Date   
Re: 7904 - Very Dim Trace

David DiGiacomo
 

On Wed, Feb 10, 2016 at 10:56 AM, <jimmcintyre22@...> wrote:

The caps are shown in thr parts list as .001 uF, 4 kV - no problem.

The diodes,( e.g. CR1678, CR1679) are not listed. Anyone have a favorite HV diode for this application?
Tek used 152-0242-00 = selected 1N486A

I like 1N4937, but they are a little larger.

2465BCT Refurbishing

Michael
 

With the last set of part replacements, I now have the 2465BCT working! It
passed the smoke test, and after a few connector glitches, I got everything
reassembled and it passes all diagnostics. Just playing around with the
calibrator signal, everything that I know how to test looks good. I have to
learn how to use all of the features to give it a really good test, but so it
looks great.

I still plan on making some modifications, but I am waiting on parts for most
of those. I am not sure that the fan is working, the case appears fairly warm
but I don't feel any fan exhaust. It may not be warm enough to kick on yet, or
the fan could need replacing or the fan control circuit could be bad. I will
look into that and see what I find.


Mike

Re: 7904 - Very Dim Trace

Jim McIntyre
 

The caps are shown in thr parts list as .001 uF, 4 kV - no problem.

The diodes,( e.g. CR1678, CR1679) are not listed. Anyone have a favorite HV diode for this application?

Re: TDS 380 calibration and vertical scale problem

Ed Breya
 

Yes, that's exactly what we've been hinting at - making measurements and observations to fill in some pieces of the puzzle. Similar parts and circuit info plus the collective smarts here may provide some more pieces, to get closer to figuring out what's in there.

Ed

Re: TDS 380 calibration and vertical scale problem

Siggi
 

Hey David,

If there were an existing schematic of these attenuators, the odds are the
member of this mailing list would know of them and/or have found them
already.

I think the mission we're trying to push on you, is to reverse the
schematic of the attenuator by inspecting and measuring the original you
have in your possession. Here's an EEVBlog video on how this is done <
https://www.youtube.com/watch?v=lJVrTV_BeGg>, though Dave doesn't do a
super job of it :). Thankfully your attenuator is MUCH simpler than the
front-end he's trying to reverse.

If you take a look at the attenuator schematic in the 2465 <
http://www.ko4bb.com/manuals/download.php?file=Tektronix/Tektronix_-_2465_Oscilloscope/Tek_2465A_Service_Manual_070-6019-01_May87.pdf>
you'll see a high-level picture of what's inside. Here <
https://groups.yahoo.com/neo/groups/TekScopes/photos/albums/501546574> are
some pictures of the attenuator hybrids from my 2430 with the relays
popped. If you compare the schematic to the thing, you e.g. see where the
AC coupling cap is, where the 50Ohm resistor is and where each of 10X
attenuators are. We know each one of the attenuators will have pair of
resistors, and we know there's a 1M termination resistor there. Squint a
bit, and you can see all of those, plus some other passives that have
(presumably) to do with the frequency response of the attenuator.
If you look at the service manuals for older scopes (Tek 485 is my fave)
you'll see full schematics for their all-discrete attentuators.

What I expect you have in your attenuator is similar to any other
attenuator, e.g. there will switching for AC/DC coupling, for the CAL
signal, and there will be resistive dividers for the attenuation ratios
(possibly 25/100) each with 1M resistance. There may also be some series
resistance in the input path to allow for current limiting on overload, and
there is some evidence that you have an open series resistor on your CH2.
There may also be multiple resistive dividers dividing the input by
different ratios into different inputs of the preamp IC, in which case the
dividers will have 2M resistance.


Siggi

On Wed, 10 Feb 2016 at 11:29 david.wilson92@... [TekScopes] <
TekScopes@...> wrote:



Thanks for that info,

I uploaded a attuenuator schematic showing the hybrid's connectivity to
the mainboard, no it doesn't show the schematics for the attenuators
themselves but it is information to review at least. If you haven't
already, useful information can be found on a post I made on eevblog.com
http://www.eevblog.com/forum/repair/tds-380-calibration-error/, click
that link to take you directly to the post.


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Re: 7904 - Very Dim Trace

David DiGiacomo
 

On Wed, Feb 10, 2016 at 12:52 AM, David <@DWH> wrote:
Diagnostics on DC restorers are not much fun. Measurements require a
high voltage probe and component tests require a high voltage power
supply.
In the ones I have repaired, the diode leakage has been pretty obvious
when tested with a 50V power supply. Of course that might not always
be the case. As you say, the parts are cheap.

Re: TDS 380 calibration and vertical scale problem

David Wilson
 

Thanks for that info,

I uploaded a attuenuator schematic showing the hybrid's connectivity to the mainboard, no it doesn't show the schematics for the attenuators themselves but it is information to review at least. If you haven't already, useful information can be found on a post I made on eevblog.com http://www.eevblog.com/forum/repair/tds-380-calibration-error/, click that link to take you directly to the post.

New file uploaded to TekScopes

TekScopes@...
 

Hello,


This email message is a notification to let you know that
a file has been uploaded to the Files area of the TekScopes
group.


File : /TDS380 data/tds att schm.pdf
Uploaded by : david.wilson92 <david.wilson92@...>
Description : Schematic of the attenuators connectivity on the mainboard


You can access this file at the URL:
https://groups.yahoo.com/neo/groups/TekScopes/files/TDS380%20data/tds%20att%20schm.pdf


To learn more about file sharing for your group, please visit:
https://help.yahoo.com/kb/index?page=content&y=PROD_GRPS&locale=en_US&id=SLN15398


Regards,


david.wilson92 <david.wilson92@...>

Re: Tek 555 part needed.

zerousair
 

Could you please send me your private email address Mr. Knox? Mine is lbfulton@....


Thank you,
Garrett

Re: Tek 555 part needed.

Keith Knox
 

Garrett,
If you email me your shipping address I will send you a replacement HV Supply for your 555 scope. You can replace the full supply or just T901 as you wish. I will test HV Supply in one of my working 555 scopes before shipping.
I have a collection of 75+ of the Tek 500 series scopes. Included in this collection is 6 of the 555 scopes.3 of the 555 scopes have been fully refurbished and are working great. I hope to get 1 more 555 scope refurbished, but the other 2 will most likely be parts units.
I will test the HV Supply this afternoon and have it ready to ship.
Keith Knox
hptekman@...

On Tuesday, February 9, 2016 12:16 PM, "lbfulton@... [TekScopes]" <TekScopes@...> wrote:


  Morris/John,
Here's the pin voltages I read today on both beam HV supplies:
V900 pin1 +223.6 V800 pin 1 +47.6
pin 4 0 pin 4 0
pin 5 -.294 pin 5 -.278
pin 6 -17.9 pin 6 -51.5
pin 7 0 pin 7 0
pin 9 +310 pin 9 +311

V914 pin 1 -145.6 V814 pin 1 -1.3
pin 2 -149.8 pin 2 -160.8
pin3 -150 pin 3 -150
pin 4 -.292 pin 4 -.267
pin 5 -.292 pin 5 -.267
pin 6 -145.6 pin 6 +52.0
pin 8 0 pin 0
pin 9 0 pin 0


The high voltage test points are at the anodes of V962, LB and V862 UB.


CRT pin 11 -681
pin 12 -760
pin 4 -1275
pin 2 -1337


My tube tester won't work on V900/800, but I swapped them side to side with no change in the problem. V914/814 both check good. With the help of you guys, I'm getting a better understanding of how this circuit works and seems to me T901 might be putting an excessive load on the circuit as was already mentioned. Haven't worked much at all with these old tube circuits since '68 when I was a Marine in Navy avionics school. Can't unsolder the trans, and check the resistance as my left hand is in a cast for 2 more months. Emailed a fellow today who might be able to rewind T901 for me though. I really appreciate the input from you guys.


Garrett




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Re: External TO-3 Cover for Tek equipment on Ebay right now

Tothwolf
 

On Wed, 10 Feb 2016, Malcolm Hunter malcolm.r.hunter@... [TekScopes] wrote:

Thanks Dennis, these were available when I was asking but I thought that it was a lot to pay for only one. I bought these instead: http://www.ebay.com/itm/390959168464
That was a pretty good deal. I bought the same insulators from Mouser not too long ago. The two #6 splitlock washers they include for use as spacers are type 304 (A2, 18/8) stainless steel.

Re: 7904 - Very Dim Trace

Jim McIntyre
 

I looked at TP1876 with a DVM and saw +20 to +80-ish volts, as I varied the intensity control.

What's the recommended way to check the Z-axis amp?

Re: OT: Win 8.1 and 10?

Mark Wendt
 

Rich,

What flavors and versions of Linux have you tried? I'm running Ubuntu 14.04 LTS on this laptop, and I have CentOS 7 on another desktop machine. My CNC machine runs LinuxCNC on Ubuntu 10.04 LTS.

The more modern versions of Linux install a lot easier than the old ones. And if you don't want to go under the hood, there are enough GUI admin tools that you probably wouldn't have to ever use a command line. Though that's what I tend to do since I've been a Unix/Linux sysadmin for the last 25 or so years.

Mark

On 02/09/2016 08:18 PM, 'Richard R. Pope' mechanic_2@... [TekScopes] wrote:
Mark and et al,
I want to thank everyone for their inputs and their discussions on
this subject. I have done a lot of reading and I have considered all
that has been said here. I knew that this was the right place to come. I
believe that it is time to stop this thread.
I am going to stay with 8.1 for right now. There is a lot to learn
here. I have also done some playing around with Linux going back more
that a decade. My other machine is triple boot with XP, Server 2003, and
Linux. Something that keeps holding me back on Linux is the learning curve.
There is something else that I would like to cover. I tried to
install VB6 on this machine and it won't work. Is Visual Studio 11
compatible with Visual Studio 6?
Again thanks for everything,
rich!

On 2/9/2016 7:01 AM, Mark wendt.mark@... [TekScopes] wrote:
Or better yet, upgrade to Linux. ;-)

Mark

Re: Ebay Rip-off ? - "Global Shipping Program"

Mike Usher
 

Hi,

The shipping charde was a total of $54.01, which comprised of post & packing
$15.91, and International delivery $38.10.

The package is now in Warrington with the courier,

Re: TDS 380 calibration and vertical scale problem

 

The manufacturer of a 165-nnnn-nn part in a Tektronix 'scope almost always Tektronix themselves. Microckt - just an abbreviation for micro-circuit. I'm surprised the numeric manufacturer code isn't shown (80009 for Tektronix).

Dave

-----Original Message-----
From: TekScopes@... [mailto:TekScopes@...]
Sent: 09 February 2016 23:49
To: TekScopes@...
Subject: Re: [TekScopes] TDS 380 calibration and vertical scale problem

I wish I knew as getting that schematic is proving very difficult to find. I did come up with Microck as the manufacturer though, their website can be found here http://microckt.com/. I dug around in the manual and that is what I found below, make sure you have enough horizontal space to view this properly



Comp Number tektronix number Name / Description Mfr Code Mfr Part Number

A13AT205 165–2565–00 MICROCKT,HYBRID:1MEG OHM ATTEN/PREAMP TK2601 165–2565–00

A13AT206 165–2565–00 MICROCKT,HYBRID:1MEG OHM ATTEN/PREAMP TK2601 165–2565–00

Re: External TO-3 Cover for Tek equipment on Ebay right now

Malcolm Hunter
 

Thanks Dennis, these were available when I was asking but I thought that it
was a lot to pay for only one. I bought these instead:
http://www.ebay.com/itm/390959168464

Malcolm

On 10 February 2016 at 00:57, 'Dennis Tillman' @Dennis_Tillman_W7pF
[TekScopes] <TekScopes@...> wrote:



If I recall correctly, a few months ago somebody was looking for the
plastic
/ rubber cover for a TO-3 transistor that was mounted on the outside of a
rear panel of a piece of Tek equipment.

There is one of these on Ebay at the moment for a Buy It Now price of
$4.75.
There are 3 available at


http://www.ebay.com/itm/Tektronix-200-0692-00-Transistor-Cover-/361316897529
?hash=item54202a52f9:g:xjYAAOSwpdpVdyUo

I have no connection with the seller, etc.

Dennis Tillman W7PF

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Re: 7904 - Very Dim Trace

 

Diagnostics on DC restorers are not much fun. Measurements require a
high voltage probe and component tests require a high voltage power
supply.

The most common failure is leakage in the high voltage capacitors and
diodes but since testing would require their removal anyway, it is
usually easiest to just replace them if a fault is suspected. New
parts are not expensive so if I had to order them, I would rebuild
both the z-axis and focus DC restorers.

The grid bias control and the output of the z-axis amplifier together
clip the peak-to-peak value of the high voltage drive from the
transformer. The clipped peak-to-peak voltage drives the charge pump
to produce the high negative DC output voltage. High frequency AC
from the z-axis amplifier it capacitively coupled to the high voltage
negative output.

Before messing with the DC restorer, I would verify that the output
from the z-axis amplifier is correct. This can be done with just a
voltmeter if necessary.

On 09 Feb 2016 21:23:08 -0800, you wrote:

OK - reading p 3-65 (Control Grid DC restorer) from the 7904 manual...

Starting to make sense...

Re: 7904 - Very Dim Trace

Jim McIntyre
 

OK - reading p 3-65 (Control Grid DC restorer) from the 7904 manual...

Starting to make sense...

Re: 7904 - Very Dim Trace

Ed Breya
 

There are typically two ways to get DC-coupled Z-axis control on scope CRTs. One is to generate a high voltage, similar to that used for the cathode supply, and stack it onto the ground-referenced Z-axis signal. This is what's applied to the control grid. The other way is to use a DC-restorer circuit, which is basically an AC-coupled charge pump, with the AC swing proportional to the ground-referenced Z-axis signal. It's coupled capacitively and rectified, and stacked onto the cathode supply, then applied to the control grid.

Either way, the control grid is indeed usually negative with respect to the cathode, by maybe up to 100V or so, and it controls the beam current. There are pluses and minuses to each approach.

Ed

Re: OT: Win 8.1 and 10?

n4mf_sc
 

VS6 ? and VS11 are basically 2 different animals. Code written in 6 ? will have to be reworked for 11 or 13 or 15 or Community which I am running now. The coding models and commands have changed greatly over the years, as has so much more. I had to revamp code 2 times for a Fire Flow (water needed) calculations program I wrote that started in QuickBasic and I ported to VS 95 in VB. It's no longer being reworked but I do have some other items I have been playing around with...

Yes I know how my PC runs "under the hood"....

The installer is getting a out of range response from the OS query and going to the unknown OS error out.

Mitch
N4MF

VS Community is free. The EULA lays out what you can do with it which is a bit relaxed from Express. If It's gonna be commercial you will still need pro or better, The EULA is different.