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Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders.

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Old 16th Nov 2011, 9:35 am   #1
John Engineer
Diode
 
Join Date: Nov 2011
Location: London
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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Old 16th Nov 2011, 12:59 pm   #2
John Engineer
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Join Date: Nov 2011
Location: London
Posts: 6
Default Re: Problem With My Gould 1604 Oscilloscope

This post is to help other people who has the same issue of poor focus as me with the Gould 16xx range of Oscilloscopes

I have just cured the focus issue with my 1604, I was fast running out of ideas after completing everything I had done in the above post.

After studying the service manual Power Supply Area I decided to replace all the 10uf electrolytic Capacitors on the Power Supply and the Main Scope PCB along with the 470uf on the main board.

Hey Presto the focus problem was cured, I think I was looking too deep in other areas, yet again dry capacitors were the problem. I have had this scope since 1989 about 22 years so I not surprised there getting a little dry.

So if anyone is having focus issues, this is a good area to start looking at.

If you did not see my last post about battery damage to the main PCB and wave form processors pcb, I can not stress enough how important it is to remove these batteries away from the main PCB and waveform processor PCB. The batteries leak and will destroy the tracks and can create many more faults due to pcb damage.

Simply replace the varta 3.6v battery and take fly leads of the two pcb terminals and remote site the battery away from the PCB, so if it does leak in the future it will not cause any damage. Its also a good idea to seal the battery how ever you feel works for you.

Hope this helps others, its been a long journey getting my two scope's back to full working condition, but I'm there.

These are great oscilloscopes and as I use to work for Gould, thus I lived and breathed these scopes in the late 80's, sadly now I am a little rusty around the edges. Having as service manual helped me and knowing there's a great forum here is invaluable.

Regards


John
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Old 16th Nov 2011, 7:40 pm   #3
valveman49
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Location: Gateshead, Tyne & Wear.
Posts: 179
Default Re: Problem With My Gould 1604 Oscilloscope

Hello John
If you have a read of the posts in the following link, I think you will find that the focus problem with your 1604 is likely to be due to the smoothing capacitors in the power supply.

http://www.vintage-radio.net/forum/s...ght=Gould+1604

You can use the “Search Facility” on the forum to find lots of information on the Gould 1604 and 1624 oscilloscopes.

Regards Stan.
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Old 17th Nov 2011, 12:18 pm   #4
John Engineer
Diode
 
Join Date: Nov 2011
Location: London
Posts: 6
Default Re: Problem With My Gould 1604 Oscilloscope

Hello Stan

Thank you for your reply,

before you kindly posted, I replaced all the +12v / -12v caps in the scope as these voltages are used on the CRT board.

I was running out of ideas and this was a final hunch just in case they had gone dry, they had the scope looks like new again with all text crystal sharp.
I'm so happy,

As this was a slow degrade over many years, you don't tend to notice the focus issue until it gets really bad.

Anyway thank you very much for your reply, the link you posted makes great reading.

Thanks again

John
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