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Tek 7834 Question

Gerhard Hofbauer <gerhard.hofbauer@...>
 

Has anyone experience with the TEK 7834 400 MHz mainframe?

About 20 years ago I bought a used 7834 mainframe for the 7S11/7T11
plug-ins. At that time I wondered about the storage function.

When "Bistable" is pressed, the screen starts dark and gets completly
bright after abot 5 seconds. No adjustments of intensity etc. can adjust
the right brightness to get a good stored image.
"Var Persistence" is fine.

At the time I did not care, since I did not need any storage function.
Last year I decided to repair the scope, and I did all the tests and
adjustments of the service manual, but could not get even a bad
"bistable" screen. I read the "Storage Cathode-Ray Tubes and Circuits"
and "Oscilloscope Cathode-Ray Tubes" books and came to conclusion that
the CRT is probably defective. So I bought another 7834 with some other
defects (vertical), but it had the same screen effects.

So my question is: Is this a common failure of CRT aging, or am I doings
something wrong. (All voltages on the CRT are perfectly fine in each
operation mode)

br,

Grhard.

--
XERXES electronics GmbH
Dammgasse 75
A-9020 Klagenfurt

Tel.: +43-(0)463-890061-0
Fax.: +43-(0)463-890061-23
Mob.: +43 (0) 680 4405842

office@...

www.xerxes-tech.com

Firmenbuch : FN 307552h
UID : ATU64037018

Brian
 

Hi GerhardMine does the same , or it did before the power supply went into tick mode , not had time to fix that yet . I put it down to expectations of a bi-stable screen like that in a 564 or a 549 but I think it performs differently because of the multi-mode features as every one I have seen a photo of in bi-stable mode shows the same bright background giving you only something like a 3 or 4 to 1 contrast ratio .
Brian

On Wednesday, 22 April 2020, 16:31:30 BST, Gerhard Hofbauer <gerhard.hofbauer@...> wrote:

Has anyone experience with the TEK 7834 400 MHz mainframe?

About 20 years ago I bought a used 7834 mainframe for the 7S11/7T11
plug-ins. At that time I wondered about the storage function.

When "Bistable" is pressed, the screen starts dark andĀ  gets completly
bright after abot 5 seconds. No adjustments of intensity etc. can adjust
the right brightness to get a good stored image.
"Var Persistence" is fine.

At the time I did not care, since I did not need any storage function.
Last year I decided to repair the scope, and I did all the tests and
adjustments of the service manual, but could not get even a bad
"bistable" screen. I read theĀ  "Storage Cathode-Ray Tubes and Circuits"
and "Oscilloscope Cathode-Ray Tubes" books and came to conclusion that
the CRT is probably defective. So I bought another 7834 with some other
defects (vertical), but it had the same screen effects.

So my question is: Is this a common failure of CRT aging, or am I doings
something wrong. (All voltages on the CRT are perfectly fine in each
operation mode)

br,

Grhard.

--
XERXES electronics GmbH
Dammgasse 75
A-9020 Klagenfurt

Tel.: +43-(0)463-890061-0
Fax.: +43-(0)463-890061-23
Mob.: +43 (0) 680 4405842

office@...

www.xerxes-tech.com

Firmenbuch : FN 307552h
UID : ATU64037018

 

I also own a 7834.
Unless you'd really like to use bistable mode or just to be sure your 'scope is ok, I wouldn't bother about bistable storage. Its only benefit is the long storage time. For practical use, all other modes are far superior. Bistable mode is a relic from the time that no other modes existed.

Raymond

ycui7
 

I am seeing the same thing on mine. The same behavior also extends to my 7633.

Yang Cui

On Wed, Apr 22, 2020, at 8:31 AM, Gerhard Hofbauer wrote:
Has anyone experience with the TEK 7834 400 MHz mainframe?

About 20 years ago I bought a used 7834 mainframe for the 7S11/7T11
plug-ins. At that time I wondered about the storage function.

When "Bistable" is pressed, the screen starts dark and gets completly
bright after abot 5 seconds. No adjustments of intensity etc. can adjust
the right brightness to get a good stored image.
"Var Persistence" is fine.

At the time I did not care, since I did not need any storage function.
Last year I decided to repair the scope, and I did all the tests and
adjustments of the service manual, but could not get even a bad
"bistable" screen. I read the "Storage Cathode-Ray Tubes and Circuits"
and "Oscilloscope Cathode-Ray Tubes" books and came to conclusion that
the CRT is probably defective. So I bought another 7834 with some other
defects (vertical), but it had the same screen effects.

So my question is: Is this a common failure of CRT aging, or am I doings
something wrong. (All voltages on the CRT are perfectly fine in each
operation mode)

br,

Grhard.

--
XERXES electronics GmbH
Dammgasse 75
A-9020 Klagenfurt

Tel.: +43-(0)463-890061-0
Fax.: +43-(0)463-890061-23
Mob.: +43 (0) 680 4405842

office@...

www.xerxes-tech.com

Firmenbuch : FN 307552h
UID : ATU64037018



Michael W. Lynch <mlynch003@...>
 

On Wed, Apr 22, 2020 at 11:26 AM, Raymond Domp Frank wrote:


I also own a 7834.
Unless you'd really like to use bistable mode or just to be sure your 'scope
is ok, I wouldn't bother about bistable storage. Its only benefit is the long
storage time. For practical use, all other modes are far superior. Bistable
mode is a relic from the time that no other modes existed.

Raymond
Raymond,

I have a 7623A and a 7633 and I was worried that they both had problems, since they both exhibit this same characteristic with a bright background and a very low contrast stored trace. I found the "bistable" mode was pretty much useless for my application. Good to know that this is "normal" and not a failure mode.


--
Michael Lynch
Dardanelle, Arkansas

 

On Wed, Apr 22, 2020 at 06:51 PM, Michael W. Lynch wrote:


a bright background and a very low contrast stored trace
Hi Michael,
Yeah, that's what bistable is in all its glory on these machines. It looks much better on machines that only have bistable, like the tube 'scopes.
Bistable is only there on the 7K 'scopes to be "complete".

Raymond