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Old 16th Nov 2011, 11:35 am   #1
John Engineer
Retired Dormant Member
 
Join Date: Nov 2011
Location: London, UK.
Posts: 6
Default Problem With My Gould 1604 Oscilloscope

Hello
From my previous post you will see the problems I had with my 1624 Oscilloscope and how I cured them due to major damage to the PCB's from battery acid from the on board batteries.

With my 1604 I have been experiencing a focusing issue over the past few years, after turning on the scope I can not sharpen this trace or text, its slightly out of focus, it improves with time when the scope warms up, but its still not pin sharp like the 1624 scope is.

First of all I removed the on board battery and replaced it with fly lead, It had damaged the pcb the same problem with acid damage on my 1624 !!

I have cut and remade some of the tracks that were damaged around the battery area of the pcb just in case there was noise being induced to the damaged tracks ? Though I don't think there is to many tracks around the battery that relate to display / focus area.

I am lucky enough to have a 2nd Spare CRT board that I inserted hoping that it would cure the focusing problem, sadly it did not.

After inserting the 2nd CRT board I did a full calibration on the scope from the service manual and the focusing issue still exists ?

I then proceeded to take fly leads from the CRT board to the Power Supply Board (+75v, +180v, -12V, +12 and Ov) just in case these voltages were not good through the main pcb) sadly this did not improve the focus issue.

One strange thing I have noticed in relation to this sharp focusing issue is.. if I remove the four channel (Chan 3/4) PCB board the text is slightly sharper, when I add the four channel board it adds a fringe shadow around the text thus causing the text to be blurred and appearing to be out of focus.

It could be a CRT tube issue ?? but I don't think so.
It could be tied up with dot join / blanking issue ?
It could be tied up with the composite signal where the 4 traces and text merged together ?
It could be tied up with pcb damage from battery, though I don't think so ?

I am not really sure what else I should be looking for to cure this problem ?
I can not workout why the 4 channel pcb board would slightly degrade the text image even more and make a shadow around the text.
It's almost as if it adds a fringe / shadow around the text to give an out of focus effect.

Any help to cure this very bugging issues will be very much appreciated
I have spent quite a lot of time already trying to solve this, so any further ideas will really help me.

Regards
John
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