Date   

Re: LF Compensation of a 468 scope

Colin Herbert
 

Hi Fabio,

I too have a 464, which was giving me problems a year or more ago. John Sykes, who is a member of this forum and lived not far from me, gave it a look-over and got it working fine. I also have two non-working 466s and a 475A as well as the 468 I am trying to get calibrated. I have original Tek manuals for all of these scopes, plus the 465 and 465B manuals (I don’t own these scopes, so it must be Acquisition Syndrome on my part). It is only the 465B and 468 that have this procedure in the manuals. It has to be said that the Vertical Output Amplifiers of these two look similar, but the others being decidedly different. The 475A Vertical Output Amplifier uses some hybrids which are no doubt proprietary. My electronic knowledge is limited and self-taught, so I find difficulty working out some things. I, too cannot see how the procedure is operating – what does “Vert Alt Sync” have to do with anything here?

David Hess has said that the 468 is basically a 465B with the added DSO hardware. So, while it is a complex and strange beast, there should be probably more people who have a 465B and might have come across this.

Colin.

From: TekScopes@... [mailto:TekScopes@...]
Sent: 15 February 2017 11:20
To: TekScopes@...
Subject: Re: [TekScopes] LF Compensation of a 468 scope





Hello Colin,
You may get disappointed that my answer is more like a validation of your
problem than an answer properly said.
I own a 464 which Is slightly off in the low freq. compensation as well.
No matter I do, even setting all those trimpots to their minimum, the
square wave tops and bottoms remain still lightly inclined (the tops begin
higher and then fall a little and the bottoms the opposite).
I never noticed any instruction to disconnect some peltola internal cable
on my service manual, but I may have skipped something accidentally.
I fail to understand what in the world this signal of alternate trace sync
has anything to do with the subject of adjusting the lo-freq compensation.
Now you triggered my curiosity and I will look into the 468's SM to see if
I can see any explanation to your issue and perhaps I'll find some
explanation to my problem as well.
I was holding this problem (of mine) for a later time when I'd have solved
other minor issues that are also pending, but now it's itching!
Brgrds,
Fabio


Re: B92A no sweep

Joseph Tatum
 

You are right. I was not satisfied with the term mylar when I typed it. The description I gave fits a polystyrene cap but I did have the name wrong. But that is what it was.


Re: LF Compensation of a 468 scope

Fabio Trevisan
 

Hello Colin,
You may get disappointed that my answer is more like a validation of your
problem than an answer properly said.
I own a 464 which Is slightly off in the low freq. compensation as well.
No matter I do, even setting all those trimpots to their minimum, the
square wave tops and bottoms remain still lightly inclined (the tops begin
higher and then fall a little and the bottoms the opposite).
I never noticed any instruction to disconnect some peltola internal cable
on my service manual, but I may have skipped something accidentally.
I fail to understand what in the world this signal of alternate trace sync
has anything to do with the subject of adjusting the lo-freq compensation.
Now you triggered my curiosity and I will look into the 468's SM to see if
I can see any explanation to your issue and perhaps I'll find some
explanation to my problem as well.
I was holding this problem (of mine) for a later time when I'd have solved
other minor issues that are also pending, but now it's itching!
Brgrds,
Fabio

On Feb 14, 2017 4:24 PM, "'Colin Herbert' colingherbert@...
[TekScopes]" <TekScopes@...> wrote:



Hi,

Does no-one have any observations on this? Perhaps I am being too impatient.

I have ordered two of these BNC-to-Peltola adapters from Qservice, so I have
to wait a while for the delivery before I can do much more. I remain puzzled
that this scope and the 465B and no others in the 46x series (or the 475A)
use this method.

Colin.

From: TekScopes@... [mailto:TekScopes@...]
Sent: 11 February 2017 20:45
To: TekScopes@...
Subject: RE: [TekScopes] Gain calibration of a 468 scope

Continuing..

I have now got to the point of trying to adjust the Low-Frequency
Compensation. I believe that I have a little too much overshoot. The manual
states that on the Vertical Output Board there are five pre-sets which
affect the compensation at 1, 10 and 100KHz. That is all very well, but
there is also a requirement set the 486 vertical mode to CH1 & CH2 alternate
and disconnect P686 from J686 on the interface board. This J686 is the "Vert
Alt Sync". Now, either a 1KHz square-wave from a low-frequency generator (an
SG502?), or the fast-rise negative output from the PG506 is connected to
J686 with a BNC-to-Peltola adaptor. I don't understand why this is
considered to be necessary or what it is actually doing.

Neither the 464 nor the 465 scopes use this protocol, but the 465B does. Is
it really necessary, or could one simply leave P686/J686 connected and just
adjust the pre-set on the Vertical Output Board?

Any help and information appreciated. I am learning a lot fiddling with this
beast.

Colin.

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Re: OT Ripple Leader LTC-905

Fabio Trevisan
 

Hi Jerry,
I realize now may be too late, as you made up tour mind to sell the thing
but...
It may be a long shot and I don't know your leader in particular but, since
Mark pointed out that the two wire model is susceptible to mains lead
neutral to phase inversion, I wonder if even the 3 wire model is also
susceptible.
In that case, the neutral and phase wires may be wired wrong in your wall
outlet and since the 3 prong plug won't let you reverse it, you could be
stuck to the problem just because of the wrong wiring of the wall
receptacle.
Even if you're not keeping it, it may still worth to check your wall outlet.
Brgrds,
Fabio

On Feb 14, 2017 11:36 PM, "Jerry Massengale jmassen418@...
[TekScopes]" <TekScopes@...> wrote:



Hi,

Yes, mine has a 3 wire power cord and the green wire is tied to the chassis
as is the system ground. I looked at the 3 dc power busses and they are
clean and at the correct voltage. The output of the step generator looks
good at the output of the buffer. I am concerned with a very long ground
bus directly tied to earth. I was tempted to disconnect chassis gnd from
signal gnd but decided to sell it instead. Another issue is the 3 banana
jacks for the transistor connection are not on the standard 0.75 inch
spacing that fit my adapters. This is all part of my downsizing efforts. I
recently sold my 576 that I really liked. One option was to use a 7CT1N
with my 7704A, The other was to acquire the Leader LTC-905 and use it with
my 2465A. I put the 905 on ebay for a very low price and will soon put the
2465A up for sale.

jerry

On Tue, Feb 14, 2017 at 3:24 PM, Clark bclark207@... [TekScopes] <

TekScopes@...> wrote:

What does the earth connection connect to in the curve tracer? Mine has
an original two-wire cord with standard two-prong plug - not even
polarized.


On 02/14/2017 02:24 PM, Jerry Massengale jmassen418@...
[TekScopes] wrote:

Hi,

Replacing the 4 rectifiers greatly reduced the ripple. My trace looks
like
that shown in manual. I have decided to sell the LTC-905 and keep my
7CT1N.
This unit has the 3 wire power cable.

On Tue, Feb 14, 2017 at 6:33 AM, Clark bclark207@... [TekScopes] <
TekScopes@...> wrote:

Ripple, or phase error? - see section B on pg 3 in the users manual. I
had the same problem, and solved it by reversing the curve tracer plug
in the wall outlet.


On 02/13/2017 03:01 PM, Jerry Massengale jmassen418@...
[TekScopes] wrote:

Hi,

My just recieved Leader LTC-905 Curve Tracer has a small ripple on
the
display curves as displayed on my 2465A scope. The electrolytics in
the box
have good ESR. Suggestions?

jerry

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Re: Tek492 blank CRT. Please help

Artek Manuals <manuals@...>
 

First look at page 3-7 of the operators manual "turn on procedure" to be
sure that after a year some switch or control is properly set, They can
get moved bumped, etc when you put it away last year.

The next thing to do is verify that all the LV power supply buses are on
spec per the service manual, Volume 1, page 3-43.


Dave



On 2/15/2017 3:16 AM, pjwalczak@... [TekScopes] wrote:

I have an old Tek492. Bought it second hand, but was working fine
for a couple of years. Today when I have switched it on, after a long
break (almost a year) - it powered OK, all controls seems to be ok,
but there is nothing shown on the CRT.

Can anybody share some tips what can be done to find the cause
and fix it ?






------------------------------------------------------------------------
Posted by: pjwalczak@...
------------------------------------------------------------------------









Dave
Manuals@...
www.ArtekManuals.com


Re: Tek492 blank CRT. Please help

lawrenceahlstrom
 

Look for shorted tantal capacitors (general, typical) and check psu voltages.
/Lars


-------- Originalmeddelande --------
Från: "pjwalczak@... [TekScopes]" <TekScopes@...>
Datum:2017-02-15 09:16 (GMT+01:00)
Till: TekScopes@...
Kopia:
Rubrik: [TekScopes] Tek492 blank CRT. Please help

I have an old Tek492. Bought it second hand, but was working fine for a couple of years. Today when I have switched it on, after a long break (almost a year) - it powered OK, all controls seems to be ok, but there is nothing shown on the CRT. Can anybody share some tips what can be done to find the cause and fix it ? [Non-text portions of this message have been removed]

[Non-text portions of this message have been removed]


Tek492 blank CRT. Please help

pjwalczak@...
 

I have an old Tek492. Bought it second hand, but was working fine
for a couple of years. Today when I have switched it on, after a long
break (almost a year) - it powered OK, all controls seems to be ok,
but there is nothing shown on the CRT.

Can anybody share some tips what can be done to find the cause
and fix it ?


Re: B92A no sweep

Michael A. Terrell
 

That sounds more like a polystyrene capacitor.

-----Original Message-----
From: "tatumj1@... [TekScopes]" <TekScopes@...>
Sent: Feb 14, 2017 6:36 PM
To: TekScopes@...
Subject: Re: [TekScopes] B92A no sweep

It was a small mylar cap. The ones that are cased in clear plastic. They look silver as you can see the foil inside. I doubt it would work on an electrolytic. I do not remember ever making anything work by heating an electrolytic. I suppose it could, maybe does, happen. I remember trying to heat the exposed metal on some but do not remember that it ever helped.



Michael A. Terrell


Re: B92A no sweep

 

Everything, even a humble piece of solid wire, has failure mechanisms. Humans have lots of them. Stars have them on a longer scale. The fundamental particles in the universe have failure mechanisms too and eventually decay although the timescale for those is hundreds of orders of magnitude longer. It is all just a matter of time and of failure rates.

Good engineering involves balancing things like failure rates, costs, space constraints, manpower, parts availability, repairability, usability, uniqueness, etc.

Dennis Tillman W7PF

-----Original Message-----
Sent: Tuesday, February 14, 2017 7:41 PM
Subject: Re: [TekScopes] B92A no sweep

Apparently electrolytic's aren't the only cap that can fail.

From: "tatumj1@... [TekScopes]" <TekScopes@...>
To: TekScopes@...
Sent: Tuesday, February 14, 2017 3:36 PM
Subject: Re: [TekScopes] B92A no sweep

It was a small mylar cap. The ones that are cased in clear plastic. They look silver as you can see the foil inside. I doubt it would work on an electrolytic. I do not remember ever making anything work by heating an electrolytic. I suppose it could, maybe does, happen. I remember trying to heat the exposed metal on some but do not remember that it ever helped.

------------------------------------
Posted by: Brent Watson <brentleew2003@...>
------------------------------------


O.T.schematic

wa6bsw@...
 

Thought I would try this group as it seems to have more knowledgeable members than most. The compass/temp module in my '94 Dakota has died and I can't find a replacement. I need a schematic for it or a working used unit. The same unit is used in the '92-93 LaBaron. Thanks for any help.
Jerry


Re: B92A no sweep

Brent Watson <brentleew2003@...>
 

But fail very rarely


From: "Brent Watson brentleew2003@... [TekScopes]" <TekScopes@...>
To: "TekScopes@..." <TekScopes@...>
Sent: Tuesday, February 14, 2017 7:40 PM
Subject: Re: [TekScopes] B92A no sweep

  Apparently electrolytic's aren't the only cap that can fail.

From: "tatumj1@... [TekScopes]" <TekScopes@...>
To: TekScopes@...
Sent: Tuesday, February 14, 2017 3:36 PM
Subject: Re: [TekScopes] B92A no sweep

  It was a small mylar cap. The ones that are cased in clear plastic. They look silver as you can see the foil inside. I doubt it would work on an electrolytic. I do not remember ever making anything work by heating an electrolytic. I suppose it could, maybe does, happen. I remember trying to heat the exposed metal on some but do not remember that it ever helped.

[Non-text portions of this message have been removed]

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Re: B92A no sweep

Brent Watson <brentleew2003@...>
 

Apparently electrolytic's aren't the only cap that can fail.

From: "tatumj1@... [TekScopes]" <TekScopes@...>
To: TekScopes@...
Sent: Tuesday, February 14, 2017 3:36 PM
Subject: Re: [TekScopes] B92A no sweep

  It was a small mylar cap. The ones that are cased in clear plastic. They look silver as you can see the foil inside. I doubt it would work on an electrolytic. I do not remember ever making anything work by heating an electrolytic. I suppose it could, maybe does, happen. I remember trying to heat the exposed metal on some but do not remember that it ever helped.

[Non-text portions of this message have been removed]

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Tektronix 2755AP/494AP Video Processor Adjustment Procedure

rast tro
 

I hope I'm not too off topic asking about a spectrum analyzer on this forum.

I'm looking for information on adjusting the Video Processor on a Tek 2755/494AP Spectrum analyzer.
A40 Video Processor PCB 670-8389-01

I have the service manual but adjustments for this board is not covered.
There are a few paragraphs on theory and a schematic but no explanation on how to adjust 22 potentiometers. These mostly effect band-4 leveling.

Any insights or suggestions would be appreciated.

-rastro


Re: B92A no sweep

Joseph Tatum
 

You are right. I don't ever remember finding another one bad. That one was in an old CRT type computer monitor I bought at Fort Rucker Alabama DOD sale.


Re: OT Ripple Leader LTC-905

Jerry Massengale <jmassen418@...>
 

Hi,

Yes, mine has a 3 wire power cord and the green wire is tied to the chassis
as is the system ground. I looked at the 3 dc power busses and they are
clean and at the correct voltage. The output of the step generator looks
good at the output of the buffer. I am concerned with a very long ground
bus directly tied to earth. I was tempted to disconnect chassis gnd from
signal gnd but decided to sell it instead. Another issue is the 3 banana
jacks for the transistor connection are not on the standard 0.75 inch
spacing that fit my adapters. This is all part of my downsizing efforts. I
recently sold my 576 that I really liked. One option was to use a 7CT1N
with my 7704A, The other was to acquire the Leader LTC-905 and use it with
my 2465A. I put the 905 on ebay for a very low price and will soon put the
2465A up for sale.

jerry

On Tue, Feb 14, 2017 at 3:24 PM, Clark bclark207@... [TekScopes] <
TekScopes@...> wrote:

What does the earth connection connect to in the curve tracer? Mine has
an original two-wire cord with standard two-prong plug - not even
polarized.


On 02/14/2017 02:24 PM, Jerry Massengale jmassen418@...
[TekScopes] wrote:

Hi,

Replacing the 4 rectifiers greatly reduced the ripple. My trace looks
like
that shown in manual. I have decided to sell the LTC-905 and keep my
7CT1N.
This unit has the 3 wire power cable.

On Tue, Feb 14, 2017 at 6:33 AM, Clark bclark207@... [TekScopes] <
TekScopes@...> wrote:

Ripple, or phase error? - see section B on pg 3 in the users manual. I
had the same problem, and solved it by reversing the curve tracer plug
in the wall outlet.


On 02/13/2017 03:01 PM, Jerry Massengale jmassen418@...
[TekScopes] wrote:

Hi,

My just recieved Leader LTC-905 Curve Tracer has a small ripple on
the
display curves as displayed on my 2465A scope. The electrolytics in
the box
have good ESR. Suggestions?

jerry









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Re: B92A no sweep

 

Generally speaking these are very reliable, and have very low leakage if
this is the one I am thinking of. That is important for a linear ramp.

Dennis Tillman W7PF

-----Original Message-----
Sent: Tuesday, February 14, 2017 3:37 PM
Subject: Re: [TekScopes] B92A no sweep

It was a small mylar cap. The ones that are cased in clear plastic. They
look silver as you can see the foil inside. I doubt it would work on an
electrolytic. I do not remember ever making anything work by heating an
electrolytic. I suppose it could, maybe does, happen. I remember trying to
heat the exposed metal on some but do not remember that it ever helped.
------------------------------------
Posted by: tatumj1@...
------------------------------------


Re: B92A no sweep

Joseph Tatum
 

It was a small mylar cap. The ones that are cased in clear plastic. They look silver as you can see the foil inside. I doubt it would work on an electrolytic. I do not remember ever making anything work by heating an electrolytic. I suppose it could, maybe does, happen. I remember trying to heat the exposed metal on some but do not remember that it ever helped.


Re: OT Ripple Leader LTC-905

tronix_cal
 

What does the earth connection connect to in the curve tracer? Mine has
an original two-wire cord with standard two-prong plug - not even polarized.


On 02/14/2017 02:24 PM, Jerry Massengale jmassen418@...
[TekScopes] wrote:

Hi,

Replacing the 4 rectifiers greatly reduced the ripple. My trace looks like
that shown in manual. I have decided to sell the LTC-905 and keep my
7CT1N.
This unit has the 3 wire power cable.

On Tue, Feb 14, 2017 at 6:33 AM, Clark bclark207@... [TekScopes] <
TekScopes@...> wrote:

Ripple, or phase error? - see section B on pg 3 in the users manual. I
had the same problem, and solved it by reversing the curve tracer plug
in the wall outlet.


On 02/13/2017 03:01 PM, Jerry Massengale jmassen418@...
[TekScopes] wrote:

Hi,

My just recieved Leader LTC-905 Curve Tracer has a small ripple on the
display curves as displayed on my 2465A scope. The electrolytics in
the box
have good ESR. Suggestions?

jerry

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[Non-text portions of this message have been removed]



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Re: B92A no sweep

brentleew2003@yahoo.com <brentleew2003@...>
 

I wonder if you recall what kind of cap that was that you found with the resista-heater. I only think of electrolytics being subject to age. But I imagine others could fail as well.
Happy Connecting. Sent from my Sprint Phone.

------ Original message------From: tatumj1@... [TekScopes] Date: Tue, Feb 14, 2017 10:11To: TekScopes@...;Subject:RE: [TekScopes] B92A no sweep
  On the 2465 I just got going, heating the board with a hair drier worked to make it start working right. But freezing would not make it act up. Had to heat the MUX with a soldering iron to isolate the problem.

When you do need freeze spray and do not have easy access to it; get a can of compressed air that is used to blow dust from computers. You can turn it upside down and get the same effect as the freeze spray.

I once had a problem with a computer monitor that would come on when heated. I put a wire wound resister on the end of a dowel and connected it to a 12 v supply. I used that to reach into its innards and isolate a small cap that was causing the problem.

Probably none of the is news to most on here, but it might help sombody. Hope so anyway.

[Non-text portions of this message have been removed]



[Non-text portions of this message have been removed]


Re: OT Ripple Leader LTC-905

Jerry Massengale <jmassen418@...>
 

Hi,

Replacing the 4 rectifiers greatly reduced the ripple. My trace looks like
that shown in manual. I have decided to sell the LTC-905 and keep my 7CT1N.
This unit has the 3 wire power cable.

On Tue, Feb 14, 2017 at 6:33 AM, Clark bclark207@... [TekScopes] <
TekScopes@...> wrote:

Ripple, or phase error? - see section B on pg 3 in the users manual. I
had the same problem, and solved it by reversing the curve tracer plug
in the wall outlet.


On 02/13/2017 03:01 PM, Jerry Massengale jmassen418@...
[TekScopes] wrote:

Hi,

My just recieved Leader LTC-905 Curve Tracer has a small ripple on the
display curves as displayed on my 2465A scope. The electrolytics in
the box
have good ESR. Suggestions?

jerry









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