Oscilloscope GOS-3110 not displaying right

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brosskgm said:
I just had a big shock. One of the 0.5uf 1500vdc capacitors are $50/ea and there is three of them in it. MAybe it's time to work on getting or trying to build one to run on the laptop I guess.
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Oooh.. That's very expensive.. now I'm shocked too :/
I tried to calibrate mine now, but I can't get the v. variable pot to give the right response.. I turned the VR201 and VR202 like it says but I can't get it like they say, it's getting close but not perfekt.. But it's good enough for me..

Build one yourself? Then it must be through USB to get the best frequency range. Sounds like a fun project, have you thought about it and have a plan?
 

Still looking in to it. There is a few that are using the LPT port. One is even with Linux that I might be more willing to give a try.

I'm trying to locate an alternative that will do the same thing with just a little bit lower in cost and do what is needed.
 

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Those capacitors do not need replacing, they are the reservoirs for the high voltage to the tube and if they were faulty you wouldn't see any display at all. The $50 price tag is silly, you can buy them for MUCH less than that. If you needed them, look for the standard value 0.47uF rather than 0.5uF and you will see there are many available on the market.

Brian.
 

Thank Brian, That's good to know the 0.47uf will work. Those are much lower in cost. I'll work on getting all the others and cleaning all the switches. With the wire in J105 yellow wire for a moment give the sin waves. If I pull it out or put it in just like moving the switch I will also get a moment of seeing the sin waves.

Hopfully the capacitors and cleaning will do the trick.
 

I should have most of the caps any day now. Then next week I should be able to go in and replace them and clean all the contacts. Would be nice to get this working so I might actually be able to use it. I've never used it since it was built in 1990. I'll let you know what happens.
 


Yes please do that Bob, I'm curious and am looking forward to know how it goes.

Regards
 

I received most the caps friday. They couldn't get all of them as 1st thought. I'm also having problem with a smaller one .01uf 1500v,
can the .47uf work on this one also or does this require a different. It's an Electrolytic Capacitor. It keeps showing up as a Multilayer Ceramic.

Thanks
 

Having trouble finding a couple electrolytic capacitors .01uf 1500v has no ESR and the C rating is way off. It does not show up on any list as available. It has the lead on each end as with these two 3.3uf 350v is not stocked. The same with 47uf 350v. They require several hundred to a few thousand minimum order.

Any help with alternatives would be great.
 

Hi brosskgm,
As Betwixt is writing for you over the 0.5uF, its the same; you have to find for a foile capacitor of 10nF and1.5KV, in lower working voltages it is an allday capacitor...
LCR COMPONENTS|PC/HV/S/WF 10NF 1.5KV|KONDENSATOR, 10NF, 1500V | Farnell Deutschland
Similar is to say over 3.3uF/350V, if you have place, please selet a 400/500V type, btw is it an axial type too?
Eventually you can use instead 3,3uF a 4,7uf too:**broken link removed**
In tese serie is only the 47uF/350V an electrolythic, but bid you searched at Farnell i.e. please?
Greetings!
K.
P.S.:
I beleave, in north America is the best way to find a component is to check it i.e. by Octopart - Electronic Parts, Electronic Components, Datasheets...
 
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The 0.01uF capacitors will not be electrolytic and they normally fail short circuit so if there is no smoke, they are probably OK.
For the other capacitors, bear in mind that most electrolytic capacitors have very poor tolerances, often -50% to +100% of their marked values so the designer will have catered for values not being exact. In power supply filtering, which is what I think these are used for, you can generally move up one or two value steps without any side effects. The working voltage can also be higher than specified but do not go lower.

Brian.
 

This time the .01uf shows a C= 12.339 nf so I guess this is close. One side of the plastic coating has split but could be because it's 20 years old.
So far this is the only one that failed no reading at all. One of the 47uf 350v showed ESR of 618 mOhm and the other 676 mOhm, the 3.3 350v shows ESR of 7.26 Ohm. One of the 0.5uf 1500v show ESR of 6.00 Ohm and C = 485.296 nf
 

While not perfect, those readings are not unreasonable and shouldn't stop it working. Even an ESR of 7.26 Ohms is of little consequence in a low current supply.

From your original description I would look at a problem in either the input amplifier stage or the trigger stage. One of two things is happening to make your trace vanish after a moment, it could be displaced off the screen because the input amp is out of balance, or, the timebase is not running so there is no sweep across the screen.

Try putting the scope in X-Y mode and see if you can use the shift controls to find the dot.
If you can find a dot, the power supply is working so you can forget the high voltage capacitors.
If the dots there, try putting a signal (anything will do) into the Y input socket, if the trace shows some height it means the Y amplifiers are probably working.

Let me know what happens, my guess is the timebase is not running until it something 'kicks' it into life, if I'm right the fault is in the trigger level circuits.

Brian.
 

It won't comeplete the calibration steps. With the step that was having the problem is why it was mentioned I should replace the capacitors and clean all the contacts in the switchs since it is almost 20 years old and was never run after it was built until now.
 

I put it all back together. When going through the calibration of the scope I still have problems the "Calibrate Signal Adjustments" on page 21 of the assembly setup booklet I gave the link to. When I put the wire to pull the 20 V 60 Hz AC signal on page 22 I do not get the Six cycles, but if I pull the wire slightly as I first talked about I can get the cycles for a short moment. This is the same problem I've been having. I did replace the capacitors it was mentioned above, and cleaned all contacts on the slide switchs but the same problem is still there. I tested and checked the capacitors out of circuit and they all had good ESR even after just sitting there for 19 years. This scope was built and never used and stored and wrapped in plastic. Still new with no dirt or dust when opped to start learning on.

Any other ideas would be a great help. Please remember I do not know how to use this yet so any tests needing to be done please give some detail to do them, and I don't have much in the way of laying around parts.

Thanks
Bob
 

When I put the wire to pull the 20 V 60 Hz AC signal on page 22 I do not get the Six cycles and the outer left center edge is lit, but if I pull the wire slightly as I first talked about I can get the cycles for a short moment. If I pull the wire out of the 60 Hz location I get a pulse line across the screen.

---------- Post added at 03:59 ---------- Previous post was at 03:31 ----------

If I put it in X-Y the outer left center is lit. If I move the H. Position I can get my dot in the center.

---------- Post added at 04:06 ---------- Previous post was at 03:59 ----------

I did find when I put the wire to pull the 20 V 60 Hz AC signal and moved the H. Position I get a straight virtical line and if I pull the Level control out I get the Sin Waves. The instructions say Level control in.
 

I think my suspicion is correct then. Your problem is that the timebase (that sweeps the dot from side to side) is not free running or triggering properly. It should work in one of three modes, X-Y relies on you providing you own sweep signal, single sweep means just that, it sweeps once but you have to manually reset it before it sweeps again and normal mode is when it sweeps by itself but can be synchronized to an incoming signal. You appear to be either stuck in single sweep mode or the timebase isn't free running and needs a 'kick' to get it going. Check the voltage on the wiper of the trigger level control and make sure it adjusts properly.

Brian.
 

Wiper ? There is nothing about this. Where would this be?

---------- Post added at 07:51 ---------- Previous post was at 07:32 ----------

Something else I found. With the trigger out and the sin waves showing, if I turn the H. Variable all the way to the left I get the solid virtical line but this time it's moving across the screen.
 

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