开云体育

Just wanted to thank you for the detailed reply. I read Glydeck's web page (the one you linked to)
and
have yet to start on the 29 page dissertation but look forward to doing so. I may be your next
customer for a board. One question based on your note,... given that you targeted compatibility with
a
range of systems (575, 576, 577, 7CT1N, 5CT1N), is there any reason to prefer one (or some) over the
others as I continue my hunt?

The main problem over here in the Tek dead-zone that is the UK, is procuring a tube tester for the
project. I chuckled at Denis's estimate, in his thoroughly excellent paper, that a suitable tube
tester could be procured for $30 at a swap meet.

In the UK, such a tester would typically work out at least a factor of ten more than that, and becomes
by far the most expensive part of the project.

Craig

Dennis,

Just wanted to thank you for the detailed reply. I read Glydeck's web page
(the one you linked to) and have yet to start on the 29 page dissertation
but look forward to doing so. I may be your next customer for a board. One
question based on your note,... given that you targeted compatibility with
a range of systems (575, 576, 577, 7CT1N, 5CT1N), is there any reason to
prefer one (or some) over the others as I continue my hunt?

Thank you again.

On Mon, May 14, 2018 at 4:31 PM, Dennis Tillman W7PF <dennis@...>
wrote:

Hi David,

A little over a year ago I completed my Vacuum Tube Curve Tracer adapter
which worked with ALL Tek curve tracers. After seeing the beautiful job
Glydeck did on his simple triode curve tracer adapter for a 576 I decided I
must make one myself if I ever got a 576.


Then one day a 576 fell into my lap for $25 and I set to work. My goal
gradually evolved past Glydeck's. I wanted to test all kinds of tubes, not
just a few triodes. With great advice from George Lydecker (Glydeck) I came
up with a low cost solution for an easy to make adapter that, in
conjunction with an inexpensive tube tester, would test any tube on any Tek
curve tracer.

My goal was to make something anyone with a curve tracer could build at
the absolute lowest cost that would test the greatest number of tubes. It
had to work on any Tek curve tracer without modification (575, 576, 577,
7CT1N, 5CT1N) and perform most of the tests the original Tek 570 tube
tester could do. Those were pretty aggressive goals but I met most of them
and wrote about how I did it in a very detailed 29 page paper complete with
parts lists and schematics. It may help guide you in your design. You can
download a copy from:


To my amazement I almost immediately got requests from 75+ members of
Tekscopes for the PC Board I made for the VTCT Adapter. I gave a talk on
the adapter at SeaPac last June and I sold 10 more there. I have sold about
105 of them all total by now including a few completely assembled units and
a few kits that include all the parts.

In between everything else I am doing I'm investigating what it would take
to design a new version that would be capable of testing tubes under the
exact conditions in a Williamson amplifier and its derivatives that many
audiophiles will tell you is the ultimate in tube amplifiers.


Dennis Tillman W7PF

-----Original Message-----
From: David Berlind, Sent: Monday, May 14, 2018 12:02 PM

My main interest in a curve tracer would be for tube testing/matching. A
few months back, I believe there was discussion of a home-grown 576

fixture

for that. For now, one of my upcoming projects is to build my own tube
testing rig. For example, I'd wire up a single socket to some voltage and
amperage gauges and power the rig with an external DC supply across a
mixture of plate voltage and cathode resistance ranges. But that's a a

lot

of work for each tube. I've seen a few hacks that convert old

oscilloscopes

into curve tracers but haven't really studied any of them.

On Mon, May 14, 2018 at 2:43 PM, Kevin Oconnor <kjo@...> wrote:

Just chiming in...
I would agree with Chuck on this. Some other factors...
A 576 is way more complex inside with all the display lighting and

control.

If something fails, you have a lot more work to do. I just sold a 576
for
$750 and I think, for a fully working unit, it was a buyer bargain.
The owner just wanted it gone....

I use a 577 for just about anything discrete. I have a dozen fixtures.
(No IC testing though as mine has the 177 fixture) . Both are
versatile, and you can build fixtures to do things Tek didn't
anticipate or support. I'm working on a fixture to test Nuvistors.. A

work in progress though.

One caution (among many) If you get one and then go looking for
fixtures, be ware that many of the Tek plug-in fixtures have reached
EOL. The covers are screwed into bosses in the base boxes. Both the
threaded bosses and the covers themselves are now failing. As the
plastics aged they became brittle and the stresses have fractured the
bosses and the covers now pull away from the base. I have seen top
covers laced with hairline cracks causing the top to break up like a
jig-saw puzzle. So take a good look at what you are buying.

kjo

David Berlind wrote:
. . .
I saw this 577 Curve Tracer show up on eBay and it sold for $256. Not
sure if that power-up trace indicates an issue (not having had or
operated a curve tracer, I don't know what the power-up trace should

look

like).

Following-on to conversations in this forum about the the 576, I've
been keeping my eyes out for a 576. Is there a significant difference
between the two?

--
Dennis Tillman W7PF
TekScopes Moderator

On Mon, May 14, 2018 at 04:44 pm, lop pol wrote:

Anyone have a source for ribbon cables? I would like to get a new one. I know
the dependability of those cables after a certain age is questionable.

Most of the ribbon cables rarely fail and there should be no need for replacement. However, in the late 70's / early 80's, I guess in an effort to save money, Tek started
to use a different type of connectors on the ribbon cables. The originals were gold plated all over while these new ones were only plated on the spring that connects to
the pin. They are known as "Spot-Of-Gold" or "Spot-O-Gold". With time they may develop corrosion between the wire and connector resulting in intermittent faults.
Typical symptoms would be intermittent failures which go away when the cable is wiggled and which not necessarily will reappear until much later. These connectors
can be identified by their pale color compared to the true gold ones. However there is also a later "pale" version that should be OK.
Here is some further explanation:

/H?kan

Good Day,

Thank you for the step-by-step description, Craig - and for the burst of laughs I had over this:

"Any way you look at it, winding 1400 turns of hair thin wire is a royal pain in the ass ;-)"

Cheers,

Magnus

What are we throwing a resistor across??

Glenn

--
-----------------------------------------------------------------------
Glenn Little ARRL Technical Specialist QCWA LM 28417
Amateur Callsign: WB4UIV wb4uiv@... AMSAT LM 2178
QTH: Goose Creek, SC USA (EM92xx) USSVI LM NRA LM SBE ARRL TAPR
"It is not the class of license that the Amateur holds but the class
of the Amateur that holds the license"

On Tue, May 15, 2018 at 02:30 pm, Dennis Tillman W7PF wrote:

Other things I learned:

* One thing that I never gave a thought to until now is why does the 7S12 have
no problem triggering at all? That tells me there must be a way to get stable
triggering in a 7T11.

* I never before thought of powering an S-52 in a 7S11 and it has some
internal triggering advantages.

* Just now I inserted an S-4 in a 7S12 to achieve the fastest risetime (36ps)
with the lowest time jitter (on the high resolution setting) as I have been
able to do ever! The results were as smooth as a 7854 might provide. And there
was no fussy triggering to play with.

Dennis Tillman W7PF

Hi Dennis,

I think the true reason why the 7S12/S-52/S-x does it so much better has not been mentioned yet. In this setting the S-52 pre-trigger pulse is merely used as a "ready" signal to tell the 7S12 that the TD is properly armed. The S-52 itself does not initiate TD firing and its internal delay to firing is not used -- all is done by the 7S12. At pre-trigger pulse arrival the 7S12 starts the Fast Ramp. Two level comparators, Strobe comparator and Pulse comparator (Fig. 3-4a), on the Fast Ramp voltage determine the next instant of sampling head strobe and TD firing. Time jitter in detecting the pre-trigger pulse does not affect the time difference between the two comparator events.

Albert

On Tue, May 15, 2018 at 09:20 pm, lop pol wrote:

I was going to calibrate my 7a26 plugins and immediately i found the rise time
on channel one is horrible
/g/TekScopes/photo/49370/1?p=Name,,,20,1,0,0

That's the symptom of one of the trimmer capacitors going open-circuit on that channel. I think it's the one labelled 'LF' or 'MF' but I can't remember exactly. It's easy to identify because adjusting it will have no effect.

I've seen exactly that symptom on more than one of my 7A26s. I haven't yet replaced the offending trimmers so can't advise on a suitable part, I'm afraid.

Chris

You can also use PVC pipe cement, commonly available at hardware stores. Ed

Oops - I was going to say, "don't worry about diode reverse leakage hurting the LED, and if you are, just throw a resistor across it..." Ed

So throw a resistor across it - no big deal. Ed

On Mon, May 14, 2018 at 08:06 pm, tinkera123 wrote:

Looks like I will have to convert to an Email system ..... thanks for the
input.

Not really. I use web based access and the groups are just in bookmarks. However, you can also create bookmarks to individual threads, or the individual photo albums. You can also make subdirectories within bookmarks, or favorites in IE.

In IE the actual directory will be in your documents as a subfolder called favorites. In windows Explorer you get there and just go to File>New>Folder, once you click that a new folder will show up and the name will be blued up, that is the time to type in a name like "io posts" or "iophotoalbs" whatever you need. Once a post or album is in favorites just drag it in there.

In Firefox, open the bookmarks and right click, it will show "New Folder", click that and it will ask you to name it. So type in whatever and click OK or hit Enter. This is your chance to rename it, do it because it only stores from this site as "Tekscopes@io|album. You don't get a chance to nameit after it is moved in that directory. The folder will then appear whenever you go to Bookmarks. At that point just drag whatever 9renamed) bookmarks in there. They will disappear from the main list but when you click it it will open to a list on one side, run your cursor over and click whatever you want.

In Chrome it is similar, click bookmarks and right click anywhere except an existing folder. It has New Folder, click that, it asks you to name it and boom, you got it. Then you just drag whatever link in there, of course after naming it appropriately.

In any case you have to name it right in the first place, that will be a lesson to name things right so that it facilitates groups.io's endevour to make the images searchable. It would be a good idea to get used to it, though right now no matter what you name an album it does nor transfer to the bookmarks. Individual posts do.

Any browser that still has a menu at the top with File, Edit, View and so forth in File you go to Save As and it will save it i=on your HD wherever the default is. I don't know how to get that in Chrome but right clicking the page area itself will bring up the save option.

In any case, know where your OS and browser store saved webpages, usually it is in your documents but not always. Wherever it is, it pays to right click it and go to "Send To" and then "Desktop, Create Shortcut". That way you don't have to screw around looking in Explorer all the time.

Note that even if you load the page locally, the links will work as long as your PC is connected to the internet, And I THINK that includes "Reply". That's something you can just try. If it doesn't then you should have a bookmark and loaded from the web it will definitely work.

I was going to calibrate my 7a26 plugins and immediately i found the rise time on channel one is horrible
/g/TekScopes/photo/49370/1?p=Name,,,20,1,0,0

Channel 2 seems fine
/g/TekScopes/photo/49370/0?p=Name,,,20,1,0,0

Any thoughts as what to look at would be appreciated. Thanks guys

QService has the rear covers for sale.? There are others on eBay.? The usual price is around $35.00 US plus shipping.? But if you are careful and patient they can be had for around $20.00.? I have bought two that way.

On Tue, May 15, 2018 at 04:37 pm, Bruce Griffiths wrote:

With oly a series diode the LED can suffer reverse breakdown albeit at the
reverse leakage current of the series diode.

Of course, Bruce, I was a bit lazy and expected the diode's reverse leakage current to be significantly less than the LED's or else, the breakdown current of the LED with the diode in reverse to be non-destructive for the LED. I thought it would do for the test though as said, I was being lazy. Alternatively, I might consider a 1 MOhm resistor instead of the antiparallel diode.
Thanks for pushing me to be a bit more thorough.

Raymond

A series diode by itself offers no protection against reverse breakdown of the LED.
A shunt diode connected in inverse parallel to the LED together with the series diode guarantees the LED will not suffer reverse breakdown. With oly a series diode the LED can suffer reverse breakdown albeit at the reverse leakage current of the series diode.

Bruce

Dennis,

So that brings me back to my principal complaint about the 7T11/7T11A which is lack of a trigger light. It seems to me
that the Pulse Out signal is a very good indicator that you have a trigger. WHY COULDN'T TEK HAVE USED THE
PULSE OUT SIGNAL TO DRIVE A ONE SHOT TO TURN ON A TRIGGER LIGHT? As soon as the trigger is lost
the waveform drops to zero and the trigger light would go out.

Have you considered just connecting a high-efficiency LED from "Sweep Out" to Gnd, even just to see if that gives enough of an indication? Connect the *anode* to Gnd and the *cathode* to Sweep Out (feels like reverse mounted). Sweep Out has a 10 kOhm resistor in series so no harm can be done to the 7T11. You may violate the max. reverse voltage of the LED so maybe you should put a diode in series.

Raymond

Wear a good chemical respirator mask and do it outside if possible. Use
plenty of ventilation if you need to work inside. The stuff is a known
powerful carcinogen!
Be careful!
John Justin

Methylene Chloride is one type, usually meant for plexyglass.
Others come in little glass bottles that have a brush inside
the cap. The solvent is water clear and thin.

Hobby shops are a good source, if you don't mind the mustard
oil added to foil the glue sniffers.

I buy metal cans of IBC solvent for plexyglass. Usually from
an ebay seller, or possibly Amazon.

-Chuck Harris

miketakeguess via Groups.Io wrote:

Thanks Dennis,
?I guess I'll have to wait for another day, since I was beat out on both of these units. ? ?
?So, I presume I could *display* simultaneous tracks from the 7D10, just not digitize them simultaneously? ? Honestly I would probably end up using it to view multiple traces, but would never really need it's full parallel display capabilities. ? I would be playing with PIC chips, the 8 bit, 8 pin series, which only have but 6 bits of I/O, so not even sure how much benefit I would get from a logic analyzer, but just fun to add plugins to the collection.
? Actually, I am vaguely aware from discussions here that the 7854 also has problems with certain combinations of sampling heads and sampling timebases, right? ?Can you give a 3 sentence summary of which ones work and which ones don't? (I won't ask for more than 3 sentences because I can start looking at the manuals and past messages myself, so just off the top of your head....).
? Dan

2 never tested $30 each -- parts not working function unknown. $20 back if DOA.
now that both 7D01/DF1 sets are claimed and outbound.

One has its original leads, the other has 4 orig and I will fill out with Chinese leads and
HP microclips.