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Tek Scope Issue
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Cursitor Doom
Jul 11, 2015, 1:27:04 PM7/11/15
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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.
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.
Wolfgang Allinger
Jul 11, 2015, 1:47:37 PM7/11/15
to
On 11 Jul 15 at group /sci/electronics/repair in article mnrjif$2bm$1...@dont-email.me
<cu...@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.
Check the supply for the Wehnelt cylinder, PWR dead, bad contact, broken
>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.
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
c4urs11
Jul 11, 2015, 2:29:43 PM7/11/15
to
whit3rd
Jul 12, 2015, 1:09:17 AM7/12/15
to
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
Probably not. Noise, if you mean interference, would be affected by change
> 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
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...
Mark Zacharias
Jul 12, 2015, 8:30:15 AM7/12/15
to
"c4urs11" <c4u...@domain.hidden> wrote in message
news:14366393...@news.evonet.be...
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.
news:14366393...@news.evonet.be...
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.
jurb...@gmail.com
Jul 12, 2015, 11:56:23 AM7/12/15
to
Model number ?
Cursitor Doom
Jul 12, 2015, 1:48:28 PM7/12/15
to
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.
> 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.
M Philbrook
Jul 12, 2015, 2:11:29 PM7/12/15
to
In article <mnrjif$2bm$1...@dont-email.me>, cu...@notformail.com says...
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
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
jurb...@gmail.com
Jul 12, 2015, 5:17:18 PM7/12/15
to
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 ?
M Philbrook
Jul 12, 2015, 8:09:21 PM7/12/15
to
In article <163ba80f-04b0-474b...@googlegroups.com>,
jurb...@gmail.com says...
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
jurb...@gmail.com says...
come over here and remove it!
I don't care what you have in mind for it! :)
Jamie
Mark Zenier
Jul 13, 2015, 11:17:54 AM7/13/15
to
In article <8455f89d-430d-4bc6...@googlegroups.com>,
<jurb...@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 mze...@eskimo.com
Googleproofaddress(account:mzenier provider:eskimo domain:com)
<jurb...@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 mze...@eskimo.com
Googleproofaddress(account:mzenier provider:eskimo domain:com)
Dave Platt
Jul 13, 2015, 2:59:37 PM7/13/15
to
In article <55a25dd1$0$13652$4c5e...@fastusenet.org>,
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.
Mark Zacharias <mark_za...@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.
The Tek 2235 and its cousins have a fairly common problem show up.
>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.
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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