Tek Scope Issue

C

Cursitor Doom

Guest
Hi all,

Forgive me for not having very much useful detail on this, but a friend
has a scope that's unfocusable and produces a thick trace. My immediate
reaction was maybe noise getting into the signal path from a faulty mains
filter or maybe an internal component in the smps section failed, but he
reckons he's ruled out the latter as apparently it's a linear supply. He
doesn't have another scope to check the rails for noise with so he's kind
of limited. Anyway, that was only my hunch, I don't know the precise
model of scope this is; I just wondered if anyone would like to toss in
their 2c worth if they've encountered this issue themselves and what
might be the cause of it?
thanks,
cd.
 
On 11 Jul 15 at group /sci/electronics/repair in article mnrjif$2bm$1@dont-email.me
<curd@notformail.com> (Cursitor Doom) wrote:

Forgive me for not having very much useful detail on this, but a
friend has a scope that's unfocusable and produces a thick trace.
Click to expand...

Check the supply for the Wehnelt cylinder, PWR dead, bad contact, broken
cable...

https://en.wikipedia.org/wiki/Wehnelt_cylinder


Saludos (an alle Vernünftigen, Rest sh. sig)
Wolfgang

--
Wolfgang Allinger, anerkannter Trollallergiker :) reply Adresse gesetzt!
Ich diskutiere zukünftig weniger mit Idioten, denn sie ziehen mich auf
ihr Niveau herunter und schlagen mich dort mit ihrer Erfahrung! :p
(lt. alter usenet Weisheit) iPod, iPhone, iPad, iTunes, iRak, iDiot
 
On Sat, 11 Jul 2015 17:25:35 +0000, Cursitor Doom wrote:

Hi all,

Forgive me for not having very much useful detail on this, but a friend
has a scope that's unfocusable and produces a thick trace. My immediate
reaction was maybe noise getting into the signal path from a faulty mains
filter or maybe an internal component in the smps section failed, but he
reckons he's ruled out the latter as apparently it's a linear supply. He
doesn't have another scope to check the rails for noise with so he's kind
of limited. Anyway, that was only my hunch, I don't know the precise
model of scope this is; I just wondered if anyone would like to toss in
their 2c worth if they've encountered this issue themselves and what
might be the cause of it?
thanks,
cd.
Click to expand...

Anything Tek one address:
https://groups.yahoo.com/group/TekScopes

Cheers!
 
On Saturday, July 11, 2015 at 10:27:04 AM UTC-7, Cursitor Doom wrote:

Forgive me for not having very much useful detail on this, but a friend
has a scope that's unfocusable and produces a thick trace. My immediate
reaction was maybe noise
Click to expand...

Probably not. Noise, if you mean interference, would be affected by change
of timescales.
More likely, a HV electrode in the electrode gun is used for focus, and the
adjustment is off because a high-ohms fixed resistor has failed, open circuit.
Look for range-setting fixed resistors connected to the focus control, taking
all precautions against HV and breakage of the glass...
 
"c4urs11" <c4urs11@domain.hidden> wrote in message
news:1436639380.773261@news.evonet.be...
On Sat, 11 Jul 2015 17:25:35 +0000, Cursitor Doom wrote:

Hi all,

Forgive me for not having very much useful detail on this, but a friend
has a scope that's unfocusable and produces a thick trace. My immediate
reaction was maybe noise getting into the signal path from a faulty mains
filter or maybe an internal component in the smps section failed, but he
reckons he's ruled out the latter as apparently it's a linear supply. He
doesn't have another scope to check the rails for noise with so he's kind
of limited. Anyway, that was only my hunch, I don't know the precise
model of scope this is; I just wondered if anyone would like to toss in
their 2c worth if they've encountered this issue themselves and what
might be the cause of it?
thanks,
cd.

Anything Tek one address:
https://groups.yahoo.com/group/TekScopes

Cheers!
Click to expand...

Well, there's no real substitute for actual troubleshooting - but having
said that, I understand some Tek's have had bad focus potentiometers, and
there's always the possibility of a bad high-value resistor in such a
circuit. A bad 2.2 meg resistor caused a B&K 'scope of mine to not quite
focus. The focus pot ran out of range first. Replacing the resistor fixed
it.

If you do attempt to troubleshoot, be aware there are some rather high
voltages in such circuits.


Mark Z.
 
On Sun, 12 Jul 2015 08:56:20 -0700, jurb6006 wrote:

> Model number ?

Not known, I'm afraid. And the person who was acting as intermediary
between myself and the scope owner has declared he no longer wishes to
spend a single second more on the issue, so all the suggestions so far
have been passed on to the owner, but no more will be.
Thanks, guys.
 
On Sunday, July 12, 2015 at 12:48:28 PM UTC-5, Cursitor Doom wrote:
On Sun, 12 Jul 2015 08:56:20 -0700, jurb6006 wrote:

Model number ?

Not known, I'm afraid. And the person who was acting as intermediary
between myself and the scope owner has declared he no longer wishes to
spend a single second more on the issue, so all the suggestions so far
have been passed on to the owner, but no more will be.
Thanks, guys.
Click to expand...

Then offer the guy ten bucks for it. It would be damn hard to find any Tektronix scope worth less than ten bucks.

And then if you get a ten grand scope fro ten bucks, fukum. they bother you, get you to look into T?HEI?R problem and then bloww you off like that ?

I hope you do get a ten grand scope for ten bucks and enjoy the fuck out of the $9,990. If so, pick me up some weed wouldya ?
 
In article <mnrjif$2bm$1@dont-email.me>, curd@notformail.com says...
Hi all,

Forgive me for not having very much useful detail on this, but a friend
has a scope that's unfocusable and produces a thick trace. My immediate
reaction was maybe noise getting into the signal path from a faulty mains
filter or maybe an internal component in the smps section failed, but he
reckons he's ruled out the latter as apparently it's a linear supply. He
doesn't have another scope to check the rails for noise with so he's kind
of limited. Anyway, that was only my hunch, I don't know the precise
model of scope this is; I just wondered if anyone would like to toss in
their 2c worth if they've encountered this issue themselves and what
might be the cause of it?
thanks,
cd.
Click to expand...

First of all, you should have a service print on it..

Some clues..

If the width control seems to be operating in a different place
than where It use to be, this indicates that HV is not where it
should be, since this can cause a deeflection change.

The focus circuit voltage dividers may have failed and or the
focus pots.

Another issue is over brightness etc....

But like I said, you need some points of reference to fo this
sort of work.

Some of the analog tek scopes use custom hybrid boards and were
prone to failure, good luck with that.

Jamie
 
In article <163ba80f-04b0-474b-8efd-a42faf7377a6@googlegroups.com>,
jurb6006@gmail.com says...
On Sunday, July 12, 2015 at 12:48:28 PM UTC-5, Cursitor Doom wrote:
On Sun, 12 Jul 2015 08:56:20 -0700, jurb6006 wrote:

Model number ?

Not known, I'm afraid. And the person who was acting as intermediary
between myself and the scope owner has declared he no longer wishes to
spend a single second more on the issue, so all the suggestions so far
have been passed on to the owner, but no more will be.
Thanks, guys.

Then offer the guy ten bucks for it. It would be damn hard to find any Tektronix scope worth less than ten bucks.

And then if you get a ten grand scope fro ten bucks, fukum. they bother you, get you to look into T?HEI?R problem and then bloww you off like that ?

I hope you do get a ten grand scope for ten bucks and enjoy the fuck out of the $9,990. If so, pick me up some weed wouldya ?
Click to expand...

I got some in my back yard, just growing all over, you're welcome to
come over here and remove it!

I don't care what you have in mind for it! :)

Jamie
 
In article <8455f89d-430d-4bc6-9e6b-2aa274d76ed6@googlegroups.com>,
<jurb6006@gmail.com> wrote:
>Model number ?

If it's a 2235, 2236, and I think the 2215, it's because they
used a bunch of underrated 1/2 watt carbon comp resistors in the
focus divider chain. Put too high a voltage on them and they
shift in value.


Mark Zenier mzenier@eskimo.com
Googleproofaddress(account:mzenier provider:eskimo domain:com)
 
In article <55a25dd1$0$13652$4c5efc6d@fastusenet.org>,
Mark Zacharias <mark_zacharias@labolgcbs.net> wrote:

Well, there's no real substitute for actual troubleshooting - but having
said that, I understand some Tek's have had bad focus potentiometers, and
there's always the possibility of a bad high-value resistor in such a
circuit. A bad 2.2 meg resistor caused a B&K 'scope of mine to not quite
focus. The focus pot ran out of range first. Replacing the resistor fixed
it.
Click to expand...

The Tek 2235 and its cousins have a fairly common problem show up.
The focus chain uses high-value carbon-composition resistors, which
tend to shift value with age... the focus pot runs out of range as a
result.

I bought a 2235 with this problem at a local flea market for all of
$60. An hour's work and a few replacement resistors fixed it.
 
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