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Beam problems with an old Advance OS2100 oscilloscope

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radioactives

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My old Advance oscilloscope, which I got recently show some disorted traces. There is a ripple, hard to say the freq. but around 1000 Hz on both beams. It has nothing to do with the plugins. The ripple show even with these plugins removed. Secondly, the trace is bent at both ends. I cannot move the trace all the way up or dow, just about 1/3 up and down. See images at: **broken link removed** The upper image show the ripple and the lower the bent edges of the trace.

I have cleaned the scope, removed old dust and have used Teslanol contact spray. I have checked the voltage to the high voltage unit and it does deliver +18V and -12V as it should.

Does anyone have a clue to what could be wrong? Coud it be the deflection of the beam that starts to malfunction, ie getting old?

Appreciate any help and advice.

Lasse
 
I still have problem with my old Advance scope. I have tried to describe it on my website (text is both swedish and english) and have made two videos that hopefull can shed some light to my problems.

I have cleaned it, checked all the solderings, sprayed all contacts and pot's with contact spray, still the same problems with ripple and disorted trace. Please visit my website and have a look: **broken link removed**

If anyone have a clue to what could be wrong, I would be thankful to any suggestions.

Lasse
 
I'm bumping this thread in hope of getting some help. I have a website that describes the problem and two videos. Please visit to see my problems at **broken link removed** The site is in both english and swedish.

Lasse
 
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I think you need to look at the deflection supplies. What's confusing is that if both H & V should be affected equally. That has to be much higher than 18 V. More like 65 or higher.

Would you happen to have a schematic of the verticle section past the plug in?

Using a jumper, you can isolate the faulty stage, but need the schematic.
 
Thanks for your input. The supply to the high voltage EHT should be 18V. The deflection plates have higher, 65V for the X-plate and 55V for the Y-plate. I'm not sure where to measure this although I have a scematic. I have to look into this. I have a description how to recalibrate, but need a kV-multimeter to run it completely. Most voltage is not that high so I might be able to measure most voltage.

Lasse
 
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Your not ready to re-calibrate yet.

Can you scan & post a schematic of the vertical amplifier?

Power supply voltages probably can be measured relative to chassis. Chassis should be the at the potential of the probe ground clip.

If the deflection plate voltages are truely differnt on the schematic, then you may have a problem with the the deflection supply for the vertical section. Look at the DC and AC value of the DC supplies of the H and V sections and compare.
 
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I have put the manual on my website **broken link removed** It's at the bottom of the page. I'm not sure if I am allowed to do that, so I probably remove it in a day or two.

Thanks for looking into my problem

Lasse
 
The first step in fixig anything is the inspection step.Looks like you;ve done that, Look for missing items, evidenceof burning and corrosion etc.

2nd step. Check the power supplies. Unfortunately you don't have a scope to check the scope.

On page p0037, fig 5

With power off and caps discharged (off for a few hours at least) or check voltage across C101A & B first and make sure it's zero.

Check R101 in circuit and R across C101A and 101B. The latter should not be steady. You can also try to reverse the leads on A and B On the old analog meters, you should generally see a kick to a low value and the charge when you do that.

Locate A1 and A2 which are both common. Didn't check to see if they connect to common of the the probe input. It probably does. You can verify wirh an ohms check.

Since your having an effect with brightness, let's check with signal applied and no brightness and max brightness and/or distortion.

Ideally we are interested in the DC value and if there is significant ripple. No scope,so see if the voltmeter on the AC scale will pick up anything significant

We want to look at C101A/A9, C101B, A5, A4, A8 and A6 relative to A1 or A2 in DCV, ACV under min and max brightness.

I'll print the pages and see what else I can come up with.
 
Thanks. I'll take look on your suggestions and come back when I have done it. It may take a day until I have checked everything.

Edit: Someone has replaced the rectifier MR105-108. R101 seem ok, 46.8 ohm. C101 is only one, not two.


Lasse
 
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I briefly read the manual after converting it to a single PDF. Page 9 contains the limits and some alternate test points.

Without any measurements, my guesses are:

1.Power supply Golden rule: always check this first

I do remember once when acting as a support specialist, I asked wheter or not the equipment was plugged in. After a short pause, I got the answer No.

2. An internal short in the CRT possibly caused by moving the scope before the filaments cooled. I once worked on a CRT terminal with brightness issues and I found a CRT short to another control surface in the CRT.
 
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