Date   
Re: 485

Mlynch001
 

Their Knob part number is 366-1338-00

--
Michael Lynch
Dardanelle, AR

Re: 485

 

perhaps you would have better luck if you had the 366 part number.

regards,
walter

--
Walter Shawlee 2
Sphere Research Corp. 3394 Sunnyside Rd.
West Kelowna, BC, V1Z 2V4 CANADA
Phone: +1 (250-769-1834 -:- http://www.sphere.bc.ca
+We're all in one boat, no matter how it looks to you. (WS2)
+All you need is love. (John Lennon)
+But, that doesn't mean other things don't come in handy. (WS2)
+Nature is trying very hard to make us succeed, but nature does not depend on us.
We are not the only experiment. (R. Buckminster Fuller)

Re: 454 HV regulation off

Roger Evans
 

Surely 10Mohm reverse resistance for D1440 is indicative of a fault? The diode itself should not show a measurable reverse conduction at a few Volts and the path through the resistor chain R1442 - R1446 and the transformer secondary should be more than 40Mohm. The culprit could be D1440 itself, C1440 or C1449. You would need a few of the resistors to all be low to get 10Mohm through that route. I had to replace C1452 which is a similar 0.015uF capacitor in my original 454, It barely moved the needle on an analogue multimeter but showed several Mohm with a 1000Volt insulation tester. If you can borrow a high voltage insulation tester I would strongly recommend it for tracking down faulty high voltage components.

If D1440 were open circuit there would be a somewhat lower load on the HV oscillator but with a leaking diode or capacitor the HV driver could be running flat out trying to reach -1960Volt. I have to admit I am not sure how the reduced drive power would relatively affect the grid and cathode voltages. Since there is just less flux in the transformer core you might expect the two supplies to track each other but a loss of capacitance or large leakage means that the grid voltage will 'drop' ie become more positive on the non-conducting half cycle.

I agree, the 454 high voltage box is a pain to work on! You are supposed to use high silver content solder on the ceramic tag strips.

Regards,

Roger

Re: 485

Robert Muth
 

I’ve Been looking for one for a long time. No luck from all the usual sources. Considering casting a substitute knob.

On Jan 11, 2020, at 9:43 AM, Steve Lindberg <steve_tech@...> wrote:

Looking for volts per div knob.

Steve


Re: Tek 576 Curve Tracer USB port to a cpu ... ?

JJ
 

Gents,
A few observations. You can pick off the horizontal and vertical analog
bipolar voltages on the Display Sensitivity Switching board - diagram 5 in
the manual. The same nodes are also available on the Display Amplifier
board diagram 9. These nodes represent the voltage signals taken across the
sensing resistors and they are before the amplification stages - the latter
of which also have the calibration pots.

Unfortunately, those nodes are not readily available - the display
switching board is buried under another board, and the display amplifier
board has power resistors in the way of those nodes. It's probably easier
to get to the former. I saw a youtube video of a 546 owner who took the
board out - which may not be necessary for us.

Since the voltage is true bipolar, one would need a differential ADC like
the ADS7808P 12-Bit device. That digital signal can then be sent to an
arduino and passed through the USB port to by processed by Python or
whatever or whatever SW you're into.

Linear scaling of the XY data would be needed to initially "calibrate" the
data to the 546 - which is simple. Some of the display controls on the 546
would need to be offered on the GUI - to essentially tell the program what
you are measuring e.g., what is being measured (e,g., Ic vs Vce) and the
corresponding units - so when you change scale on the 576 for example, you
would click a radio button on the GUI accordingly. Some things may be able
to be derived from the data, so PNP and NPN may be distinguishable with
knowing other inputs like Ic vs Vce on the corresponding axis.

If plotting XY data using MatLib, which is what I suggested earlier, the
data is scaled automatically by the Matlib program, and the display is
updated - but you still need to inform the program via the GUI so that the
labels can be changed accordingly.

This all sounds interesting, fun to implement, and very doable but I'm not
sure of its value. It's not a weekend project - it's more like weeks. And,
with inevitable feature creep, it could be a few months!

There's also the issue of wear and tear on our 546s during development. I
added many miles onto my CNC machine when developing my PCB auto driller
program!

Best,
John Justin

485

Steve Lindberg
 

Looking for volts per div knob.

Steve

SC502 still have 80% of display with HV cable unplugged, multiplier disconnected?

Yeun-Jung Wu
 

Yesterday my little cute scope SC502's trace disappeared after half an hour operation. Brief inspection revealed F800 fuse was blown. I removed AUX board near T800 to expose C850/C851; they were O.K. K6JCA had an interesting discussion on repair job of SC502/504. I followed his guidance and unplugged HV cable, unsoldered input to multiplier. Reinstall F800, I can measure +- 70V. Q860, Q855 were healthy, Q850 was hard to reach. The culprit could be the multiplier P/N 152-0634-00?

I had another SC502 with similar F800 blown fuse problem. Maybe I can retrieve its HV multiplier? I did the same to this SC502. Surprisingly, I can have a trace displayed on 80% of the screen; focusing worked as expected, Ch1/Ch2, triggering all work as expected! But it's CRT's red HV cable was disconnected, even multiplier's input was disconnected from T800! +-70V were correct too.

The other HV unplugged SC502 was as expected: no screen display. +-70V O.K.

Why CRT still have trace under control even HV cable was removed; even multiplier's input unsoldered? Leakage? Can its multiplier still be salvaged? How to restore both SC502's to working condition?

This is my first zombie experience of scope. It seemed that that scope was still usable, in certain sense.

Yeun-Jung Wu

Re: 454 HV regulation off

Albert Otten
 

On Sat, Jan 11, 2020 at 12:58 AM, Jack Ohme wrote:


Albert, the R1447 measures from 0 to 1.28M from wiper to the C1440 end, and
1.28M from end to end (Pot is supposed to be 2M according to schema). Since
I already cracked open the HV, I decided to measure the feedback resistors
as well. The entire string (3M x 8) measured 11M, but each resistor
measures within spec, so I can only assume that the 11M is just a path
somewhere else, probably normal.
Apologies for my lack of knowledge and
thank y'all for bearing with me, this is the first scope I've ever worked
on, so I'm new to the theory and such. Anyway, could that lower resistance
be a bad R1447, and if so, could resistance loss in 1447 even cause my
problem? Or is this just parasitics/other resistances.
Hi Jack,

The 454 cabinet is so easy to open, but I forget that part of the HV circuits is buried in the HV-box. I saw that at least the anode lead has to be unsoldered; probably even more than that. (In the older 5xx scopes access usually is much simpler.) So that's what you mean with "cracked" I guess.

My idea of an interrupted carbon trace in R1447 can be rejected now. You results are strange though. Because of twice 1.28M the wiper seems to be in the extreme upper (in schematic) end. But the pot resistance normally never gets smaller and the parallel resistance is many M. Strange. What happens with the resistance when you turn the wiper from end to end? If the pot resistance really decreased for some reason then the grid would get more negative.

11 M is OK.

Also HV diode D1440 measured 8M across with my meter and 10M in reverse. Is
this just because of the low voltage in my meter, or is this a bad diode?
Probably low voltage (see Harvey's message). However, an open D1440 would be my next candidate to be the culprit. Hence as a guide I measured the diode types with my 576 curve tracer.
152-0192-00 visibly starts to conduct at 4.5 V, reaches 0.2 mA at 5 V and 0.8 mA at 6 V. (D1440 and D1452.) The spec is < 13 V at 50 mA.
152-0218-00 starts at 7.5 V, reaches 0.1 mA at 10 V. (Multiplier diodes.) Spec < 25 V at 20 mA.
Just feed D1440 from a 9V battery in series with a 22k resistor and measure the voltage across the diode; should be about 5 V or so. If 9 V the diode is probably open (confirm with larger series resistance and if you have higher voltage source).
When D1440 is open the grid will become positive w.r.t. the cathode. The voltage difference will be limited either by the grid current (through the high resistance chain) or the neon bulbs.

Albert

Re: Sony/Tek 318 Logic Analyser - parts needed

Gala Dragos
 

Making progress with my repair...

I think I've got the MPU/display board repaired, I now get a "Fail 06" message on screen when booting.

Re: Troubleshooting tips for a Tek 485 scope

Reed Dickinson
 

Hi Kevin:
There are two types of Tantalum caps used by Tektronix in their 485's and other scopes.  The first is the hermetically sealed model and the second is the axial dipped model.  In refurbishing over 200 485's I have only found one bad hermetically sealed cap.  I have found untold numbers of dipped Tantalum caps so I must conclude that moisture seeps into the interior of the dipped model causing it to short out.  This appears to be aggravated by the Vr/Va ratio as caps with Vr/Va ratios near 2 are much more prone to shorting out.  And, as you have observed, age and operating time aggravate the situation.
Here is how I find the shorted cap.  Plug in the scope and power on, if it ticks then the chance of a shorted cap is high.  Power off, wait 10 minutes for all caps to discharge and measure resistance to ground of all 14 voltages.  Once you find a short leave the ohm meter on that voltage and start pulling out, one by one, the 5 pin inter PCB jumpers while watching the meter.  Once the reading goes up you have isolated the bad cap, trace it out and replace the bad one.
RegardsReed

On Friday, January 10, 2020, 07:39:59 AM PST, Kevin Oconnor <@KO3Y> wrote:

Hi Reed,
Great text in ur eBay listing on the 485!
I have a theory on the low Vr/Va tantalum failures, but not much data to support it. I suspect that the 485 tantalum “system” follows some form of Arrhenius behavior that is linked directly to the “live on time” of the scope. As a portable unit, some users would install the 485 on a bench and power it through the work week and maybe for many hours when the lab lights were out. Others were used only on rare occasions when a high performance portable scope was needed. After 35-40 years, these units would fall in very different places on an Arrhenius curve.
My 485 is from the latter case. A few 1000’s of hours rather than 60,000 (8hrs/day x 20years service life). I have never done a full recap. I did replace one transistor and one tantalum at some past date.
But it is also true that every time I push that on/off button it is like a one-armed bandit. Sooner or later I will get three cherries!

Kevin KO3Y

Re: RM547 Twins

Shaun M
 

Hi Richard,

Picked them up from the Calgary e-recycling depot. This is old Calgary (railroad and industrial) along Ogden Road SE. Heretically, I am an Edmontonian, but TEK ignores such petty boundaries.

Shaun M.

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Richard Loken
Sent: Friday, January 10, 2020 21:52
To: TekScopes@groups.io
Subject: Re: [TekScopes] RM547 Twins

On Fri, 10 Jan 2020, Shaun M wrote:

Just wanted to share with the group that I picked up a pair of RM547's
for $cdn 33 + gasoline: About $cdn 88 ($usd 67) total cost. They are
mechanically complete,have all their tubes and a patina of Alberta
prairie dust. They were destined for the scrap pile otherwise.
And were did all this occur? I being in Alberta and all. And having a
547 (not RM) sleeping nearby.
--
Richard Loken VE6BSV : "...underneath those tuques we wear,
Athabasca, Alberta Canada : our heads are naked!"
** rlloken@... ** : - Arthur Black

Re: RM547 Twins

Richard Loken
 

On Fri, 10 Jan 2020, Shaun M wrote:

Just wanted to share with the group that I picked up a pair of RM547's for $cdn 33 + gasoline: About $cdn 88 ($usd 67) total cost. They are mechanically complete,have all their tubes and a patina of Alberta prairie dust. They were destined for the scrap pile otherwise.
And were did all this occur? I being in Alberta and all. And having a
547 (not RM) sleeping nearby.
--
Richard Loken VE6BSV : "...underneath those tuques we wear,
Athabasca, Alberta Canada : our heads are naked!"
** rlloken@... ** : - Arthur Black

Re: Private: Re: [TekScopes] Tek 576 Curve Tracer USB port to a cpu ... ?

 

Rick asked me to correct the post he sent where he said the 576 HV transformer is also used for the voltage applied to the DUT.



I haven’t looked at the 576 schematic in any detail because of my preference for 577s. What I can speak about is how the 577 works in specific terms, and in the paragraph following that one, how a common design concept, first applied by John Kobbe in the 570 for the plate voltage, was so simple and effective that it is used for the collector voltage in the 575, 576, and 577.



In the specific case of the 577 there is a separate winding for each collector supply voltage selection: 6.3V, 25V, 100V, 400V, and 1600V. Each of these individual secondary windings (not taps) are on the collector power transformer. The primary of this transformer is directly connected to the Variac. By controlling how much voltage is applied to the primary, the Variac controls how much voltage comes out of the secondary at each of these collector voltage windings. An elegantly simple design.



I am not familiar with how the 576 generates the collector supply voltage, but I am virtually certain it would be done the same way it was done on the 570, 575, and 577. A fundamental design principle of the 570, 575, 576, and 577 is they all supply full wave rectified power line frequency AC to the collector in the most commonly used configuration.



The HV generated in any of the curve tracers would be DC only. Reading the Theory of Operation section for any of Tek’s curve tracers would explain why they use full wave rectified AC taken directly from the power line. The HV supply would only be capable of a few microamps of current. Also, if the collector voltage came from the HV transformer then every time you toggled the A/B switch and connected a transistor to the high voltage, the CRT would dim and go out of focus due to the current drain.



Dennis Tillman W7PF

Re: RM547 Twins

John Griessen
 

On 1/10/20 9:44 PM, Shaun M wrote:
They are mechanically complete,have all their tubes and a patina of Alberta prairie dust.
OK! I want to see before and after photos.

RM547 Twins

Shaun M
 

Just wanted to share with the group that I picked up a pair of RM547's for $cdn 33 + gasoline: About $cdn 88 ($usd 67) total cost. They are mechanically complete,have all their tubes and a patina of Alberta prairie dust. They were destined for the scrap pile otherwise.

The sight of the industrial scale metal shredding/recycling operation next door did not escape my notice when loading the twins into my vehicle. My best guess is that they were part of an estate that ended up at the electronic recycling depot.

Shaun M.

Re: 577 Curve Tracer question

Harvey White
 

excellent point, and I'll have to guess.  It's one with a small brass tip, but not completely conductive.  As you note, completely nonconductive would be anticipated to have no effect.

I'm not thinking pots here, but the variable capacitors in the delay line.  Having mentioned that, it would likely be whatever tek mentioned to adjust the line itself, but I'm guessing.

Harvey

On 1/10/2020 9:06 PM, Dave Daniel wrote:
Conductive or non-conductive screwdriver? A conductive screwdriver will couple body capacitance to the pot, while a non-conductive screwdriver will not, but may apply a static charge to the pot unless it is discharged first.

DaveD

Sent from a small flat thingy

On Jan 10, 2020, at 20:52, Harvey White <madyn@...> wrote:

One trick I heard of was to touch the adjustment with a screwdriver. If it affected the place you wanted to change, then adjusting it was a good idea. If not, then don't bother with it.

Harvey


On 1/10/2020 1:24 PM, Dennis Tillman W7PF wrote:
Hi Jason,
You are not alone. Now that you mention your experience adjusting the distributed amplifier delay line I am reminded that engineering school graduates who were interviewing at Tek (who we shall call the 'victims") were often introduced to the (mostly) women in the department that adjusted the delay line amplifier for a flat response. Of course they could do it quickly because they learned by repetition how each adjustment affected the response of the amplifier.

The "victims" were given one that hadn't been adjusted yet and asked to tune it for a flat response. After about 30 minutes the interviewer came back to check the "victims" progress. I haven't heard that anyone ever passed this test. It was a humbling experience for the "victims".

Dennis Tillman W7PF

<SNIP>
The same thing took multiple days of my life after having to replace some tubes in my 535A - the Delay Line is another one of those adjustments. By the time I was done messing with it about a week later, I came to the conclusion "I don't ever want to do that again..

-----Original Message-----
From: Jason A. via Groups.Io
Sent: Friday, January 10, 2020 9:39 AM
Subject: Re: [TekScopes] 577 Curve Tracer question

The same thing took multiple days of my life after having to replace some tubes in my 535A - the Delay Line is another one of those adjustments. By the time I was done messing with it about a week later, I came to the conclusion "I don't ever want to do that again.. But at least if there is a next time, I know what I'm in for." I have had a similar experience adjusting the storage on 7834, 5111, 5113 and 7844. Thankfully adjusting the storage is no worse than the delay line in a 535A. That said, it's not much less frustrating either. I would agree with Dennis on this one and would offer what my experience taught me:

0 - Go to your kitchen pantry, dust off your jar of patience and have a good heaping spoonful. :-)

1 - Read the entire section on the adjustment you're wanting to make before beginning.

2 - When you think you have a good understanding, read through it again, locating the adjustment points and test points and go through a "dry run," just verifying where each test and adjustment point is.

3 - make sure you set aside more time than you think you're going to need.

4 - Using tape or some other method, mark anything you can adjust before you start changing things so you know you can at least get back to where you started from. The same goes for the voltage test points - write down what the voltages were before you started so you can hopefully end back up there if needed.

5 - As you start adjusting, it may be worth turning the trimmers an 1/8 of a turn back and forth once or twice from where you think they should be to see the effect of each one, and to make sure there's no dust or anything else in the trimmer that will make things jump around on you later. (Note 1: I noticed this more with 500 series scopes and the older equipment, and it's probably more due to the age of the trimmers/potentiometers having time to oxidize or collect pollution. Note 2: some trimmers have a small useful life of turns, so don't go crazy winding them back and forth dozens of times or you may put a lot of wear out the wiper contact or resistance strip.) Cleaning of trimmers/caps/cam switches, etc. is another subject altogether. Hopefully you won't need to clean them, but if you do, make sure you look carefully in the manual and near the adjustment points to make sure there isn't any advice on cleaning things. Some Tektronix parts have very specific instructions on how to clean them properly.

6 - You should start to get a feeling about what interacts with what the 2nd time through the adjustment process and chances are you'll be pretty darned close at the end.

Best of luck and best regards,

Jason




Re: 577 Curve Tracer question

Dave Daniel
 

Conductive or non-conductive screwdriver? A conductive screwdriver will couple body capacitance to the pot, while a non-conductive screwdriver will not, but may apply a static charge to the pot unless it is discharged first.

DaveD

Sent from a small flat thingy

On Jan 10, 2020, at 20:52, Harvey White <madyn@...> wrote:

One trick I heard of was to touch the adjustment with a screwdriver. If it affected the place you wanted to change, then adjusting it was a good idea. If not, then don't bother with it.

Harvey


On 1/10/2020 1:24 PM, Dennis Tillman W7PF wrote:
Hi Jason,
You are not alone. Now that you mention your experience adjusting the distributed amplifier delay line I am reminded that engineering school graduates who were interviewing at Tek (who we shall call the 'victims") were often introduced to the (mostly) women in the department that adjusted the delay line amplifier for a flat response. Of course they could do it quickly because they learned by repetition how each adjustment affected the response of the amplifier.

The "victims" were given one that hadn't been adjusted yet and asked to tune it for a flat response. After about 30 minutes the interviewer came back to check the "victims" progress. I haven't heard that anyone ever passed this test. It was a humbling experience for the "victims".

Dennis Tillman W7PF

<SNIP>
The same thing took multiple days of my life after having to replace some tubes in my 535A - the Delay Line is another one of those adjustments. By the time I was done messing with it about a week later, I came to the conclusion "I don't ever want to do that again..

-----Original Message-----
From: Jason A. via Groups.Io
Sent: Friday, January 10, 2020 9:39 AM
Subject: Re: [TekScopes] 577 Curve Tracer question

The same thing took multiple days of my life after having to replace some tubes in my 535A - the Delay Line is another one of those adjustments. By the time I was done messing with it about a week later, I came to the conclusion "I don't ever want to do that again.. But at least if there is a next time, I know what I'm in for." I have had a similar experience adjusting the storage on 7834, 5111, 5113 and 7844. Thankfully adjusting the storage is no worse than the delay line in a 535A. That said, it's not much less frustrating either. I would agree with Dennis on this one and would offer what my experience taught me:

0 - Go to your kitchen pantry, dust off your jar of patience and have a good heaping spoonful. :-)

1 - Read the entire section on the adjustment you're wanting to make before beginning.

2 - When you think you have a good understanding, read through it again, locating the adjustment points and test points and go through a "dry run," just verifying where each test and adjustment point is.

3 - make sure you set aside more time than you think you're going to need.

4 - Using tape or some other method, mark anything you can adjust before you start changing things so you know you can at least get back to where you started from. The same goes for the voltage test points - write down what the voltages were before you started so you can hopefully end back up there if needed.

5 - As you start adjusting, it may be worth turning the trimmers an 1/8 of a turn back and forth once or twice from where you think they should be to see the effect of each one, and to make sure there's no dust or anything else in the trimmer that will make things jump around on you later. (Note 1: I noticed this more with 500 series scopes and the older equipment, and it's probably more due to the age of the trimmers/potentiometers having time to oxidize or collect pollution. Note 2: some trimmers have a small useful life of turns, so don't go crazy winding them back and forth dozens of times or you may put a lot of wear out the wiper contact or resistance strip.) Cleaning of trimmers/caps/cam switches, etc. is another subject altogether. Hopefully you won't need to clean them, but if you do, make sure you look carefully in the manual and near the adjustment points to make sure there isn't any advice on cleaning things. Some Tektronix parts have very specific instructions on how to clean them properly.

6 - You should start to get a feeling about what interacts with what the 2nd time through the adjustment process and chances are you'll be pretty darned close at the end.

Best of luck and best regards,

Jason





Re: 577 Curve Tracer question

Harvey White
 

One trick I heard of was to touch the adjustment with a screwdriver.  If it affected the place you wanted to change, then adjusting it was a good idea.  If not, then don't bother with it.

Harvey

On 1/10/2020 1:24 PM, Dennis Tillman W7PF wrote:
Hi Jason,
You are not alone. Now that you mention your experience adjusting the distributed amplifier delay line I am reminded that engineering school graduates who were interviewing at Tek (who we shall call the 'victims") were often introduced to the (mostly) women in the department that adjusted the delay line amplifier for a flat response. Of course they could do it quickly because they learned by repetition how each adjustment affected the response of the amplifier.

The "victims" were given one that hadn't been adjusted yet and asked to tune it for a flat response. After about 30 minutes the interviewer came back to check the "victims" progress. I haven't heard that anyone ever passed this test. It was a humbling experience for the "victims".

Dennis Tillman W7PF

<SNIP>
The same thing took multiple days of my life after having to replace some tubes in my 535A - the Delay Line is another one of those adjustments. By the time I was done messing with it about a week later, I came to the conclusion "I don't ever want to do that again..

-----Original Message-----
From: Jason A. via Groups.Io
Sent: Friday, January 10, 2020 9:39 AM
Subject: Re: [TekScopes] 577 Curve Tracer question

The same thing took multiple days of my life after having to replace some tubes in my 535A - the Delay Line is another one of those adjustments. By the time I was done messing with it about a week later, I came to the conclusion "I don't ever want to do that again.. But at least if there is a next time, I know what I'm in for." I have had a similar experience adjusting the storage on 7834, 5111, 5113 and 7844. Thankfully adjusting the storage is no worse than the delay line in a 535A. That said, it's not much less frustrating either. I would agree with Dennis on this one and would offer what my experience taught me:

0 - Go to your kitchen pantry, dust off your jar of patience and have a good heaping spoonful. :-)

1 - Read the entire section on the adjustment you're wanting to make before beginning.

2 - When you think you have a good understanding, read through it again, locating the adjustment points and test points and go through a "dry run," just verifying where each test and adjustment point is.

3 - make sure you set aside more time than you think you're going to need.

4 - Using tape or some other method, mark anything you can adjust before you start changing things so you know you can at least get back to where you started from. The same goes for the voltage test points - write down what the voltages were before you started so you can hopefully end back up there if needed.

5 - As you start adjusting, it may be worth turning the trimmers an 1/8 of a turn back and forth once or twice from where you think they should be to see the effect of each one, and to make sure there's no dust or anything else in the trimmer that will make things jump around on you later. (Note 1: I noticed this more with 500 series scopes and the older equipment, and it's probably more due to the age of the trimmers/potentiometers having time to oxidize or collect pollution. Note 2: some trimmers have a small useful life of turns, so don't go crazy winding them back and forth dozens of times or you may put a lot of wear out the wiper contact or resistance strip.) Cleaning of trimmers/caps/cam switches, etc. is another subject altogether. Hopefully you won't need to clean them, but if you do, make sure you look carefully in the manual and near the adjustment points to make sure there isn't any advice on cleaning things. Some Tektronix parts have very specific instructions on how to clean them properly.

6 - You should start to get a feeling about what interacts with what the 2nd time through the adjustment process and chances are you'll be pretty darned close at the end.

Best of luck and best regards,

Jason



Re: 454 HV regulation off

Harvey White
 

some HV diodes are made of stacks of lower PIV diodes.....

I'd expect the forward voltages to add.......

Harvey

On 1/10/2020 7:27 PM, Jack Ohme wrote:
Yeah I'm an idiot, the diode just has a big voltage drop/fwd voltage. Also
as Roger mentioned, I measured R1404 to be about .85M, .15 away from its
spec of 1M.

On Fri, Jan 10, 2020 at 4:05 PM Jack Ohme via Groups.Io <machinamancerjack=
gmail.com@groups.io> wrote:

Also HV diode D1440 measured 8M across with my meter and 10M in reverse. Is
this just because of the low voltage in my meter, or is this a bad diode?

On Fri, Jan 10, 2020 at 3:59 PM Jack Ohme via Groups.Io <machinamancerjack=
gmail.com@groups.io> wrote:

Albert, the R1447 measures from 0 to 1.28M from wiper to the C1440 end,
and
1.28M from end to end (Pot is supposed to be 2M according to schema).
Since
I already cracked open the HV, I decided to measure the feedback
resistors
as well. The entire string (3M x 8) measured 11M, but each resistor
measures within spec, so I can only assume that the 11M is just a path
somewhere else, probably normal. Apologies for my lack of knowledge and
thank y'all for bearing with me, this is the first scope I've ever worked
on, so I'm new to the theory and such. Anyway, could that lower
resistance
be a bad R1447, and if so, could resistance loss in 1447 even cause my
problem? Or is this just parasitics/other resistances.

On Fri, Jan 10, 2020 at 10:43 AM Albert Otten <aodiversen@...>
wrote:

On Fri, Jan 10, 2020 at 05:31 PM, Jack Ohme wrote:

Albert, I've read all of your messages, I've just been attempting to
rule
everything out before having to tear into the HV supply, though at
this
point I suppose its necessary. Wonderful.
Hi Jack,

Sorry, I don't want to hurry you up, but I'm very curious to see if my
suspect of a bad R1447 was right. Did you check that this pot is not
interrupted (internally) at the C1440 end of the carbon trace? If the
connection to C1440 end is broken then there is at least 7.5 M between
the
C1440 and the grid, reducing the grid voltage considerable in positive
direction. The pot is only 2M so easy to check with a DMM.
I understood from your findings that the grid is positive w.r.t. the
cathode, right?

Albert





Re: Tek 576 Curve Tracer USB port to a cpu ... ?

Jim Ford
 

Hi, Dennis and others. I had the good fortune to meet Barrie Gilbert at a talk several years ago.  He told the story about the fiber optic readout and how that is the reason for the 4 holes in the plastic tabs.  Sure as shootin' I found them there on my 7A26.Professor Asad Abidi of UCLA introduced Barrie saying something like, "How many people do you know with no college degree whatsoever but with multiple honorary PhDs?  Such is Barrie Gilbert."  I later saw Barrie's home lab in an online photo, complete with multiple synthesizers, both of the RF and musical instrument type.  Truly drool -worthy! Jim Ford Sent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------From: Dennis Tillman W7PF <@Dennis_Tillman_W7PF> Date: 1/10/20 10:06 AM (GMT-08:00) To: TekScopes@groups.io Subject: Re: [TekScopes] Tek 576 Curve Tracer USB port to a cpu ... ? Hi Christian,The 7CT1N has no readout capability so it was irrelevant that the DSA602 couldn't display readout information.The 7CT1N should also work in the 11403 and 11403A. I should actually give this a try to see what it looks like.But you reminded me of another important point to mention: Many 7K plugins work in the 11K series of scopes. There is a simple mechanical change you need to make to the rear of the 7K plugin before they will fit. The 4 holes that extend out at the top of the plastic rear connector cover of the 7K plugins will need to be cut off first or the plugin won't go in far enough to make contact with the backplane of the 11K scope. The 11K scopes have no use for the fiber optic bundles that were going to go through those holes to display the readout information in the original design concept of the 7K scopes. Picture the fiber-optic readout on the side of the 576 curve tracer to get an idea of what might have been.This fiber-optic readout idea would have been a disaster to make work with plugins. It was an idea proposed by a senior engineer at Tek. Along comes a young, brash, new hire, who hears about this and tells enough people that this is a dumb idea. Fortunately Tek management challenges him to come up with a better way to do it. That was Barrie Gilbert. His solution was to write the plugin's settings on the CRT screen itself. This was a brilliant idea but it had never been done. They wanted to know how this could be done. Barrie knew how he would do it and he gave a demonstration using Teledeltos paper to management that showed them the principle it was based on and how it would be implemented in a CRT. The rest is history.-----Original Message-----From: santa0123456Sent: Thursday, January 09, 2020 1:35 PMSubject: Re: [TekScopes] Tek 576 Curve Tracer USB port to a cpu ... ?Hi to all,In 2011, I used the partial compatibility between 7K and 11K families modules to insert my 7CT1N in my DSA602A.Pictures in the folder 7CT1N-DSA602A.Of course, the current/voltage range is nowhere near the 576 and the 7CT1N selector positions are unknown to the DSA, so the display units are either meaningless or arbitrary (indicated by a U).But this is better than nothing since it doesn't need any modification for small transistor testing and pairing.Christian-- Dennis Tillman W7PFTekScopes Moderator