Date   

Re: 475 With a bowed display. . . .Ideas?

Michael W. Lynch
 

Raymond,

I am not familiar at all with the 475. This is the first one that I have tried working on. I do have a perfectly functional 475A/DM44, but have not had to open it up at this point. I have heard about these"distributed plates" but never took the time to explore the theory behind them. I suppose that these higher speed scopes require them at the higher bandwidths which they are capable of displaying. Most of my work has been on slower scopes.

Thanks for taking the time to explain this to me. I will do some additional reading.

Sincerely,

--
Michael Lynch
Dardanelle, AR


Re: TM500 Plug-in Extention

Stephen
 

Thank you Göran.


Re: 475 With a bowed display. . . .Ideas?

 

On Mon, Aug 10, 2020 at 08:59 PM, Raymond Domp Frank wrote:


both "ends".
Trying to say here that there's an impedance matching terminator connecting the "far side" of the top plate and the "far side" of the bottom plate.

Raymond


Re: 475 With a bowed display. . . .Ideas?

 

On Mon, Aug 10, 2020 at 08:28 PM, Michael W. Lynch wrote:


Raymond,

Unfortunately, the 475 CRT has an extra set of pins on the side of the CRT,
which the 465 CRT lacks. The extra pins are adjacent to and aligned with the
Vertical Deflection plate pins. There is about 1 1/2 - 2 inches between the
two sets of pins (I did not measure, just from memory). So there are a total
of 4 pins on the side of the CRT, where the 465 only has 2 pins. The
Horizontal pins come in from the bottom exactly like the 465. Even though the
465 and 475 are similar, I am much more familiar with the 465 and it is not at
all clear in the schematic or the service manual what these pins do. I am
certainly not experienced enough to say what these are for. These two extra
pins do not show in the schematic, at least not that I can find. I don't want
to risk trying without those extra pins connected. This might damage the
scope, the CRT or worst of all both of them. Clearly different from the
465/465B CRT. Do you have any idea what these extra 2 pins might be for?
I'm not familiar with the CRT of the 475, I have to admit. The extra pins almost certainly are distributed plate connections. In general, there's just a terminator connected between both "ends". I didn't know the 475 had distributed vertical plates. The main idea of distributed plates is to make sure that those electrons that make up the beam at any moment, traveling from cathode to screen at a certain (limited) speed, aren't deflected first to one side then to the other by the same vertical plate('s charge) because they take time to pass the plate which sits along the beam's path for a "significant time". The distributed plate artificially lengthens the signal path and causes the applied signal to travel in parallel with the beam at the beam's speed toward the screen. Using very "short" vertical plates instead isn't an option because deflection sensitivity depends (a.o.) on the time that the charge of a plate works on the beam. You should be able to measure a DC connection between both ends of each distributed plate.

Raymond


Re: 7834 Missing Trace

sdferg7@...
 

Here is the bottom of mine: https://imgur.com/a/B0FAYRI

I'm not sure how to get to the spring or plastic without taking the whole bottom frame apart to remove the black guide rails. I can't access them from the side of the plugin either as far as I can tell.

Shane


Re: Fuzzy Trace that Auto-Corrects Itself

n4buq
 

That certainly sounds a lot like what's going on with my scope and I wonder if trying to chase supposedly bad parts on the HV board will be fruitless.

I have monitored the focus voltage and it appears that it takes a slightly different voltage to focus it when it is fully warmed up versus when it first begins to display a (fat) trace. It only varies by about 20 volts or so (e.g. 1730VDC to 1750VDC) and the HV supply values don't seem to change much, if any, so perhaps it's just a matter of having to wait on the CRT to be fully functional. I even went so far as to attempt to pre-heat the components on the HV board but it still took about the same time to flatten that huge trace.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Dave Wise" <david_wise@phoenix.com>
To: TekScopes@groups.io
Sent: Monday, August 10, 2020 12:29:30 PM
Subject: Re: [TekScopes] Fuzzy Trace that Auto-Corrects Itself

Puts me in mind of my Tek 321A. After sitting power-off for a day or more,
the geometry is wrong. It will gradually straighten out, or if I turn
intensity to max, in a couple seconds. Then it's fine until it's powered
down, when it will gradually go bad again. All the pin voltages are good.
I've concluded that some metal part inside the CRT is floating - perhaps a
weld has come loose. (Floating electrically, not mechanically; nothing is
rattling around.) High beam current charges it to normal potential, and it
gradually discharges again while power is off. That's the story, at least.

FWIW,
Dave Wise
________________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of n4buq via
groups.io <n4buq=knology.net@groups.io>
Sent: Saturday, August 08, 2020 1:34 PM
To: TekScopes@groups.io
Subject: [TekScopes] Fuzzy Trace that Auto-Corrects Itself

I have a Hameg scope and if this question/thread needs to be deleted, then
may the moderator please intervene; however, I think it may be generic
enough for this list and I've run out of other sources so I'll try here.

When first powered on and the CRT starts displaying a trace, it is very fuzzy
and wide - approximatrly 1.5 cm. Given about two minutes, the trace
gradually becomes very sharp, focuses where it should, and stays that way
for as long as the scope is powered up.

During that "warm up" time, the trace gradually becomes focusable near one
extreme of the focus control and then gradually is focusable at/near center
of the knob rotation and stays that way.

If I increase the intensity to fully bright as soon as the display becomes
visible, the fuzziness disappears much faster but still doesn't settle out
fully until about two minutes after power on.

I have replaced the HV resistors in the chain that makes up the focus voltage
divider as well as a couple of other HV resistors in the intensity circuit
but the problem persists.

There are a few 0.1uf 1kV film caps that are part of that focus circuit and I
am thinking it could be one or more of those but not sure.

Anyone have any ideas as to what's going wrong and what to look for?

Again, if this is too far OT, then please let me know and I will not continue
the thread.

Thanks,
Barry - N4BUQ









Re: TM500 Plug-in Extention

Göran Krusell
 

You need to check every pin if you suspect anything being wrong.


Re: eBay / PayPal Changes and our alternatives

Dave Daniel
 

There is the groups.io Test-Equipment-For-Sale group.

DaveD

On Aug 10, 2020, at 14:14, Dick Wilson at DiLette Sales via groups.io <cmdrdick42=yahoo.com@groups.io> wrote:

Just a quick question, since I'm buried in unused tech stuff. Where is the best place to find new owners given that we will no longer sell on ebay?Does this forum have a For Sale area?
On Saturday, August 8, 2020, 12:34:42 PM EDT, Dick Wilson at DiLette Sales via groups.io <cmdrdick42=yahoo.com@groups.io> wrote:

Eastern Airlines had a high concentration of refugees from Cuba. I suppose that I should have said Cuban Americans. They were known to be staunch supporters of their unions and willing to fight for their rights. My own route often included Miami as a layover. I partied with and know several of them personally. I supported their cause. Carl Icahn was a cold blooded corporate raiding SOB whose greed had no bounds.
On Friday, August 7, 2020, 12:28:15 PM EDT, DaveC via groups.io <davec2468=yahoo.com@groups.io> wrote:

Cubans?

Dave


... What totally shocks me given the high percentage of Cubans that were affected, is that he is still walking around.CmdrDick









Re: TM500 Plug-in Extention

Stephen
 

Yes Andy, you were the one who raised that issue.

And also thank you Harvey for asking about pin 6. I should’ve understood the hint.


Re: 7834 Missing Trace

Harvey White
 

On the bottom of the plugin, behind the latch, is a spring.  That spring (in mine) is attached to a plastic piece which is essentially the stem for  the pull tab.  Push that white piece of plastic towards the front of the scope.

Harvey

On 8/10/2020 1:23 PM, sdferg7@gmail.com wrote:
I attempted adjusting R551, however I reached its maximum and the 9V pin was at about 8.86V. I tried wiggling the board to make sure it was seated properly. The signal shown on the positive of both channels now shows about double the voltage and the trace is much noisier; the inverse setting seems about the same as before, as I haven't changed R570. For the gain adjustments I would just calibrate the traces to the calibrator signal, correct?

Unfortunately I don't know anyone personally who owns an oscilloscope, let alone a 7000 series. I've been keeping an eye out for plugins on ebay, I thought a 7A24 or 26 would be nice, but they seem quite expensive. I might settle for another 7A12 for now, I'd like to not spend too much until I know I can get her working properly.

I still haven't been able to get the 7A12 out through pulling and wiggling. I think today I'm just going to start unscrewing the bottom portions to see if I can get the latching mechanism out.

Shane



Re: TM500 Plug-in Extention

Dave Daniel
 

There’s also a TM500 interface reference manual for all of this. There’s probably a copy on TekWiki.

DaveD

On Aug 10, 2020, at 14:03, Colin Herbert via groups.io <colingherbert=blueyonder.co.uk@groups.io> wrote:

I will use the Tektronix nomenclature, since this is more concerned with Tektronix than with JAMMA. The numbers of the connectors go from 1 at the bottom to 28 at the top. Looking at the backplane connector from its front (the side that things plug into, rather than that where thing are soldered onto), the connectors on the left are the "A" connectors and those on the right are the "B" connectors.

A2 and B2 are both connected to +11.5 filtered DC
A3, B3, A4 and B4 are all connected to +11.5 V Common Return
8A and 8B are both connected to -33.5 v filtered DC
12A and 12B are both connected to +33.5 V filtered DC
6A is the base lead of the NPN series-pass transistor and should be included in the extender wiring.
6B has no connection
All connectors, both A and B sides from 14 upwards are not assigned, but might have connections to some plug-ins in order to interconnect them. The Manual for the plug-in will indicate anything like this.

I think that any Power Module will give pin assignments to the backplane.
Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Stephen
Sent: 10 August 2020 18:06
To: TekScopes@groups.io
Subject: Re: [TekScopes] TM500 Plug-in Extention

On Mon, Aug 10, 2020 at 05:45 AM, Colin Herbert wrote:

It is maybe a pity that I can't show a photo of the extender, which might make the arrangements clearer.
Colin
I don’t know if I can explain it correctly, but what I did is pretty straight forward.
I have a wire on both sides of the male connector (the one that plugs into the chassis) connected to each side of the other end. As if they were the same unit, if you will. Only pin 2,3,4,8 and 12 are bridged together. Exactly as the instructions above suggest. 6A and 6B, as well as everything from 14 up are left blank.







Re: 475 With a bowed display. . . .Ideas?

Michael W. Lynch
 

On Mon, Aug 10, 2020 at 12:27 PM, Raymond Domp Frank wrote:


It might be worthwhile to check and see if one of your -0731's will do. The
'scopes are very alike, except for BW of course and ISTR that CRT's of
different models were used during the production life of the 465/475 series.
At least I'd think that they are pin compatible. ISTR that the expansion mesh
construction in the 465 was changed/improved at some stage but that's probably
just the -0x mod level in the -0731.
Possibly worth a try after establishing that nothing will blow up.
Raymond,

Unfortunately, the 475 CRT has an extra set of pins on the side of the CRT, which the 465 CRT lacks. The extra pins are adjacent to and aligned with the Vertical Deflection plate pins. There is about 1 1/2 - 2 inches between the two sets of pins (I did not measure, just from memory). So there are a total of 4 pins on the side of the CRT, where the 465 only has 2 pins. The Horizontal pins come in from the bottom exactly like the 465. Even though the 465 and 475 are similar, I am much more familiar with the 465 and it is not at all clear in the schematic or the service manual what these pins do. I am certainly not experienced enough to say what these are for. These two extra pins do not show in the schematic, at least not that I can find. I don't want to risk trying without those extra pins connected. This might damage the scope, the CRT or worst of all both of them. Clearly different from the 465/465B CRT. Do you have any idea what these extra 2 pins might be for?


--
Michael Lynch
Dardanelle, AR


Re: TM500 Plug-in Extention

Andy Warner
 

I was the one that raised the spectre of external pass transistors
oscillating when used by a module via an extender.

I have seen it myself on an FG504, and remember rumblings on the list about
it.

Was simply suggesting to the list in response to Stephen that in my
experience some modules can provoke this behaviour, while others do not.
I do not have a large enough sample set to determine if the issues are
per-module-design, per-physical-module, per-enclosure, or a mix of all.
However, I am planning to test a modified extender which seeks to address
this particular backwater.

I don't know where the idea of unused transistors oscillating came from,
it's not an issue.

On Mon, Aug 10, 2020 at 1:04 PM Stephen <stephen.nabet@gmail.com> wrote:

I don’t know if I do have oscillation.
But if there were any, wouldn’t the PS503 not be working as well?

Where should I check for oscillation? Pin 7 and 12? Respectively
“collector lead to NPN and PNP pass transistors”?



--
Andy


Re: TM500 Plug-in Extention

Stephen
 

Thank you Colin.

Yes, it’s better to use the Tektronix nomenclature. And after reading your post I realized that I left both the A an B sides of pin 6 disconnected whereas 6A should be.
Thank you for pointing that out.


Re: eBay / PayPal Changes and our alternatives

Dick Wilson at DiLette Sales <cmdrdick42@...>
 

Just a quick question, since I'm buried in unused tech stuff. Where is the best place to find new owners given that we will no longer sell on ebay?Does this forum have a For Sale area?

On Saturday, August 8, 2020, 12:34:42 PM EDT, Dick Wilson at DiLette Sales via groups.io <cmdrdick42=yahoo.com@groups.io> wrote:

Eastern Airlines had a high concentration of refugees from Cuba. I suppose that I should have said Cuban Americans. They were known to be staunch supporters of their unions and willing to fight for their rights. My own route often included Miami as a layover. I partied with and know several of them personally. I supported their cause. Carl Icahn was a cold blooded corporate raiding SOB whose greed had no bounds.
    On Friday, August 7, 2020, 12:28:15 PM EDT, DaveC via groups.io <davec2468=yahoo.com@groups.io> wrote: 

Cubans?

Dave


... What totally shocks me given the high percentage of Cubans that were affected, is that he is still walking around.CmdrDick


Re: TM500 Plug-in Extention

Stephen
 

I don’t know if I do have oscillation.
But if there were any, wouldn’t the PS503 not be working as well?

Where should I check for oscillation? Pin 7 and 12? Respectively “collector lead to NPN and PNP pass transistors”?


Re: TM500 Plug-in Extention

Colin Herbert
 

I will use the Tektronix nomenclature, since this is more concerned with Tektronix than with JAMMA. The numbers of the connectors go from 1 at the bottom to 28 at the top. Looking at the backplane connector from its front (the side that things plug into, rather than that where thing are soldered onto), the connectors on the left are the "A" connectors and those on the right are the "B" connectors.

A2 and B2 are both connected to +11.5 filtered DC
A3, B3, A4 and B4 are all connected to +11.5 V Common Return
8A and 8B are both connected to -33.5 v filtered DC
12A and 12B are both connected to +33.5 V filtered DC
6A is the base lead of the NPN series-pass transistor and should be included in the extender wiring.
6B has no connection
All connectors, both A and B sides from 14 upwards are not assigned, but might have connections to some plug-ins in order to interconnect them. The Manual for the plug-in will indicate anything like this.

I think that any Power Module will give pin assignments to the backplane.
Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Stephen
Sent: 10 August 2020 18:06
To: TekScopes@groups.io
Subject: Re: [TekScopes] TM500 Plug-in Extention

On Mon, Aug 10, 2020 at 05:45 AM, Colin Herbert wrote:

It is maybe a pity that I can't show a photo of the extender, which might make the arrangements clearer.
Colin
I don’t know if I can explain it correctly, but what I did is pretty straight forward.
I have a wire on both sides of the male connector (the one that plugs into the chassis) connected to each side of the other end. As if they were the same unit, if you will. Only pin 2,3,4,8 and 12 are bridged together. Exactly as the instructions above suggest. 6A and 6B, as well as everything from 14 up are left blank.


Re: Fuzzy Trace that Auto-Corrects Itself

Tom Gardner
 

On 10/08/20 18:29, Dave Wise wrote:
Puts me in mind of my Tek 321A. After sitting power-off for a day or more, the geometry is wrong. It will gradually straighten out, or if I turn intensity to max, in a couple seconds. Then it's fine until it's powered down, when it will gradually go bad again. All the pin voltages are good. I've concluded that some metal part inside the CRT is floating - perhaps a weld has come loose. (Floating electrically, not mechanically; nothing is rattling around.) High beam current charges it to normal potential, and it gradually discharges again while power is off. That's the story, at least.
Sounds like my 485.

Beginning of day it took 60s to turn on.
Turn off and on again and it started instantly.
Turn off, wait an hour, and it took 5s to turn on.
Turn off, wait a morning, and it took 20s to turn on.

It felt as if the dielectric in the startup electrolytic dissipated when turned off, and had to be reformed before it would startup.


Re: 2465 Fan Collet Thingy

n4buq
 

If I'm not mistaken, the end of the stud that goes into the collet is #4-40 and the other end that protrudes through the impeller is #6-32. The stud has a shoulder between the two threaded ends that bottoms out on the collet. The intent was for the user to loosen the nut and turn the stud CCW with the screwdriver slot which would force the shoulder against the inside of the impeller and push the collet free. Of course, if you try that these days, the plastic has gotten brittle and you're very likely to break things. As Chuck has iterated, best to loosen the nut and give the stud a gentle tap which will force it to open it without twisting it.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Siggi" <siggi@undo.com>
To: TekScopes@groups.io
Sent: Monday, August 10, 2020 12:28:55 PM
Subject: Re: [TekScopes] 2465 Fan Collet Thingy

On Mon, Aug 10, 2020 at 1:17 PM Dave Ahrendt <dave@dkahrendt.net> wrote:

I do have two fdm printers but do not own a 2465 only a 2236. I assume
that the threaded portion is 6-32 or is it metric (M3.5)?
The threaded portion is 4-40, if I remember correctly.


I'm not sure what the threaded portion threads in to so how much torque is
normally applied?
The stud that threads into the collet is used on one hand to pull the
collet into the impeller, which clamps it to the motor shaft. This happens
when the 8-32 nut on the outside of the impeller is tightened, and I'd say
there's a fair bit of torque involved. On the other hand, the 4-40 thread
is used to eject the collet from the impeller when loosening it. This is
done by turning the stud with a flat-blade screwdriver, which pushes the
collet via the 4-40 threads.




Re: Fuzzy Trace that Auto-Corrects Itself

Dave Wise
 

Puts me in mind of my Tek 321A. After sitting power-off for a day or more, the geometry is wrong. It will gradually straighten out, or if I turn intensity to max, in a couple seconds. Then it's fine until it's powered down, when it will gradually go bad again. All the pin voltages are good. I've concluded that some metal part inside the CRT is floating - perhaps a weld has come loose. (Floating electrically, not mechanically; nothing is rattling around.) High beam current charges it to normal potential, and it gradually discharges again while power is off. That's the story, at least.

FWIW,
Dave Wise
________________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of n4buq via groups.io <n4buq=knology.net@groups.io>
Sent: Saturday, August 08, 2020 1:34 PM
To: TekScopes@groups.io
Subject: [TekScopes] Fuzzy Trace that Auto-Corrects Itself

I have a Hameg scope and if this question/thread needs to be deleted, then may the moderator please intervene; however, I think it may be generic enough for this list and I've run out of other sources so I'll try here.

When first powered on and the CRT starts displaying a trace, it is very fuzzy and wide - approximatrly 1.5 cm. Given about two minutes, the trace gradually becomes very sharp, focuses where it should, and stays that way for as long as the scope is powered up.

During that "warm up" time, the trace gradually becomes focusable near one extreme of the focus control and then gradually is focusable at/near center of the knob rotation and stays that way.

If I increase the intensity to fully bright as soon as the display becomes visible, the fuzziness disappears much faster but still doesn't settle out fully until about two minutes after power on.

I have replaced the HV resistors in the chain that makes up the focus voltage divider as well as a couple of other HV resistors in the intensity circuit but the problem persists.

There are a few 0.1uf 1kV film caps that are part of that focus circuit and I am thinking it could be one or more of those but not sure.

Anyone have any ideas as to what's going wrong and what to look for?

Again, if this is too far OT, then please let me know and I will not continue the thread.

Thanks,
Barry - N4BUQ

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