开云体育

-----Original Message-----
From: TekScopes@... [mailto:TekScopes@...] On Behalf Of David
Sent: 18 March 2013 20:47
To: TekScopes@...
Subject: Re: [TekScopes] Re: How to upgrade a 7854 to opt 2D

There are two versions of board A29 divided at 7854 serial number
B085124 and below but the schematics are basically identical. DG181 is the part number used for a bunch of the analog multiplexors. The newer version replaced the LF13333 multiplexor (U1720) with a pair of
DG181 multiplexors (U2 and U3).



Accounting for the minor part number differences:

I think you will find the problem around U1620A or *U1720* on schematic 34. I have read about reliability problems with the
*LF13333* before. There are old posts in the message archive about possible substitutions for it.

The TL072 used for U1620 has lots of possible replacements including the TL082 and any number of other FET and MOSFET input operational amplifiers.

There could be a bad part in the networks surrounding U1620A.

On Mon, 18 Mar 2013 19:51:21 -0000, "g_kupka" <ghm1@...> wrote:

Hi David,
On "my" schematic 34 there is no U1620A or U2 and no D181 or U3.
I found the TL 72 OpAmp.
I have a U900 aa vertical D/A converter an a U1010 as horizontal D/A converter.
Gerhard

--- In TekScopes@..., David <davidwhess@...> wrote:

I assume that the character display works correctly even when the
stored signal has no or a low vertical deflection.

I think you will find the problem around U1620A or U2 on schematic 34.
If reseating those ICs or the A40 connections does not resolve the
problem, then you could swap U2 with a different DG181 like U3 to see
if the problem moves to the horizontal axis. I have read about
reliability problems with the DG181 before.

The TL072 used for U1620 has lots of possible replacements including
the TL082 and any number of other FET and MOSFET input operational
amplifiers.

There could be a bad part in the networks surrounding U1620A.

On Mon, 18 Mar 2013 16:44:53 -0000, "g_kupka" <ghm1@...> wrote:

After a warmup time of approx 2 hours the stored signal is displayed in the stored mode but only with an ampltude of 35% of the applied signal.

Gerhard

--- In TekScopes@..., "g_kupka" <ghm1@> wrote:

I swapped the RAM Board and now the 2nd 7854 has the opt 2D.
The 1st 7854 has still the problem, that it doesn't display the stored signal in the store mode, it shows only a horizontal line.
Where can I find the failure?
Many thanks.
Gerhard

--- In TekScopes@..., "David C. Partridge" <david.partridge@> wrote:

Yes

Dave
-----Original Message-----
From: TekScopes@...
[mailto:TekScopes@...] On Behalf Of g_kupka
Sent: 17 March 2013 10:22
To: TekScopes@...
Subject: [TekScopes] How to upgrade a 7854 to opt 2D

I have two 7854.
1st one opt 2D(extended memory):
I can store a signal, but it doesn't show the stored signal in the store mode, it shows only a horizontal line.
2nd one opt 78(P11 CRT):
It works well. Can I upgrade this mainframe to opt 2D by swapping the memory board from the 1st one to the 2nd one?

Gerhard

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