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Re: How to upgrade a 7854 to opt 2D

 

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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