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For whatever it might be worth, I tried six variations of 2N3055 on a 577 that has had only enough repairs to keep it functioning.
The 3055's varied with a 3055H and a 3055HV mixed in with epitaxial and non-epitaxial 3055's, including an actual Tektronix 151-0140-?
All of the traces looked like what you would expect, and nothing like what Wolfgang is seeing.
The gain of the 3055's varied widely, with the 3055HV having the lowest gain as you might expect.
All of the above means absolutely nothing in this current discussion, but any discussion about my favorite curve tracer model needs to be followed and looked at.
tom jobe...

Hi All
The CATS (Crawley Amateur Transmitting Society) rally is correctly known as the CATS Bazaar, it was not last month but is was held on the 15th November.
If you are into Amateur Radio or T&M kit it is a must go to event.
Just for the record I have nothing to do with the organising of the event.
73 George G6HIG

Here are some pictures I took with a 2N3055 at various step settings:
/g/TekScopes/album?id=79121

I'm not at all surprised - a 2N3055 is a power transistor with a very large junction area. So it has a
very high capacitance.

I'd have to look it up, but one of Tek's curve tracer manuals sets out a procedure to match the
looping with removing the transistor and putting a capacitor instead. When the capacitor looping
matches the transistor looping, the capacitor value is the same as Ccb of the transistor.

Craig

On Fri, 23 Nov 2018 15:17:15 -0800, you wrote:

Still working on my 577 (see my other post regarding power supply restoration). Voltages are all good now (after replacing all electrolytic caps and tantalums on the power supply and collector supply boards).

That part is good.

I read the other posts regarding retracing of curves but can't seem to get anywhere. In my case, it seems to be a lot worse that what I saw with the other posts so I think my problem must be different (especially since I already replaced the caps that were mentioned in one other post).
Here are some pictures I took with a 2N3055 at various step settings: /g/TekScopes/album?id=79121

That is a bit on the nasty side. I'm more concerned not with the
doubling of traces (which could be argued), but the lack of blanking
showing through.

Is there a blanking waveform? Is there scope blanking for traces? If
so, what's the waveform look like and what should be generating it?

Harvey

I am going to dig deeper into the collector supply board but appreciate any thoughts/feedback.

Thank you,
Wolfgang

Sometimes there are good reasons to disconnect that ground and make a measurement that is not
relative to the AC power input ground.

This link will take you to a Tektronix ?white paper? about making floating measurements.

This has, as one recommendation, using an isolation transformer. However, it is an absolute
requirement that there is ground continuity between primary and secondary of an isolation transformer.

Think about it. The scope has line, neutral and chassis connections - a three wire system. An
isolation transformer has a primary and secondary only. The only way to connect the oscilloscope (or
any connected equipment) with a chassis connection safely is with ground continuity from chassis to
safety ground.

Which means you have a non-floating scope with transformer isolated line and neutral.

I'm really surprised that Tek missed that, because it has been part of electrical codes for longer
than that note was written.

For site use of site power tools isolated line and neutral is just fine - because connected power
tools are double insulated or even intrinsically safe.

But test equipment, like the vast majority of Tek test equipment, requires a hard chassis ground
irrespective of isolation transformer.

Craig

Still working on my 577 (see my other post regarding power supply restoration). Voltages are all good now (after replacing all electrolytic caps and tantalums on the power supply and collector supply boards).
I read the other posts regarding retracing of curves but can't seem to get anywhere. In my case, it seems to be a lot worse that what I saw with the other posts so I think my problem must be different (especially since I already replaced the caps that were mentioned in one other post).
Here are some pictures I took with a 2N3055 at various step settings: /g/TekScopes/album?id=79121

I am going to dig deeper into the collector supply board but appreciate any thoughts/feedback.

Thank you,
Wolfgang

Hi,

It is a 5L4N Accessory. Some clues are given in its Manual.

Greetings,

Egge Siert

I bought a Hantek dual trace 200 mhz scope about a year ago. It cost about 350 bucks. I also have a couple of 465 scopes. The Hantek has its advantages in some situations. Of course be reminded it is no Tek 465. I can work on stereos with that Hantek. It it immediately syncs to the signal and automatically adjusted to the right vertical scale. It gives an automatic readout of P-P voltage, offset voltage and frequency. Probably more that I don't remember. The trace on this Chinese product is not beautifully smooth and crisp like my Tek scopes. This is actually a matter of aesthetics rather than function. I just love seeing that beautiful crisp display on a 465. I got an update a couple of months ago for this Chinese scope. It corrected a problem for me. This scope would try frantically try to sync on an SSB signal that was being modulated by my voice and would just show garbage. The update fixed this. I can say that the Hantek model is useful for me and is excellent for low frequency troubleshooting. When I want to trace HF frequencies through a transceiver I always fall back on my Tek scopes. I repaired a 1948 Philco AM/FM shortwave receiver. It was a dream with the Chinese scope. I even calibrated the dial by looking at the LO frequency on this scope. I suspect I would have to spend a lot more money on a Chinese scope that would out perform my 465. The Tek scope and the Hantek both have a useful place on my workbench.

Randy,
Please read my entire mail and then respond appropriately.
Dennis Tillman W7PF

I recently "inherited" two 2215 Tek scopes both dead... Both have cover screws missing....
Unit #1: Someone ripped the anode lead off the CRT! Is there any way way to reattached the anode lead to the CRT? It also has an inverter issue which I can handle.
Unit #2: Bright wide traces across the screen. Intensity controls the traces from bright to very bright. Vert/Horz amps and sweep functions seem to be operating correctly. The start of the trace "dot" can be focused correctly. Grid bias has little to no effect on the trace brightness. Looking for ideas on this one.
Thanks in advance.
Scott
AB4SL

On Tue, Nov 13, 2018 at 07:31 PM, Chuck Harris wrote:

I had a consulting contract years ago to help a
Swedish company with a problem they had in converting
from European 240V to the USA 120V. The engineer that
did the conversion didn't understand the ratings of the
molex connector.

He saw the 17A rating, and saw the 15A drawn by the heater,
and said, "Looks good, ship it!"

And, then the problems began. In the US, the connectors
burned up after the third or fourth cycle of the instrument.

The customers were not amused, and even less amused was
the guy that relocated his family to the US to become the
president of the USA division... My customer.

What happened?

Well, molex rates their connector at 17A with the following
stipulations:

1) 25C ambient temperature.
2) 12 inches of #14ga stranded wire on each side of the
connector with everything suspended in free air.
3) only one pin set per connector shell.

Does that sound like what you are doing? If so, you will
be fine.

It didn't sound like the Swedish company's 4 circuits in a
shell, with 3 inches of wire between connectors, and placed
next to a 700W heater... OOPS!

-Chuck Harris

Harvey White wrote:

On Wed, 14 Nov 2018 07:33:38 +1000, you wrote:

...

On the current ratings, from what I understand, the current rating is
good, but goes down with the number of insertions.

I completed the overhaul including the installation of Molex connectors for the transformer leads. I posted before and after pictures here: /g/TekScopes/album?id=79113

Overall, it went well. A little crowded now inside with the addition of the Molex connectors.

I still have other issues with the 577 I need to track down - traces look OK for diodes but don't line up for transistors; as other have stated "the out and back I-V curves do not lie on top of each other". I saw other posts on that topic and will pursue this next. And the storage option doesn't work either (it's a D1).

Thank you,
Wolfgang

Thanks a lot everybody. It seems just for my 2465B it's not a very useful part...
But the link from Dale Chayes was very interesting i didn’t find it. Thanks
Rolf

I to would like this link if available.

The “low” side of every BNC instrument I’ve looked at closely is tied to the AC power ground.

Sometimes there are good reasons to disconnect that ground and make a measurement that is not relative to the AC power input ground.

This link will take you to a Tektronix “white paper” about making floating measurements.



-Dale

It would only work if your input was already floating, say for example a
TPS2024 or scope meter, and allow you to attach two probes in a
differential configuration.
The shell is unlikely to present a useful input impedance to attenuator
probes, so it would only work with X1 probes.
Quite limited use, I would say.

ST

On Fri, 23 Nov 2018 04:26:56 -0800, you wrote:


For measuring AC ripple at 120 Hz, I'd look at the ripple, but
triggered on line. Measure anything that stands still....

Ought to get you close.

Harvey

On Tue, Nov 6, 2018 at 08:03 AM, Chuck Harris wrote:

Hey! Don't muck with the DAC adjustment, unless you are prepared
to do a full calibration!

It is not supposed to be +1.25 and -1.25 volts, but rather a 2.500V span.

Sure, if you are a perfectionist, and diddle with the 10K reference
resistor values, and put in perfect opamps, it can achieve those values,
but that is not a necessary goal: 2.500V span when doing the calibration
routine is the necessary goal. -1.25 and +1.36V references that are *stable*
is the goal, as any errors in them get stored in the calibration constants,
and as such calibrated out, when the scope is calibrated.

Any tweaking, or replacement of DAC parts that you do will require a
full calibration of your scope. Why? Because you have no idea what they
were like when it was last calibrated.

If they were on the low (or high) side of spec when last calibrated, and
you adjust them to be right on, with a DVM that was on the high (low) side
of spec), they errors could add up to be wrong enough to perform poorly.

-Chuck Harris

OK understood. I have not touched the adjustment at R2010. Only replaced both 10K 0.1% resistors (the original ones where both open). Also replaced R2016 1K 1% because I pulled it out by mistake and one of the contacts looked a bit iffy, so that one was also needing replacement anyway. The original value of this last resistor checked on my HP3478A was 1.00248K and the substitute measured 1.00302K, so only a 0.0539% difference between them. The voltages from the +1.36 and -1.25 references did not vary very much from what the where while still using the temporary 5% resistors. I initially had +1.3848 and now it is 1.3836v. And -1.2688 went to -1.2681v. Not much of a difference.

I was looking at the procedure to check the 2.5V DAC voltage span in the service manual (page 5-3) and plan on verifying it at pin 13 of J119. But I will not be making any adjustments to it, since as explained above this might actually be detrimental and worsen the calibration state of the scope. So for now I will only record the voltage range, and they will stay as is.

I have received my new GQ-4X4 programmer, and the DS1225 from Mouser, but before I pull out my original NVRAM still need the machined 28-DIP socket which I had to reorder as I messed up the PN, and also ordered a FW16W08 FRAM to play with and an Aries SOIC to DIP converter board.

After getting the cal data rewritten on a fresh D1225 I am assuming I will have to tackle the power supply caps next. Sometimes see a very small almost unnoticeable horizontal jitter on a displayed waveform, so this is probably ripple in one or more power supplies. I last time the scope was open also took a glance into the power supply board and noticed I do have the infamous RIFA exploding caps and at least the one that sits closer to the angle I was able to peer onto the board shows the typical small cracks. I'm on 120V so I understand the risk of them exploding is less than on 220v mains, but I will replace them asap once I have all the other PS caps on hand as well. Already have the replacements for those, but since pulling out the PS boards as a pair its not exactly easy, will probably wait until I have all the required elco caps on hand as well and get it done once.

BTW can someone please explain how does one take the power supply ripple reading for 120Hz only, as opposed to the total ripple reading? By using the HF reject triggering option?

Thanks.

On Fri, 23 Nov 2018 05:40:12 -0800, you wrote:

Picture of the part here:

I'm going to guess, and an ohmmeter would tell you. One BNC is
straight through to the male BNC. The other center pin is wired to
the ground on the male BNC. The two shells are connected together,
but not to anything else.

It floats your scope.

Best used on a battery scope if at all.

Another option (if there's a short on the pin to ground, and the
wiring is not as described) would be for a 7A14 and a current probe
(needs an adaptor to tell the difference between a P6021 and a P6022).

Unlikely, though.

Harvey

Picture of the part here:

I got for free such an adapter. Ha anybody an idea how to use such a floating ground. I know what floating ground is but I have no idea for what the double BNC should be useful.
Google didn’t help me and a manual or application has not been around.
Any hints would be helpful.
Rolf

Link above is only for one picture. Full album is really here:

/g/TekScopes/album?id=76874&p=Name,,,20,1,0,0