger level very above 0 V. The level spans from -8V to +5.2V. In normal operation the trigger level should be near 0. You can vary trigger level only if you knows what you are doing.... for instance, when there are noisy signals, they can generate spurious or false triggering; in that case it's obvious to raise the trigger level just above 0 level, up to the point where a stable waveform can be displayed.

Moreover, if you have touched R534 (A trig centering), it's easy that you have altered the 0 level for the trigger level knob....

Conclusion: study carefully the manual first, then resume the process on your 475. The calibration procedures are somewhat complicated in some cases, and they require a lot of patience and calm.
No problem if you want to contact me directly, but I think that it's better that you post your questions here, since "many brains are better tha one :-)

Don't rely strong on my suggestion to read +80mV, it's an extreme simplification to help you to make your scope functioning with the instrumentation in your possess. Read the manual first, then ask with no problem!

Max

--- In TekScopes@..., "stan_katz" wrote:

I've finally downloaded REAL Tek 457 manual. MUCH better manual. Thanks Dave. Max, I think I've fiddled with R565 to get the best sensitivity possible. That is + trigger slope cranked fully clockwise, and max attenuation possible of .5v/div. I'll keep on trying to do better. I might try to upload sketches of the waveforms I now have to Archive 2. It would be easier to just email. Can I get permission to email direct?..Max?..Dave? As for detecting +80mv on my little D51, that's a stretch. Do my best tho.

Stan

Stan

Stan

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

Yahoo! Groups Links

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On Wed, 20 Feb 2013 00:24:09 -0000, "Philip" ndpmcintosh@...>
wrote:

>The publication on scope probes mentioned earlier is good and I am working my way through it. I already had it in my document collection and it was on my reading list.
>
>If I ohm out a 10x 10Mohm probe in the same way, I get about 10 MOhms. I'll keep reading though...

I get almost exactly 9.00 MOhms on each of several different x10
probes within reach.

On Tue, Feb 19, 2013 at 3:12 PM, <cleyson@...> wrote:

Unused new old stock and comes with a full set of leads.
Price might be more than you want to pay, but you can't make your
own probes for the same money.

I have to disagree, the price of $100 per probe is not viable. The
Tek 308 is a primitive 20MHz logic analyzer, it would make no sense at
all to spend $200 to get it going. You could get a much better logic
analyzer for less than that (Tek 1240, HP 16500, HP 1662, etc.).

Then there's the issue that these are the normal P6451s, which might
not even plug in to the 308, since it seems to require a special
version with a right angle connector.

And, of course you could make your own probes for much less than that,
if you could find the connectors, or if you just patched in to the
logic analyzer input. You would just need ECL line receivers (10115
etc.) with your choice of input buffer.

Hi,
I've just acquired a Tektronix 318 logic?analyzer, but it came without the pods.
It's a nice unit, and by the looks of it, it works, well it displays random logic levels on screen as no pods are plugged in.
Can I make those pods myself ?
If not, what pods do I need and where do I find them ?

Hi,
First posting on this group, hope someone can help....
I have a T935A scope which has developed a problem and I'd like to try and fix it as its a very useful portable scope.
Basically two of the front panel variable pots, the Y2 axis variable and the X axis variable have seized solid. Y1 seems okay.
So before I strip the scope down, which looks to be quite a job to get the relevant pcbs out, has anybody come across this before?
Is there much hope that I can fix the existing pots or do they need to be replaced (any suggestions for good suppliers that will ship to the UK?).
Many thanks,
Andrew

From: David DiGiacomo
Subject: Re: [TekScopes] tektronix 318 logic analyzer probe
To: TekScopes@...
Date: Tuesday, February 19, 2013, 8:14 PM

?

On Tue, Feb 19, 2013 at 10:46 AM, Gala Dragos gala_dragos@...> wrote:
> I've just acquired a Tektronix 318 logic analyzer, but it came without the pods.
>
> It's a nice unit, and by the looks of it, it works, well it displays random logic levels on screen as no pods are plugged in.
>
> Can I make those pods myself ?
>
> If not, what pods do I need and where do I find them ?

The 318 used a special version of the P6451 probe, with a right angle
connector. I don't know if a standard P6451 can be made to work.

You can make the probe circuit, but I don't think you can find the
connectors, except on a probe.