开云体育

Triangle generator is stand alone, doesn't need anything else to work. I try to put all the relevant information in the post, sometimes I may miss somethings. Triangle generator starts (and works normal) at some different frequency ranges (se my original post).
I'll try all the ideas expressed here and see where it goes; unfortunately, after retiring, I find time available to do what you like is (much) less than desired... :)
TT

Yes it should be good enough at those speeds, after all the 1S1 itself is built with leaded components. The ground connection is as responsible as anything to keep inductance down.

Unfortunately I often talk about PCB design, where you can easily add a probe resistor to a trace by putting its pad directly on the trace and use much smaller connectors like H.FL, etc.

This is how I probe fast stuff when it's my own designs.

Sometimes I guess I'm not clear about this when people are talking about flying lead probing on existing circuits.

-3.7 vs -5.3 when I switch between 10 and 5

From what I have seen of Tek equipment you have an early production unit.
The later case allowed for the four scope calibration units the 106, 191,
184 and 067-0502 to be stacked on top of each other so that they wouldn't
slide off.

The type 106 arrived today from Germany.
It’s in quite a very good condition, albeit a bit dusty. Which is to be expected.
I haven’t fired it up yet. The reasons being that the line cord the seller sent, doesn’t fit, and I’m inclined to recap it before I power it up.

On the other hand, the enclosure, although unusual, seems pretty legit to me.
It hasn’t been cut down to fit this unit, as you can see by looking at the edges. They have the original paint on them. It “may” not be original to this unit, but I don’t know of any other Tek that it would have been for...
Could it be a transition unit before they went to the more traditional case? Maybe?
It’s quite an older unit with the gold plated boards. Serial is 001467, if that tells you experts anything...

Pictures here: /g/TekScopes/album?id=261997

I think the problem is in horizontal amplifier because I can see nice A
sweep on R1307 and nice B sweep on R1322 coming in and what comes out
(TP1364) is rubbish. Whatever is switching between the two is not working

Signal at TP1335 is responsible for A vs B sweep.

well. I can see the horizontal position just changing the shape of the
pulse but I think in correct operation this should just be moving the pulse
but not change its shape drastically.

You observed that B sweep works in 5/2/1n mode (is my memory correct?). B sweep is used in 5/2/1n settings even in A mode and as far as I can tell sheet <11> doesn't know whether you are in A or B sweep other than the control signal coming in from connector N4. In sheet <12> N4 is expected to be -3V in B sweep and 5/2/1n mode. What voltage do you see at N4 when you are in B sweep vs A sweep 5/2/1n?

Ozan

The through-hole resistor on the end of the coax seems to be OK down to 1 ns risetimes, maybe as far as 0.5 ns, but I wouldn't try and do anything faster than that. On the other hand, it's essentially free.

I think the problem is in horizontal amplifier because I can see nice A
sweep on R1307 and nice B sweep on R1322 coming in and what comes out
(TP1364) is rubbish. Whatever is switching between the two is not working
well. I can see the horizontal position just changing the shape of the
pulse but I think in correct operation this should just be moving the pulse
but not change its shape drastically.

On Fri, 19 Mar 2021, 22:18 Ozan, <ozan_g@...> wrote:

I noticed when I move the picture all the way to the left in 521 mode

there

is something on the screen but it's all crooked

I can think of two possibilities: B sweep delay is not reset to zero in
5/2/1n mode (there is a circuit to do that), or there is a little circuit
that shifts the screen left in B sweep mode (Q1331 in <11>) that is not
working.

Delay not set to zero:
In 5/2/1n mode B timebase is used but delay is set to zero. It could be
that the delay is applied still because of some issue. On <7> switch A9
opens in 5/2/1n mode to set time delay zero independent of delay knob. It
is possible the delay pot is dirty and not making a good contact. What
voltages do you see at pin 3 of U910 and base of Q902B in 5/2/1n mode?

There is voltage I set at the delay pot in non 521 position and fixed 13V
in 521 position

This is both on the U910 as well as the base of Q902B


B sweep shift:

B18, B22, B1-4, control left shift of trace in B sweep. You can check B18
and B22 by measuring voltages at J3 and J5 on sheet <11>

These switch correctly between -15 and -5 on J3 and 0 and -5 on J5

I looked at A sweep, A gate, and B gate signals on my 485. A sweep and A
gate signals stay same as 10ns setting when you are in 5/2/1n. When in A
sweep B gate is not there until you hit 5/2/1n, then B gate starts at the
same time as A gate (zero delay).

I remember you didn’t see A gate in 5/2/1n. Could you re-measure again
between 10ns and 5ns settings? May be "B ends A" is active although 5/2/1n
should turn it off. On front panel you will see “B ends A” next to the
hold-off knob. Does it make any difference if it is not in “B ends A”? If
it does A2 switch on <9> is dirty.

Makes no difference it works correctly

B sweep in the positions 10us to 0.2us is showing it 10x wrong

I read as B sweep runs slower.

So 100ns is shown as 1us

Is 0.1us also 10x slower? Above statement was for 10us to 0.2us.

How is 2ms, is it also 10x slower?

You may want to check relay K1241, caps C1443, C1442.

Switch B18 turns on a 2x multiplier, if it is not working you will get 2x
slower.

Ozan

The A sweep signal is so low I can barely measure it, this doesn't look
right

I hope no one is using a through-hole 1/4W resistor for this. The biggest I'd go is 0603, usually a 0402 placed on the PCB at design time.

Hello: We use several P6156, to use on 7104 aand 7904 TEK with 7A29 Vert.

They are the best but beware used on epay, often abused and missing parts. The best have the original case and all accessories.

We found them over the years at $40-65, but not often.

A 50 Ohm cable SMA is OK. The PCB mount SMA connectors are available from Semtech, etc. to place on your board designs.

Making a probe with a series R will not give best response due to series L and shunt C of the resistor.

Bon chance,

Jon

Hi Charles,

I suggest Picosecond Pulse Labs (PSPL) 5520C's as alternative for P6156 + 013-0237-00 and P6150 + 013-0251-00/01's. The 013 PN's are the SMA Voltage Pick-Offs for these two Probes.

Greetings,

Egge Siert

I would in your case take a magnifying glass and really strong light source
and thoroughly check one and every solder joint. I known you said you
resoldered components around triangle generator but what about the rest?
I repair synthesisers for living and with intermittent faults like this
this thorough optical inspection shown the problem in most of the cases. I
would specifically look around where mechanical twisting / pushing of the
controls can introduce stress to the component connections.

Removed solder and
re-soldered all components from triangle generator, checked all diodes for
normal behavior (in circuit).

Did you already check CR245/CR248/CR250/CR246 and resistors R245, R248, R250? The voltages you measured at two sides of the bridge are not consistent if all the components are good. Perhaps component tester failed to catch the intermittent behavior. Do you measure 1.116-0.6=0.516V at cathode of CR248 in stuck state? Or do you measure a negative voltage (bad CR248)?

Ozan

Cleaned cam switch contacts twice, no difference between the first and second. Replaced both JFETs (constant current source one, lower part on schematic, was good when cold, stopped working in a minute or so); not a great pair when it comes to characteristics - at least according to my 7CT1N. Removed solder and re-soldered all components from triangle generator, checked all diodes for normal behavior (in circuit).
TT

On Sun, Mar 21, 2021 at 07:38 PM, Charles wrote:

I only found the two as listed in my original post.

I wouldn't even consider these "probes", they're part of a system and I bet that these "probes" have to be soldered in-circuit to get best performance. At a previous job I had to solder in some Infiniium probes for 20+ Gbps stuff and it's basically a tiny ceramic PCB with the magic on it and there's two tiny wires to solder in-circuit. It was a differential system for measuring the eye of digital systems. There's simply no way to probe stuff like this the same way you tool around inside a Commodore 64 or Tektronix 547...

Also, the link on the last post of the EEVblog thread takes you to a homemade version that is good to 1.6 GHz (1 dB), -3 dB is 1.7 GHz...

It does appear to be less than perfect... you get what you pay for!

On Sun, Mar 21, 2021 at 09:15 PM, snapdiode wrote:

of course there are few 500MHz+ passive probes since they usually have too
high an input capacitance.

For the GHz range, I only found the two as listed in my original post... I hadn't considered an active probe, figuring that it had to cost more (and be subject to electrical damage from overload) than a passive one.

Jonathan Pyle 9:19pm #180728

I just ordered one of these, which I think does basically the same thing:

Now that's reasonable... $12 plus $8 shipping. That'd probably work fine with the S-1 head (350 ps), but it would definitely be the slowest part when feeding the 75 ps S-2, or the 25 ps S-4. I think I'll order a couple to play with too. Thanks for the link! Please post risetimes if you have a fast enough pulse to measure it.

Yikes, with that layout, I am skeptical. What is the flatness over its bandwidth and what is its true -3dB point? It's basically an antenna: sure, it'll get a signal through, but you can't really rely on it for any kind of absolute measurements.

An SMA attenuator has to be 50 ohms on both its ports, so I don't see how it would be a problem, unless its terrible. Of course each extra connection is itself a potential discontinuity but that's unavoidable. Keep 'em clean, specifically inside the connector where you can see the dielectric. Any junk in there that creates an air gap can get problematic as you get up there.