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7704A Readout Capability

 

I recently acquired a Tek 7704A with 7A26 and 7B53A plugins. The 'scope seems to operate fine except I have no readout functions on the CRT. I am not sure if these plugins have the capability or if there is a problem with the readout circuitry in the mainframe.

Any thoughts would be appreciated.

Tom
 

7000 series Plug-ins that lack readout capability have an N suffix.

You could check if the 7704A has option 1 which removes the readout,
look at the third of four potentiometers from the top which should be
the readout intensity control, or look to see if the readout PC board
is even inside.

On Sun, 01 Jul 2012 22:00:24 -0000, "dabyram" <tom.byram@...>
wrote:

I recently acquired a Tek 7704A with 7A26 and 7B53A plugins. The 'scope seems to operate fine except I have no readout functions on the CRT. I am not sure if these plugins have the capability or if there is a problem with the readout circuitry in the mainframe.

Any thoughts would be appreciated.

Tom
 

Hi,

Try running the readout intensity control throughout its range to make sure it is not sitting on a bad spot. Press your beam finder and see it dots appear above and below the reduced trace. Both plugins support readout. If you have not done so, get a manual and get familiar with your fine machine.

Jerry Massengale



-----Original Message-----
From: dabyram
To: TekScopes
Sent: Sun, Jul 1, 2012 5:00 pm
Subject: [TekScopes] 7704A Readout Capability

?
I recently acquired a Tek 7704A with 7A26 and 7B53A plugins. The 'scope seems to operate fine except I have no readout functions on the CRT. I am not sure if these plugins have the capability or if there is a problem with the readout circuitry in the mainframe.

Any thoughts would be appreciated.

Tom
 

<snip> Press your beam finder and see it dots appear above and below the reduced trace.
<snip>

Thanks for the tip Jerry.

I see the blurry blobs for the readout when holding beam finder. The Readout control feels smooth. Any further thoughts as where to look? I have downloaded a manual and will begin digesting that.

Tom




I recently acquired a Tek 7704A with 7A26 and 7B53A plugins. The 'scope seems to operate fine except I have no readout functions on the CRT. I am not sure if these plugins have the capability or if there is a problem with the readout circuitry in the mainframe.

Any thoughts would be appreciated.

Tom
 

Hi,

There is a separation adjustment on the readout board. Otherwise your vertical amplifier gain may be too high. Use the built in calibrator with your trace amplifier to check. There is a gain and a centering adjustment on the vertical amp.

Jerry Massengale



-----Original Message-----
From: dabyram
To: TekScopes
Sent: Tue, Jul 3, 2012 6:25 am
Subject: [TekScopes] Re: 7704A Readout Capability

?
Press your beam finder and see it dots appear above and below the reduced trace.


Thanks for the tip Jerry.

I see the blurry blobs for the readout when holding beam finder. The Readout control feels smooth. Any further thoughts as where to look? I have downloaded a manual and will begin digesting that.

Tom
>
>
>
> I recently acquired a Tek 7704A with 7A26 and 7B53A plugins. The 'scope seems to operate fine except I have no readout functions on the CRT. I am not sure if these plugins have the capability or if there is a problem with the readout circuitry in the mainframe.
>
> Any thoughts would be appreciated.
>
> Tom
>
 

I agree with Jerry. Check the vertical gain using the calibration
signal and a vertical amplifier.

The 7854 I repaired had a similar readout problem. The gain was high
in the vertical CRT amplifier because of a partially open trimmer
potentiometer which shifted the top and bottom readouts out of the CRT
display area. The readout had been adjusted to move them back within
the CRT display area without fixing the gain problem.

A low acceleration voltage will also cause excessive CRT deflection
which will move the readout out of the display area. The service
manual includes a check of the +54 volt supply which if low will
indicate a low acceleration voltage.

On Tue, 3 Jul 2012 10:25:48 -0400 (EDT), jerry massengale
<j_massengale@...> wrote:

Hi,

There is a separation adjustment on the readout board. Otherwise your vertical amplifier gain may be too high. Use the built in calibrator with your trace amplifier to check. There is a gain and a centering adjustment on the vertical amp.

Jerry Massengale

-----Original Message-----
From: dabyram <tom.byram@...>
To: TekScopes <TekScopes@...>
Sent: Tue, Jul 3, 2012 6:25 am
Subject: [TekScopes] Re: 7704A Readout Capability

<snip> Press your beam finder and see it dots appear above and below the reduced trace.
<snip>

Thanks for the tip Jerry.

I see the blurry blobs for the readout when holding beam finder. The Readout control feels smooth. Any further thoughts as where to look? I have downloaded a manual and will begin digesting that.

Tom

I recently acquired a Tek 7704A with 7A26 and 7B53A plugins. The 'scope seems to operate fine except I have no readout functions on the CRT. I am not sure if these plugins have the capability or if there is a problem with the readout circuitry in the mainframe.

Any thoughts would be appreciated.

Tom
Rob
 

The fact that you can see the readout with beam finder more than likely
means my following advice is down the wrong ally. Said another way, pursue
earlier advice first.

However it is slightly possible your facing an intensity issue. The
intensity pot on the readout system needs the negative 15 volt on one side.
If it is missing you will not get enough intensity. However I would think
low intensity should be the same with bean finder on or off so cannot
explain the symptoms your facing other than the advice already given..

-----Original Message-----
From: TekScopes@... [mailto:TekScopes@...] On Behalf
Of David
Sent: Tuesday, July 03, 2012 10:06 AM
To: TekScopes@...
Subject: Re: [TekScopes] Re: 7704A Readout Capability

I agree with Jerry. Check the vertical gain using the calibration signal
and a vertical amplifier.

The 7854 I repaired had a similar readout problem. The gain was high in the
vertical CRT amplifier because of a partially open trimmer potentiometer
which shifted the top and bottom readouts out of the CRT display area. The
readout had been adjusted to move them back within the CRT display area
without fixing the gain problem.

A low acceleration voltage will also cause excessive CRT deflection which
will move the readout out of the display area. The service manual includes
a check of the +54 volt supply which if low will indicate a low acceleration
voltage.

On Tue, 3 Jul 2012 10:25:48 -0400 (EDT), jerry massengale
<j_massengale@...> wrote:

Hi,

There is a separation adjustment on the readout board. Otherwise your
vertical amplifier gain may be too high. Use the built in calibrator with
your trace amplifier to check. There is a gain and a centering adjustment on
the vertical amp.

Jerry Massengale

-----Original Message-----
From: dabyram <tom.byram@...>
To: TekScopes <TekScopes@...>
Sent: Tue, Jul 3, 2012 6:25 am
Subject: [TekScopes] Re: 7704A Readout Capability

<snip> Press your beam finder and see it dots appear above and below the
reduced trace.
<snip>

Thanks for the tip Jerry.

I see the blurry blobs for the readout when holding beam finder. The
Readout control feels smooth. Any further thoughts as where to look? I have
downloaded a manual and will begin digesting that.

Tom

I recently acquired a Tek 7704A with 7A26 and 7B53A plugins. The 'scope
seems to operate fine except I have no readout functions on the CRT. I am
not sure if these plugins have the capability or if there is a problem with
the readout circuitry in the mainframe.

Any thoughts would be appreciated.

Tom

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